- Email: [email protected]
Excimer and holmium yttrium aluminum garnet laser coronary angioplasty
February
Ribeiro et al.
American
20. Van der Giessen WJ, Woerkens LJ, Beatt K, Serruys PW, Verdouw PD. Coronary stenting with a radiopaque, a thrombogenic, balloon expandable stent [Abstract]. Circulation 1989;80:11-173. 21. Barth KH, Virmani R, Strecker EP, Savin MA, Lindisch D, Matsumuto AH, Teitelbaum GP. Flexible tantalum stents implanted in aortas and iliac arteries: effects in normal canines. Radiology 1990;175:91-6. 22. Rousseau H, Puel J, Joffre F, Sigwart U, Duboucher C, Iubert C, Knight C, Knopf L, Wallsten H. Self-expanding endovascular prosthesis: an experimental study. Radiology 1987; 164:709-14.
MD, Jan Kvasnicka,
Laser angioplasty differs from balloon angioplasty in that the former ablates the obstructing material from the coronary artery lumen, whereas the latter acts by pushing it aside and stretching the vessel wall.lT3 Recently access to the coronary arteries became available to laser angioplasty because of a new technique that utilizes (1) a pulsed laser source, (2) multifiber catheters that consist of rings of thin optical fibers concentrically arranged around a central lumen for the passage of a guide wire, and (3) a mechanical guidance device that uses the same guide wires as those commonly used for balloon angioplasty. Multicenter trials on excimer laser coronary angioplasty are ongoing.4-6 The first published data showed this technique to be rather safe and the early results to be satisfactory as compared with those obtained by balloon dilatation, especially in types B and C lesions.7
From the Cardiac Catheterization Laboratory and the Interventional Cardiology Unit, the INSERM U 2 and the Division of Cardiology, University Hospital Henri-Mondor. Received
for publication
Feb.
28, 1992;
accepted
Aug.
24, 1992.
Reprint requests: Herbert J. Geschwind, MD, Unit6 d’HBmodynamique et de Cardiologie Interventionnelle, Service d’Rxplorations Fonctionnelles, University Hospital Henri-Mondor, 51, Av. de Tassigny, 94010 CrBteil, France.
AM HEART J 1993:125:510
garnet
MD, and
However, few clinical studies are available on other pulsed laser sources such as the infrared holmium yttrium aluminum garnet laser (Ho-YAG).s g Thus the purpose of this study was to evaluate the immediate and early results obtained by excimer laser coronary angioplasty and to determine whether a shift in the laser wavelength from ultraviolet to infrared will affect these results. Further, the study was aimed at evaluating the side effects of coronary laser angioplasty, namely, the consequence of laser irradiation on the arterial wall and the rate of complications. Finally, we sought to determine the influence of both catheter size and design on the early results of this method of treatment. METHODOLOGY Study population. All patients
who were selected to undergo laser angioplasty were candidates for balloon angioplasty. They all showed evidence of ischemia such as angina or positive results of stress tests including exercise ECG and/or thallium scintigraphy. Eighty-six consecutive patients were included in the study. Patient selection for laser angioplasty was based on easy access to proximal lesions at the early stage of the study. The following lesions were considered suitable: total occlusions; restenoses; suboptimal results after balloon dilatation; long, tunnelCopyright
510
1993 Journal
23. Levine MJ, Bradley BM, Burke JA, Nash ID, Satian RD, Diver DJ, Bairn DS. Clinical and angiographic results of balloon expandable intracoronary stents in right coronary artery stenosis. J Am Co11 Cardiol 1990;16:332-9. 24. Roubin GS, King SB III, Douglas JS, Lembo NJ, Robinson KA. Intracoronary stenting during percutaneous transluminal coronary angioplasty. Circulation 1990;81:IV-92-116. 25. Sigwart U, Golf S, Kaufmann V, Kappenberger L. Analysis of complication associated with coronary stenting [Abstract]. J Am Co11 Cardiol 1988:2:66A.
Excimer and holmium yttrium aluminum laser coronary angioplasty Herbert J. Geschwind, MD, Fumitaka Nakamura, Jean L. Dubois-Rand& MD Crkteil, France
Heart
1993
by Mosby-Year
OOK-8703/93/$1.00
+ .lO
Book,
4/l/42640
Inc.
Volume Number
125 2, Part
1
shaped, calcified lesions; and ostial lesions. In the first stage of the study (which started in March 1990), the Ho-YAG laser was used because of technical availability (patients in group I). In the second stage of the study (which started in June 1990) an excimer laser was used (patients in group II). Then both lasers were used. The selection was made according to the availability of catheters. Patient characteristics are presented in Table I. The study, which focused especially on the results obtained after use of an extimer laser, is part of a nonrandomized European multicenter trial.6 All patients gave informed consent before participating in the study after approval of the protocol was given by the Ethical Committee of the University Hospital Henri-Mondor. The same laser sources were used during the study. Gradual improvements were made in the number of fibers and in the flexibility of the catheter. Catheter size was selected according to the size of the artery to be treated to make the catheter-artery diameter ratio close to 1. Laser sources. Two laser sources were used in the study. In the first group of patients coronary laser angioplasties were performed with a pulsed infrared laser. The equipment consisted of a Ho-YAG laser, which operated at a wavelength of 2.1 nm, a pulse width of 250 psec, a repetition rate of 3.5 Hz, and a fluence of 1 to 2 J/mm2 (MCM-Eclipse Laboratories, Mountain View, Calif.). In the second group of patients, an ultraviolet laser source was used; it consisted of a xenon chloride excimer laser, which operated at a wavelength of 308 nm, a pulse duration of 135 nsec, a repetition rate of 25 Hz, and a fluence of 30 to 60 mJ/mm2 (CVX-300, Spectranetics, Colorado Springs, Colo.). The Ho-YAG laser was coupled into a multifiber catheter with a diameter of 1.5 or 2.0 mm, which consisted of 26 and 37 optical fibers of 100 pm each, respectively, concentrically arranged around a central lumen for the passage of a 0.014 inch or 0.018 inch guide wire. The excimer laser was coupled to a multifiber catheter with a diameter of 1.4,1.7, and or 2.0 mm, which consisted of 21,45, and 87 fibers of 100 pm each, respectively, concentrically arranged around a central lumen for the passage of a 0.014 inch or 0.018 inch guide wire. Procedure. The procedure was derived from that which is commonly used for balloon angioplasty. Briefly, through a percutaneous femoral arterial approach with a 9F sheath, an 8F or 9F large lumen guiding catheter was positioned in the ostium of the target vessel. Next, an 0.014 inch or 0.018 inch Hi Torque floppy guide wire (ACS, Inc., Temecula, Calif.) was inserted into the artery to be treated with the laser catheter, which was maintained behind the dis-
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Table I. Patient and angiographic baseline characteristics Group II (excimer)
Group I (Ha-YAG)
No. of patients Mean age (yr) Sex distribution (% men) Previous treatment
40 56
PTCA CABG Site of lesion LAD LCX LMT RCA SVG
Stenosis Total occlusion Calcification Minimal luminal diameter (mm) Diameter stenosis (%)
46
+ 9 88
55
f
12
85
5 3 26
0.12
NS NS
22 12
NS NS NS NS NS
8
8 4
5 22 13 24 16 17
5 28 13 26 20 13
*
0.21
95 + 9
0.13
NS NS
10
0
Lesion characteristics* Type A Type B Type C
p Value
f
0.23
94 * 11
NS NS NS NS NS NS NS NS
NS, not significant at p < 0.05; PZ’CA, percutaneous transluminal coronary angioplasty; CAM, coronary artery bypassgrafting; LAD, left anterior descending artery; LCX, left circumflex artery; LMT, left main trunc; RCA, right coronary artery; SVG, aaphenous vein graft. *American College of Cardiology/American classification.
Heart Association
Task Force
tal tip of the guide wire. The lesion was crossed with the guide wire under fluoroscopic control, and its distal tip was positioned distal to the lesion. The multifiber catheter was then advanced over the guide wire, and its distal end was positioned against the lesion. Laser was emitted while the catheter was maintained in a stationary position at the entry of the lesion. The Ho-YAG laser was emitted in bursts of 10 or 20 pulses, whereas the excimer laser was delivered in bursts of 125 pulses each, which were separated by at least 15 seconds. After the catheter was pulled back, repeat coronary angiography was performed to assess the results of laser irradiation. When no complications were detected, the procedure was continued by slightly advancing the catheter through the lesion under laser emission. Particular caution was taken to avoid any high manual pressure to the proximal catheter tip to prevent. a mechanical “dottering” effect. The rate of advancement was kept as slow as possible to allow the laser to actually ablate tissue rather than pushing it mechanically ahead. After penetration of the lesion was completed, the catheter was pulled back to allow for contrast medium injection to reveal the effects of laser irradiation. If no
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significant reduction in the stenosis diameter or no evidence for recanalization of a total occlusion could be obtained, multiple passes were performed. The results were considered satisfactory and the laser procedure was terminated when the residual stenosis was <30 @O . When the residual stenosis was ~30 Cr, an adjunctive balloon angioplasty was performed. Cineangiograms were performed in the same projections as those that were done before the procedure. An early follow-up coronary cineangiogram was performed within 24 hours after the procedure before the sheath was removed. Patients were pretreated with aspirin, which was given in doses of 250 mg daily and started no later than the day before the procedure. Before and during the procedure, heparin was administered intravenously (10,000 U). When the procedure was completed, patients were given a selective intracoronary bolus of heparin (3000 U) and isosorbide dinitrate (300 pg). Heparin was infused overnight until the early follow-up coronary cineangiogram was performed. Quantitative coronary angiography. Cineangiograms in all patients were performed with isocentric Arcomax General Electric CGR equipment (Issy-lesMoulineaux, France). The angiograms were recorded on 35 mm cinefilm at a speed of 50 frames/set and on videotape (U Matic SP VO-96OOP, Sony, Tokyo, Japan). Quantitation was performed on at least two perpendicular projections at the baseline, after laser angioplasty, and after balloon angioplasty when additional dilatation was required. One of the two projections was selected because it most clearly demonstrated the minimal diameter of stenosis. After the coronary lesion was centered, end-diastolic video frames were selected by two experienced interventional cardiologists and digitized with a computer (DART/lB, Advanced Logic Research Inc., Phoenix, Ariz.). The frames that were selected for analysis were digitized on a matrix size of 512 X 512 pixels with an eight-bit gray scale. With the use of a 7-inch image intensifier field size the resolution of the digitized frame was 4 pixels/mm. Calibration was done with the use of the known size of the guiding catheter. Calibrated grids that were filmed at the isocenter were used to convert the data from pixels into millimeters. No correction for pincushion distortion was made because our measurements showed that at the periphery it was less than 3% as compared with the data obtained at the center of the image. Automatic detection of the vessel contours was achieved with a computerized system that was developed by TSI (Marne-la-Vallee, France). Briefly, after the centerline was interactively delineated within the vessel
American
February 1993 Heari Journal
segment to be measured, the computer automatically generated scan lines perpendicular to the centerline. The first derivative of the densograms along each scan line was then computed. The detected contour points were used by the computer to automatically generate a refined centerline of the vessel segment. A software smoothing procedure was then applied to the edges, and the arterial diameter and length of t,he lesion (in millimeters) were displayed. The reliability and accuracy of the method have been validated in phantom studies. *’ Definition of lesions. Lesions were classified with the guidelines established by the joint American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures as type A, B, or C.ll Categorization was performed on the basis of both qualitative and quantitative evaluation of the lesions. Definition
of acute
laser
and
procedural
success.
