ENDOVASCULARSURGERY

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STATUS OF PERIPHERAL ATHERECTOMY Samuel S. Ahn, MD

BASIC CONCEPTS

Atherectomy is the removal of atheroma from diseased arteries. The procedure is performed percutaneously or through a small arteriotomy remote from the diseased site. During the development of this technique, three theoretical advantages of atherectomy over transluminal angioplasty were postulated: (1) a higher immediate success rate with less subintimal dissection and subsequent occlusion; (2) wider therapeutic options for lesions currently not amenable to angioplasty alone (diffusely diseased vessels or totally occluded lesions); and (3) reduction of the restenosis rate by debulking of the atheromatous mass. 1 Many atherectomy devices have been devised, and each offers unique advantages as well as disadvantages. The four that are currently approved by the US Food and Drug Administration for clinical use are discussed below.

SIMPSON ATHEROCATH

Description The Simpson peripheral atherectomy catheter (Devices for Vascular Intervention Inc., Redwood City, California) is a flexible 7-Fr to ll-Fr catheter whose cutting element is a small circular cutter spinning at about 2000 rpm inside a metal housing with a 15- or 20-mm window (Fig. 1). The plaque is forced through the window into the housing by inflating a balloon (20-40 Ib/in2; PSI) on the opposite side of the housing. The plaque is then cut by advancing the rotating cutter in the housing, and the pieces are trapped in the distal collection chamber. Some of the newer systems have an ultrasound chip in the cutting From the Section of Vascular Surgery, University of California at Los Angeles Center for Health Sciences, Los Angeles, California

SURGICAL CLINICS OF NORTH AMERICA VOLUME 72 • NUMBER 4 • AUGUST 1992

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Figure 1. Action of Simpson Atherocath. A, Vessel with plaque. B, Catheter in position in area. C, Balloon is inflated, forcing cutting element against plaque. 0, Cutting element is activated, removing plaque (E). F, Vessel after treatment. (From Hinohara T, Robertson GC, Selmon MR, et al: Transluminal atherectomy: The Simpson atherectomy catheter. In Moore WS, Ahn SS (eds): Endovascular Surgery. Philadelphia, WB Saunders, 1989, p 312.)

window to guide correct alignment of the window with the lesion prior to cutting and to evaluate the result after a cut is made. Indications

The optimal lesion for the Simpson atherectomy device is a short, discrete, eccentrically placed atheroma. Stenoses are amenable to treatment, whereas occlusions generally are not unless the housing can penetrate the lesion. Ulcerative atherosclerotic plaques and intimal hyperplasia lesions are also treatable. Heavily calcified lesions create some difficulties for the cutter but do not pose a particular contraindication. The Simpson Atherocath has been used as a preliminary to balloon angioplasty to debulk calcific eccentric stenoses not normally amenable to dilatation. Techniques

Figure 1 illustrates the Simpson Atherocath procedure. First, the atherectomy catheter must advance past the stenotic lesion. Second, the catheter must be torqued appropriately to position the cutting window toward the plaque. Fluoroscopy facilitates this process. With the catheter properly positioned, the balloon is inflated to 20 to 40 PSI to push the open chamber against the arterial lesion, thereby wedging the atheroma into the window. The motor drive of the cutter is activated, and the rotating circular blade slices and pushes the atheroma into the distal collecting chamber. The collecting chamber is then rotated, and the procedures are repeated. Multiple cuts and passages are required for complete atherectomy. Once the collecting chamber is full, the

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catheter is withdrawn, and the atheroma slices are removed. Repeated atherectomy is performed as needed to obtain complete recanalization. Results

