- Email: [email protected]
Mechanical rotational atherectomy
Mechanical
Rotational William W. O’Neill,
Percutaneous transiuminai coronary an@opiasty (PEA) is practii wideiy in the United States and is indiied for the majority of stenosed vessels that have de novo, type A lesions. Despite extensive experience with the procedure and improvements in balloon technology, periprocedurai diiion and restenosis remain major iimRations of PTCA. Research indicates that certain iesion types and patient populations may be treated more efkctiieiy with other technologies. New mechanical devices have been desiined to help improve the safety of PTCA and hoid promise for correcting coronary diiion and abrupt closure-the sources of such angiopiasty complications as myocardiii infarction, urgent bypass surgery, and death. Among the resutts achieved with the new atherectomy techniques are a more stable lumen after atherectomy; a decrease in elastic recoil; a smoother, less thrombogenic lumen; and the feasibility of extensive debuiking or endarterectomy. Experience indicates that mechanical rotational atherectomy will be an extremely useful addition to the armamentarium for percutaneous revascuiarizatin. (Am J Cardiii 1992;69zlZF-lSF)
From the Division of Cardiology, Department of Internal Medicine, William Beaumont Hospital, Royal Oak, Michigan. Address for reprints: William O’Neill, MD, Cardiology Division, William Beaumont Hospital, 3601 W. 13 Mile Road, Royal Oak, Michigan 48072.
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Atherectomy MD
ith the vast experience, easy applicability, and excellent safety record of balloon angioplasty, it is unlikely that any percutaneous revascularization modality will supersede this technology in general use. However, new devices must be used to overcome the problems and deficiencies of angioplasty. These problems include a persistent rate of coronary dissection, coronary restenosis, poor efficacy in total coronary occlusions, poor results in elastic lesions, and lesions too stenotic to penetrate successfully. Atherectomy clearly can assist in overcoming some of those problem areas. Research indicates that the subgroups in which atherectomy shows promise include lesions that are elastic or too rigid to dilate, lesions that are complex and at high risk for dissection, restenosis lesions, and ostial lesions. Further study using mechanical rotational atherectomy to partially debulk diffusely diseased vessels also is needed. Among the advantages of atherectomy are a stable lumen after the procedure, a decrease in elastic recoil, and a smoother, less thrombogenic lumen. Our experience indicates that mechanical rotational atherectomy will be extremely useful in percutaneous revascularization.
W
PERCUTANEOUS TRANSLUMINAL ANGIOPLASTY
CORONARY
Percutaneous transluminal coronary angioplasty (PTCA) has achieved widespread clinical acceptance in the United States. The technique allows effective treatment of patients with coronary artery disease without the surgical procedure entailed by coronary artery bypass grafts. It has surpassed coronary artery bypass surgery in procedural volume in the United States. Despite its widespread use, PTCA has major limitations and is not optimal therapy for some types of lesions. Several other types of catheter-delivered implements have been designed to address these limitations. PTCA is still indicated for diseased vessels that have de novo, type A lesions. However, certain lesion types and patient populations may be treated more effectively with other technologies. MAY 7, 1992
Procedural safety of PTCA: Periprocedural abrupt closure is the most serious complication of PTCA. Despite extensive experience with the procedure and improvements in balloon technology, the incidence of this complication has remained steady at 2-5%.i The recently published National Heart, Lung, and Blood Institute registry documented a 6.8% incidence of periprocedural abrupt occlusion among 1,801 patients, and 4.7% incidence among 2,891 1esions.r The incidence of occlusion in the catheterization laboratory was 4.9%; the incidence of postprocedure occlusion was 1.9%. Several demographic factors were associated with increased risk for periprocedural occlusion; it occurred at a 9.9% rate in 312 patients with acute coronary insufficiency, compared with a 6.0% rate in patients without this condition (p <0.05). Other factors significantly associated with periprocedural occlusion were 3-vessel disease (9.8% incidence in 367 patients, compared with 6.1% for 2-vessel and 6.0% for l-vessel disease), and inoperable or highrisk surgical status (12.3% incidence in 138 patients compared with 6.3% in other patients). Lesion factors significantly associated with periprocedural occlusion included stenosis of r 90% vessel diameter, diffuse or multiple discrete disease, lesions in segments supplying collaterals, and evidence of thrombus or calcification. Intimal tears occurred in 780 of 2,882 lesions (27%) and extensive dissection occurred in 89 of 2,891 lesions (3%).l These procedural events were most significantly associated with occlusion. Occlusion occurred in 9.9% of patients with intimal tears compared with 2.7% of others (p
periprocedural occlusion. In this study, we examined the balloon inflation rate to test the hypothesis that rapid balloon inflation increases the risk of dissection. In this randomized trial, no significant difference in dissection rates was found between gradual balloon inflation over 30 seconds and rapid balloon inflation in <5 seconds in 142 lesions. However, the association of dissection with complex lesion morphology was highly significant (p = 0.00001); dissection occurred in 33% (S/24) of type A lesions, 63% (57/91) of type B lesions, and 96% (26/27) of type C lesions. Periprocedural occlusion, or even the temporary occlusion resulting from balloon inflation, can result in hemodynamic collapse. This event can be especially dangerous to individuals who have poor ventricular function or a single remaining patent coronary conduit. A multicenter study indicates that the morbidity and mortality associated with PTCA in such high-risk patients can be reduced with the addition of cardiopulmonary bypass to the procedure.3 In 105 patients with an ejection fraction < 25% or a target vessel supplying > 50% at the myocardium, the overall hospital mortality rate was 7.6%. This rate was only 2.6% in patients who were younger than age 75 and not affected by left main coronary artery stenosis. The mortality rate was 60% for patients with abrupt occlusion after discharge from the catheterization laboratory. Thus, dissection and abrupt occlusion are most dangerous in high-risk patients. In these patients, it is imperative that an optimal angiographic result be achieved. PTCA has a number of benefits. Overall, it has extremely low rates of mortality and need for emergency bypass surgery. Elective cases also are associated with extremely high successrates. PTCA also is a simple procedure. An ongoing study of the procedure at William Beaumont Hospital4 indicates that conventional postprocedure heparin therapy may be eliminated with no detrimental effect on patient outcomes. In 200 patients (of a planned 400), 22% of patients in the no-heparin group have been able to go home on the day of the procedure, and a total of 42% have gone home within 24 hours. Thus, PTCA remains an important and appropriate procedure for the majority of lesions. Yet, it falls short of optimal therapy in many cases involving complex morphology or high-risk patients. Limiting factors in PTC& Coronary restenosis is a second major limitation of PTCA. Many factors contribute to the incidence of restenosis and some of these factors are inherent in PTCA. Up to 30% A SYMPOSIUM: COMPLEX ANGlOPtASTY
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FlGURE l. The Auth h&h-speed cotary atherectomy device. A brass burr coated wlth dlamond chips is welded to a drive shaft that is cotated at h&b speed. The dsvka Is inserted over a gulds wire, and placement is dbected by fluorooCOPY-
investigators initially supported coronary laser angioplasty in the late 1970~,~high rates of perforation and thrombosis dampened enthusiasm for this treatment modality. Others began to investigate the feasibility of mechanical peripheral and coronary atherectomy.7-9 Among the results achieved with the new atherectomy techniques are a more stable lumen after atherectomy; a decrease in elastic recoil; a smoother, less thrombogenic lumen; and the feasibility of extensive debulking or endarterectomy. Mechanical rotational atherectomy: Auth et al have developed a high-speed rotary atherectomy device inserted over a guide wire and directed with fluoroscopy.s The device consists of a brass burr coated with diamond chips measuring 30-120 pm in diameter (Figure 1). Available in various sizes, the burr is selected to match the diameter of the MECHANICAL ATHERECTOMY The clinical need for improved technology was vessel being treated. The burr is welded to a drive recognized in the early 1980s. Although some shaft that is rotated by a turbine at high speeds.