Acute laser angioplasty successwas defined as a decrease of ~20”~ in the absolute minimal stenosis diameter and the ability for the laser catheter to cross the lesion during laser irradiation. In order for the laser catheter diameter to be taken into account for an accurate assessmentof t.he results obtained by laser therapy alone, an “ablation ratio” was calculated. It was defined as the ratio of the stenosis diameter after laser emission to the catheter diameter. Acute procedural success was defined as a final diameter stenosis of <30 (‘, as determined by quantitative angiography. Definition of complications. An acute closure was defined as a reduction in flow after the procedure, which leads to the absence of any visible antegrade flow. Minor dissection was defined as a tear within the arterial wall without any reduction in flow, and major dissection was defined as a tear associated with a reduction in flow. Perforation was defined as an extravasation of contrast material from the outlines of the vessel wall. Spasm was defined as a temporary reduction in size of the vessel lumen, which could be relieved by nitrates and/or calcium channel blockers. Distal embolization was defined as the absence of contrast material within the vessel lumen after the procedure. This condition could not be treated with vasodilators. Myocardial infarction was defined as creatine kinase elevation of >200 U with an MB fraction of >3”, . Follow-up study. The seven patients who experienced procedural failure had no angiographic followup. They were treated by medical therapy, which was sufficient to avoid coronary artery bypass grafting because they had either single-vessel disease, total occlusion, or an artery that is well protected by col-
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Table II. Success of excimer and Ho-YAG laser angioplasty by lesion location Laser
Location LAD LCX LMT RCA
SVG ALL
Group I n (%) 13/26 4/4 O/l 4/a 4/4 22/40
LAD, left anterior descending saphenous vein graft.
(50) (100) (0) (50) (100) (55)
artery;
Procedural
successes Group II n (%)
p Value
19/22 (86) 6/12 (50)
NS NS NS
4/a (50) 4/4 (100) 33/46 (72)
NS NS
NS, not significant
25/26 4/4 l/l 818 4/4 39/40
NS
at p < 0.05; LCX, left circumflex
laterals. Follow-up coronary angiography was performed 4 to 7 months after coronary angioplasty. Any earlier recurrence of symptoms prompted earlier arteriography. Control coronary angiography was performed in 51 of the 79 patients who had procedural success. The remaining 28 patients were followed up for symptoms of angina, myocardial infarction, coronary bypass surgery, and death at 2,4, and 6 months by means of patient visits, which included exercise ECG and thallium scintigraphy. Definition of restenosis. Restenosis was defined as a loss of more than 50 % of the gain achieved by either laser angioplasty or laser and additional balloon an8gioplasty at the time of follow-up angiography. Statistical analysis. Continuous values are expressed as means f SD. The chi square test was used to compare discrete values. The unpaired Student’s t test was used to compare continuous values between the groups, and the paired Student’s t test was used to compare continuous values within the groups. A p value of less than 0.05 was considered significant. OBSERVATIONS
Patient characteristics are shown in Table I. A total of 86 patients were included in the study: 40 patients were treated by Ho-YAG and 46 patients were treated by excimer laser. There was no difference in baseline characteristics (age, gender, previous intervention, lesion type and characteristics, minimal luminal diameter) between the groups. Fifteen patients had had previous percutaneous transluminal coronary angioplasty, and 10 had had coronary artery bypass grafting. Most of the patients (n = 48) had lesions located on the left anterior descending artery. Lesions on the right coronary artery and the left circumflex artery were less common, and five patients were treated for lesions that were located on a saphenous vein graft. Thirty-six patients (42 % ) had totally occluded vessels, and 50 patients (58 % ) were treated
Group I n (%“o)
artery;
(96) (100) (100) (100) (100) (98)
LMT.
successes Group II n f!%)
p Value
21122 (95) 10/12 (83)
NS NS NS
518 (63) 4/4 (100) 40/46 (87)
NS NS
left main trunk;
RCA, right coronary
NS artery;
SVG,
for restenosis. Most of the patients had type B or C lesions, whereas only 10 patients (12%) had type A lesions. There was no difference in the distribution of patients who had Ho-YAG and those who had excimer laser angioplasty. The mean minimal luminal diameter was 0.12 f 0.21 mm and 0.13 + 0.23 mm for the patients who had Ho-YAG and those who had excimer laser angioplasty, respectively. The percent diameter stenosis was 95% + 9% and 94% + 14%) for the patients who had Ho-YAG and those who had excimer laser angioplasty, respectively. Laser success. The success rate for laser angioplasty was lower in patients in group I (55.0%) than in those in group II (71.7%), except for left circumflex lesions, but these differences did not reach statistical significance (Table II). The primary laser success rate was highest in saphenous vein grafts (100 % ). Excimer laser angioplasty tended to be more effective than Ho-YAG laser angioplasty except for left circumflex lesions. Laser angioplasty was less frequently successful in complex than in type A lesions (Fig. 1). Although calcified lesions did not decrease the primary success rate of laser angioplasty (Fig. 2), the success rate was lower in longer lesions than in shorter ones (42.1% vs 70.0 % ) (Fig. 3). Thirty-six of 86 patients had a totally occluded vessel, and 50% of these vessels in group I and 80% in group II could be recanalized by laser angioplasty (Fig. 4). These results were similar to those that were obtained for stenoses (Fig. 4). Laser angioplasty tended to be less frequently successful in 1.4 or 1.5 mm catheters than in 2.0 or 1.7 mm catheters (Fig. 5), but the difference did not reach statistical significance. Laser stand-alone therapy. The proportion of standalone laser therapy was significantly higher (p < 0.05) in group II than in group I. Ten (22 % ) patients who had excimer laser angioplasty compared with two (5%) patients who had Ho-YAG laser angioplasty could continue to receive stand-alone laser therapy
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February 1993 Hem Journal
%
100
I
80 60 40
20
0
n Ho-YAG
Non-calcified
Type C
Type B
Type A
0 Excimer
100
n Ho-YAG
Calcified 0 Excimer
%
80 60 40 20 01
Non-calcified n Ho-YAG
Calcified
n Ho-YAG 0 Excimer
0 Excimer
Fig. 1. Bar graphs of laser (top panel) and procedural success rates (bottom panel) for type A, type B, and type C lesions (American College of Cardiology/American Heart Association lesion classification system)
Fig. 2. Bar graphs of laser [top panel) and procedural success rates (bottom panel) for noncalcified and calcified lesions.
Table
canalization was 16 + 12 J and 40 + 22 J for excimer and Ho-YAG lasers, respectively. The total duration of irradiation was 36 + 20 seconds and 25 + 13 seconds for excimer and Ho-YAG lasers, respectively. Laser failures. Failures were less frequent with extimer laser angioplasty than with Ho-YAG laser angioplasty (28% vs 45%), but the difference was not
III. Technical
data and results Group
Laser Wavelength (nm) Range of fluence (J/mm”) Total energy (J) Duration of irradiation (set) Catheter size 1.4/1.5 (mm) 1.7 (mm) No. of procedures 2.0
I
Ho-YAG
Group
II
Excimer
2100 1-2 40 t 22 25 -t 13
308 30-60 16 + 12 36 + 20
18 NA
13
22
14
significant 19
NA, Not available.
without plasty.
any need for an additional balloon angio-
Technical results. The technical results are shown in Table III. The mean total energy required for re-
(Table
IV). Four laser angioplasty
failures
were due to inability to reach the lesion (two patients in group I and two patients in group II) because of: (1) mechanical friction between the inner lumen of the guiding catheter and the outer diameter of the laser catheter, (2) subcritical proximal stenosis, or (3) sharp bends of the target vessel proximal to the lesion to be treated. Failures were also due to the inability of the laser catheter to cross the obstruction (1’7Pa and 4 % for groups I and II, respectively). Most of the failures were due to the inability to obtain a signifi-
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< 10mm
2 10mm
n Ho-YAG
100
laser coronary angioplasty
Stenosis
El Excimer
515
Occlusion
n Ho-YAG
Cl Excimer
._
%
100
a0
a0
a0
a0
40
40
20
20 01
0I
< 10mm
2 10mm
W Ho-YAG
Stenosis
0 Excimer
Fig. 3. Bar graphs of laser (top panel) and procedural successrates (bottom parcel) for lesions
Table
and holmium
Occlusion
4 Ho-YAG
0
Excimer
Fig. 4. Bar graphs of laser (top panel) and procedural successrates (bottom panel) for stenosesand occlusions.
IV. Failures of excimer and Ho-YAG laser coronary angioplasty procedures Type
of failure
Inability to reachthe lesion Mechanical friction between laser and guiding catheters Subcritical proximal stenosis Sharp bends proximally Inability to cross the lesion Insufficient effect
Group I n (s”,)
Group II n (76)
2 (5.0) 1 (2.5) 1 (2.5) 0 7 (17.5) 9 (22.5)
2 (4.3) 0 1 (2.5) 1 (2.5) 2 (4.3) 8 (17.4)
p Value
NS NS NS NS NS NS
NS, Not significant.
cant reduction in stenosis (22% and 17% for groups I and II, respectively) despite the use of incremental energy levels for each laser source. Procedural success. The overall procedural success rate was similar in groups I and II. It was equally high in total occlusions and in stenoses for both groups
(=92%). It was negatively influenced only by the length of the lesion as far as the excimer laser was concerned (Fig. 3). The highest rates were obtained in saphenous vein grafts and in the left anterior descending artery (Table II). The procedural success rate tended to be lower in the right coronary artery
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%
Table V. Complications in laser coronary angioplasty
1
procedures -.____-------.~~~.-----.-.--.-..--
100
----~----~.
-.
C:roup I n i 5)
Group II n (5)
0 0 0 1 (25) 3 (7.5) :1 (7.5) 0 3 (75)
0 0 0 1 13 9 4 8
p VlllUP
79 %
l----l 1.7
H
0
Ho-YAG
Excimer
100
In-hospital death Myocardial infarct,ion Emergency CARG Perforation Dissection Minor Major Vessel occlusion during procedure Vessel occlusion after procedure 524 hr 24-72 hr Coronary spasm Arrhythmia CABG,
Coronary
artery
(2.5) (28.3) (19.6) (8.7) (17.1)
NS NS NS NS 0.04 NS NS NS
6 (15.0)
4 (6.5)
NS
4 2 4 1
3 (6.5) 0 6 (13.0) 2 (4.3)
NS NS NS NS
(10.0) (6.0) (10.0) (2.51
bypass grafting;
NS, not significant
at p < 0.05.