Simpson and associates lO reported their initial atherectomy experience of 136 iliac, superficial femoral, and popliteal artery lesions in 61 patients. Atherectomy was initially successful in 87% of the patients. Among the satisfactorily treated patients, only 69% had continued exercise tolerance at 6month follow-up. The angiographic studies available in 30 of these patients revealed a restenosis rate of at least 36%. Restenosis was more common in patients with residual stenosis exceeding 30% at the time of the atherectomy procedure. Polnitz and coworkers9 reported Simpson atherectomy procedures in 60 patients with 94 lesions (63 stenoses and 31 total occlusions) in 77 superficial femoral arteries, 8 popliteal arteries, 8 iliac arteries, and 1 anterior tibial artery. Immediate clinical success was obtained in 82% (49/60) of the patients. Twentyfive of the successfully treated patients reached a I-year follow-up and achieved a 72% clinical patency rate; 16% required repeat atherectomy, and 8% required surgery for restenosis or occlusion. Six-month angiographic evaluation found restenosis in 13 (24%) of 55 lesions: 3/13 of the concentric lesions (23%), 3/27 of the eccentric lesions (11 %), and 7/15 of the occlusions (47%). Graor et aF reported a 100% and 93% initial success rate in patients with lesions shorter than 5 cm and longer than 5 cm, respectively. The 12-month patency rates were 93% and 83%, respectively. There was a 7.1 % rate of major complications including one fatal myocardial infarction. Complications and Limitations

The Atherocath is a relatively safe device with a low complication rate. Dissection occurred in 3 of 61 patients in the series of Simpson and associates and was related primarily to the guidewire or introducer.1O Distal embolization occurred in less than 3% of the patients. No perforations were seen, and no patient required surgical salvage. The main limitations of the Simpson Atherocath are its relative ineffectiveness in long, diffusely diseased segments and long occluded lesions. Treatment of these long segments may take 2 to 3 hours. Furthermore, restenosis rates are significantly higher in these long lesions, for which bypass is more expeditious and has better patency. Finally, the catheters are somewhat bulky and stiff to use in the tibial arteries or tortuous vessels. KENSEY ATHERECTOMY DEVICE Description

The Kensey atherectomy device (Dow-Coming-Wright, Arlington, Tennessee), now known as the Trac-Wright system, is a flexible catheter with a distal cam-tip attached to a central drive shaft (Fig. 2). The cam rotates at 100,000 rpm and seeks the path of least resistance. A high-pressure irrigating system dilates the artery while the rotating cam pulverizes the atherosclerotic

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Figure 2. Kensey atherectomy (TracWright) catheter device removing plaque. (From Kensey KR, Nash JE, Abrahams C, et al: Recanalization of obstructed arteries with a flexible, rotating tip catheter. Radiology 165: 387-389, 1987; with permission.)

intima. The rotating tip selectively pulverizes fibrous or firm atheromatous tissue while leaving viscoelastic tissue uninjured. Indications The Kensey atherectomy catheter is designed particularly for occlusive lesions of the superficial femoral artery. No coaxial central guidewire needs to cross the lesion first. The catheter has also been touted to work expeditiously so that long lesions can be treated as easily as short lesions. Techniques Kensey atherectomy can be performed percutaneously or through a small arteriotomy in the common femoral artery. A 9-Fr introducer sheath is first placed, and the Kensey catheter is placed through it into the artery being treated. The catheter tip is placed directly against the obstructing plaque under fluoroscopic guidance. Through the irrigation channel, an infusion of contrast medium, urokinase, dextran, and heparin is started with an infusion rate of 30 ml/minute. Afterward, the electric motor drive is activated to rotate the tip at approximately 100,000 rpm. The catheter is advanced diligently and slowly in a to-and-fro manner, allowing time for the rotating cam to pulverize the atheroma adequately. The catheter is advanced gradually under direct fluoroscopic control. Once the catheter has recanalized the occlusive lesion, standard balloon angioplasty techniques dilate any residual stenosis.

