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Percutaneous laser probe femoropopliteal angioplasty: A preliminary experience
Percutaneous laser probe femoropopliteal angioplasty: A preliminary experience Bruce A. Perler, M D , a Floyd A. Osterman, M D , b R o b e r t I. Wh/.te, Jr., M D , b and G. Melville Williams, M D , a Baltimore, 2Vfd. Percutaneous laser probe "hot tip" angioplasty procedures were performed on 47 occluded femoropopliteal artery segments in 27 men and 10 women ranging in age from 31 to 92 (mean, 64.7) years. Indications for the procedure included claudica£1on in 29 (78%) segments, and the occlusion lased was >7 cm in length in 51% of the procedures. Failure to recanalize the occlusion occurred in 14 (30%) segments, and recanalization foUowed by in-hospital reocclusion occurred in seven (15%) segments, yielding an initial failure rate of 45%. Initial failures were noted in 40% of the <3 cm occlusions, 33% of the 4 to 7 cm occlusions, and 54% of the >7 cm occlusions. In nine (43%) instances in these 21 failures there was extension of the occluded segment or decline of the ankle/brachial index or both, precipitating the need for surgery in three (18%) of these 17 patients. Among the successfully treated group, 17 (65%) of these vessels in 15 patients reoccluded from 1 to 14 (mean, 3V2) months after the procedure. Cumulative patency among the successfully lased vessels was 69% at 1-month, 38% at 6 months', 29% at 12 months', and 14% at 15 months' follow-up. Fifteen-month patency was 7% of the entire series of 47 vessels treated. Eighteen complications occurred after 15 (32%) of these 47 procedures. Based on these results, the widespread application of laser probe angioplasty cannot be justified without further clinical and laboratory investigation. (J VASC SURG 1989; 10:351-7.)
For nearly 40 years after its introduction saphenous vein femoropopliteal bypass grafting has remained an optimal method for treating superficial femoral artery occlusive disease, and it remains the "gold standard" against which other treatment modalities should be judged. 1 Even during its earliest years of application initial success rates of 72% to 100% were reported from many centers. 2-4 In one of the first long-term follow-up studies, 5-year patency of 76% was reported for saphenous vein femoropopliteal bypass grafting performed between 1954 and 1965. ~Contemporary reviews have continued to document such favorable results. 6 Despite this record, alternative techniques to revascularize the ischemic limb continue to be pursued to spare the patient the risks of an open surgical procedure. We are currently seeing the rapid development of new technology aimed at treating arterioFrom the Departments of Surgery~ and Radiology,b The Johns Hopkins Hospital. Presented at the Thirteenth AnnualMeetingof the SouthernAssociation for Vascular Surgery, Key West, Fla., Jan. 25-28, 1989. Reprint requests: BruceA. Perter,MD, Divisionof Vascular Surgery, Department of Surgery, The Johns Hopkins Hospital, 600 N. Wolfe St., Baltimore,MD 21205. 24/6/13656
sclerotic disease. For example, percutaneous transluminal angioplasty (PTA) has clearly assumed an important role in the treatment of large numbers of patients with peripheral vascular disease. 7 In our institution femoropopliteal PTA has achieved a 4-year patency of 54% for stenotic lesions and patency of 73% for focal occlusions. 8 However, PTA has its limitations. Initial f~Liluresand early recurrent lesions are most likely to occur in vessels with diffusely stenotic lesions and longer total occlusions. 9 This shortcoming and the inability of the guide wire to cross highly calcified total occlusions in some patients have stimulated interest in laser ablation of atherosclerotic occlusive femoropopliteal lesions. 1° The concept of laser ablation of atherosclerotic disease has generated great expectations among the public and has received enthusiastic coverage in the lay press. However, although laser angioplasty has been studied extensively in the laboratory, little objective clinical data are available to evaluate its potential. Therefore the present time seems appropriate to assess whether those expectations are being met and whether that enthusiasm is justified. This article will document our initial experience with percutaneous laser probe "hot tip" angioplasty for femoropopliteal occlusive disease. 351
Journal of VASCULAR SURGERY
352 Perter et al.
Table I. Indications for laser angiophsty
Table II. Length of lesions treated
Indication
No.
%
Length of lesion
No.
%
Clandication Nonhealing ulcer Rest pare Gangrene Total
29 6 1 _~1 37
78% 16% 3% 3% 100%
~<3 cm 4-7 cm > 7 cm Total
5 18 2_44 47
11% 38% 51% 100%
PATIENTS AND METHODS
Laser equipment and protocol
From March 1986 through July 1988 percutaneous laser probe hot tip angioplasty procedures were performed on 47 occluded femoropopliteal artery segments in 37 patients. Twenty-nine patients underwent a single procedure; the same vessel was treated twice in three patients and three times in two patients, and bilateral procedures were performed on three patients. Participants included 27 men and 10 women ranging in age from 31 to 92 (mean, 64.7) years. Seventy percent of the patients were over 60 years old, and 27% were over 70 years of age. Risk factors for atherosclerosis were common, including cigarette smoking in 63%, hypertension in 46%, diabetes mellitus in 37%, and hypedipidemia in 9%. The indications for treatment are noted in Table I. The 29 patients with claudication had experienced symptoms for 1 to 60 (mean, 19.2) months before referral, including 72% who had experienced symptoms for more than 6 months, 52% for more than 1 year, 24% for more than 2 years, and 20% for more than 3 years. Seventy-seven percent of the patients with claudication experienced symptoms after walking less than two blocks and 48% after walking less than one block. Eleven (30%) of the 37 patients had undergone previous peripheral vascular operations including carotid endarterectomy in two (6%), a lower extremity inflow procedure in two (6%), and an infrainguinal reconstruction in seven (19%) (two of which were performed on the side of the laser angioplasty). Four patients (11%) had undergone previous coronary bypass surgery. Forty-five lesions were located in the superfF cial femoral artery (with or without extension into the popliteal), and two lesions were limited to the popliteal artery. The lesions ranged from 3 to 30 cm in length (Table II). Runoff occurred in three vessels in 26% of the cases, two vessels in 32% of the cases, and one vessel in 39% of the cases. Runoff occurred in an isolated popliteal segment in 3% of the cases. Significant inflow disease was excluded in
The laser probe (Model 900, Trimedyne Inc., Santa Ana, Calif.) with a 400 ~m core diameter was coupled to an 8 W argon laser. The argon laser light travels down a fiberoptic fiber to heat a metal alloy tip (1 to 2 mm diameter), and the heat is distributed circumferentially inside the vessel. The protocol for this series was approved by the Joint Committee for Clinical Investigation of The Johns Hopkins Medical Institutions. After written informed consent was obtained, the procedure was performed via percutaneous antegrade puncture of the femoral artery with the patient under local anesthesia in a catheterization suite within the radiology, department. One patient with multiple previous groin operations required a femoral artery cutdown for sheath placement. The laser-heated probe was advanced through an 8F introducer sheath or guiding catheter to the obstructing lesion, and the patient was given 5000 units ofheparin intraarterially. Repetitive 2-second pulses of 2 to 8 W of argon laser energy were delivered during normal blood flow as the probe was advanced until vessel patency was documented angiographically. Progression of the probe through the lesion was monitored fluoroscopically (General Electric, LUA System, Milwaukee, Wis.) with small injections of contrast material. Three to 5 seconds were allowed to elapse between laser pulses. After the lumen had been established, the laser probe was removed and a standard balloon angioplasty procedure was carried out with 5 to 6 mm balloons and conventional techniques as previously described.8'9 A completion arteriogram was obtained, the catheter and sheath were removed, and systemic heparin infusion was continued for 24 hours, unless a hematoma formed or bleeding precluded this. Patients were placed on 325 mg aspirin per day and 75 mg dipyridamole three times a day, underwent Doppler ankle/brachial examination, and were usually discharged 24 to 48 hours after the procedure. The patients were seen as outpatients 2 weeks after the procedure, and then usually at 3-month intervals, at which time complete histories, physical examina-
all cases.