80
60
40
20 -
0 1.7 n
Ho-YAG
Cl Excimer
Fig. 5. Bar graphs of laser (top panel) and procedural successrates (bottom panel) for 1.4/l.& 1.7, and 2.0 mm catheters.
when angioplasty was performed with the excimer laser (Table II). The procedural successwas not related to the size of the catheters (Fig. 5). Reduction in percent stenosis. Lesions were reduced from 94% f 14 % at baseline to 68% f 27 9h, and 58% -+ 34 % after laser angioplasty in groups I and II, respectively. The results were similar in stenoses and total occlusions and in calcified and noncalcified lesions. The type of lesion did not significantly influence the results. The ablation ratio when the diameter of the laser catheter was taken into account was 0.61 + 0.45 and 0.42 f 0.38 for excimer and HoYAG laser angioplasty, respectively, but the difference did not reach statistical significance. Complications. No major complication such as death, myocardial infarction, or the need for emergency coronary artery bypass graft surgery occurred
(Table V). The most frequent complication was acute closure, which occurred during the procedure, or early occlusion, which occurred within 24 hours after the procedure. However, all but two reocclusions could be treated successfully with repeat balloon angioplasty. Dissections occurred more frequently in patients in group II than in those in group I (28.3”;. vs 7.5% ; p < 0.05), but all could be reduced by dilatation. Perforation was uncommon and occurred in only two cases (one in group I and one in group II) without any clinical consequence, since extravasation of contrast medium was limited to the myocardium and did not expand into the pericardium. Spasm occurred frequently (13.0 !; and lO.O? for Ho-YAG and excimer laser angioplasty, respectively) regardlessof the laser used and could be relieved in all cases. Arrhythmia was infrequent and was observed in X5? of cases only during delivery of laser pulses. Follow-up results. Among the 51 patients who were followed up by repeat angiography, 27 had Ho-YAG laser angioplasty (group I) and 24 had excimer laser angioplasty (group II). In group I, eight patients had a reocclusion and 10 patients had a restenosis. Thus nine patients (33 % ) had a patent artery without restenosis. In group II, reocclusion occurred in 10 patients and restenosis in seven patients. Thus seven patients (29 YO) had a patent artery. None of the remaining 28 patients (12 patients in group I and 16 patients in group II) had evidence of ischemia. Only 25 % of patients in group I and 10% of patients in group II with a totally occluded artery had a patent artery at the time of follow-up cineangiography. The angiographically documented patency rate for pa-
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tients with stenosis was 37 % and 40 % for groups I and II, respectively. There was a trend for patients who could be left on stand-alone excimer laser therapy to have a higher patency rate than those who had laser-assisted balloon angioplasty (62.5% vs 19.4%). COMMENTS
This study showed that laser angioplasty is currently a feasible method for recanalization of obstructed coronary arteries. 4l 5 The technique in which a mechanically guided laser catheter is used is derived from the commonly used balloon angioplasty technique and provides easy access to the coronary vasculature. It appeared that multifiber catheters were able to deliver a fluence sufficient for ablation of atheromatous tissue.i2* I3 The catheters used with Ho:YAG or excimer lasers were still limited by a stiff distal tip and an inadequate coverage of the area at the distal end of the laser catheter. The active area (i.e., the sum of individual fiber tip areas) of the first generation of catheters was only 15 % . The ultimate device for excimer laser angioplasty consisted of more densely packed fibers that provided a significant reduction in the dead space but still an inadequate coverage of laser irradiation (23 % ). This is the reason for the “Swiss cheese” appearance, which consisted of small holes within the crater with unirradiated tissue between them. If all of the obstructing tissue has not been ablated, a residual obstruction should be present. This may well be related to the haziness that can be observed by angiography at the channel site in numerous cases (Fig. 6) and some preliminary data obtained from angioscopy, which showed that tissue remnants were left behind after laser angioplasty. l4 However, the gaseous debris generated by excimer laser irradiation will disrupt tissue that is located at the dead space between the fibers.15, l6 Another problem with the currently available catheters is channel size. The clinical results obtained by laser angioplasty in terms of channel size were not in agreement with the experimental data. Indeed, it has been shown that in in vitro studies on postmortem normal or atheromatous tissue, the diameter of craters created by laser irradiation was similar to that of the catheter.17 Moreover, in our clinical study the mean “ablation ratio” was roughly 60 % , which means that the channel diameter created by laser irradiation was 40% smaller than the catheter diameter. It might have been due to elastic recoil, vasomotor tonus of the arterial wall, insufficient ablation as a result of the “Swiss cheese” appearance, or the “dottering” mechanical effect caused by pushing the
Fig. 6. Coronary angiogram (right anterior oblique cra-
nial view) after excimer laser angioplasty of proximal left anterior descending artery showing “haziness” at the laser-irradiated site (arrow). catheter (which could have been advanced at too fast a pace). The difference in channel diameter between patients who had excimer laser angioplasty and those who had Ho-YAG laser angioplasty might have been due to the more densely packed excimer catheter. Some of our failures were due to a lack of trackability of the laser catheter. A drawback of using large catheters was also the inability to assess the immediate results after laser irradiation by contrast medium injections. Because the catheter that was selected for recanalization was large enough to debulk the target artery, no space was left between the lumen and the wall to allow contrast medium injection. Therefore to assess the results after laser angioplasty, a pullback of the catheter was required. Our study was not randomized. Lesions were selected for laser angioplasty because they were expected to offer easy access to the laser catheters. This was the reason for selection of proximal type A lesions. However, once feasibility was established, type B or C lesions (both proximal and distal) were selected. This is in agreement with the patient selection described by Cook et a1.7 Contrary to their results, our data showed a tendency for a lower success rate in types B and C lesions than in type A lesions. In our study the success rate was higher with the. excimer laser than with the Ho-YAG laser. Although this could reflect a learning curve, this hypothesis cannot be confirmed because of a further overlap between the use of the two laser sources. However, even with the excimer laser our primary success rate was lower than that published by other groups, including
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Fig. 7. Coronary angiogram (right anterior oblique view) of excimer laser angioplasty of a total occlusion of left anterior descending artery before treatment (panel A), after laser irradiation (panel B), and after balloon angioplasty (panel C).
those involved in multicenter trials.4* 6 7 The reason for this discrepancy is not well established. Although no statistical significance could be established between the groups, our results suggest that long lesions could not be recanalized as frequently as short ones and that the laser success rate in right coronary arteries was lower than that in left anterior or circumflex arteries. Yet there seems to be a concordance between the favorable results obtained in saphenous vein grafts and ostial lesions. Both of them may be reasonable indications for laser angioplasty. Interestingly, our results also showed that the success rate in calcified lesions was similar to that obtained in noncalcified lesions. Thus laser angioplasty may be an adequate adjunct to balloon angioplasty in the presence of hard obstructing tissue or may actually be the first-choice treatment. Our success rate in totally occluded vessels was
relatively high (Figs. 7 and 8). This was due not only to the ablation capabilities of laser energy but also to the ability of guide wires to penetrate total occlusions. We had to recanalize not only fresh lesions but also occlusions, which were as old as 18 months. Success could also be achieved in the latter. It may be argued that in these older lesions recanalization was not indicated either because fibrous tissue was already present in the territory of the occluded vessel or because collaterals were able to supply the necrotic myocardium. However, caution was taken in all cases to make sure that viable myocardium was still present. Total occlusions may thus be considered good indications for use of this technique. This was especially the case for excimer laser irradiation for which primary laser success rate was high as compared with Ho-YAG laser angioplasty. Comparison between Ho-YAG and excimer laser
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Fig. 8. Coronary angiogram(left anterior oblique view) of Ho-YAG laser angioplasty of a total occlusion of right coronary artery before treatment (panel A), after laserirradiation (panel B), and after balloon angioplasty (panel C).
sources showed an overall but inconsistent advantage of the latter over the former. The overall laser success rate was higher, channel size was greater, and more stand-alone laser therapy could be achieved with the excimer laser. However, the catheter design used with excimer laser was not exactly the same as that which was used with the Ho-YAG laser. The excimer laser catheters were more densely packed with several rings of optical fibers concentrically arranged around the central lumen, whereas the Ho-YAG laser catheters had a single ring of fibers arranged at the outer ring of the distal tip. Our experimental studies have shown that the active area played a greater role in terms of ablation efficiency than the amount of energy delivered to the target tissue. This observation leads to the discussion of the role of laser angioplasty in case of dilatation failure. In eight patients, dilatation was the first-choice tech-
nique but the balloon failed to penetrate the lesion. Thus laser energy was delivered. In five cases, the laser catheter was able to cross the lesion, which allowed subsequent dilatation to be successfully achieved. In the three other cases, the laser catheter could not be advanced and remained against the entry of the obstruction during irradiation. In all three cases it was then possible for the balloon catheter to cross the lesion and to be successfully inflated. Such a “facilitation” has been reported by u& g and by Israel et al.” The reason for such a result is not yet determined. It may be speculated that laser energy was able to alter the structure of the obstruction and the arterial wall by the mechanical effect, which consists of pressure and acoustic shock waves. Tissue alteration may have consisted of the splitting and fracturing of hard tissue which would lead to a softening of the arterial structure. Ho-YAG and excimer lasers
520
Geschwind
et al.