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Results

Snyder et al reported 23 procedures to recanalize superficial femoral artery occlusions. s Atherectomy was successful in 14. Eleven of these extremities underwent subsequent balloon angioplasty to enlarge the initial channel further. Perforation by the rotating cam was the main complication and occurred in 8 of 23 patients. The cumulative patency rate was recently reported to be 37% at 2 years. s Desbrosses et al reported an 87% (40/46) success rate in recanalizing femoropopliteal occlusions 2 to 24 cm long. 6 Four perforations occurred, requiring no further intervention. Failures occurred in calcified arteries. Of the successfully treated vessels, 13% (5/40) re-occluded within 48 hours. Three patients had embolic complications postoperatively. Follow-up revealed a primary patency of 72% (18/25) at 6 months and 70% (14/20) at 12 months. Complications and Limitations

Perforation induced by the rotating cam is the main complication. Whittemore!2 reported 2 perforations in 10 procedures, and Snyder and associates ll reported 8 perforations in 23 procedures. The catheter follows the path of least resistance, which is often away from hard calcified atherosclerotic lesions. Although fibrous lesions are amenable to atherectomy, the hard calcified lesions, particularly at the adductor canal, have been resistant. Thromboembolic complications have not yet been reported. The high perforation rate and difficulty with recanalizing calcific plaque limit the use of the catheter, particularly in the iliac and tibial arteries. AUTH ROTABLATOR Description

The Auth Rotablator (Biophysics International, Bellevue, Washington) is a flexible catheter-deliverable atherectomy device with a variable-size, footballshaped metal bur on the distal tip (Fig. 3). The bur is studded with multiple 22- to 45-,..... diamond chips that function as microblades. Burs ranging from 1.25

Figure 3. Auth Rotablator with 1.25·mm (top) and 4.5-mm (bottom) diamond-studded metal burs. (From Ahn SS, Auth DP, Marcus DR, et al: Removal of focal atherectomy: Preliminary experimental observations. J Vasc Surg 7:292-300, 1988; with permission.)

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to 6.0 mm in diameter are chosen to fit the artery being treated. Smaller burs are used initially, and progressively bigger ones are used as the lumen enlarges. The bur rotates at 100,000 to 200,000 rpm and tracks along a central guidewire that must traverse the lesion before rotational atherectomy can proceed. The high-speed rotation allows the diamond microchips to attack hard calcified atheroma preferentially while leaving the surrounding elastic soft tissue of normal arterial wall intact. The device leaves a smooth, polished intraluminal surface and no intimal flaps (Fig. 4). The pulverized particles are generally smaller than red blood cells and pass harmlessly through the circulation. 3 Indications

The Auth Rotablator is ideally suited for hard calcified atheroma, especially in patients with diabetes. Tibial lesions can be treated as well as those of the popliteal, superficial femoral, and iliac arteries. Stenotic lesions are preferred because a central guidewire must first traverse the lesion, but occlusions can be treated if the guidewire can cross the lesion. Eccentric plaques can be treated, because the bur preferentially attacks the rigid atheroma. Techniques

Atherectomy is performed preferentially through an open arteriotomy. Although percutaneous methods can be used, this technique limits the bur size to 3 mm and usually requires subsequent balloon angioplasty. A 9-Fr, 12-Fr, or 14-Fr introducer sheath is inserted into the artery through the arteriotomy. Under angioscopic or fluoroscopic guidance, a small atraumatic guidewire is passed through the lesion, followed by an exchange guide catheter.

Figure 4. Effect of treatment with Auth Rotablator. (From Ahn SS, Auth DP, Marcus DR, et al: Removal of focal atherectomy: Preliminary experimental observations. J Vasc Surg 7:292-300, 1988; with permission.)

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The initial guidewire is exchanged for a 0.009-inch atherectomy guidewire, which is more stiff and rigid than most standard guidewires. The exchange guide catheter is then removed, and the bur is passed over the stiff atherectomy guidewire to the site of the obstructive lesion. The turbine drive is activated to maintain a rotating speed of 100,000 to 200,000 rpm. The rotating atherectomy bur is advanced slowly in a vibrato-like to-and-fro manner over the guidewire to recanalize the artery. Following this initial atherectomy, the bur is removed, leaving the guidewire in place. The next size bur is inserted, and atherectomy is repeated until an adequate-size lumen is obtained. The patient is placed on anticoagulation therapy for the first 24 hours postoperatively to prevent early thrombosis. Aspirin is maintained long term.