Volume 10 Number 3 September 1989
Femoropopliteallaserprobe angioplasty 353 100
'
~2R 90 ~-
>.
H
"
SUCCESSFULLYLASED VESSELS
7O
O
uJZl.,. 60 50 /15 13 13 12 "~ a.
40
~
30
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1
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5
_
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2_.~1 ~
20 10
0
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l
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I
1
2
3
4
5
6
7
8
9
10
11
12.
13
14
15
MONTHS
Fig. 1. Fifteen-month patency data for successfullylased vessels and all vessels treated.
Table III. Failures versus length of lesions treated Length of lesion (cm)
No. treated
Failed to recanalize (%)
<3 4-7 >7 Total
5 18 2_.44 47
2 (40%) 3 (17%) 9 (37%) 14 (30%)
tions, and Doppler ankle/brachial examinations were performed. Reocclusion of the treated segment was defined by a recurrence of symptoms and return of Doppler ankle/brachial index to pretreatment levels. An initial failure was defined by inability to successfully recanalize the entire diseased segment, or successful recanalization with reocclusion occurring before hospital discharge. All early and most late reocclusions were confirmed angiographically. RESULTS Twenty-one (45%) of the 47 procedures in 17 patients were initially unsuccessful. In 14 (30%) of the procedures the lesion could not be completely recanalized, and in seven (15%) the lesionwas successfi~y recanalized and dilated but became reoceluded during the hospitalization, almost always within 24 hours. Excepting the small number of 3 cm occlusions, initial failures tended to correlate with the length of the lesion treated (Table III). No correlation existed between success rate and the status ofrunoffvessels. Based on angiographic appearance, Doppler anlde/brachial indices, and symptoms, the
Recanalize early reocclusion (%) 0 3 4 7
(0%) (17%) (17%) (15%)
Failed (%) 2 6 13 21
(40%) (33%) (54%) (45%)
condition of seven (41%) of these 17 patients was worse after the failed procedure. Three (18%) of these patients underwent femoropopliteal bypass grafting within 1 month of the laser procedure. Conversely, 26 (55%) of the procedures in 22 patients were completed successfully. Among this group 17 (65%) lesions in 15 patients reoccluded from 1 to 14 (mean, 31/2) months after the procedure. Lifetable analysis for the lesions that were initially successfully treated yielded patency rates of 69% at 1month, 38% at 6rnonths', 29% at 12 months', and 14% at 15 months' follow-up (Fig. 1). Three (20%) of these 15 patients underwent femoropopliteal bypass grafting, and two (13%) underwent a standard PTA after the lased artery reoccluded. However, if one considers all vessels treated in the life-table analysis, patency was only 33% at 1-month, 18% at 6 months', 14% at 12 months', and 7% at 15 months' follow-up (Fig. 1). Eighteen complications were noted after 15 (32%) of the 47 procedures (Table IV). Surgical exploration was required only for an acute femoral artery hemorrhage. One femoral false aneurysm was
journal of
VASCULAR
354 Perler et al.
SURGERY
Table IV. Complications Complication
Pulmonary embolus Groin hematoma Retroperitoneal hematoma Distal thromboemboli False aneurysm Acute femoralhemorrhage Superficialfemoral artery arteriovenous fistula Vasovagal: hypotension Total
No.
1 7 1 5 1 i 1 1 18 (32%)
electively repaired at the time of femoropopliteal bypass grafting, and a femoral arteriovenous fistula sealed spontaneously. Four patients who experienced distal thromboemboli were successfully treated with brief local infusions ofurokinase, and in a fifth patient this complication resolved on systemic heparin therapy. No patient required emergency surgery for an ischemic complication. No limb or digit loss or deaths occurred in this series. O f note, angiographically documented asymptomatic arterial perforations occurred during 14 (30%) of the laser procedures. In four (29%) of these cases the procedure was completed successfully despite the perforation. Perforations occurred during 44% of the procedures performed in our initial year but in only 26% of the procedures performed subsequently.