have been shown to generate mechanical effects that may be propagated to the surrounding tissue.17 Indeed, the Ho-YAG laser was reported to generate superheated vapor, which rapidly expands and thus dislodges hard tissue from the crater.lg Recent studies have shown that arterial recanalization by the excimer laser is associated with the release of gas bubbles; the presence of photoacoustic effects such as rapidly expanding and collapsing bubbles results in shock waves.15* l6 In our study, few patients could benefit from stand-alone laser therapy. This is in contradiction to the results published by other groups4, 5. 7 who obtained an almost 50 % primary laser stand-alone rate. We had only a 22 % and a 5°C success rate for excimer and Ho-YAG lasers, respectively. The discrepancy was due to the different criteria that were used for stand-alone laser therapy. We wanted to obtain a residual stenosis of <30 % after completion of the laser procedure, whereas the other groups decided not to use additional balloon dilatation when the residual stenosis was not >50%. If we had applied this threshold for indication of subsequent dilatation, our stand-alone laser therapy success rate would have been 50% and 40% for excimer and Ho-YAG laser angioplasty, respectively. Our rate of major complications was remarkably low. This was obviously due to the mechanical guidance with the guide wire, which maintained the laser catheter in a coaxial position. The low rate of perforation was thought to be due to the very slow progression and minimal pressure applied at the proximal catheter tip. In contrast, the rate of acute closure was high. It could be explained by insufficient tissue ablation, which was suggested by some haziness, which was observed after the laser catheter passed through the obstruction, and by some angioscopic observations, which showed that a great amount of obstructing tissue was left behind after the laser angioplasty procedure. Also, thrombus formation and protracted spasm cannot be ruled out. The fact that more dissections were frequently observed at a higher rate with the excimer laser than with the Ho-YAG laser cannot yet be explained. It might have been due to deep mechanical damage inflicted to the layers of the arterial wall by shock waves generated by the laser pulses.15-i7 However, our previous experimental studies have shown the excimer laser to generate lower pressure waves than the HoYAG laser.17 Finally, the high rate of dissection may have occurred because at this early stage of the study the goal of the procedure was to debulk arteries by using large catheters with a catheter-lumen diameter close to 1. To decrease the dissection rate and
Amewan
February 1993 Heart Journal
increase the safety of the laser procedure the trend was to use subsequently smaller (1.4 mm) rather than large (2.0 mm) catheters. This in turn could have induced a low stand-alone success rate. Obviously, a compromise should be found between a greater possibility of improved efficacy and a higher risk of side effects that are likely to occur with large catheters. Spasm might also have been due to a mechanical effect on the tissue surrounding the area of irradiation, which is a side effect of pulsed lasers.‘“, I6 Importantly, these complications could almost all have been treated successfully by dilatation and vasodilators, respectively. No final conclusion on the patency rate at &month follow-up can be drawn from our results, since the 15number of patients with angiographically documented patency was too small. Moreover, the clinical follow-up cannot be included in the study, since both reclosures and restenoses may occur in patients who are free of symptoms, especially those who presented initially with a totally occluded artery. This may be due to the presence of a well-developed collateral circulation, which can preserve an adequate supply to the myocardium. Thus only angiographically documented data should be taken into account for the assessment of long-term patency. In this respect, our results showed that the patency rate was low in both groups of patients. It tended to be even lower in vessels that were totally occluded initially than in stenoses. However, if we had assumed that patients without evidence of ischemia had a patent artery at follow-up, the restenosis rate would have been 46?( and 43 ?C for patients in groups I and II, respectively. This figure is acceptable, given the severity of the lesions that had been treated. One of the encouraging results of our study stems from the relatively favorable outcome obtained after stand-alone laser therapy as compared with the poor outcome observed after laser-assisted balloon angioplasty. However, the small number of patients does not allow any final conclusion. The reason for the high restenosis and reclosure rates is not yet well understood. However, it is hypothetized that it might have been due to either insufficient tissue ablation14 (Fig. 6) or smooth muscle cell proliferation. The reason for a higher restenosis rate after laser-assisted balloon angioplasty than after stand-alone laser therapy is not well understood. It may be hypothetized that the damage to the arterial wall, which induces tissue proliferation, might have been greater after both laser-induced shock waves and wall stretching by balloon inflation than after the mechanical damage that results from pulsed laser irradiation alone. Further studies are required to elucidate the mech-
Volume Number
125 2, Part 1
anism of restenosis or reclosure after pulsed laser angioplasty. Clinical implications. Our study is in accordance with others as to the ideal indications for laser angioplasty (i.e., saphenous vein grafts; ostial lesions; and to a lesser degree, calcified lesions and total OCC~Usions). Although the new multifiber “over-the-wire” catheters provide easy and rather safe access to the coronary arteries, progress should be made to obtain larger channels and to ablate more tissue. The side effects that are generated by pulsed lasers must be elucidated to decrease the rate of complications and possibly also the restenosis rate. Our study also showed that excimer laser angioplasty was more effective but induced more dissections than Ho-YAG laser angioplasty. Whether those effects were due to the laser source, the catheter design, or both is not yet clearly understood. SUMMARY
Recently access to the coronary arteries became available to laser angioplasty because of a new technique utilizes a pulsed laser source and multifiber, “over-the-wire” guided catheters. The aim of this study was to evaluate the early and long-term results and the side effects of coronary angioplasty with an excimer or a Ho-YAG laser. Forty consecutive patients were treated with the Ho-YAG laser (group I) and 46 consecutive patients were treated with the excimer laser (group II). The primary laser angioplasty success rate was 55 % and 72 % (NS) for groups I and II, respectively. This success rate was highest in saphenous vein grafts. It was similar in calcified and noncalcified lesions and in total occlusions and stenoses. It tended to be lower in long lesions than in short ones (40 % vs 60 % ; p < 0.05 and 44 % vs 78 % ; NS for groups I and II, respectively). Laser standalone therapy was performed in 5% of patients in group I compared with 22% in group II 0, < 0.05). Failures were due to the inability of the laser catheter tip to reach the lesion, to cross the obstruction, or to obtain a significant reduction in stenosis. They were more frequent in patients in group I than in those in group II (45 % vs 28% ). There were no deaths, no myocardial infarctions, and no need for emergency coronary artery bypass grafting because most patients had total occlusions or a well-protected coronary artery. Complications included acute closure in 8 % of patients in group I and in 17 % of patients in group II and spasm in 10 % and 13 % of patients in groups I and II, respectively. Dissection occurred more frequently in patients in group II than in those in group I (28% vs 7% ; p < 0.04). The angiographic patency rate at 6-month follow-up was
Excimer
and holmium
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33% and 29% for patients groups I and II, respectively. Multifiber, wire-guided catheters provide easy access to the coronary arteries. Excimer laser angioplasty is effective but induces a high rate of dissections. Technical improvements are required to ablate more tissue to possibly reduce the restenosis rate. Further studies are needed to elucidate the mechanism of side effects and to reduce the restenosis rate. We thank Franqoise Veyssiere and Margaret Tissot-Geschwind for technical assistance and Mireille David for secretarial assistance. REFERENCES
1. Isner JM, Donaldson RF, Deckelbaum LI, Clarke RH, Laliberte SM, Ucci AA, Salem DN, Konstam MA. The excimer laser: gross, light microscopic and ultrastructural analysis of potential advantage for use in laser therapy of cardiovascular disease. J Am Coil Cardiol 1985;6:1102-91 2. Waller BF. “Crackers. breakers. stretchers. drillers. scraners, _ shavers, burners, welders and melters”-the future treatment of atherosclerotic coronary artery disease? A clinical-morphologic assessment. J Am Co11 Cardiol 1989;13:969-87. 3. Block PC, Myler RK, Sterzer S, Fallon JT. Morphology after transluminal angioplasty in human beings. N Engl J Med 1981;305:382-5. 4. Litvack F, Eigler NL, Margolis JR, Grundfest WS, Rothbaum D, Linnemeier T, Hestrin LB, Tsoi D, Cook SL, Krauthamer D, Goldenberg T, Laudenslager JR, Segalowitz J, Forrester JS. Percutaneous Excimer laser angioplasty. Am J Cardiol 1990;66:1027-32. 5. Sanborn TA, Bitt1 JA, Hershman RA, Siegel RM. Percutaneous coronary excimer laser-assisted angioplasty: initial multicenter experience in 141 patients. J Am Co11 Cardiol 1991; 17:169B-73B. 6. The European Study Group on Coronary Excimer Laser Angioplasty. Initial results of the European multicenter registry on coronary Excimer laser angioplasty [Abstract]. Circulation 1991;84(suppl II):II-362. 7. Cook SL, Eigler NL, Shefer A, Goldenberg T, Forrester JS, Litvack F. Percutaneous excimer laser coronary angioplasty of lesions not ideal for balloon anaionlastv. Circulation 1991: 84:632-43. 8. Geschwind HJ, Dubois-Rande JL, Murphy-Chutorian D, Tomaru T, Zelinski R, Loisance D. Percutaneous excimer laser angioplasty with mid-infrared laser and a new multifibre catheter [Letter]. Lancet 1990;336:245-6. 9. Geschwind HJ, Dubois-Rande JL, Zelinski R, Morelle JF, Boussignac G. Percutaneous coronary mid-infra-red laser angioplasty. AM HEART J 1991;122:552-8. 10. Orion LP, Geschwind H, Lorino H, Richalet JP, El Badaoui G. Assessment of coronary lesions: validation and future. European Review of Biomedical Technology. 1991;13:265-71. 11. Ryan TJ, Faxon DP, Gunnar RM, ACC/AHA Task Force on Assessment of Diagnostic and Therapeutic Procedures (Subcommittee on Percutaneous Transluminal Coronary Angioplasty). Guidelines for percutaneous transluminal angioplasty. Circulation 1988;78:486-502. 12. Goldenberg T, Anderson WB, Kupfer SH, Narciso HL, Shaolian S, Laudenslager JB. Percutaneous excimer laser angioplasty in humans. Proceedings of the Society of Photo-opt&al Instrumentation Engineers 1989:1067:145-52. 13. Duda SH, Karsch KR, Haase KK, Huppert PE, Claussen CD. Laser ring catheters in excimer laser angioplasty. Radiology 1990;175:269-70. 14. Diethrich EB, Hanafy HM, Santiago OJ, Bahadir I. Angioscopy after coronary excimer laser angioplasty. J Am Co11Cardiol 1991;18:634-5. --
I
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15. Gijsbers GHM, Sprangers RLH, van Gemert MJC. Excimer laser coronary angioplasty: laser-tissue interactions at 308 nm. In: Ginsburg R, White JC, eds. Primer on laser angioplasty. 2nd ed. Mount Kisco, New York: Futura Publishing Co., 1992:217-41. 16. Grundfest WS, Seagalowitz J, Goldenberg T, Laudenslager J. Papaioannou T. The effect of fiber optic delivery system geometry, power density and energy on excimer laser luminal recanalization [Abstract]. Circulation 1990;82(suppl IIIl:III495. 17. Tomaru T, Geschwind HJ, Boussignac G, Lange F, Tahk S-.7.
BOUND
VOLUMES
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February 1993 Heart Journal
Comparison of ablation efficacy of excimer, pulsed dye and holmium YAG laser relevant to shock waves [Abstract]. Cir culation 1991;84(suppl II):H-423. 18. Israel DH. Marmur JD, SanbornTA. Excimer laser-facilitated balloon angioplasty of a nondilatable lesion. ,J Am Co11 Cardiol 1991;18:1118-9. 19. Geschwind HJ. Mid-infrared laser coronary angioplasty--experimental study. In: Karsch KR, Haase KK, eds. Coronary laser angioplasty. Darmstadt: FLG, Steinkopff Verlag, 1991: 43-7.