Results

The UCLA series included 41 arteries in 25 patients. 4 Limb threat was present in 56% of these patients. Initial technical success was achieved in 23 of 25 patients (92%) and in 39 of the 41 arterial segments (93%). The in-hospital success rate was 18 of 25 (72%). The primary patency rate in these 18 patients was 67% at 6 months. However, at 24 months, the overall primary and secondary patency rates for the 25 patients were only 9.5% and 20%, respectively. The Stanford series had 38 patients with stenoses of the superficial femoral and popliteal arteries. 8 Limb threat was present in 45%. A 71 % (27/38) angiographic success rate was reported. Eighteen (47%) demonstrated immediate angiographic and hemodynamic successes. Of these, 11 still were improved clinically and hemodynamically at 6 months. Six of the nine immediate angiographic successes without hemodynamic benefit required adjunctive procedures within 6 months. Of the other patients, two were lost to follow-up, and one was clinically improved but hemodynamically worse.

Complications and Limitations

Combining the UCLA and Stanford data on 63 patients, complications included eight instances of peripheral emboli (one significant enough to cause thigh skin loss), seven of transient hemoglobinuria, seven wound hematomas (in six percutaneous and one open procedure), five early rethromboses, three wound infections, two equipment breakages, two perforations, one intimal dissection, and three limb losses. Thromboemboli were mostly microscopic and clinically inSignificant. However, a hypercoagulable patient at UCLA developed diffuse microemboli and ultimately lost her limb. Microscopic hemoglobinuria has occurred in several patients, particularly when the larger burs (4 mm or greater) are used. However, the effects have been clinically benign and transient. Burs that are too large or that are advanced too rapidly are subject to entanglement and breakage. The inability to bur through chronic thrombus or rubbery atherosclerotic intima limits the Auth Rotablator. These lesions preferentially deflect away from the rotating bur, leading to suboptimal recanalization. The need for multiple burs and the exchange of burs over the guidewire slow the procedure. Although particles are generally small, a large particle burden is a potential problem, particularly in dealing with long occluded lesions.

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TRANSLUMINAL EXTRACTION CATHETER Description

The Transluminal Extraction Catheter (TEC Catheter, Interventional Technologies, Inc., San Diego, California) is a semiflexible, torque-controlled, hollow 5-Fr to 9-Fr catheter with a conical cutting tip that is passed over a guidewire (Fig. 5). As the catheter is advanced, the surface of the plaque is cut by internal cutting blades as it enters the rotating (700 rpm) conical housing. The plaque particles are aspirated into 125-cc vacuum bottles. Continuous heparin irrigation through the introducer sheath is required to maintain effective particle aspiration. Adjunctive standard balloon angioplasty is often required in the superficial femoral and popliteal arteries to achieve a final channel that is adequate. Indications

The indications are the same as those described for the Simpson Atherocath. Techniques

The procedure generally has been performed percutaneously but can be used intraoperatively as well. After an appropriate-size introducer sheath has been placed in the artery, a standard guidewire is passed through the introducer sheath and the obstructive lesion. A 4-Fr or 5-Fr polyethylene exchange catheter is inserted, and the initial guidewire is replaced with the TEC 0.014-inch wire. The exchange catheter is removed followed by the passing of the TEC catheter over the TEC guidewire until the catheter meets resistance at the obstructive lesion. The atherectomy catheter is then activated, and the motor drive rotates the cutter at 700 rpm while suction is applied. The torque tube cutter is passed freely but gently over the guidewire until the occluded segment has been

Figure 5. Transluminal extraction catheter (TEC Catheter, Interventional Technologies, Inc., San Diego, California). Rotating housing (white arrows) cuts plaque into particles (black arrows) that are aspirated into vacuum bottles.