of restenotic vessels exhibit elastic recoil, limiting the ability of the balloon to relieve the obstruction.5 The inflated balloon can also cause deep medial smooth muscle injury. This stimulates smooth muscle proliferation in the vessel, contributing to restenosis. Finally, PTCA leaves ragged, irregular lesions in the lumen, which stimulate platelet and fibrin deposition. Several other technical problems limit the efficacy of PTCA in certain cases. Current balloon and guide wire technology is unable to recanalize total coronary occlusions or fibrotic, elastic lesions such as those in ostial locations. Other lesions that are too severe, hard, or calcified may not allow passage of the balloon even after guide wire placement, and some rare lesions simply do not respond to balloon inflations.
FIGURE 2. The Rotablator (Heart Technolo@, Inc., Rellevue, WashIMton) operates at 1GO,OOO-l90,OOO rpm.
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Commercial models (e.g., Rotablator, Heart Technology, Bellevue, Washington) rotate at speeds of 160,000-190,000 rpm (Figure 2). The rotating burr selectively removes hard tissue, whereas soft tissue is deflected by the elastic recoil of normal segments of vessel. The device thus selectively ablates the firmer atherosclerotic plaque. The tissue is chipped off as microparticles and embolizes downstream. Microparticle embolization was an early concern with this device. When the device was tested on 68 cadaver arteries, however, the pulverized atheroma particles (in colloidal suspension) were generally smaller than red blood cells, and injection of the suspension into canine femoral arteries failed to produce tissue injury.* We further analyzed the impact of atheromatous microparticles on canine coronary blood flow and found no deleterious effects.lO In our experience with rotary atherectomy we have seen no significant adverse effects of microparticle embolization. A series of 39 patients treated at William Beaumont Hospital showed no impairment of regional function or ventricular wall motion with this device (Figure 3). In procedures involving the right coronary arteries or circumflex artery, bradycardia, transient complete heart block, or transient asystole is invariably seen. A recent multicenter studyll of percutaneous transluminal coronary rotational ablation in 315 patients reported no in-hospital deaths and a 95% rate of acute success ( < 50% residual stenosis). Of all lesions, 87% were complex (type B or C). Complications included myocardial infarction in 5.6% of patients and urgent coronary artery bypass graft in 1.6%. There were 26 cases (8.2%) of angiographic evidence of flap or dissection. Only one case required a coronary artery bypass graft.i* Percutaneous transluminal coronary rotational ablation also has shown excellent results in lesions
FIGURE 3. EJection fraction changes wlth mechanical rotational atherectomyemploylngtheRotablatorcatheter. The global eJectlon fraction In 39 patlents wasseflallyassessed treated. No deterloratlon In ventrlcular function was noted between studlesobtalwdatb-,at34 hours, and at 9 months post-catheterlzatlon. NS = difference not slgnlfhtant (ANOVA).
TABLE I Results of Mechanical Type C Lesions
Rotational
Outcome
MRA 01 = 27)
Successful Major cardiac event Emergency CABG Abrupt closure Death
26 (96%) 1 (3.7%) 1 (3.7%) 0 0
Ablation
of
PTCA (n = 196) 149 11 5 4 2
p
(76%) (5.6%) (2.6%) (2.0%) (1.0%)
Value
<0.03 NS NS NS NS
CABG = coronary bypass surgery; MRA = mechanical rotational ablation; NS = not significant; PTCA = percutaneous transluminal coronary angioplasty. I
L
that have unfavorable morphologic characteristics, including eccentricity, calcification, tortuosity, and location at a bifurcation.13 In our experience, type C lesions appear to be better treated with rotational ablation (Table I). Follow-up at 6 months in 94% of patients in the multicenter study showed a restenosis rate of 32%.11 The following have been identified as risk factors for coronary restenosis following rotation angioplasty: lesions in the left anterior descending coronary artery, ostial and proximal lesions, and lesions in saphenous vein bypass grafts.i4 The Rotablator may be useful in casesof restenosis after PTCA. Ostial lesions also are appropriate for mechanical rotational atherectomy treatment, as are heavily calcified lesions, diffusely diseased arteries, and lesions at bend points in the vessel. Heavily calcified lesions and lesions at bend points should not be treated with a transluminal extraction catheter or directional coronary atherectomy. Unlike balloon angioplasty, the high-speed rotary burr grinds atheroma into fine particles that pass harmlessly through the capillary circulation. Furthermore, rotary atherectomy leaves a smooth, polished intraluminal surface and no intimal flaps. Unlike the laser, its energy requirements are minimal, its machinery is trim, and it selectively removes rigid tissue such as calcified or fibrous
67.2
SASELIME
69.4
24 HOURS
l
6 MONTHS
f p = NS (ANovA)
A SYMPOSIUM:
COMPLEX
ANGIOPLASTY
15F:
atherosclerotic plaque, whereas rubbery or elastic tissue, such as the outer media, remains relatively uninjured.8 Despite these advantages, the Auth device needs further improvement. Investigators have identified problems with the guide wire that lead to perforation or inability to pass the guide wire past totally occluded arteries.8 The atherectomy burr is relatively ineffective for arteries completely occluded with chronic thrombus. Finally, large vessels cannot be completely treated by this device alone. Directional coronary atherectomy: Simpson and colleagues at Sequoia Hospital in Redwood City, California, have developed a technique called directional coronary atherectomy.15 The Atherocath is characterized by a cylindrical metal housing attached to the end of a braided double-lumen catheter. The cylindrical housing has a “longitudinal window” that can be positioned snugly against the atheroma with the help of a small balloon opposite the window. Inside the window, a rotating cutter blade shaves off atherosclerotic material and deposits it in the distal part of the metal housing. A
FlQURE 4. llw Bliimpson Coronary Atherocath
(John B.