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Bound volumes of the AMERICAN HEART JOURNAL are available to subscribers (only) for the 1992 issues from the Publisher at a cost of $57.00 for domestic, $78.99 for Canadian, and $75.00 for international subscribers for Vol. 123 (January-June) and Vol. 124 (July-December). Shipping charges are included. Each bound volume contains a subject and author index and all advertising is removed, Copies are shipped within 60 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Mosby-Year Book, Inc., Subscription Services, 11830 Westline Industrial Dr., St. Louis, MO 63146, USA; phone (800)325-4177. ext. 4351,br (3141453-4351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular Journal subscription.
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20. Van der Giessen WJ, Woerkens LJ, Beatt K, Serruys PW, Verdouw PD. Coronary stenting with a radiopaque, a thrombogenic, balloon expandable stent [Abstract]. Circulation 1989;80:11-173. 21. Barth KH, Virmani R, Strecker EP, Savin MA, Lindisch D, Matsumuto AH, Teitelbaum GP. Flexible tantalum stents implanted in aortas and iliac arteries: effects in normal canines. Radiology 1990;175:91-6. 22. Rousseau H, Puel J, Joffre F, Sigwart U, Duboucher C, Iubert C, Knight C, Knopf L, Wallsten H. Self-expanding endovascular prosthesis: an experimental study. Radiology 1987; 164:709-14.
MD, Jan Kvasnicka,
Laser angioplasty differs from balloon angioplasty in that the former ablates the obstructing material from the coronary artery lumen, whereas the latter acts by pushing it aside and stretching the vessel wall.lT3 Recently access to the coronary arteries became available to laser angioplasty because of a new technique that utilizes (1) a pulsed laser source, (2) multifiber catheters that consist of rings of thin optical fibers concentrically arranged around a central lumen for the passage of a guide wire, and (3) a mechanical guidance device that uses the same guide wires as those commonly used for balloon angioplasty. Multicenter trials on excimer laser coronary angioplasty are ongoing.4-6 The first published data showed this technique to be rather safe and the early results to be satisfactory as compared with those obtained by balloon dilatation, especially in types B and C lesions.7
From the Cardiac Catheterization Laboratory and the Interventional Cardiology Unit, the INSERM U 2 and the Division of Cardiology, University Hospital Henri-Mondor. Received
for publication
Feb.
28, 1992;
accepted
Aug.
24, 1992.
Reprint requests: Herbert J. Geschwind, MD, Unit6 d’HBmodynamique et de Cardiologie Interventionnelle, Service d’Rxplorations Fonctionnelles, University Hospital Henri-Mondor, 51, Av. de Tassigny, 94010 CrBteil, France.
AM HEART J 1993:125:510
garnet
MD, and
However, few clinical studies are available on other pulsed laser sources such as the infrared holmium yttrium aluminum garnet laser (Ho-YAG).s g Thus the purpose of this study was to evaluate the immediate and early results obtained by excimer laser coronary angioplasty and to determine whether a shift in the laser wavelength from ultraviolet to infrared will affect these results. Further, the study was aimed at evaluating the side effects of coronary laser angioplasty, namely, the consequence of laser irradiation on the arterial wall and the rate of complications. Finally, we sought to determine the influence of both catheter size and design on the early results of this method of treatment. METHODOLOGY Study population. All patients
who were selected to undergo laser angioplasty were candidates for balloon angioplasty. They all showed evidence of ischemia such as angina or positive results of stress tests including exercise ECG and/or thallium scintigraphy. Eighty-six consecutive patients were included in the study. Patient selection for laser angioplasty was based on easy access to proximal lesions at the early stage of the study. The following lesions were considered suitable: total occlusions; restenoses; suboptimal results after balloon dilatation; long, tunnelCopyright
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1993 Journal
23. Levine MJ, Bradley BM, Burke JA, Nash ID, Satian RD, Diver DJ, Bairn DS. Clinical and angiographic results of balloon expandable intracoronary stents in right coronary artery stenosis. J Am Co11 Cardiol 1990;16:332-9. 24. Roubin GS, King SB III, Douglas JS, Lembo NJ, Robinson KA. Intracoronary stenting during percutaneous transluminal coronary angioplasty. Circulation 1990;81:IV-92-116. 25. Sigwart U, Golf S, Kaufmann V, Kappenberger L. Analysis of complication associated with coronary stenting [Abstract]. J Am Co11 Cardiol 1988:2:66A.
Excimer and holmium yttrium aluminum laser coronary angioplasty Herbert J. Geschwind, MD, Fumitaka Nakamura, Jean L. Dubois-Rand& MD Crkteil, France
Heart
1993
by Mosby-Year
OOK-8703/93/$1.00
+ .lO
Book,
4/l/42640
Inc.
Volume Number
125 2, Part
1
shaped, calcified lesions; and ostial lesions. In the first stage of the study (which started in March 1990), the Ho-YAG laser was used because of technical availability (patients in group I). In the second stage of the study (which started in June 1990) an excimer laser was used (patients in group II). Then both lasers were used. The selection was made according to the availability of catheters. Patient characteristics are presented in Table I. The study, which focused especially on the results obtained after use of an extimer laser, is part of a nonrandomized European multicenter trial.6 All patients gave informed consent before participating in the study after approval of the protocol was given by the Ethical Committee of the University Hospital Henri-Mondor. The same laser sources were used during the study. Gradual improvements were made in the number of fibers and in the flexibility of the catheter. Catheter size was selected according to the size of the artery to be treated to make the catheter-artery diameter ratio close to 1. Laser sources. Two laser sources were used in the study. In the first group of patients coronary laser angioplasties were performed with a pulsed infrared laser. The equipment consisted of a Ho-YAG laser, which operated at a wavelength of 2.1 nm, a pulse width of 250 psec, a repetition rate of 3.5 Hz, and a fluence of 1 to 2 J/mm2 (MCM-Eclipse Laboratories, Mountain View, Calif.). In the second group of patients, an ultraviolet laser source was used; it consisted of a xenon chloride excimer laser, which operated at a wavelength of 308 nm, a pulse duration of 135 nsec, a repetition rate of 25 Hz, and a fluence of 30 to 60 mJ/mm2 (CVX-300, Spectranetics, Colorado Springs, Colo.). The Ho-YAG laser was coupled into a multifiber catheter with a diameter of 1.5 or 2.0 mm, which consisted of 26 and 37 optical fibers of 100 pm each, respectively, concentrically arranged around a central lumen for the passage of a 0.014 inch or 0.018 inch guide wire. The excimer laser was coupled to a multifiber catheter with a diameter of 1.4,1.7, and or 2.0 mm, which consisted of 21,45, and 87 fibers of 100 pm each, respectively, concentrically arranged around a central lumen for the passage of a 0.014 inch or 0.018 inch guide wire. Procedure. The procedure was derived from that which is commonly used for balloon angioplasty. Briefly, through a percutaneous femoral arterial approach with a 9F sheath, an 8F or 9F large lumen guiding catheter was positioned in the ostium of the target vessel. Next, an 0.014 inch or 0.018 inch Hi Torque floppy guide wire (ACS, Inc., Temecula, Calif.) was inserted into the artery to be treated with the laser catheter, which was maintained behind the dis-
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and holmium
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Table I. Patient and angiographic baseline characteristics Group II (excimer)
Group I (Ha-YAG)
No. of patients Mean age (yr) Sex distribution (% men) Previous treatment
40 56
PTCA CABG Site of lesion LAD LCX LMT RCA SVG
Stenosis Total occlusion Calcification Minimal luminal diameter (mm) Diameter stenosis (%)
46
+ 9 88
55
f
12
85
5 3 26
0.12
NS NS
22 12
NS NS NS NS NS
8
8 4
5 22 13 24 16 17
5 28 13 26 20 13
*
0.21
95 + 9
0.13
NS NS
10
0
Lesion characteristics* Type A Type B Type C
p Value
f
0.23
94 * 11
NS NS NS NS NS NS NS NS
NS, not significant at p < 0.05; PZ’CA, percutaneous transluminal coronary angioplasty; CAM, coronary artery bypassgrafting; LAD, left anterior descending artery; LCX, left circumflex artery; LMT, left main trunc; RCA, right coronary artery; SVG, aaphenous vein graft. *American College of Cardiology/American classification.
Heart Association
Task Force
tal tip of the guide wire. The lesion was crossed with the guide wire under fluoroscopic control, and its distal tip was positioned distal to the lesion. The multifiber catheter was then advanced over the guide wire, and its distal end was positioned against the lesion. Laser was emitted while the catheter was maintained in a stationary position at the entry of the lesion. The Ho-YAG laser was emitted in bursts of 10 or 20 pulses, whereas the excimer laser was delivered in bursts of 125 pulses each, which were separated by at least 15 seconds. After the catheter was pulled back, repeat coronary angiography was performed to assess the results of laser irradiation. When no complications were detected, the procedure was continued by slightly advancing the catheter through the lesion under laser emission. Particular caution was taken to avoid any high manual pressure to the proximal catheter tip to prevent. a mechanical “dottering” effect. The rate of advancement was kept as slow as possible to allow the laser to actually ablate tissue rather than pushing it mechanically ahead. After penetration of the lesion was completed, the catheter was pulled back to allow for contrast medium injection to reveal the effects of laser irradiation. If no
512
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significant reduction in the stenosis diameter or no evidence for recanalization of a total occlusion could be obtained, multiple passes were performed. The results were considered satisfactory and the laser procedure was terminated when the residual stenosis was <30 @O . When the residual stenosis was ~30 Cr, an adjunctive balloon angioplasty was performed. Cineangiograms were performed in the same projections as those that were done before the procedure. An early follow-up coronary cineangiogram was performed within 24 hours after the procedure before the sheath was removed. Patients were pretreated with aspirin, which was given in doses of 250 mg daily and started no later than the day before the procedure. Before and during the procedure, heparin was administered intravenously (10,000 U). When the procedure was completed, patients were given a selective intracoronary bolus of heparin (3000 U) and isosorbide dinitrate (300 pg). Heparin was infused overnight until the early follow-up coronary cineangiogram was performed. Quantitative coronary angiography. Cineangiograms in all patients were performed with isocentric Arcomax General Electric CGR equipment (Issy-lesMoulineaux, France). The angiograms were recorded on 35 mm cinefilm at a speed of 50 frames/set and on videotape (U Matic SP VO-96OOP, Sony, Tokyo, Japan). Quantitation was performed on at least two perpendicular projections at the baseline, after laser angioplasty, and after balloon angioplasty when additional dilatation was required. One of the two projections was selected because it most clearly demonstrated the minimal diameter of stenosis. After the coronary lesion was centered, end-diastolic video frames were selected by two experienced interventional cardiologists and digitized with a computer (DART/lB, Advanced Logic Research Inc., Phoenix, Ariz.). The frames that were selected for analysis were digitized on a matrix size of 512 X 512 pixels with an eight-bit gray scale. With the use of a 7-inch image intensifier field size the resolution of the digitized frame was 4 pixels/mm. Calibration was done with the use of the known size of the guiding catheter. Calibrated grids that were filmed at the isocenter were used to convert the data from pixels into millimeters. No correction for pincushion distortion was made because our measurements showed that at the periphery it was less than 3% as compared with the data obtained at the center of the image. Automatic detection of the vessel contours was achieved with a computerized system that was developed by TSI (Marne-la-Vallee, France). Briefly, after the centerline was interactively delineated within the vessel
American
February 1993 Heari Journal
segment to be measured, the computer automatically generated scan lines perpendicular to the centerline. The first derivative of the densograms along each scan line was then computed. The detected contour points were used by the computer to automatically generate a refined centerline of the vessel segment. A software smoothing procedure was then applied to the edges, and the arterial diameter and length of t,he lesion (in millimeters) were displayed. The reliability and accuracy of the method have been validated in phantom studies. *’ Definition of lesions. Lesions were classified with the guidelines established by the joint American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures as type A, B, or C.ll Categorization was performed on the basis of both qualitative and quantitative evaluation of the lesions. Definition
of acute
laser
and
procedural
success.