DISCUSSION Learning period Many patients experience significant ischemic symptoms caused by fairly limited arteriosclerotic arterial lesions, and PTA has been very effective in their treatment. Those patients with lesions too extensive to be treated by PTA usually require surgical reconstruction. The desire to extend the limits of conventional PTA and thus avoid open surgical reconstruction in some of these patients has stimulated great interest in the development of other nonoperative techniques for treating such patients. The application of laser energy to this clinical challenge is one such logical approach. The theoretic advantage of laser angioplasty is that it can debulk the atherosclerotic lesion rather than simply crack the plaque or stretch the host artery as occurs in standard balloon angioplasty procedures? 2
Physical properties of laser Extensive in vitro research has confirmed that laser radiation in the infrared and the visible ranges can ablate atherosclerotic plaque) 3-1s Other in vivo
studies showed that argon laser catheter thrombectomy was successful in dog and rabbit models. In 1984 Choy et al. 16 reported the first case of in vivo laser angioplasty of the coronary arteries at the time of bypass surgery. Gerschwind et al.17 reported the initial clinical experience with neodyniun:yttriumaluminum-garnet (Nd: YAG) laser recanalization of arteriosclerotic femoral and popliteal arteries, and recanalization of the profunda femoris artery with argon laser was also reported by Lee et al.la As a result of this and other studies, the argon laser emerged as the most widely used laser in human clinical trials. ~9 Argon laser energy has two major wavelength lines at 488 nm and 514 nm that pass easily through flexible glass fibers and water. It is strongly absorbed by hemoglobin but only poorly absorbed by plaque and normal artery wall. Therefore argon laser must be used either in a bloodless field or in very close proximity to the vascular lesion) 9 In a series of 16 patients with femoropopliteal arteriosclerotic lesions, Ginsberg et al. ~2 achieved patency or improvement in luminal diameter in only 50% of cases when they used a bare-fiber argon laser, despite its promise. In three of these 16 patients the laser perforated the arterial wall. ~2 Other clinical and experimental studies have documented a substantial inddence of arterial wall perforation and late aneuwsm formation after bare-fiber laser treatment. 16,18,2°,2~ The argon-heated metal probe hot tip laser was introduced in an attempt to reduce this incidence of arterial wall perforation. 22,23The theoretic advantages of using a laser-heated metal cap are the absence of beam dispersion, less mechanical trauma, consistency of thermal energy delivered, and the ability to vary the size of the metal probe and thus the diameter of the channel created, since recanalization is accomplished only by direct tissue contact as opposcd to both light absorption and direct tissue contact when a bare fiber is used. Furthermore, the laser-heated metal cap fiber heats and cools rapidly, thus reducing adherence of the cap to the local tissue. 24,25Experimental work has shown the argon hot tip fiber to be more effective in recanalizing occluded vessels with less risk of perforation of the normal artery than the argon bare-fiber technique? 6
Reported clinical experience Clinically, the hot tip has been used in most centers as an adjunct to standard PTA, rather than as the sole therapeutic intervention. After the laser creates a channel through an occluded or diffusely stenotic segment of an artery, the arterial lumen is then enlarged by conventional balloon dilation. 8,9 In the
Volume i0 Number 3 September 1989
initial Food and Drug Administration-approved clinical study of this technique in the United States, Sanborn et al. at Boston University reported an initial success rate of 80% (I2 of 15 vessels). Furthermore, i0 (83%) of these 12 vessels remained patent at a mean follow-up of 6 months. 27 Cumberland et al.28 at Sheffield, England, and Sanborn et al.29 have continued to report excellent results with this technique in a combined series of patients from their respective centers. For example, most recently they have documented a i-year patency of 77% and suggested that the laser-heated metal tip may allow PTA to be successfully performed on vessels that previously were too extensively diseased for this procedure.29
Future expectations Despite a fairly limited clinical experience with laser angioplasty, there has been an overwhelming public awareness of and enthusiasm for the potential to treat peripheral vascular disease with lasers. The " P o o p goes the plaque with experimental laser angioplasty"n kind of article epitomizes our patients' understandable desire to achieve relief of symptoms of ischemia in a relatively painless "high technology" fashion. Therefore the present time seemed appropriate to question whether this public enthusiasm is justified by ongoing clinical experience. This article would suggest that it is not. Very simply, three fundamental questions need to be addressed to place the technique of laser angioplasty in perspective: Is laser probe femoropopliteal angioplasty safe; is it effective; and are the results durable? Our data would suggest that the hot tip procedure is relatively safe. Although a careful analysis of this experience documented complications after nearly one third of the procedures, urgent surgical intervention was required in only one case (Table IV). As noted, laser arterial perforations occurred in 30% of the procedures. Clearly there is a learning curve inherent in this technique, since the rate of perforation was 44% for our first 16 cases and dropped to 26% for the subsequent 31 proce~tures. We would agree with others that this is a fairly benign occurrence, and in fact in four of our cases it did not preclude completing the procedure successfully. However, on the basis of the other key questions, namely the efficacy and durability of laser angioplasty, we would have to argue that the exact role of this technique in the treatment of peripheral arterial occlusive disease remains to be defined and presently seems to be somewhat overrated. Nearly one half of the procedures performed at this institution were deemed unsuccessful by the time of discharge from
Femoropopliteallaserprobe angioplasty 355 the hospital. Furthermore, the condition of 41% of these patients was made worse by the failed procedure, including three (18%) who had femoropopliteal bypass grafting within 1 month. The substantial attrition rate we observed in arteries that were initially successfully treated was even more disconcerting. One-year patency for these vessels was 29%, and if one considers all vessels treated (including initial failures) it was 14% (Fig. 1). These data conflict somewhat with the results of others, although the reasons are not immediately apparent? 9 It would seem that patient and lesion selection have an important bearing on eventual results. Seventy percent of our patients were over the age of 60 years, and more than one quarter of them were older than 70 years. More than half of our patients with clandication had experienced symptoms for more than 1 year, and 48% of them experienced symptoms after walking less than one block. These observations suggest that we were treating significantly advanced, well-established occlusive disease, and in fact 51% of the lesions treated were greater than 7 cm in length (Table !I). In other words, we have been lasing the longer lesions that were generally considered to be beyond the scope of standard PTA, whereas other centers may be lasing lesions that could also be treated by conventional balloon dilation. Furthermore, whereas others have been treating stenotic as well as total occlusive lesions with the hot tip technique, all the lesions treated in our series were essentially total occlusions.27"29 Even if one can achieve satisfactory initial success rates with the hot tip laser, thus sufficiently fulfilling the "effectiveness" question, we feel that the durability issue may still remain a crucial problem. Although the patient population and type of lesions treated arc not strictly comparable, the 1-year patency of vessels that undergo PTA after an initial channel is created by the hot tip laser is distinctly inferior to patency achieved in vessels treated only by PTA in our center. 8,9 That observation, in addition to the relatively early onset of vessel reocclusion (mean, 3 V2 months), raises the possibility of laser thermal injury at the time of the procedure itself as a potential etiologic factor in tb.is early reocclusion phenomenon. Histologic studies have documented charring along the luminal surface after hot tip dissolution of atherosclerotic plaque. 26'3° Therefore the potential thrombogenicity of this residual luminal surface is a real concern. This might explain, at least in part, the inferior results we noted in attempting to recanalize totally occluded vessels, where more atheromatous bulk is to be lased, as opposed to those vessels with
356
Journal of VASCULAR SURGERY
Perler et al.