l0 mm window runs along&e side and a balloonidong the opposite side. A cyilndrkal cutter wRhln the houhg Is powered by a hanckheld motor. Under fluoroscopy, the dlstal end of the catheter ls placed across tbs stenosls and the balloon ls Inflated to 30 psl to hold the houslm against the steno&. The motor ls turned on and the cutter Is advanced, shavle off any atberoma that protrudes Into the wlndow openlng. The shavings are pushed fowawl andthedevlcelsrepoandstoredlnaco&cUonchamber, addtthal passes. 4 before sltlowdforanynecessary atherectomy; 6, the Atherocath Is posltlonedi C, atheroma Is shaved and stored In tbe wlndow opening; 0, after atheWCtOlll&
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separate hand-held battery-powered motor drive is attached to a cable connected to the cutter blade. During a procedure, the Atherocath is advanced over the wire under fluoroscopic guidance (Figure 4). The window of the cylindrical housing is positioned across the stenosis. The positioning balloon is inflated, the attached motor drive is activated, and the cutter blade is slowly advanced through the metal housing, shaving off atheroma and depositing it distally. The positioning balloon is deflated, the catheter is torqued about 60-90” to reposition the window and to remove additional atheroma. When the collection chamber is full, the catheter is withdrawn from the patient and the cutter blade retracted into the proximal portion of the housing. Repeated passes are made until the desired result is achieved.16 Simpson and colleagues recently reported their experience in 502 procedures (578 lesions). I5 Patients’ mean age was 59 years and 42% had unstable angina. Sixteen of the procedures were performed as salvage for failed PTCA, and 55% of the lesions treated had been previously treated with angioplasty. The overall success rate was 88.2%, with individual vessel success rates ranging from 79% in the left anterior descending coronary artery (n = 279) to 100% in the diagonal artery (n = 3). A multicenter study of this techniqueI reported a 4.2% rate of abrupt closure (periprocedural stenosis) in 1,018 procedures (1,138 lesions), a rate roughly comparable to the rates seen with PTCA and mechanical rotational atherectomy. Among the risk factors identified were right coronary artery lesions, de novo lesions, and eccentric lesions. Abrupt closure was less frequent during procedures on saphenous vein grafts. The Sequoia group investigated the effect of angiographic risk factors on the outcome of directional coronary atherectomy in a series of 499 lesions in 441 procedures.18 The overall success rate was 88% per lesion (87% per procedure). The investigators evaluated several risk factors for their effect on patient outcome, including lesion eccentricity, abnormal contour, ostial location, and length > 10 mm. Only calcification and difise disease were significantly associated with failed procedures. In 211 successfully treated lesions followed up angiographically at 3-12 months (or earlier if symptoms recurred), the overall restenosis rate was 36%: 29% (24/82) for de novo lesions and 40% (52/129) for restenosis lesions.19 Factors significantly associated with restenosis were lesion length > 10 mm, vessel diameter < 3 mm, and overdilation.lg This group has also used directional coroMAY 7, 1992
nary atherectomy successfully in rescue procedures for failed PTCA (success in 87% of 30 patients)20 and in saphenous vein graft lesions (91% success rate in 87 lesions). 21However, restenosis rates are high in vein graft lesions, especially those treated previously with PTCA. Appropriate indications for directional coronary atherectomy include ostial lesions and focal lesions. De novo lesions can be treated effectively and have a very low risk of restenosis. Highly eccentric lesions in the left anterior descending artery are well suited to directional coronary atherectomy. Directional coronary atherectomy is also effective as a bailout device for discrete occlusive flaps present after PTCA. Heavily calcified lesions and lesions at bend points should not be treated with directional coronary atherectomy. Transluminal extraction catheter: Another type of intraluminal catheter atherectomy device is the transluminal extraction catheter, which allows the transluminal extraction of atherosclerotic plaque, thus reducing the risks of downstream embolization and leaving a smooth, undissected lumen.7 It consists of a rotary cutting device advanced over a 0.014 inch PTCA guide wire (Figure 5). The flexible torque tube device is introduced percutaneously and tracks over the flexible steerable guide wire under fluoroscopic control. When the radiopaque tip is properly positioned near the origin of the lesion, a 2-stage trigger is activated on the hand-held control piece. The conical cutter rotates at 750 rpm while suction is applied through the opening of the cutting window to extract the plaque fragments through the catheter and out of the patient’s body. I5 The device is well suited for large, bulky lesions with extensive intraluminal thrombus. Stack et al9 demonstrated the safety and efficacy of the device in reducing stenosis and increasing
FIGURE 5. Stack Ransluminal Extractlon Catheter (Interventlonal Technologies, San Dlego, California). Uke the Auth device, this device also travels along a gWde wire and uses a vacuum to extract mkropartlcles and prevent patilculate embollzatlon. Potential advantages Include the lack of dlstal partleulate embellzatlen and the ablllty ofthe devke to extract atheromatous material tihout changing the catheter houslng during the prccedure.