Acute laser angioplasty successwas defined as a decrease of ~20”~ in the absolute minimal stenosis diameter and the ability for the laser catheter to cross the lesion during laser irradiation. In order for the laser catheter diameter to be taken into account for an accurate assessmentof t.he results obtained by laser therapy alone, an “ablation ratio” was calculated. It was defined as the ratio of the stenosis diameter after laser emission to the catheter diameter. Acute procedural success was defined as a final diameter stenosis of <30 (‘, as determined by quantitative angiography. Definition of complications. An acute closure was defined as a reduction in flow after the procedure, which leads to the absence of any visible antegrade flow. Minor dissection was defined as a tear within the arterial wall without any reduction in flow, and major dissection was defined as a tear associated with a reduction in flow. Perforation was defined as an extravasation of contrast material from the outlines of the vessel wall. Spasm was defined as a temporary reduction in size of the vessel lumen, which could be relieved by nitrates and/or calcium channel blockers. Distal embolization was defined as the absence of contrast material within the vessel lumen after the procedure. This condition could not be treated with vasodilators. Myocardial infarction was defined as creatine kinase elevation of >200 U with an MB fraction of >3”, . Follow-up study. The seven patients who experienced procedural failure had no angiographic followup. They were treated by medical therapy, which was sufficient to avoid coronary artery bypass grafting because they had either single-vessel disease, total occlusion, or an artery that is well protected by col-
Volume Number
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and holmium
laser coronary angioplasty
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Table II. Success of excimer and Ho-YAG laser angioplasty by lesion location Laser
Location LAD LCX LMT RCA
SVG ALL
Group I n (%) 13/26 4/4 O/l 4/a 4/4 22/40
LAD, left anterior descending saphenous vein graft.
(50) (100) (0) (50) (100) (55)
artery;
Procedural
successes Group II n (%)
p Value
19/22 (86) 6/12 (50)
NS NS NS
4/a (50) 4/4 (100) 33/46 (72)
NS NS
NS, not significant
25/26 4/4 l/l 818 4/4 39/40
NS
at p < 0.05; LCX, left circumflex
laterals. Follow-up coronary angiography was performed 4 to 7 months after coronary angioplasty. Any earlier recurrence of symptoms prompted earlier arteriography. Control coronary angiography was performed in 51 of the 79 patients who had procedural success. The remaining 28 patients were followed up for symptoms of angina, myocardial infarction, coronary bypass surgery, and death at 2,4, and 6 months by means of patient visits, which included exercise ECG and thallium scintigraphy. Definition of restenosis. Restenosis was defined as a loss of more than 50 % of the gain achieved by either laser angioplasty or laser and additional balloon an8gioplasty at the time of follow-up angiography. Statistical analysis. Continuous values are expressed as means f SD. The chi square test was used to compare discrete values. The unpaired Student’s t test was used to compare continuous values between the groups, and the paired Student’s t test was used to compare continuous values within the groups. A p value of less than 0.05 was considered significant. OBSERVATIONS
Patient characteristics are shown in Table I. A total of 86 patients were included in the study: 40 patients were treated by Ho-YAG and 46 patients were treated by excimer laser. There was no difference in baseline characteristics (age, gender, previous intervention, lesion type and characteristics, minimal luminal diameter) between the groups. Fifteen patients had had previous percutaneous transluminal coronary angioplasty, and 10 had had coronary artery bypass grafting. Most of the patients (n = 48) had lesions located on the left anterior descending artery. Lesions on the right coronary artery and the left circumflex artery were less common, and five patients were treated for lesions that were located on a saphenous vein graft. Thirty-six patients (42 % ) had totally occluded vessels, and 50 patients (58 % ) were treated
Group I n (%“o)
artery;
(96) (100) (100) (100) (100) (98)
LMT.
successes Group II n f!%)
p Value
21122 (95) 10/12 (83)
NS NS NS
518 (63) 4/4 (100) 40/46 (87)
NS NS
left main trunk;
RCA, right coronary
NS artery;
SVG,
for restenosis. Most of the patients had type B or C lesions, whereas only 10 patients (12%) had type A lesions. There was no difference in the distribution of patients who had Ho-YAG and those who had excimer laser angioplasty. The mean minimal luminal diameter was 0.12 f 0.21 mm and 0.13 + 0.23 mm for the patients who had Ho-YAG and those who had excimer laser angioplasty, respectively. The percent diameter stenosis was 95% + 9% and 94% + 14%) for the patients who had Ho-YAG and those who had excimer laser angioplasty, respectively. Laser success. The success rate for laser angioplasty was lower in patients in group I (55.0%) than in those in group II (71.7%), except for left circumflex lesions, but these differences did not reach statistical significance (Table II). The primary laser success rate was highest in saphenous vein grafts (100 % ). Excimer laser angioplasty tended to be more effective than Ho-YAG laser angioplasty except for left circumflex lesions. Laser angioplasty was less frequently successful in complex than in type A lesions (Fig. 1). Although calcified lesions did not decrease the primary success rate of laser angioplasty (Fig. 2), the success rate was lower in longer lesions than in shorter ones (42.1% vs 70.0 % ) (Fig. 3). Thirty-six of 86 patients had a totally occluded vessel, and 50% of these vessels in group I and 80% in group II could be recanalized by laser angioplasty (Fig. 4). These results were similar to those that were obtained for stenoses (Fig. 4). Laser angioplasty tended to be less frequently successful in 1.4 or 1.5 mm catheters than in 2.0 or 1.7 mm catheters (Fig. 5), but the difference did not reach statistical significance. Laser stand-alone therapy. The proportion of standalone laser therapy was significantly higher (p < 0.05) in group II than in group I. Ten (22 % ) patients who had excimer laser angioplasty compared with two (5%) patients who had Ho-YAG laser angioplasty could continue to receive stand-alone laser therapy
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%
100
I
80 60 40
20
0
n Ho-YAG
Non-calcified
Type C
Type B
Type A
0 Excimer
100
n Ho-YAG
Calcified 0 Excimer
%
80 60 40 20 01
Non-calcified n Ho-YAG
Calcified
n Ho-YAG 0 Excimer
0 Excimer
Fig. 1. Bar graphs of laser (top panel) and procedural success rates (bottom panel) for type A, type B, and type C lesions (American College of Cardiology/American Heart Association lesion classification system)
Fig. 2. Bar graphs of laser [top panel) and procedural success rates (bottom panel) for noncalcified and calcified lesions.
Table
canalization was 16 + 12 J and 40 + 22 J for excimer and Ho-YAG lasers, respectively. The total duration of irradiation was 36 + 20 seconds and 25 + 13 seconds for excimer and Ho-YAG lasers, respectively. Laser failures. Failures were less frequent with extimer laser angioplasty than with Ho-YAG laser angioplasty (28% vs 45%), but the difference was not
III. Technical
data and results Group
Laser Wavelength (nm) Range of fluence (J/mm”) Total energy (J) Duration of irradiation (set) Catheter size 1.4/1.5 (mm) 1.7 (mm) No. of procedures 2.0
I
Ho-YAG
Group
II
Excimer
2100 1-2 40 t 22 25 -t 13
308 30-60 16 + 12 36 + 20
18 NA
13
22
14
significant 19
NA, Not available.
without plasty.
any need for an additional balloon angio-
Technical results. The technical results are shown in Table III. The mean total energy required for re-
(Table
IV). Four laser angioplasty
failures
were due to inability to reach the lesion (two patients in group I and two patients in group II) because of: (1) mechanical friction between the inner lumen of the guiding catheter and the outer diameter of the laser catheter, (2) subcritical proximal stenosis, or (3) sharp bends of the target vessel proximal to the lesion to be treated. Failures were also due to the inability of the laser catheter to cross the obstruction (1’7Pa and 4 % for groups I and II, respectively). Most of the failures were due to the inability to obtain a signifi-
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Excimer
< 10mm
2 10mm
n Ho-YAG
100
laser coronary angioplasty
Stenosis
El Excimer
515
Occlusion
n Ho-YAG
Cl Excimer
._
%
100
a0
a0
a0
a0
40
40
20
20 01
0I
< 10mm
2 10mm
W Ho-YAG
Stenosis
0 Excimer
Fig. 3. Bar graphs of laser (top panel) and procedural successrates (bottom parcel) for lesions
Table
and holmium
Occlusion
4 Ho-YAG
0
Excimer
Fig. 4. Bar graphs of laser (top panel) and procedural successrates (bottom panel) for stenosesand occlusions.
IV. Failures of excimer and Ho-YAG laser coronary angioplasty procedures Type
of failure
Inability to reachthe lesion Mechanical friction between laser and guiding catheters Subcritical proximal stenosis Sharp bends proximally Inability to cross the lesion Insufficient effect
Group I n (s”,)
Group II n (76)
2 (5.0) 1 (2.5) 1 (2.5) 0 7 (17.5) 9 (22.5)
2 (4.3) 0 1 (2.5) 1 (2.5) 2 (4.3) 8 (17.4)
p Value
NS NS NS NS NS NS
NS, Not significant.
cant reduction in stenosis (22% and 17% for groups I and II, respectively) despite the use of incremental energy levels for each laser source. Procedural success. The overall procedural success rate was similar in groups I and II. It was equally high in total occlusions and in stenoses for both groups
(=92%). It was negatively influenced only by the length of the lesion as far as the excimer laser was concerned (Fig. 3). The highest rates were obtained in saphenous vein grafts and in the left anterior descending artery (Table II). The procedural success rate tended to be lower in the right coronary artery
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%
Table V. Complications in laser coronary angioplasty
1
procedures -.____-------.~~~.-----.-.--.-..--
100
----~----~.
-.