diffuse stenoses. 27-29Excluding the small number of 3 cm occlusions, we did note a trend correlating failure rate with the absolute length of the lesion treated (Table III), as others have observed. 29 Our institution has a long history of interest and leadership in the field of interventional radiology. The angiographers, working in collaboration with the vascular surgeons, have achieved consistently outstanding results in a number of areas, including femoropopliteal PTA. 8'9 The application of hot tip laser angioplasty to the more advanced lesions in this patient population was a logical challenge for us and one that has been thoughtfully pursued, so clearly the results presented herein are disconcerting. Although preliminary treatment with the hot tip laser has the potential of making more vessels with totally occluded or diffusely stenotic lesions amenable to PTA, in our series that potential has not been realized with an acceptable degree of success. The results of this series are substantially inferior to our experience with conventional femoropopliteal PTA 8,9 and do not measure up to results achieved with femoropopliteal bypass grafting, even if one compares this laser experience in its infancy with bypass grafting performed 30 to 40 years ago, essentially its infancy.ls Conversely, the potential of this technique should not be dismissed out of hand. The message from our experience is that much remains to be learned about the application of laser energy in the treatment of peripheral vascular disease. Outstanding questions concerning proper patient selection, length and nature of the lesions to be treated, and appropriate forms, doses, and methods of delivery of laser energy, such as newer probe designs, remain to be defined. Until these issues can be more thoroughly studied, the widespread application of laser probe angioplasty as a "routine" method of treating patients with peripheral arterial disease cannot be justified; nor can the excessive enthusiasm encountered in some segments of the population and stimulated by some members of the medical profession be condoned. REFERENCES
1, Ktmlin J. Le traitement de l'arterite obliterante par la graffe venieuse. Arch Mal Coeur 1949;42:371-2. 2. Linton RR, Darling RC. Autogenous saphenous vein bypass grafts in femoropopliteal obliterative arterial disease. Surgery 1962;51:62-73. 3. DeWeese JA, Baruer HB, Mahoney EB, Rob CG. Autogenous venous bypass grafts and thromboendarterectomies for atherosclerotic lesions of the femoropopliteal arteries. Ann Surg 1966;163:205-14. 4. Valhnar J, Trede M, Clair B, Laubach K, Forrest H. Principles
o f reconstructive procedures for chronic femoropop]iteal oc-
5,
6.
7.
8.
9.
10.
11. 12.
13.
14.
15.
16.
17. 18.
clusions: report on 546 operations. Ann Surg 1968;168:21523. Darling RC, Linton RR, Razzuk MA. Saphenous vein bypass grafts for femoropopliteal occlusive disease: a reappraisal. Surgery 1967;61:31-40. Leather RP, Shah DM, Chang BB, Kaufman JC. Resurrection of the in situ saphenous vein bypass: 1000 cases later. Ann Surg 1988;208:435-42. Doubilet P, Abrams HL. The cost of tmderutilization: percutaneous transluminal angioplasty for peripheral vascular disease. N Engl I Med 1984;310:95-102. Hewes RC, White RI Jr, Murray RR, et al. Long term results of superficial femoral artery angioplasty. M R 1986;146: 1025-9. Murray RR, Hewes RC, White RI lr, et al. Long segment femoropopliteal stenoses: is angioplasty a boon or a bust? Radiology 1987;162:473-6. Choy DSI, Stertzer S, Rotterdam HZ, Sharrock N, Kaminov IP. Transluminal laser catheter angioplasty. Am I Cardiol 1982;50:1206-8. Gunby P. "PooP' goes the plaque with experimental laser angioplasty. JAMA 1983;250:3135-41. Ginsberg R, Wexler L, Mitchell R, Profitt D. Percutaneous transluminal laser angioplasty for the treatment of peripheral vascular disease: clinical experience with 16 patients. Radiology 1983;156:619-24. Abeta GS, Norman S, Cohen D, Feldman RL, Geiser EA, Conti CR. Effects of carbon dioxide, Nd-YAG, and argon laser radiation on coronary atheromatous plaques. Am I Cardiol 1982;50:1199-205. Choy DS, Stertzer SH, Rotterdam HZ, Bruno MA. Laser coronary angioplasty: experience with 9 cadaver hearts. Am I Cardiol 1982;50:1209-11. Lee G, Ikeda RM, Kozina l, Mason DT. Laser dissolution of coronary atherosderotic obstruction. Am Heart J 1981; 102:1074-5. Choy DSJ, Stertzer SH, Myler ill(, Mareo J, Fortmial G. Human coronary laser recanalization. Clin Cardiol 1984; 7:377-81. Gerschwind H, Boussignac C, Teisseire B, et al. Percutaneous transluminal laser angioplasty in man. Lancet 1984; 1:844. Lee G, Reis RL, Bossan MD, et al. Laser recanalization in severe end-stage peripheral vascular disease. Am I Cardiol
1987;59:386-7. 19. Chutorian-Murphy D, Seizer P, Wexler L, Ginsberg R, Pracrical issues in laser angioplasty: a new technique, Contemp Surg 1985;27:13-20. 20. Steismann GV, Kahn D, Rose AG, Bornman AC, Terblanche J. Endoscopic laser endarterectomy. Surg Gynecol Obstet 1984;158:529-34. 21. Lee G, Ikeda RM, Theis IH, et al. Acute and chronic complications of laser angioplasty: vascular wall damage and formarion of aneurysms in the atherosclerotic rabbit. Am J Cardiol 1984;53:290-3. 22. Lee G, Ikeda RM, Chan MC, et al. Desolurion of human athersclerotic disease by fiber optic laser-treated cautery cap. Am Heart I 1984;107:777-8. 23. Sanborn TA, Faxon DP, Hudenschild CC, Ryan TJ. Laser radiation of atherosclerotic lesions: decreased incidence of vessel perforation with a fiberoptic laser heated metallic tip [Abstract]. J Am Coil Cardiol 1984;3:490.
Volume i0 Number 3 September 1989
24. Abela GS, Norman SJ, Cohen D, et al. Laser recanalization of occluded arteriosclerotic arteries: an in vivo and in vitro study. Circulation i985;71:403-1i. 25. Sanborn TA, Faxon DP, Haudenschild CC, Ryan TI. Experimental angioplasty: circumferential distribution of laser thermal energy with a laser probe. I Am CoIl Cardiol I985;5:934-8. 26. Abela GS, French A, Crea F, Conti CR. "Hot tip": another method of laser vascular recanalization. Lasers Surg Med 1985;5:327-35. 27. Sanborn TA, Greenfield AJ, Guben JK, Menzoian IO, LoGerfo FW. Human percutaneous and intraoperative laser thermal angioplasty: initial clinical results as an adjunct to balloon angioplasty, l VASC SUV,G 1987;5:83-90.