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traversed. Fluoroscopy documents the progress of the atherectomy and the final lumen. If there is significant residual stenosis, standard balloon angioplasty is performed to dilate the artery to the final size. Results

Wholey and Jarmolowski reported the initial results in 126 lesions in the first 95 patients from a multicenter trial. 13 The vessels treated were the superficial femoral artery (97 patients), femoropopliteal grafts (2), popliteal artery (14), and the external iliac (8) and tibial vessels (4). Sixty of the patients had claudication. Initial technical success was achieved in 92% of the procedures. Atherectomy alone treated 67 of the 126 lesions (53%). The other lesions required adjunctive balloon angioplasty. Sixteen patients underwent repeat angiography at 6-month follow-up. Four had angiographic evidence of reocclusion. Limitations and Complications

In addition to the complications listed for the Simpson Atherocath, the TEe atherectomy procedure has one unique limitation. The suction applied to aspirate the plaque particles may lead to significant blood loss that necessitates transfusion, especially during atherectomy of longer lesions. In addition, TEe atherectomy should be halted if the suction bottle is not working or is full of blood. Otherwise, distal embolization may occur. SUMMARY

So far, all atherectomy devices have failed to reduce the restenosis rate of standard balloon angioplasty. Despite actual removal, debulking, and even polishing of the atherosclerotic intima, the arterial wall trauma invariably incites intimal hyperplaSia. Until the problem of restenosis can be solved, atherectomy will be limited to those instances when balloon angioplasty is ineffective or contraindicated. Each device has its own peculiarities. We prefer to use the Simpson catheter for eccentric lesions in the iliofemoral or femoropopliteal regions, the Auth Rotablator for short lesions in the infrageniculate vessels, and the TEe for longer lesions in the femoropopliteal regions. Adjunctive balloon angioplasty mayor may not be required. Ahn and Moore have illustrated specific clinical strategies for peripheral atherectomy.2 References 1. Ahn 55: Peripheral atherectomy. Semin Vasc Surg 2:143-154, 1989 2. Ahn 55, Moore WS: Lesions amenable to mechanical atherectomy: Clinical strategies. In Moore WS, Ahn 55 (eds): Endovascu1ar Surgery. Philadelphia, WB Saunders, 1989, pp 299-309 3. Ahn 55, Auth DP, Marcus DR, et al: Removal of focal atherectomy: Preliminary experimental observations. J Vasc Surg 7:292-300, 1988 4. Ahn 55, Yeatman LR, Deutsch LS, et al: Intraoperative peripheral atherectomy: Preliminary clinical results. Ann Vasc Surg 1992, in press 5. Cull DL, Feinberg RL, Wheeler JR, et al: Experience with laser-assisted baIIoon

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angioplasty and a rotary angioplasty instrument: Lessons learned. J Vasc Surg 14:332339, 1991 Desbrosses D, Petit H, Torres E, et al: Percutaneous atherectomy with angioplasty. Ann Vasc Surg 4:550-552, 1990 Graor R, Whitlow P: Transluminal atherectomy for occlusive peripheral vascular disease. J Am Coli Cardiol 15:1551-1558, 1990 Jennings LJ, Mehigan JT, Ginsberg R, et al: Rotablator atherectomy: Early experience and six month follow-up. Presented at the Western Vascular Society, Rancho Mirage, CA, January 1991 Polnitz A, Nerlich A, Berger H, et al: Percutaneous peripheral atherectomy. J Am Coli Cardiol 15:682-688, 1990 Simpson JB, Selman MR, Roberson Gc, et al: Transluminal atherectomy for occlusive peripheral vascular disease. J Am Coli Cardiol 61:96-101, 1988 Snyder SO, Wheeler JR, Gregory RT, et al: Kensey catheter: Early results with a transluminal endarterectomy tool. J Vasc Surg 8:541-543, 1988 Whittemore AD: The Kensey catheter: Indications, technique, results, and complications. In Moore WS, Ahn SS (eds): Endovascular Surgery. Philadelphia, WB Saunders, 1989, pp 323-326 Wholey MH, Jarmolowski CR: New reperfusion devices: The Kensey catheter, the atherolytic reperfusion wire device, and the transluminal extraction catheter. Radiology 172:947-952, 1989

Address reprint requests to Samuel S. Ahn, MD Department of Surgery Section of Vascular Surgery UCLA Center for Health Sciences 10833 LeConte Avenue Los Angeles, CA 90024-6904

Status of peripheral atherectomy.

So far, all atherectomy devices have failed to reduce the restenosis rate of standard balloon angioplasty. Despite actual removal, debulking, and even...
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