flow in peripheral vascular disease. They treated 71 atherosclerotic lesions during 41 procedures in 41 extremities of 36 patients. The procedural success rate was 98% (40/41), with success defined as ~50% residual stenosis in all lesions; the patient success rate was 97% (35/36). Mean luminal diameter stenosis was reduced from 72 +_ 17% to 29 -C 16% (p < 0.0001). No arteriographic or clinical signs of distal embolization were present and no vessel perforations occurred. The transluminal extraction catheter has also shown good results in treatment of coronary lesions, even those normally deemed unfavorable for PTCA. Leon et a122recently reviewed the transluminal extraction catheter for efficacy, safety, and long-term reocclusion in 281 patients with recent acute myocardial infarction, diffise disease, ostial disease, or eccentric lesions. In 31 patients with recent myocardial infarction, efficacy was 97%, although 66% of patients required both the transluminal extraction catheter and PTCA. Efficacy was defined as 2 20% reduction with the transluminal extraction catheter alone or I 50% residual stenosis with the transluminal extraction catheter and PTCA. Efficacy was high (>90%) for all lesion subsets, and few complications were reported. Eccentric lesions were associated with a slightly lower success rate than concentric lesions (91% vs 95%), and with a slightly higher complication rate (7% vs 2%). Restenosis rates assessed angiographically at 6-month follow-up were similar to those reported for PTCA. The transluminal extraction catheter has shown beneficial results in saphenous vein grafts.23-24 Ostial lesions may be treated with the transluminal extraction catheter device, as well as with highspeed rotary atherectomy or directional coronary atherectomy. The transluminal extraction catheter device is appropriate for ulcerated saphenous vein grafts or those that have a very large clot burden. It is also effective for native coronaries with extensive intraluminal thrombus. Heavily calcified lesions and lesions at bend points should not be treated with the transluminal extraction catheter or directional coronary atherectomy. Ultimately, the greatest utility for this device will be in vessels containing thrombus, including patients with evolving myocardial infarction. REFERENCES l. Detre KM, Holmes DR, Holubkov R, Cowley MJ, Bowassa MG, Faxon DP, Dorms GR, Bentivoglio LG, Kent KM, Myler RK, and coinvestigators of the National Heart, Lung, and Blood Institute’s Percutaneous Transluminal Cixonary Angioplasty Registry. Incidence and consequences of periprocedural occlusion: the 1985-1986 National Heart, Lung, and Blood Institute Percutane-
A SYMPOSIUM:COMPLEXANGIOPLASTY 17F
ous Transhuninal Coronary Angioplasty Registry. Cixution 1990;82:739750. 2. Bansal A, Choksi NA, Levine AB, GangadharanV, Timmis GC, O’Neill W. Determinants of arterial dissection during PTCA: lesion type versus inflation rate. (Abstr) JAm Coil Cardiol1989;13(suppl):229A 3. Vogel RA, Shawl F, Tommaso C, O’Neill W, Overlie P, O’Toole J, Vandormael M, Top01 E, Tabari KK, Vogel J, Smith S, Freedman R, white C, George B, Teirstein P. Initial report of the National Registry of Elective Cardiopulmonary Bypass Supported Coronaq Angioplasty. .I Am CoU Car&l 1990;15:2%29. 4. Cragg DR, Friedman HZ, Ahnany St, Glazier SM, O’Neill WW. Interim safety analysisof the Beaumont outpatient angioplasty trial. (Abstr) JAm Co11 canzio 1991;17(supp1):30A 5. Nobuyoshi M, Kimura T, Nosaka H, Mioka S, Ueno K, Yokoi H, Hamasaki N, Horiuchi H, Ohishi H. Restenosisafter successfulpercutaneoustransluminal coronary angioplasw serial angiographic follow-up of 229 patients. .I Am Co[l Cardiol1988;12:61fX23. &Choy DSJ, Stertzer SH, Myler RK, Marco J, Foumial G. Human laser coronary recanalization. Clin Cardiol1984,7:377-381. 7. SimpsonJB, Johnson DE, Thapliyal HV, Marks DS, Braden L.J.Transluminal atherectomy: a new approach to the treatment of atherosclerotic vascular disease.C&&ion 1985;72(supplIII):III-46. 8. Ahn SS,Autb D, Marcus DR, Moore WS. Removal of focal atheromatous lesions by angioscopically guided high-speed rotary atherectomy. J V&c Sq 1988;7:292-300. 9. Stack RS, Perez .I, Newman GE, McCann RL, Wholey MH, Cummins FE, Galichia JT, HolIinan PU, Tcheng JE, Sketch MH Jr, Lee MM, Phillips HR. Treatment of peripheral vascular diseasewith the transluminal extraction catheter: results of a multicenter study. (Abstr). J Am Co11 Cardbl 1989;13(suppl): 227A. 10. Friedman Hz, Elliott MA, Gottlieb GJ, O’Neill WW. Mechanical rotary atherectomy: the effects of microparticle embolization on myocardial blood flow and function. J Intewen Cardi 1989;2:77-83. 1L Buchbmder M, Warth D, O’Neill W, Zacca N, Ginsburg R, Bertrand M, Erbel R, Fourier J, Leon M. Multicenter registry of percutaneous coronaq rotational ablation using the Rotablator. (Abstr) J Am Co11 Cardiol 1991; 17(suppl):31k ¶2. Bertrand M, Fourier J, Buchbinder M, Warth D, O’Neill W, Zacca N, Erbel R, Leon M. Abrupt closure following rotational ablation with the Rotablator-short term clinical followup. (Abstr) J Am Co11 Cardio[ 1991;17(suppl): 22A
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la. Warth D, Bachbinder M, O’Neill W, Zacca N, Bertrand M, Fourier J, Erbel R. Rotational ablation using the Rotablator for angiographicaIlyunfavorable lesions.(Abstr) JAm Co11Cardio~1991;17(supp1):12.%. 14. Niazi K, Cragg DR, Strzelecki M, Friedman HZ, GangadharanV, O’Neill W. Angiographic risk factors for coronary restenosis following mechanical rotational atherectomy. (Abstr) JAm Co11Car& 1991;17(supp1):21&4. 15. Robertson GC, SimpsonJB, Selmon MR, Vetter JW, Bartzokis TC, Rowe MH, Braden LJ, Hinohara T. Experience of directional coronary atherectomy over four years. (Abstr) JAm Co11Cardioi 1991;17(suppl):384A. l6. Bertrand ME, Lablanche JM, Banters C. Mechanical recanaliiation of coronary arteries. In: Reiber JHC, Serruys PW, eds. Quantitative Coronary Arteriography. Amsterdam: Kluwer Academic Publisher, 1991:34-350. 17. Popma JJ, Top01 ET, Pinkerton CA, Whitlow PL, Hartzler GO, Sehnon MR. Abrupt closure following directional coronary atherectomy:clinical, angiographic and procedural outcome. (Abstr) J Am Coil Car&l 1991;17(suppl): 3OA. 18. Hinohara T, Vetter JW, Rowe MH, Robertson GC, Sehnon MR, Doucette JW, Braden W, SimpsonJB. The effect of angiographicrisk factors on the outcome of directional coronary atherectomy. (Abstr) J Am CON Cardiol 1991; 17(suppl):23A 19. Hinohara T, Selmon MR, Robertson GC, Vetter JW, Rowe MH, Bartzokis TC, Braden LJ, SimpsonJB. Angiographic predictors of restenosisfollowing directional coronary angioplasty.(Abstr) JAm Co11Cardiol 1991;17(suppl): 385.4. 20. Vetter JW, SimpsonJB, Robertson GC, Sehnon MR, Rowe MH, Bartzokis TC, Braden LJ, Hinohara T. Rescue directional coronaq atherectomyfor failed balloon angioplasty.(Abstr) JAm Coil Cardiol1991;17(suppl):384A 21 Selmon MR, Hinohara T, Robertson GC, Rowe MH, Vetter JW, Bartzokis TC, Braden LJ, SimpsonJB. Directional coronary atherectomy for saphenous vein graft stenoses.(Abstr) JAm CoU Car&l 1991;17(suppl):3OA. 22,Leon MB, Pichard AD, Kramer BL, Knopf W, O’Neill W, Stack R. Efficacious and safe transhuninaJextraction atherectomy in patients with unfavorable coronary lesions.(Abstr) JAm Coil Car&/ 1991;17(suppl):219A. 23. O’Neill W, Meany TB, Kramer B, Knopf WD, Pichard AD, Sketch MH, Stack RS. The role of atherectomy in the managementof saphenousvein graft disease. (Abstr) JAm Co11Cardiol1991;17(suppl):384A. 24. SketchMH, O’Neill WW, Galichia JP, Feldman RC, Walker CM, Sawchak SR, Tcheng JE, Wall TC, Phillips HR, Stack RS. The Duke multicenter coronary transluminal extraction-endarterectomy registry: acute and chronic results. (Abstr) JAm Coil Cardiol 1991;17(suppl):31A.