Femoropopliteallaserprobe angioplasty
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28. Cumberland DC, Taylor DI, Welsh CL, et al. Percutaneous laser thermal angioplasty: initial clinical results with a laser probe in total peripheral arterial occlusions. Lancet 1986; 1:1457-9. 29. Sanborn TA, Cumberland DC, Greenfield AJ, Welsh CL, Guben JK. Percutaneous laser thermal angioplasty: initial resuits and i year follow-up in 129 femoropopliteal lesions. Radiology 1988;168:121-5. 30. Abela GS, Seeger JM, Barbieri E, et al. Laser angioplasty with angioscopic guidance in humans. J Am Coll Cardiol 1986; 8:184-92.
For nearly 40 years after its introduction saphenous vein femoropopliteal bypass grafting has remained an optimal method for treating superficial femoral artery occlusive disease, and it remains the "gold standard" against which other treatment modalities should be judged. 1 Even during its earliest years of application initial success rates of 72% to 100% were reported from many centers. 2-4 In one of the first long-term follow-up studies, 5-year patency of 76% was reported for saphenous vein femoropopliteal bypass grafting performed between 1954 and 1965. ~Contemporary reviews have continued to document such favorable results. 6 Despite this record, alternative techniques to revascularize the ischemic limb continue to be pursued to spare the patient the risks of an open surgical procedure. We are currently seeing the rapid development of new technology aimed at treating arterioFrom the Departments of Surgery~ and Radiology,b The Johns Hopkins Hospital. Presented at the Thirteenth AnnualMeetingof the SouthernAssociation for Vascular Surgery, Key West, Fla., Jan. 25-28, 1989. Reprint requests: BruceA. Perter,MD, Divisionof Vascular Surgery, Department of Surgery, The Johns Hopkins Hospital, 600 N. Wolfe St., Baltimore,MD 21205. 24/6/13656
sclerotic disease. For example, percutaneous transluminal angioplasty (PTA) has clearly assumed an important role in the treatment of large numbers of patients with peripheral vascular disease. 7 In our institution femoropopliteal PTA has achieved a 4-year patency of 54% for stenotic lesions and patency of 73% for focal occlusions. 8 However, PTA has its limitations. Initial f~Liluresand early recurrent lesions are most likely to occur in vessels with diffusely stenotic lesions and longer total occlusions. 9 This shortcoming and the inability of the guide wire to cross highly calcified total occlusions in some patients have stimulated interest in laser ablation of atherosclerotic occlusive femoropopliteal lesions. 1° The concept of laser ablation of atherosclerotic disease has generated great expectations among the public and has received enthusiastic coverage in the lay press. However, although laser angioplasty has been studied extensively in the laboratory, little objective clinical data are available to evaluate its potential. Therefore the present time seems appropriate to assess whether those expectations are being met and whether that enthusiasm is justified. This article will document our initial experience with percutaneous laser probe "hot tip" angioplasty for femoropopliteal occlusive disease. 351
Journal of VASCULAR SURGERY
352 Perter et al.
Table I. Indications for laser angiophsty
Table II. Length of lesions treated
Indication
No.
%
Length of lesion
No.
%
Clandication Nonhealing ulcer Rest pare Gangrene Total
29 6 1 _~1 37
78% 16% 3% 3% 100%
~<3 cm 4-7 cm > 7 cm Total
5 18 2_44 47
11% 38% 51% 100%
PATIENTS AND METHODS
Laser equipment and protocol
From March 1986 through July 1988 percutaneous laser probe hot tip angioplasty procedures were performed on 47 occluded femoropopliteal artery segments in 37 patients. Twenty-nine patients underwent a single procedure; the same vessel was treated twice in three patients and three times in two patients, and bilateral procedures were performed on three patients. Participants included 27 men and 10 women ranging in age from 31 to 92 (mean, 64.7) years. Seventy percent of the patients were over 60 years old, and 27% were over 70 years of age. Risk factors for atherosclerosis were common, including cigarette smoking in 63%, hypertension in 46%, diabetes mellitus in 37%, and hypedipidemia in 9%. The indications for treatment are noted in Table I. The 29 patients with claudication had experienced symptoms for 1 to 60 (mean, 19.2) months before referral, including 72% who had experienced symptoms for more than 6 months, 52% for more than 1 year, 24% for more than 2 years, and 20% for more than 3 years. Seventy-seven percent of the patients with claudication experienced symptoms after walking less than two blocks and 48% after walking less than one block. Eleven (30%) of the 37 patients had undergone previous peripheral vascular operations including carotid endarterectomy in two (6%), a lower extremity inflow procedure in two (6%), and an infrainguinal reconstruction in seven (19%) (two of which were performed on the side of the laser angioplasty). Four patients (11%) had undergone previous coronary bypass surgery. Forty-five lesions were located in the superfF cial femoral artery (with or without extension into the popliteal), and two lesions were limited to the popliteal artery. The lesions ranged from 3 to 30 cm in length (Table II). Runoff occurred in three vessels in 26% of the cases, two vessels in 32% of the cases, and one vessel in 39% of the cases. Runoff occurred in an isolated popliteal segment in 3% of the cases. Significant inflow disease was excluded in
The laser probe (Model 900, Trimedyne Inc., Santa Ana, Calif.) with a 400 ~m core diameter was coupled to an 8 W argon laser. The argon laser light travels down a fiberoptic fiber to heat a metal alloy tip (1 to 2 mm diameter), and the heat is distributed circumferentially inside the vessel. The protocol for this series was approved by the Joint Committee for Clinical Investigation of The Johns Hopkins Medical Institutions. After written informed consent was obtained, the procedure was performed via percutaneous antegrade puncture of the femoral artery with the patient under local anesthesia in a catheterization suite within the radiology, department. One patient with multiple previous groin operations required a femoral artery cutdown for sheath placement. The laser-heated probe was advanced through an 8F introducer sheath or guiding catheter to the obstructing lesion, and the patient was given 5000 units ofheparin intraarterially. Repetitive 2-second pulses of 2 to 8 W of argon laser energy were delivered during normal blood flow as the probe was advanced until vessel patency was documented angiographically. Progression of the probe through the lesion was monitored fluoroscopically (General Electric, LUA System, Milwaukee, Wis.) with small injections of contrast material. Three to 5 seconds were allowed to elapse between laser pulses. After the lumen had been established, the laser probe was removed and a standard balloon angioplasty procedure was carried out with 5 to 6 mm balloons and conventional techniques as previously described.8'9 A completion arteriogram was obtained, the catheter and sheath were removed, and systemic heparin infusion was continued for 24 hours, unless a hematoma formed or bleeding precluded this. Patients were placed on 325 mg aspirin per day and 75 mg dipyridamole three times a day, underwent Doppler ankle/brachial examination, and were usually discharged 24 to 48 hours after the procedure. The patients were seen as outpatients 2 weeks after the procedure, and then usually at 3-month intervals, at which time complete histories, physical examina-
all cases.