C:roup I n i 5)
Group II n (5)
0 0 0 1 (25) 3 (7.5) :1 (7.5) 0 3 (75)
0 0 0 1 13 9 4 8
p VlllUP
79 %
l----l 1.7
H
0
Ho-YAG
Excimer
100
In-hospital death Myocardial infarct,ion Emergency CARG Perforation Dissection Minor Major Vessel occlusion during procedure Vessel occlusion after procedure 524 hr 24-72 hr Coronary spasm Arrhythmia CABG,
Coronary
artery
(2.5) (28.3) (19.6) (8.7) (17.1)
NS NS NS NS 0.04 NS NS NS
6 (15.0)
4 (6.5)
NS
4 2 4 1
3 (6.5) 0 6 (13.0) 2 (4.3)
NS NS NS NS
(10.0) (6.0) (10.0) (2.51
bypass grafting;
NS, not significant
at p < 0.05.
80
60
40
20 -
0 1.7 n
Ho-YAG
Cl Excimer
Fig. 5. Bar graphs of laser (top panel) and procedural successrates (bottom panel) for 1.4/l.& 1.7, and 2.0 mm catheters.
when angioplasty was performed with the excimer laser (Table II). The procedural successwas not related to the size of the catheters (Fig. 5). Reduction in percent stenosis. Lesions were reduced from 94% f 14 % at baseline to 68% f 27 9h, and 58% -+ 34 % after laser angioplasty in groups I and II, respectively. The results were similar in stenoses and total occlusions and in calcified and noncalcified lesions. The type of lesion did not significantly influence the results. The ablation ratio when the diameter of the laser catheter was taken into account was 0.61 + 0.45 and 0.42 f 0.38 for excimer and HoYAG laser angioplasty, respectively, but the difference did not reach statistical significance. Complications. No major complication such as death, myocardial infarction, or the need for emergency coronary artery bypass graft surgery occurred
(Table V). The most frequent complication was acute closure, which occurred during the procedure, or early occlusion, which occurred within 24 hours after the procedure. However, all but two reocclusions could be treated successfully with repeat balloon angioplasty. Dissections occurred more frequently in patients in group II than in those in group I (28.3”;. vs 7.5% ; p < 0.05), but all could be reduced by dilatation. Perforation was uncommon and occurred in only two cases (one in group I and one in group II) without any clinical consequence, since extravasation of contrast medium was limited to the myocardium and did not expand into the pericardium. Spasm occurred frequently (13.0 !; and lO.O? for Ho-YAG and excimer laser angioplasty, respectively) regardlessof the laser used and could be relieved in all cases. Arrhythmia was infrequent and was observed in X5? of cases only during delivery of laser pulses. Follow-up results. Among the 51 patients who were followed up by repeat angiography, 27 had Ho-YAG laser angioplasty (group I) and 24 had excimer laser angioplasty (group II). In group I, eight patients had a reocclusion and 10 patients had a restenosis. Thus nine patients (33 % ) had a patent artery without restenosis. In group II, reocclusion occurred in 10 patients and restenosis in seven patients. Thus seven patients (29 YO) had a patent artery. None of the remaining 28 patients (12 patients in group I and 16 patients in group II) had evidence of ischemia. Only 25 % of patients in group I and 10% of patients in group II with a totally occluded artery had a patent artery at the time of follow-up cineangiography. The angiographically documented patency rate for pa-
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tients with stenosis was 37 % and 40 % for groups I and II, respectively. There was a trend for patients who could be left on stand-alone excimer laser therapy to have a higher patency rate than those who had laser-assisted balloon angioplasty (62.5% vs 19.4%). COMMENTS
This study showed that laser angioplasty is currently a feasible method for recanalization of obstructed coronary arteries. 4l 5 The technique in which a mechanically guided laser catheter is used is derived from the commonly used balloon angioplasty technique and provides easy access to the coronary vasculature. It appeared that multifiber catheters were able to deliver a fluence sufficient for ablation of atheromatous tissue.i2* I3 The catheters used with Ho:YAG or excimer lasers were still limited by a stiff distal tip and an inadequate coverage of the area at the distal end of the laser catheter. The active area (i.e., the sum of individual fiber tip areas) of the first generation of catheters was only 15 % . The ultimate device for excimer laser angioplasty consisted of more densely packed fibers that provided a significant reduction in the dead space but still an inadequate coverage of laser irradiation (23 % ). This is the reason for the “Swiss cheese” appearance, which consisted of small holes within the crater with unirradiated tissue between them. If all of the obstructing tissue has not been ablated, a residual obstruction should be present. This may well be related to the haziness that can be observed by angiography at the channel site in numerous cases (Fig. 6) and some preliminary data obtained from angioscopy, which showed that tissue remnants were left behind after laser angioplasty. l4 However, the gaseous debris generated by excimer laser irradiation will disrupt tissue that is located at the dead space between the fibers.15, l6 Another problem with the currently available catheters is channel size. The clinical results obtained by laser angioplasty in terms of channel size were not in agreement with the experimental data. Indeed, it has been shown that in in vitro studies on postmortem normal or atheromatous tissue, the diameter of craters created by laser irradiation was similar to that of the catheter.17 Moreover, in our clinical study the mean “ablation ratio” was roughly 60 % , which means that the channel diameter created by laser irradiation was 40% smaller than the catheter diameter. It might have been due to elastic recoil, vasomotor tonus of the arterial wall, insufficient ablation as a result of the “Swiss cheese” appearance, or the “dottering” mechanical effect caused by pushing the
Fig. 6. Coronary angiogram (right anterior oblique cra-
nial view) after excimer laser angioplasty of proximal left anterior descending artery showing “haziness” at the laser-irradiated site (arrow). catheter (which could have been advanced at too fast a pace). The difference in channel diameter between patients who had excimer laser angioplasty and those who had Ho-YAG laser angioplasty might have been due to the more densely packed excimer catheter. Some of our failures were due to a lack of trackability of the laser catheter. A drawback of using large catheters was also the inability to assess the immediate results after laser irradiation by contrast medium injections. Because the catheter that was selected for recanalization was large enough to debulk the target artery, no space was left between the lumen and the wall to allow contrast medium injection. Therefore to assess the results after laser angioplasty, a pullback of the catheter was required. Our study was not randomized. Lesions were selected for laser angioplasty because they were expected to offer easy access to the laser catheters. This was the reason for selection of proximal type A lesions. However, once feasibility was established, type B or C lesions (both proximal and distal) were selected. This is in agreement with the patient selection described by Cook et a1.7 Contrary to their results, our data showed a tendency for a lower success rate in types B and C lesions than in type A lesions. In our study the success rate was higher with the. excimer laser than with the Ho-YAG laser. Although this could reflect a learning curve, this hypothesis cannot be confirmed because of a further overlap between the use of the two laser sources. However, even with the excimer laser our primary success rate was lower than that published by other groups, including
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Fig. 7. Coronary angiogram (right anterior oblique view) of excimer laser angioplasty of a total occlusion of left anterior descending artery before treatment (panel A), after laser irradiation (panel B), and after balloon angioplasty (panel C).
those involved in multicenter trials.4* 6 7 The reason for this discrepancy is not well established. Although no statistical significance could be established between the groups, our results suggest that long lesions could not be recanalized as frequently as short ones and that the laser success rate in right coronary arteries was lower than that in left anterior or circumflex arteries. Yet there seems to be a concordance between the favorable results obtained in saphenous vein grafts and ostial lesions. Both of them may be reasonable indications for laser angioplasty. Interestingly, our results also showed that the success rate in calcified lesions was similar to that obtained in noncalcified lesions. Thus laser angioplasty may be an adequate adjunct to balloon angioplasty in the presence of hard obstructing tissue or may actually be the first-choice treatment. Our success rate in totally occluded vessels was
relatively high (Figs. 7 and 8). This was due not only to the ablation capabilities of laser energy but also to the ability of guide wires to penetrate total occlusions. We had to recanalize not only fresh lesions but also occlusions, which were as old as 18 months. Success could also be achieved in the latter. It may be argued that in these older lesions recanalization was not indicated either because fibrous tissue was already present in the territory of the occluded vessel or because collaterals were able to supply the necrotic myocardium. However, caution was taken in all cases to make sure that viable myocardium was still present. Total occlusions may thus be considered good indications for use of this technique. This was especially the case for excimer laser irradiation for which primary laser success rate was high as compared with Ho-YAG laser angioplasty. Comparison between Ho-YAG and excimer laser
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Fig. 8. Coronary angiogram(left anterior oblique view) of Ho-YAG laser angioplasty of a total occlusion of right coronary artery before treatment (panel A), after laserirradiation (panel B), and after balloon angioplasty (panel C).
sources showed an overall but inconsistent advantage of the latter over the former. The overall laser success rate was higher, channel size was greater, and more stand-alone laser therapy could be achieved with the excimer laser. However, the catheter design used with excimer laser was not exactly the same as that which was used with the Ho-YAG laser. The excimer laser catheters were more densely packed with several rings of optical fibers concentrically arranged around the central lumen, whereas the Ho-YAG laser catheters had a single ring of fibers arranged at the outer ring of the distal tip. Our experimental studies have shown that the active area played a greater role in terms of ablation efficiency than the amount of energy delivered to the target tissue. This observation leads to the discussion of the role of laser angioplasty in case of dilatation failure. In eight patients, dilatation was the first-choice tech-
nique but the balloon failed to penetrate the lesion. Thus laser energy was delivered. In five cases, the laser catheter was able to cross the lesion, which allowed subsequent dilatation to be successfully achieved. In the three other cases, the laser catheter could not be advanced and remained against the entry of the obstruction during irradiation. In all three cases it was then possible for the balloon catheter to cross the lesion and to be successfully inflated. Such a “facilitation” has been reported by u& g and by Israel et al.” The reason for such a result is not yet determined. It may be speculated that laser energy was able to alter the structure of the obstruction and the arterial wall by the mechanical effect, which consists of pressure and acoustic shock waves. Tissue alteration may have consisted of the splitting and fracturing of hard tissue which would lead to a softening of the arterial structure. Ho-YAG and excimer lasers
520
Geschwind
et al.