MAY 7, 1992
Rotational William W. O’Neill,
Percutaneous transiuminai coronary an@opiasty (PEA) is practii wideiy in the United States and is indiied for the majority of stenosed vessels that have de novo, type A lesions. Despite extensive experience with the procedure and improvements in balloon technology, periprocedurai diiion and restenosis remain major iimRations of PTCA. Research indicates that certain iesion types and patient populations may be treated more efkctiieiy with other technologies. New mechanical devices have been desiined to help improve the safety of PTCA and hoid promise for correcting coronary diiion and abrupt closure-the sources of such angiopiasty complications as myocardiii infarction, urgent bypass surgery, and death. Among the resutts achieved with the new atherectomy techniques are a more stable lumen after atherectomy; a decrease in elastic recoil; a smoother, less thrombogenic lumen; and the feasibility of extensive debuiking or endarterectomy. Experience indicates that mechanical rotational atherectomy will be an extremely useful addition to the armamentarium for percutaneous revascuiarizatin. (Am J Cardiii 1992;69zlZF-lSF)
From the Division of Cardiology, Department of Internal Medicine, William Beaumont Hospital, Royal Oak, Michigan. Address for reprints: William O’Neill, MD, Cardiology Division, William Beaumont Hospital, 3601 W. 13 Mile Road, Royal Oak, Michigan 48072.
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Atherectomy MD
ith the vast experience, easy applicability, and excellent safety record of balloon angioplasty, it is unlikely that any percutaneous revascularization modality will supersede this technology in general use. However, new devices must be used to overcome the problems and deficiencies of angioplasty. These problems include a persistent rate of coronary dissection, coronary restenosis, poor efficacy in total coronary occlusions, poor results in elastic lesions, and lesions too stenotic to penetrate successfully. Atherectomy clearly can assist in overcoming some of those problem areas. Research indicates that the subgroups in which atherectomy shows promise include lesions that are elastic or too rigid to dilate, lesions that are complex and at high risk for dissection, restenosis lesions, and ostial lesions. Further study using mechanical rotational atherectomy to partially debulk diffusely diseased vessels also is needed. Among the advantages of atherectomy are a stable lumen after the procedure, a decrease in elastic recoil, and a smoother, less thrombogenic lumen. Our experience indicates that mechanical rotational atherectomy will be extremely useful in percutaneous revascularization.
W
PERCUTANEOUS TRANSLUMINAL ANGIOPLASTY
CORONARY
Percutaneous transluminal coronary angioplasty (PTCA) has achieved widespread clinical acceptance in the United States. The technique allows effective treatment of patients with coronary artery disease without the surgical procedure entailed by coronary artery bypass grafts. It has surpassed coronary artery bypass surgery in procedural volume in the United States. Despite its widespread use, PTCA has major limitations and is not optimal therapy for some types of lesions. Several other types of catheter-delivered implements have been designed to address these limitations. PTCA is still indicated for diseased vessels that have de novo, type A lesions. However, certain lesion types and patient populations may be treated more effectively with other technologies. MAY 7, 1992
Procedural safety of PTCA: Periprocedural abrupt closure is the most serious complication of PTCA. Despite extensive experience with the procedure and improvements in balloon technology, the incidence of this complication has remained steady at 2-5%.i The recently published National Heart, Lung, and Blood Institute registry documented a 6.8% incidence of periprocedural abrupt occlusion among 1,801 patients, and 4.7% incidence among 2,891 1esions.r The incidence of occlusion in the catheterization laboratory was 4.9%; the incidence of postprocedure occlusion was 1.9%. Several demographic factors were associated with increased risk for periprocedural occlusion; it occurred at a 9.9% rate in 312 patients with acute coronary insufficiency, compared with a 6.0% rate in patients without this condition (p <0.05). Other factors significantly associated with periprocedural occlusion were 3-vessel disease (9.8% incidence in 367 patients, compared with 6.1% for 2-vessel and 6.0% for l-vessel disease), and inoperable or highrisk surgical status (12.3% incidence in 138 patients compared with 6.3% in other patients). Lesion factors significantly associated with periprocedural occlusion included stenosis of r 90% vessel diameter, diffuse or multiple discrete disease, lesions in segments supplying collaterals, and evidence of thrombus or calcification. Intimal tears occurred in 780 of 2,882 lesions (27%) and extensive dissection occurred in 89 of 2,891 lesions (3%).l These procedural events were most significantly associated with occlusion. Occlusion occurred in 9.9% of patients with intimal tears compared with 2.7% of others (p
periprocedural occlusion. In this study, we examined the balloon inflation rate to test the hypothesis that rapid balloon inflation increases the risk of dissection. In this randomized trial, no significant difference in dissection rates was found between gradual balloon inflation over 30 seconds and rapid balloon inflation in <5 seconds in 142 lesions. However, the association of dissection with complex lesion morphology was highly significant (p = 0.00001); dissection occurred in 33% (S/24) of type A lesions, 63% (57/91) of type B lesions, and 96% (26/27) of type C lesions. Periprocedural occlusion, or even the temporary occlusion resulting from balloon inflation, can result in hemodynamic collapse. This event can be especially dangerous to individuals who have poor ventricular function or a single remaining patent coronary conduit. A multicenter study indicates that the morbidity and mortality associated with PTCA in such high-risk patients can be reduced with the addition of cardiopulmonary bypass to the procedure.3 In 105 patients with an ejection fraction < 25% or a target vessel supplying > 50% at the myocardium, the overall hospital mortality rate was 7.6%. This rate was only 2.6% in patients who were younger than age 75 and not affected by left main coronary artery stenosis. The mortality rate was 60% for patients with abrupt occlusion after discharge from the catheterization laboratory. Thus, dissection and abrupt occlusion are most dangerous in high-risk patients. In these patients, it is imperative that an optimal angiographic result be achieved. PTCA has a number of benefits. Overall, it has extremely low rates of mortality and need for emergency bypass surgery. Elective cases also are associated with extremely high successrates. PTCA also is a simple procedure. An ongoing study of the procedure at William Beaumont Hospital4 indicates that conventional postprocedure heparin therapy may be eliminated with no detrimental effect on patient outcomes. In 200 patients (of a planned 400), 22% of patients in the no-heparin group have been able to go home on the day of the procedure, and a total of 42% have gone home within 24 hours. Thus, PTCA remains an important and appropriate procedure for the majority of lesions. Yet, it falls short of optimal therapy in many cases involving complex morphology or high-risk patients. Limiting factors in PTC& Coronary restenosis is a second major limitation of PTCA. Many factors contribute to the incidence of restenosis and some of these factors are inherent in PTCA. Up to 30% A SYMPOSIUM: COMPLEX ANGlOPtASTY
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FlGURE l. The Auth h&h-speed cotary atherectomy device. A brass burr coated wlth dlamond chips is welded to a drive shaft that is cotated at h&b speed. The dsvka Is inserted over a gulds wire, and placement is dbected by fluorooCOPY-
investigators initially supported coronary laser angioplasty in the late 1970~,~high rates of perforation and thrombosis dampened enthusiasm for this treatment modality. Others began to investigate the feasibility of mechanical peripheral and coronary atherectomy.7-9 Among the results achieved with the new atherectomy techniques are a more stable lumen after atherectomy; a decrease in elastic recoil; a smoother, less thrombogenic lumen; and the feasibility of extensive debulking or endarterectomy. Mechanical rotational atherectomy: Auth et al have developed a high-speed rotary atherectomy device inserted over a guide wire and directed with fluoroscopy.s The device consists of a brass burr coated with diamond chips measuring 30-120 pm in diameter (Figure 1). Available in various sizes, the burr is selected to match the diameter of the MECHANICAL ATHERECTOMY The clinical need for improved technology was vessel being treated. The burr is welded to a drive recognized in the early 1980s. Although some shaft that is rotated by a turbine at high speeds.