Volume 10 Number 3 September 1989
Femoropopliteallaserprobe angioplasty 353 100
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MONTHS
Fig. 1. Fifteen-month patency data for successfullylased vessels and all vessels treated.
Table III. Failures versus length of lesions treated Length of lesion (cm)
No. treated
Failed to recanalize (%)
<3 4-7 >7 Total
5 18 2_.44 47
2 (40%) 3 (17%) 9 (37%) 14 (30%)
tions, and Doppler ankle/brachial examinations were performed. Reocclusion of the treated segment was defined by a recurrence of symptoms and return of Doppler ankle/brachial index to pretreatment levels. An initial failure was defined by inability to successfully recanalize the entire diseased segment, or successful recanalization with reocclusion occurring before hospital discharge. All early and most late reocclusions were confirmed angiographically. RESULTS Twenty-one (45%) of the 47 procedures in 17 patients were initially unsuccessful. In 14 (30%) of the procedures the lesion could not be completely recanalized, and in seven (15%) the lesionwas successfi~y recanalized and dilated but became reoceluded during the hospitalization, almost always within 24 hours. Excepting the small number of 3 cm occlusions, initial failures tended to correlate with the length of the lesion treated (Table III). No correlation existed between success rate and the status ofrunoffvessels. Based on angiographic appearance, Doppler anlde/brachial indices, and symptoms, the
Recanalize early reocclusion (%) 0 3 4 7
(0%) (17%) (17%) (15%)
Failed (%) 2 6 13 21
(40%) (33%) (54%) (45%)
condition of seven (41%) of these 17 patients was worse after the failed procedure. Three (18%) of these patients underwent femoropopliteal bypass grafting within 1 month of the laser procedure. Conversely, 26 (55%) of the procedures in 22 patients were completed successfully. Among this group 17 (65%) lesions in 15 patients reoccluded from 1 to 14 (mean, 31/2) months after the procedure. Lifetable analysis for the lesions that were initially successfully treated yielded patency rates of 69% at 1month, 38% at 6rnonths', 29% at 12 months', and 14% at 15 months' follow-up (Fig. 1). Three (20%) of these 15 patients underwent femoropopliteal bypass grafting, and two (13%) underwent a standard PTA after the lased artery reoccluded. However, if one considers all vessels treated in the life-table analysis, patency was only 33% at 1-month, 18% at 6 months', 14% at 12 months', and 7% at 15 months' follow-up (Fig. 1). Eighteen complications were noted after 15 (32%) of the 47 procedures (Table IV). Surgical exploration was required only for an acute femoral artery hemorrhage. One femoral false aneurysm was
journal of
VASCULAR
354 Perler et al.
SURGERY
Table IV. Complications Complication
Pulmonary embolus Groin hematoma Retroperitoneal hematoma Distal thromboemboli False aneurysm Acute femoralhemorrhage Superficialfemoral artery arteriovenous fistula Vasovagal: hypotension Total
No.
1 7 1 5 1 i 1 1 18 (32%)
electively repaired at the time of femoropopliteal bypass grafting, and a femoral arteriovenous fistula sealed spontaneously. Four patients who experienced distal thromboemboli were successfully treated with brief local infusions ofurokinase, and in a fifth patient this complication resolved on systemic heparin therapy. No patient required emergency surgery for an ischemic complication. No limb or digit loss or deaths occurred in this series. O f note, angiographically documented asymptomatic arterial perforations occurred during 14 (30%) of the laser procedures. In four (29%) of these cases the procedure was completed successfully despite the perforation. Perforations occurred during 44% of the procedures performed in our initial year but in only 26% of the procedures performed subsequently.
DISCUSSION Learning period Many patients experience significant ischemic symptoms caused by fairly limited arteriosclerotic arterial lesions, and PTA has been very effective in their treatment. Those patients with lesions too extensive to be treated by PTA usually require surgical reconstruction. The desire to extend the limits of conventional PTA and thus avoid open surgical reconstruction in some of these patients has stimulated great interest in the development of other nonoperative techniques for treating such patients. The application of laser energy to this clinical challenge is one such logical approach. The theoretic advantage of laser angioplasty is that it can debulk the atherosclerotic lesion rather than simply crack the plaque or stretch the host artery as occurs in standard balloon angioplasty procedures? 2
Physical properties of laser Extensive in vitro research has confirmed that laser radiation in the infrared and the visible ranges can ablate atherosclerotic plaque) 3-1s Other in vivo
studies showed that argon laser catheter thrombectomy was successful in dog and rabbit models. In 1984 Choy et al. 16 reported the first case of in vivo laser angioplasty of the coronary arteries at the time of bypass surgery. Gerschwind et al.17 reported the initial clinical experience with neodyniun:yttriumaluminum-garnet (Nd: YAG) laser recanalization of arteriosclerotic femoral and popliteal arteries, and recanalization of the profunda femoris artery with argon laser was also reported by Lee et al.la As a result of this and other studies, the argon laser emerged as the most widely used laser in human clinical trials. ~9 Argon laser energy has two major wavelength lines at 488 nm and 514 nm that pass easily through flexible glass fibers and water. It is strongly absorbed by hemoglobin but only poorly absorbed by plaque and normal artery wall. Therefore argon laser must be used either in a bloodless field or in very close proximity to the vascular lesion) 9 In a series of 16 patients with femoropopliteal arteriosclerotic lesions, Ginsberg et al. ~2 achieved patency or improvement in luminal diameter in only 50% of cases when they used a bare-fiber argon laser, despite its promise. In three of these 16 patients the laser perforated the arterial wall. ~2 Other clinical and experimental studies have documented a substantial inddence of arterial wall perforation and late aneuwsm formation after bare-fiber laser treatment. 16,18,2°,2~ The argon-heated metal probe hot tip laser was introduced in an attempt to reduce this incidence of arterial wall perforation. 22,23The theoretic advantages of using a laser-heated metal cap are the absence of beam dispersion, less mechanical trauma, consistency of thermal energy delivered, and the ability to vary the size of the metal probe and thus the diameter of the channel created, since recanalization is accomplished only by direct tissue contact as opposcd to both light absorption and direct tissue contact when a bare fiber is used. Furthermore, the laser-heated metal cap fiber heats and cools rapidly, thus reducing adherence of the cap to the local tissue. 24,25Experimental work has shown the argon hot tip fiber to be more effective in recanalizing occluded vessels with less risk of perforation of the normal artery than the argon bare-fiber technique? 6