have been shown to generate mechanical effects that may be propagated to the surrounding tissue.17 Indeed, the Ho-YAG laser was reported to generate superheated vapor, which rapidly expands and thus dislodges hard tissue from the crater.lg Recent studies have shown that arterial recanalization by the excimer laser is associated with the release of gas bubbles; the presence of photoacoustic effects such as rapidly expanding and collapsing bubbles results in shock waves.15* l6 In our study, few patients could benefit from stand-alone laser therapy. This is in contradiction to the results published by other groups4, 5. 7 who obtained an almost 50 % primary laser stand-alone rate. We had only a 22 % and a 5°C success rate for excimer and Ho-YAG lasers, respectively. The discrepancy was due to the different criteria that were used for stand-alone laser therapy. We wanted to obtain a residual stenosis of <30 % after completion of the laser procedure, whereas the other groups decided not to use additional balloon dilatation when the residual stenosis was not >50%. If we had applied this threshold for indication of subsequent dilatation, our stand-alone laser therapy success rate would have been 50% and 40% for excimer and Ho-YAG laser angioplasty, respectively. Our rate of major complications was remarkably low. This was obviously due to the mechanical guidance with the guide wire, which maintained the laser catheter in a coaxial position. The low rate of perforation was thought to be due to the very slow progression and minimal pressure applied at the proximal catheter tip. In contrast, the rate of acute closure was high. It could be explained by insufficient tissue ablation, which was suggested by some haziness, which was observed after the laser catheter passed through the obstruction, and by some angioscopic observations, which showed that a great amount of obstructing tissue was left behind after the laser angioplasty procedure. Also, thrombus formation and protracted spasm cannot be ruled out. The fact that more dissections were frequently observed at a higher rate with the excimer laser than with the Ho-YAG laser cannot yet be explained. It might have been due to deep mechanical damage inflicted to the layers of the arterial wall by shock waves generated by the laser pulses.15-i7 However, our previous experimental studies have shown the excimer laser to generate lower pressure waves than the HoYAG laser.17 Finally, the high rate of dissection may have occurred because at this early stage of the study the goal of the procedure was to debulk arteries by using large catheters with a catheter-lumen diameter close to 1. To decrease the dissection rate and
Amewan
February 1993 Heart Journal
increase the safety of the laser procedure the trend was to use subsequently smaller (1.4 mm) rather than large (2.0 mm) catheters. This in turn could have induced a low stand-alone success rate. Obviously, a compromise should be found between a greater possibility of improved efficacy and a higher risk of side effects that are likely to occur with large catheters. Spasm might also have been due to a mechanical effect on the tissue surrounding the area of irradiation, which is a side effect of pulsed lasers.‘“, I6 Importantly, these complications could almost all have been treated successfully by dilatation and vasodilators, respectively. No final conclusion on the patency rate at &month follow-up can be drawn from our results, since the 15number of patients with angiographically documented patency was too small. Moreover, the clinical follow-up cannot be included in the study, since both reclosures and restenoses may occur in patients who are free of symptoms, especially those who presented initially with a totally occluded artery. This may be due to the presence of a well-developed collateral circulation, which can preserve an adequate supply to the myocardium. Thus only angiographically documented data should be taken into account for the assessment of long-term patency. In this respect, our results showed that the patency rate was low in both groups of patients. It tended to be even lower in vessels that were totally occluded initially than in stenoses. However, if we had assumed that patients without evidence of ischemia had a patent artery at follow-up, the restenosis rate would have been 46?( and 43 ?C for patients in groups I and II, respectively. This figure is acceptable, given the severity of the lesions that had been treated. One of the encouraging results of our study stems from the relatively favorable outcome obtained after stand-alone laser therapy as compared with the poor outcome observed after laser-assisted balloon angioplasty. However, the small number of patients does not allow any final conclusion. The reason for the high restenosis and reclosure rates is not yet well understood. However, it is hypothetized that it might have been due to either insufficient tissue ablation14 (Fig. 6) or smooth muscle cell proliferation. The reason for a higher restenosis rate after laser-assisted balloon angioplasty than after stand-alone laser therapy is not well understood. It may be hypothetized that the damage to the arterial wall, which induces tissue proliferation, might have been greater after both laser-induced shock waves and wall stretching by balloon inflation than after the mechanical damage that results from pulsed laser irradiation alone. Further studies are required to elucidate the mech-
Volume Number
125 2, Part 1
anism of restenosis or reclosure after pulsed laser angioplasty. Clinical implications. Our study is in accordance with others as to the ideal indications for laser angioplasty (i.e., saphenous vein grafts; ostial lesions; and to a lesser degree, calcified lesions and total OCC~Usions). Although the new multifiber “over-the-wire” catheters provide easy and rather safe access to the coronary arteries, progress should be made to obtain larger channels and to ablate more tissue. The side effects that are generated by pulsed lasers must be elucidated to decrease the rate of complications and possibly also the restenosis rate. Our study also showed that excimer laser angioplasty was more effective but induced more dissections than Ho-YAG laser angioplasty. Whether those effects were due to the laser source, the catheter design, or both is not yet clearly understood. SUMMARY
Recently access to the coronary arteries became available to laser angioplasty because of a new technique utilizes a pulsed laser source and multifiber, “over-the-wire” guided catheters. The aim of this study was to evaluate the early and long-term results and the side effects of coronary angioplasty with an excimer or a Ho-YAG laser. Forty consecutive patients were treated with the Ho-YAG laser (group I) and 46 consecutive patients were treated with the excimer laser (group II). The primary laser angioplasty success rate was 55 % and 72 % (NS) for groups I and II, respectively. This success rate was highest in saphenous vein grafts. It was similar in calcified and noncalcified lesions and in total occlusions and stenoses. It tended to be lower in long lesions than in short ones (40 % vs 60 % ; p < 0.05 and 44 % vs 78 % ; NS for groups I and II, respectively). Laser standalone therapy was performed in 5% of patients in group I compared with 22% in group II 0, < 0.05). Failures were due to the inability of the laser catheter tip to reach the lesion, to cross the obstruction, or to obtain a significant reduction in stenosis. They were more frequent in patients in group I than in those in group II (45 % vs 28% ). There were no deaths, no myocardial infarctions, and no need for emergency coronary artery bypass grafting because most patients had total occlusions or a well-protected coronary artery. Complications included acute closure in 8 % of patients in group I and in 17 % of patients in group II and spasm in 10 % and 13 % of patients in groups I and II, respectively. Dissection occurred more frequently in patients in group II than in those in group I (28% vs 7% ; p < 0.04). The angiographic patency rate at 6-month follow-up was
Excimer
and holmium
laser coronary angioplasty
521
33% and 29% for patients groups I and II, respectively. Multifiber, wire-guided catheters provide easy access to the coronary arteries. Excimer laser angioplasty is effective but induces a high rate of dissections. Technical improvements are required to ablate more tissue to possibly reduce the restenosis rate. Further studies are needed to elucidate the mechanism of side effects and to reduce the restenosis rate. We thank Franqoise Veyssiere and Margaret Tissot-Geschwind for technical assistance and Mireille David for secretarial assistance. REFERENCES
1. Isner JM, Donaldson RF, Deckelbaum LI, Clarke RH, Laliberte SM, Ucci AA, Salem DN, Konstam MA. The excimer laser: gross, light microscopic and ultrastructural analysis of potential advantage for use in laser therapy of cardiovascular disease. J Am Coil Cardiol 1985;6:1102-91 2. Waller BF. “Crackers. breakers. stretchers. drillers. scraners, _ shavers, burners, welders and melters”-the future treatment of atherosclerotic coronary artery disease? A clinical-morphologic assessment. J Am Co11 Cardiol 1989;13:969-87. 3. Block PC, Myler RK, Sterzer S, Fallon JT. Morphology after transluminal angioplasty in human beings. N Engl J Med 1981;305:382-5. 4. Litvack F, Eigler NL, Margolis JR, Grundfest WS, Rothbaum D, Linnemeier T, Hestrin LB, Tsoi D, Cook SL, Krauthamer D, Goldenberg T, Laudenslager JR, Segalowitz J, Forrester JS. Percutaneous Excimer laser angioplasty. Am J Cardiol 1990;66:1027-32. 5. Sanborn TA, Bitt1 JA, Hershman RA, Siegel RM. Percutaneous coronary excimer laser-assisted angioplasty: initial multicenter experience in 141 patients. J Am Co11 Cardiol 1991; 17:169B-73B. 6. The European Study Group on Coronary Excimer Laser Angioplasty. Initial results of the European multicenter registry on coronary Excimer laser angioplasty [Abstract]. Circulation 1991;84(suppl II):II-362. 7. Cook SL, Eigler NL, Shefer A, Goldenberg T, Forrester JS, Litvack F. Percutaneous excimer laser coronary angioplasty of lesions not ideal for balloon anaionlastv. Circulation 1991: 84:632-43. 8. Geschwind HJ, Dubois-Rande JL, Murphy-Chutorian D, Tomaru T, Zelinski R, Loisance D. Percutaneous excimer laser angioplasty with mid-infrared laser and a new multifibre catheter [Letter]. Lancet 1990;336:245-6. 9. Geschwind HJ, Dubois-Rande JL, Zelinski R, Morelle JF, Boussignac G. Percutaneous coronary mid-infra-red laser angioplasty. AM HEART J 1991;122:552-8. 10. Orion LP, Geschwind H, Lorino H, Richalet JP, El Badaoui G. Assessment of coronary lesions: validation and future. European Review of Biomedical Technology. 1991;13:265-71. 11. Ryan TJ, Faxon DP, Gunnar RM, ACC/AHA Task Force on Assessment of Diagnostic and Therapeutic Procedures (Subcommittee on Percutaneous Transluminal Coronary Angioplasty). Guidelines for percutaneous transluminal angioplasty. Circulation 1988;78:486-502. 12. Goldenberg T, Anderson WB, Kupfer SH, Narciso HL, Shaolian S, Laudenslager JB. Percutaneous excimer laser angioplasty in humans. Proceedings of the Society of Photo-opt&al Instrumentation Engineers 1989:1067:145-52. 13. Duda SH, Karsch KR, Haase KK, Huppert PE, Claussen CD. Laser ring catheters in excimer laser angioplasty. Radiology 1990;175:269-70. 14. Diethrich EB, Hanafy HM, Santiago OJ, Bahadir I. Angioscopy after coronary excimer laser angioplasty. J Am Co11Cardiol 1991;18:634-5. --
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15. Gijsbers GHM, Sprangers RLH, van Gemert MJC. Excimer laser coronary angioplasty: laser-tissue interactions at 308 nm. In: Ginsburg R, White JC, eds. Primer on laser angioplasty. 2nd ed. Mount Kisco, New York: Futura Publishing Co., 1992:217-41. 16. Grundfest WS, Seagalowitz J, Goldenberg T, Laudenslager J. Papaioannou T. The effect of fiber optic delivery system geometry, power density and energy on excimer laser luminal recanalization [Abstract]. Circulation 1990;82(suppl IIIl:III495. 17. Tomaru T, Geschwind HJ, Boussignac G, Lange F, Tahk S-.7.
BOUND
VOLUMES
AVAILABLE
February 1993 Heart Journal
Comparison of ablation efficacy of excimer, pulsed dye and holmium YAG laser relevant to shock waves [Abstract]. Cir culation 1991;84(suppl II):H-423. 18. Israel DH. Marmur JD, SanbornTA. Excimer laser-facilitated balloon angioplasty of a nondilatable lesion. ,J Am Co11 Cardiol 1991;18:1118-9. 19. Geschwind HJ. Mid-infrared laser coronary angioplasty--experimental study. In: Karsch KR, Haase KK, eds. Coronary laser angioplasty. Darmstadt: FLG, Steinkopff Verlag, 1991: 43-7.
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