of restenotic vessels exhibit elastic recoil, limiting the ability of the balloon to relieve the obstruction.5 The inflated balloon can also cause deep medial smooth muscle injury. This stimulates smooth muscle proliferation in the vessel, contributing to restenosis. Finally, PTCA leaves ragged, irregular lesions in the lumen, which stimulate platelet and fibrin deposition. Several other technical problems limit the efficacy of PTCA in certain cases. Current balloon and guide wire technology is unable to recanalize total coronary occlusions or fibrotic, elastic lesions such as those in ostial locations. Other lesions that are too severe, hard, or calcified may not allow passage of the balloon even after guide wire placement, and some rare lesions simply do not respond to balloon inflations.
FIGURE 2. The Rotablator (Heart Technolo@, Inc., Rellevue, WashIMton) operates at 1GO,OOO-l90,OOO rpm.
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Commercial models (e.g., Rotablator, Heart Technology, Bellevue, Washington) rotate at speeds of 160,000-190,000 rpm (Figure 2). The rotating burr selectively removes hard tissue, whereas soft tissue is deflected by the elastic recoil of normal segments of vessel. The device thus selectively ablates the firmer atherosclerotic plaque. The tissue is chipped off as microparticles and embolizes downstream. Microparticle embolization was an early concern with this device. When the device was tested on 68 cadaver arteries, however, the pulverized atheroma particles (in colloidal suspension) were generally smaller than red blood cells, and injection of the suspension into canine femoral arteries failed to produce tissue injury.* We further analyzed the impact of atheromatous microparticles on canine coronary blood flow and found no deleterious effects.lO In our experience with rotary atherectomy we have seen no significant adverse effects of microparticle embolization. A series of 39 patients treated at William Beaumont Hospital showed no impairment of regional function or ventricular wall motion with this device (Figure 3). In procedures involving the right coronary arteries or circumflex artery, bradycardia, transient complete heart block, or transient asystole is invariably seen. A recent multicenter studyll of percutaneous transluminal coronary rotational ablation in 315 patients reported no in-hospital deaths and a 95% rate of acute success ( < 50% residual stenosis). Of all lesions, 87% were complex (type B or C). Complications included myocardial infarction in 5.6% of patients and urgent coronary artery bypass graft in 1.6%. There were 26 cases (8.2%) of angiographic evidence of flap or dissection. Only one case required a coronary artery bypass graft.i* Percutaneous transluminal coronary rotational ablation also has shown excellent results in lesions
FIGURE 3. EJection fraction changes wlth mechanical rotational atherectomyemploylngtheRotablatorcatheter. The global eJectlon fraction In 39 patlents wasseflallyassessed treated. No deterloratlon In ventrlcular function was noted between studlesobtalwdatb-,at34 hours, and at 9 months post-catheterlzatlon. NS = difference not slgnlfhtant (ANOVA).
TABLE I Results of Mechanical Type C Lesions
Rotational
Outcome
MRA 01 = 27)
Successful Major cardiac event Emergency CABG Abrupt closure Death
26 (96%) 1 (3.7%) 1 (3.7%) 0 0
Ablation
of
PTCA (n = 196) 149 11 5 4 2
p
(76%) (5.6%) (2.6%) (2.0%) (1.0%)
Value
<0.03 NS NS NS NS
CABG = coronary bypass surgery; MRA = mechanical rotational ablation; NS = not significant; PTCA = percutaneous transluminal coronary angioplasty. I
L
that have unfavorable morphologic characteristics, including eccentricity, calcification, tortuosity, and location at a bifurcation.13 In our experience, type C lesions appear to be better treated with rotational ablation (Table I). Follow-up at 6 months in 94% of patients in the multicenter study showed a restenosis rate of 32%.11 The following have been identified as risk factors for coronary restenosis following rotation angioplasty: lesions in the left anterior descending coronary artery, ostial and proximal lesions, and lesions in saphenous vein bypass grafts.i4 The Rotablator may be useful in casesof restenosis after PTCA. Ostial lesions also are appropriate for mechanical rotational atherectomy treatment, as are heavily calcified lesions, diffusely diseased arteries, and lesions at bend points in the vessel. Heavily calcified lesions and lesions at bend points should not be treated with a transluminal extraction catheter or directional coronary atherectomy. Unlike balloon angioplasty, the high-speed rotary burr grinds atheroma into fine particles that pass harmlessly through the capillary circulation. Furthermore, rotary atherectomy leaves a smooth, polished intraluminal surface and no intimal flaps. Unlike the laser, its energy requirements are minimal, its machinery is trim, and it selectively removes rigid tissue such as calcified or fibrous
67.2
SASELIME
69.4
24 HOURS
l
6 MONTHS
f p = NS (ANovA)
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atherosclerotic plaque, whereas rubbery or elastic tissue, such as the outer media, remains relatively uninjured.8 Despite these advantages, the Auth device needs further improvement. Investigators have identified problems with the guide wire that lead to perforation or inability to pass the guide wire past totally occluded arteries.8 The atherectomy burr is relatively ineffective for arteries completely occluded with chronic thrombus. Finally, large vessels cannot be completely treated by this device alone. Directional coronary atherectomy: Simpson and colleagues at Sequoia Hospital in Redwood City, California, have developed a technique called directional coronary atherectomy.15 The Atherocath is characterized by a cylindrical metal housing attached to the end of a braided double-lumen catheter. The cylindrical housing has a “longitudinal window” that can be positioned snugly against the atheroma with the help of a small balloon opposite the window. Inside the window, a rotating cutter blade shaves off atherosclerotic material and deposits it in the distal part of the metal housing. A
FlQURE 4. llw Bliimpson Coronary Atherocath
(John B.