Reported clinical experience Clinically, the hot tip has been used in most centers as an adjunct to standard PTA, rather than as the sole therapeutic intervention. After the laser creates a channel through an occluded or diffusely stenotic segment of an artery, the arterial lumen is then enlarged by conventional balloon dilation. 8,9 In the
Volume i0 Number 3 September 1989
initial Food and Drug Administration-approved clinical study of this technique in the United States, Sanborn et al. at Boston University reported an initial success rate of 80% (I2 of 15 vessels). Furthermore, i0 (83%) of these 12 vessels remained patent at a mean follow-up of 6 months. 27 Cumberland et al.28 at Sheffield, England, and Sanborn et al.29 have continued to report excellent results with this technique in a combined series of patients from their respective centers. For example, most recently they have documented a i-year patency of 77% and suggested that the laser-heated metal tip may allow PTA to be successfully performed on vessels that previously were too extensively diseased for this procedure.29
Future expectations Despite a fairly limited clinical experience with laser angioplasty, there has been an overwhelming public awareness of and enthusiasm for the potential to treat peripheral vascular disease with lasers. The " P o o p goes the plaque with experimental laser angioplasty"n kind of article epitomizes our patients' understandable desire to achieve relief of symptoms of ischemia in a relatively painless "high technology" fashion. Therefore the present time seemed appropriate to question whether this public enthusiasm is justified by ongoing clinical experience. This article would suggest that it is not. Very simply, three fundamental questions need to be addressed to place the technique of laser angioplasty in perspective: Is laser probe femoropopliteal angioplasty safe; is it effective; and are the results durable? Our data would suggest that the hot tip procedure is relatively safe. Although a careful analysis of this experience documented complications after nearly one third of the procedures, urgent surgical intervention was required in only one case (Table IV). As noted, laser arterial perforations occurred in 30% of the procedures. Clearly there is a learning curve inherent in this technique, since the rate of perforation was 44% for our first 16 cases and dropped to 26% for the subsequent 31 proce~tures. We would agree with others that this is a fairly benign occurrence, and in fact in four of our cases it did not preclude completing the procedure successfully. However, on the basis of the other key questions, namely the efficacy and durability of laser angioplasty, we would have to argue that the exact role of this technique in the treatment of peripheral arterial occlusive disease remains to be defined and presently seems to be somewhat overrated. Nearly one half of the procedures performed at this institution were deemed unsuccessful by the time of discharge from
Femoropopliteallaserprobe angioplasty 355 the hospital. Furthermore, the condition of 41% of these patients was made worse by the failed procedure, including three (18%) who had femoropopliteal bypass grafting within 1 month. The substantial attrition rate we observed in arteries that were initially successfully treated was even more disconcerting. One-year patency for these vessels was 29%, and if one considers all vessels treated (including initial failures) it was 14% (Fig. 1). These data conflict somewhat with the results of others, although the reasons are not immediately apparent? 9 It would seem that patient and lesion selection have an important bearing on eventual results. Seventy percent of our patients were over the age of 60 years, and more than one quarter of them were older than 70 years. More than half of our patients with clandication had experienced symptoms for more than 1 year, and 48% of them experienced symptoms after walking less than one block. These observations suggest that we were treating significantly advanced, well-established occlusive disease, and in fact 51% of the lesions treated were greater than 7 cm in length (Table !I). In other words, we have been lasing the longer lesions that were generally considered to be beyond the scope of standard PTA, whereas other centers may be lasing lesions that could also be treated by conventional balloon dilation. Furthermore, whereas others have been treating stenotic as well as total occlusive lesions with the hot tip technique, all the lesions treated in our series were essentially total occlusions.27"29 Even if one can achieve satisfactory initial success rates with the hot tip laser, thus sufficiently fulfilling the "effectiveness" question, we feel that the durability issue may still remain a crucial problem. Although the patient population and type of lesions treated arc not strictly comparable, the 1-year patency of vessels that undergo PTA after an initial channel is created by the hot tip laser is distinctly inferior to patency achieved in vessels treated only by PTA in our center. 8,9 That observation, in addition to the relatively early onset of vessel reocclusion (mean, 3 V2 months), raises the possibility of laser thermal injury at the time of the procedure itself as a potential etiologic factor in tb.is early reocclusion phenomenon. Histologic studies have documented charring along the luminal surface after hot tip dissolution of atherosclerotic plaque. 26'3° Therefore the potential thrombogenicity of this residual luminal surface is a real concern. This might explain, at least in part, the inferior results we noted in attempting to recanalize totally occluded vessels, where more atheromatous bulk is to be lased, as opposed to those vessels with
356
Journal of VASCULAR SURGERY
Perler et al.