l0 mm window runs along&e side and a balloonidong the opposite side. A cyilndrkal cutter wRhln the houhg Is powered by a hanckheld motor. Under fluoroscopy, the dlstal end of the catheter ls placed across tbs stenosls and the balloon ls Inflated to 30 psl to hold the houslm against the steno&. The motor ls turned on and the cutter Is advanced, shavle off any atberoma that protrudes Into the wlndow openlng. The shavings are pushed fowawl andthedevlcelsrepoandstoredlnaco&cUonchamber, addtthal passes. 4 before sltlowdforanynecessary atherectomy; 6, the Atherocath Is posltlonedi C, atheroma Is shaved and stored In tbe wlndow opening; 0, after atheWCtOlll&
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separate hand-held battery-powered motor drive is attached to a cable connected to the cutter blade. During a procedure, the Atherocath is advanced over the wire under fluoroscopic guidance (Figure 4). The window of the cylindrical housing is positioned across the stenosis. The positioning balloon is inflated, the attached motor drive is activated, and the cutter blade is slowly advanced through the metal housing, shaving off atheroma and depositing it distally. The positioning balloon is deflated, the catheter is torqued about 60-90” to reposition the window and to remove additional atheroma. When the collection chamber is full, the catheter is withdrawn from the patient and the cutter blade retracted into the proximal portion of the housing. Repeated passes are made until the desired result is achieved.16 Simpson and colleagues recently reported their experience in 502 procedures (578 lesions). I5 Patients’ mean age was 59 years and 42% had unstable angina. Sixteen of the procedures were performed as salvage for failed PTCA, and 55% of the lesions treated had been previously treated with angioplasty. The overall success rate was 88.2%, with individual vessel success rates ranging from 79% in the left anterior descending coronary artery (n = 279) to 100% in the diagonal artery (n = 3). A multicenter study of this techniqueI reported a 4.2% rate of abrupt closure (periprocedural stenosis) in 1,018 procedures (1,138 lesions), a rate roughly comparable to the rates seen with PTCA and mechanical rotational atherectomy. Among the risk factors identified were right coronary artery lesions, de novo lesions, and eccentric lesions. Abrupt closure was less frequent during procedures on saphenous vein grafts. The Sequoia group investigated the effect of angiographic risk factors on the outcome of directional coronary atherectomy in a series of 499 lesions in 441 procedures.18 The overall success rate was 88% per lesion (87% per procedure). The investigators evaluated several risk factors for their effect on patient outcome, including lesion eccentricity, abnormal contour, ostial location, and length > 10 mm. Only calcification and difise disease were significantly associated with failed procedures. In 211 successfully treated lesions followed up angiographically at 3-12 months (or earlier if symptoms recurred), the overall restenosis rate was 36%: 29% (24/82) for de novo lesions and 40% (52/129) for restenosis lesions.19 Factors significantly associated with restenosis were lesion length > 10 mm, vessel diameter < 3 mm, and overdilation.lg This group has also used directional coroMAY 7, 1992
nary atherectomy successfully in rescue procedures for failed PTCA (success in 87% of 30 patients)20 and in saphenous vein graft lesions (91% success rate in 87 lesions). 21However, restenosis rates are high in vein graft lesions, especially those treated previously with PTCA. Appropriate indications for directional coronary atherectomy include ostial lesions and focal lesions. De novo lesions can be treated effectively and have a very low risk of restenosis. Highly eccentric lesions in the left anterior descending artery are well suited to directional coronary atherectomy. Directional coronary atherectomy is also effective as a bailout device for discrete occlusive flaps present after PTCA. Heavily calcified lesions and lesions at bend points should not be treated with directional coronary atherectomy. Transluminal extraction catheter: Another type of intraluminal catheter atherectomy device is the transluminal extraction catheter, which allows the transluminal extraction of atherosclerotic plaque, thus reducing the risks of downstream embolization and leaving a smooth, undissected lumen.7 It consists of a rotary cutting device advanced over a 0.014 inch PTCA guide wire (Figure 5). The flexible torque tube device is introduced percutaneously and tracks over the flexible steerable guide wire under fluoroscopic control. When the radiopaque tip is properly positioned near the origin of the lesion, a 2-stage trigger is activated on the hand-held control piece. The conical cutter rotates at 750 rpm while suction is applied through the opening of the cutting window to extract the plaque fragments through the catheter and out of the patient’s body. I5 The device is well suited for large, bulky lesions with extensive intraluminal thrombus. Stack et al9 demonstrated the safety and efficacy of the device in reducing stenosis and increasing
FIGURE 5. Stack Ransluminal Extractlon Catheter (Interventlonal Technologies, San Dlego, California). Uke the Auth device, this device also travels along a gWde wire and uses a vacuum to extract mkropartlcles and prevent patilculate embollzatlon. Potential advantages Include the lack of dlstal partleulate embellzatlen and the ablllty ofthe devke to extract atheromatous material tihout changing the catheter houslng during the prccedure.
flow in peripheral vascular disease. They treated 71 atherosclerotic lesions during 41 procedures in 41 extremities of 36 patients. The procedural success rate was 98% (40/41), with success defined as ~50% residual stenosis in all lesions; the patient success rate was 97% (35/36). Mean luminal diameter stenosis was reduced from 72 +_ 17% to 29 -C 16% (p < 0.0001). No arteriographic or clinical signs of distal embolization were present and no vessel perforations occurred. The transluminal extraction catheter has also shown good results in treatment of coronary lesions, even those normally deemed unfavorable for PTCA. Leon et a122recently reviewed the transluminal extraction catheter for efficacy, safety, and long-term reocclusion in 281 patients with recent acute myocardial infarction, diffise disease, ostial disease, or eccentric lesions. In 31 patients with recent myocardial infarction, efficacy was 97%, although 66% of patients required both the transluminal extraction catheter and PTCA. Efficacy was defined as 2 20% reduction with the transluminal extraction catheter alone or I 50% residual