diffuse stenoses. 27-29Excluding the small number of 3 cm occlusions, we did note a trend correlating failure rate with the absolute length of the lesion treated (Table III), as others have observed. 29 Our institution has a long history of interest and leadership in the field of interventional radiology. The angiographers, working in collaboration with the vascular surgeons, have achieved consistently outstanding results in a number of areas, including femoropopliteal PTA. 8'9 The application of hot tip laser angioplasty to the more advanced lesions in this patient population was a logical challenge for us and one that has been thoughtfully pursued, so clearly the results presented herein are disconcerting. Although preliminary treatment with the hot tip laser has the potential of making more vessels with totally occluded or diffusely stenotic lesions amenable to PTA, in our series that potential has not been realized with an acceptable degree of success. The results of this series are substantially inferior to our experience with conventional femoropopliteal PTA 8,9 and do not measure up to results achieved with femoropopliteal bypass grafting, even if one compares this laser experience in its infancy with bypass grafting performed 30 to 40 years ago, essentially its infancy.ls Conversely, the potential of this technique should not be dismissed out of hand. The message from our experience is that much remains to be learned about the application of laser energy in the treatment of peripheral vascular disease. Outstanding questions concerning proper patient selection, length and nature of the lesions to be treated, and appropriate forms, doses, and methods of delivery of laser energy, such as newer probe designs, remain to be defined. Until these issues can be more thoroughly studied, the widespread application of laser probe angioplasty as a "routine" method of treating patients with peripheral arterial disease cannot be justified; nor can the excessive enthusiasm encountered in some segments of the population and stimulated by some members of the medical profession be condoned. REFERENCES
1, Ktmlin J. Le traitement de l'arterite obliterante par la graffe venieuse. Arch Mal Coeur 1949;42:371-2. 2. Linton RR, Darling RC. Autogenous saphenous vein bypass grafts in femoropopliteal obliterative arterial disease. Surgery 1962;51:62-73. 3. DeWeese JA, Baruer HB, Mahoney EB, Rob CG. Autogenous venous bypass grafts and thromboendarterectomies for atherosclerotic lesions of the femoropopliteal arteries. Ann Surg 1966;163:205-14. 4. Valhnar J, Trede M, Clair B, Laubach K, Forrest H. Principles
o f reconstructive procedures for chronic femoropop]iteal oc-
5,
6.
7.
8.
9.
10.
11. 12.
13.
14.
15.
16.
17. 18.
clusions: report on 546 operations. Ann Surg 1968;168:21523. Darling RC, Linton RR, Razzuk MA. Saphenous vein bypass grafts for femoropopliteal occlusive disease: a reappraisal. Surgery 1967;61:31-40. Leather RP, Shah DM, Chang BB, Kaufman JC. Resurrection of the in situ saphenous vein bypass: 1000 cases later. Ann Surg 1988;208:435-42. Doubilet P, Abrams HL. The cost of tmderutilization: percutaneous transluminal angioplasty for peripheral vascular disease. N Engl I Med 1984;310:95-102. Hewes RC, White RI Jr, Murray RR, et al. Long term results of superficial femoral artery angioplasty. M R 1986;146: 1025-9. Murray RR, Hewes RC, White RI lr, et al. Long segment femoropopliteal stenoses: is angioplasty a boon or a bust? Radiology 1987;162:473-6. Choy DSI, Stertzer S, Rotterdam HZ, Sharrock N, Kaminov IP. Transluminal laser catheter angioplasty. Am I Cardiol 1982;50:1206-8. Gunby P. "PooP' goes the plaque with experimental laser angioplasty. JAMA 1983;250:3135-41. Ginsberg R, Wexler L, Mitchell R, Profitt D. Percutaneous transluminal laser angioplasty for the treatment of peripheral vascular disease: clinical experience with 16 patients. Radiology 1983;156:619-24. Abeta GS, Norman S, Cohen D, Feldman RL, Geiser EA, Conti CR. Effects of carbon dioxide, Nd-YAG, and argon laser radiation on coronary atheromatous plaques. Am I Cardiol 1982;50:1199-205. Choy DS, Stertzer SH, Rotterdam HZ, Bruno MA. Laser coronary angioplasty: experience with 9 cadaver hearts. Am I Cardiol 1982;50:1209-11. Lee G, Ikeda RM, Kozina l, Mason DT. Laser dissolution of coronary atherosderotic obstruction. Am Heart J 1981; 102:1074-5. Choy DSJ, Stertzer SH, Myler ill(, Mareo J, Fortmial G. Human coronary laser recanalization. Clin Cardiol 1984; 7:377-81. Gerschwind H, Boussignac C, Teisseire B, et al. Percutaneous transluminal laser angioplasty in man. Lancet 1984; 1:844. Lee G, Reis RL, Bossan MD, et al. Laser recanalization in severe end-stage peripheral vascular disease. Am I Cardiol
1987;59:386-7. 19. Chutorian-Murphy D, Seizer P, Wexler L, Ginsberg R, Pracrical issues in laser angioplasty: a new technique, Contemp Surg 1985;27:13-20. 20. Steismann GV, Kahn D, Rose AG, Bornman AC, Terblanche J. Endoscopic laser endarterectomy. Surg Gynecol Obstet 1984;158:529-34. 21. Lee G, Ikeda RM, Theis IH, et al. Acute and chronic complications of laser angioplasty: vascular wall damage and formarion of aneurysms in the atherosclerotic rabbit. Am J Cardiol 1984;53:290-3. 22. Lee G, Ikeda RM, Chan MC, et al. Desolurion of human athersclerotic disease by fiber optic laser-treated cautery cap. Am Heart I 1984;107:777-8. 23. Sanborn TA, Faxon DP, Hudenschild CC, Ryan TJ. Laser radiation of atherosclerotic lesions: decreased incidence of vessel perforation with a fiberoptic laser heated metallic tip [Abstract]. J Am Coil Cardiol 1984;3:490.
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24. Abela GS, Norman SJ, Cohen D, et al. Laser recanalization of occluded arteriosclerotic arteries: an in vivo and in vitro study. Circulation i985;71:403-1i. 25. Sanborn TA, Faxon DP, Haudenschild CC, Ryan TI. Experimental angioplasty: circumferential distribution of laser thermal energy with a laser probe. I Am CoIl Cardiol I985;5:934-8. 26. Abela GS, French A, Crea F, Conti CR. "Hot tip": another method of laser vascular recanalization. Lasers Surg Med 1985;5:327-35. 27. Sanborn TA, Greenfield AJ, Guben JK, Menzoian IO, LoGerfo FW. Human percutaneous and intraoperative laser thermal angioplasty: initial clinical results as an adjunct to balloon angioplasty, l VASC SUV,G 1987;5:83-90.
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28. Cumberland DC, Taylor DI, Welsh CL, et al. Percutaneous laser thermal angioplasty: initial clinical results with a laser probe in total peripheral arterial occlusions. Lancet 1986; 1:1457-9. 29. Sanborn TA, Cumberland DC, Greenfield AJ, Welsh CL, Guben JK. Percutaneous laser thermal angioplasty: initial resuits and i year follow-up in 129 femoropopliteal lesions. Radiology 1988;168:121-5. 30. Abela GS, Seeger JM, Barbieri E, et al. Laser angioplasty with angioscopic guidance in humans. J Am Coll Cardiol 1986; 8:184-92.