stenosis with the transluminal extraction catheter and PTCA. Efficacy was high (>90%) for all lesion subsets, and few complications were reported. Eccentric lesions were associated with a slightly lower success rate than concentric lesions (91% vs 95%), and with a slightly higher complication rate (7% vs 2%). Restenosis rates assessed angiographically at 6-month follow-up were similar to those reported for PTCA. The transluminal extraction catheter has shown beneficial results in saphenous vein grafts.23-24 Ostial lesions may be treated with the transluminal extraction catheter device, as well as with highspeed rotary atherectomy or directional coronary atherectomy. The transluminal extraction catheter device is appropriate for ulcerated saphenous vein grafts or those that have a very large clot burden. It is also effective for native coronaries with extensive intraluminal thrombus. Heavily calcified lesions and lesions at bend points should not be treated with the transluminal extraction catheter or directional coronary atherectomy. Ultimately, the greatest utility for this device will be in vessels containing thrombus, including patients with evolving myocardial infarction. REFERENCES l. Detre KM, Holmes DR, Holubkov R, Cowley MJ, Bowassa MG, Faxon DP, Dorms GR, Bentivoglio LG, Kent KM, Myler RK, and coinvestigators of the National Heart, Lung, and Blood Institute’s Percutaneous Transluminal Cixonary Angioplasty Registry. Incidence and consequences of periprocedural occlusion: the 1985-1986 National Heart, Lung, and Blood Institute Percutane-
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ous Transhuninal Coronary Angioplasty Registry. Cixution 1990;82:739750. 2. Bansal A, Choksi NA, Levine AB, GangadharanV, Timmis GC, O’Neill W. Determinants of arterial dissection during PTCA: lesion type versus inflation rate. (Abstr) JAm Coil Cardiol1989;13(suppl):229A 3. Vogel RA, Shawl F, Tommaso C, O’Neill W, Overlie P, O’Toole J, Vandormael M, Top01 E, Tabari KK, Vogel J, Smith S, Freedman R, white C, George B, Teirstein P. Initial report of the National Registry of Elective Cardiopulmonary Bypass Supported Coronaq Angioplasty. .I Am CoU Car&l 1990;15:2%29. 4. Cragg DR, Friedman HZ, Ahnany St, Glazier SM, O’Neill WW. Interim safety analysisof the Beaumont outpatient angioplasty trial. (Abstr) JAm Co11 canzio 1991;17(supp1):30A 5. Nobuyoshi M, Kimura T, Nosaka H, Mioka S, Ueno K, Yokoi H, Hamasaki N, Horiuchi H, Ohishi H. Restenosisafter successfulpercutaneoustransluminal coronary angioplasw serial angiographic follow-up of 229 patients. .I Am Co[l Cardiol1988;12:61fX23. &Choy DSJ, Stertzer SH, Myler RK, Marco J, Foumial G. Human laser coronary recanalization. Clin Cardiol1984,7:377-381. 7. SimpsonJB, Johnson DE, Thapliyal HV, Marks DS, Braden L.J.Transluminal atherectomy: a new approach to the treatment of atherosclerotic vascular disease.C&&ion 1985;72(supplIII):III-46. 8. Ahn SS,Autb D, Marcus DR, Moore WS. Removal of focal atheromatous lesions by angioscopically guided high-speed rotary atherectomy. J V&c Sq 1988;7:292-300. 9. Stack RS, Perez .I, Newman GE, McCann RL, Wholey MH, Cummins FE, Galichia JT, HolIinan PU, Tcheng JE, Sketch MH Jr, Lee MM, Phillips HR. Treatment of peripheral vascular diseasewith the transluminal extraction catheter: results of a multicenter study. (Abstr). J Am Co11 Cardbl 1989;13(suppl): 227A. 10. Friedman Hz, Elliott MA, Gottlieb GJ, O’Neill WW. Mechanical rotary atherectomy: the effects of microparticle embolization on myocardial blood flow and function. J Intewen Cardi 1989;2:77-83. 1L Buchbmder M, Warth D, O’Neill W, Zacca N, Ginsburg R, Bertrand M, Erbel R, Fourier J, Leon M. Multicenter registry of percutaneous coronaq rotational ablation using the Rotablator. (Abstr) J Am Co11 Cardiol 1991; 17(suppl):31k ¶2. Bertrand M, Fourier J, Buchbinder M, Warth D, O’Neill W, Zacca N, Erbel R, Leon M. Abrupt closure following rotational ablation with the Rotablator-short term clinical followup. (Abstr) J Am Co11 Cardio[ 1991;17(suppl): 22A
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la. Warth D, Bachbinder M, O’Neill W, Zacca N, Bertrand M, Fourier J, Erbel R. Rotational ablation using the Rotablator for angiographicaIlyunfavorable lesions.(Abstr) JAm Co11Cardio~1991;17(supp1):12.%. 14. Niazi K, Cragg DR, Strzelecki M, Friedman HZ, GangadharanV, O’Neill W. Angiographic risk factors for coronary restenosis following mechanical rotational atherectomy. (Abstr) JAm Co11Car& 1991;17(supp1):21&4. 15. Robertson GC, SimpsonJB, Selmon MR, Vetter JW, Bartzokis TC, Rowe MH, Braden LJ, Hinohara T. Experience of directional coronary atherectomy over four years. (Abstr) JAm Co11Cardioi 1991;17(suppl):384A. l6. Bertrand ME, Lablanche JM, Banters C. Mechanical recanaliiation of coronary arteries. In: Reiber JHC, Serruys PW, eds. Quantitative Coronary Arteriography. Amsterdam: Kluwer Academic Publisher, 1991:34-350. 17. Popma JJ, Top01 ET, Pinkerton CA, Whitlow PL, Hartzler GO, Sehnon MR. Abrupt closure following directional coronary atherectomy:clinical, angiographic and procedural outcome. (Abstr) J Am Coil Car&l 1991;17(suppl): 3OA. 18. Hinohara T, Vetter JW, Rowe MH, Robertson GC, Sehnon MR, Doucette JW, Braden W, SimpsonJB. The effect of angiographicrisk factors on the outcome of directional coronary atherectomy. (Abstr) J Am CON Cardiol 1991; 17(suppl):23A 19. Hinohara T, Selmon MR, Robertson GC, Vetter JW, Rowe MH, Bartzokis TC, Braden LJ, SimpsonJB. Angiographic predictors of restenosisfollowing directional coronary angioplasty.(Abstr) JAm Co11Cardiol 1991;17(suppl): 385.4. 20. Vetter JW, SimpsonJB, Robertson GC, Sehnon MR, Rowe MH, Bartzokis TC, Braden LJ, Hinohara T. Rescue directional coronaq atherectomyfor failed balloon angioplasty.(Abstr) JAm Coil Cardiol1991;17(suppl):384A 21 Selmon MR, Hinohara T, Robertson GC, Rowe MH, Vetter JW, Bartzokis TC, Braden LJ, SimpsonJB. Directional coronary atherectomy for saphenous vein graft stenoses.(Abstr) JAm CoU Car&l 1991;17(suppl):3OA. 22,Leon MB, Pichard AD, Kramer BL, Knopf W, O’Neill W, Stack R. Efficacious and safe transhuninaJextraction atherectomy in patients with unfavorable coronary lesions.(Abstr) JAm Coil Car&/ 1991;17(suppl):219A. 23. O’Neill W, Meany TB, Kramer B, Knopf WD, Pichard AD, Sketch MH, Stack RS. The role of atherectomy in the managementof saphenousvein graft disease. (Abstr) JAm Co11Cardiol1991;17(suppl):384A. 24. SketchMH, O’Neill WW, Galichia JP, Feldman RC, Walker CM, Sawchak SR, Tcheng JE, Wall TC, Phillips HR, Stack RS. The Duke multicenter coronary transluminal extraction-endarterectomy registry: acute and chronic results. (Abstr) JAm Coil Cardiol 1991;17(suppl):31A.
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