NEW CHALLENGES IN INTERNAL MEDICINE

0025-7125/92 $0.00 + .20

OPTIONS FOR PERCUTANEOUS CORONARY AND PERIPHERAL REVASCULARIZATION Christopher J. White, MD, and Stephen R. Ramee, MD, FACC

The diagnosis and treatment of atherosclerosis have changed dramatically over the past decade. Improvements in diagnostic technique, together with advances in the percutaneous treatment for coronary ischemia and peripheral vascular disease, have resulted in a heightened interest in managing these disorders among internists and cardiologists. This article reviews the latest developments in percutaneous coronary angioplasty and peripheral angioplasty, with an emphasis on new technologies and their role in clinical practice. PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY

As we enter the 1990s, the practice of percutaneous transluminal coronary angioplasty (PTCA) continues to evolve rapidly. In the late 1970s and early 1980s, the practice of PTCA was limited to patients with single-vessel coronary disease with proximal, discrete, noncalcified stenoses. Early primary success rates were reported to be approximately 65% because of primitive equipment and operator inexperience. However, as the decade of the 1980s closed, the practice of PTCA had grown dramatically to include patients with multi-vessel coronary disease with more complex lesions, and the primary success rate had increased to 90% or more. This progress was aided by advances in catheter technology and increased operator experience and skill. From the Section on Cardiology, Department of Medicine, Ochsner Medical Institutions, New Orleans, Louisiana THE MEDICAL CLINICS OF NORTH AMERICA VOLUME 76 • NUMBER 5 • SEPTEMBER 1992

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Despite these advances, there remain several major challenges for PTCA. First, and most difficult among these problems, is the recurrence rate or restenosis following PTCA. Restenosis is estimated to occur in approximately 30%32,43 of all patients, but in certain subgroups, such as those with total occlusions and coronary bypass grafts, restenosis may exceed 50%.56 Second, patients with complex lesions, diffuse disease, and lesions on bends are at increased risk of PTCA-related complications such as abrupt occlusion, myocardial infarction, and the need for emergency coronary bypass surgery. Finally, patients with severely depressed left ventricular function and patients in whom a failed PTCA attempt would severely compromise left ventricular function are being accepted for high-risk percutaneous therapy. These limitations have stimulated the development of new techniques and devices to enhance the success rates of percutaneous revascularization. This article describes the development and clinical application of some of these new procedures and devices at the Ochsner Clinic. NEW TECHNIQUES Adjunctive Thrombolytic Therapy

Thrombolytic agents may be used in conjunction with balloon angioplasty to increase the primary success rate in totally occluded vessels and to salvage a failed angioplasty attempt (abrupt occlusion) due to thrombosis. Hartman et apo have described a technique for re canalizing occluded coronary bypass grafts with a prolonged infusion of urokinase. The technique involves the selective intubation of the bypass graft with a catheter and then advancing a hollow guide wire or catheter through the first catheter into the occluded graft. An infusion of urokinase is then begun through both catheters (total dose, 10004000 U/min). The catheters are securely anchored at the skin access site, and the patient is returned to the coronary care unit for monitoring. Four hours following the start of the infusion, the patient is returned to the catheterization laboratory for selective angiography of the graft. If the graft has re canalized, definitive balloon angioplasty may be performed. If the graft remains occluded, the infusion may be continued with repeat angiography at 4- to 8-hour intervals. The infusion may be continued for up to 72 hours. This approach is best suited to patients with refractory angina pectoris who are not considered candidates for repeat bypass surgery. In our experience, we have treated 14 patients with occluded coronary bypass grafts according to the protocol described by Hartman et apo with gratifying results (Fig. 1). Recanalization was obtained in 9 of 14 (64%) patients with totally occluded bypass grafts resolving the patient's angina. Three patients required repeat coronary bypass surgery; two patients were given medical therapy after unsuccessful PTCA. Compli-

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Figure 1. A, Proximal occlusion of saphenous vein bypass graft (arrow). B, Partial recanalization after 4-hour infusion of urokinase at 2000 U/min with residual thrombi present (arrows). C, Complete recanalization after 12 hours.

cations have been relatively minor, limited to hematoma formation at the groin site and distal embolization in the coronary artery from the dissolving thrombus in the bypass graft. We have also employed this method in native coronary arteries that were subtotally or totally occluded with thrombus. Our experience agrees with that reported by Chapekis et al,l1 and we have found that an infusion of urokinase prior to angioplasty can markedly improve the PTCA result in a vessel compromised by a heavy burden of thrombus. Adjunctive thrombolytic therapy may also be of use in salvaging a failed angioplasty attempt due to thrombosis of the artery. In this setting, usually following balloon dilation of a lesion, urokinase is infused directly through the balloon catheter to the site of thrombosis at a dose of 100,000 to 250,000 U over 30 minutes. Schieman and coworkers 63 have reported the use of adjunctive intracoronary urokinase in addition to angioplasty in patients with acute ischemic syndromes in vessels with flow-limiting thrombus. Benefits included a high angiographic success rate that was maintained throughout the hospital stay. In our experience, the adjunctive use of urokinase in this setting is frequently successful in avoiding emergency bypass surgery for these patients. Prolonged Balloon Inflations

The development of perfusion balloon catheters, which allow blood to flow through the guidewire lumen of the balloon catheter and allow perfusion to the myocardium'distal to the dilated lesion during balloon inflation, has allowed investigators to perform prolonged (5-15 minute) balloon inflations. In theory, longer inflations may be more effective in

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overcoming elastic recoil of the dilated artery and useful for treating flaps or dissections caused by the balloon inflation. It has been our experience, and that of others,3Y that prolonged inflations are an effective means of treating dissections that may precipitate abrupt occlusion of the artery following angioplasty. A unique clinical application of perfusion balloons is the extremely long balloon inflation of several hours. 7 This technique is justified when the usual prolonged inflations fail to restore arterial patency in a patient who is a poor candidate for surgical intervention. We have had experience with two such patients, both of whom had excellent results after balloon inflations of 4 hours, having already failed 15~ and 30minute inflations. In both patients, an excellent angiographic result was obtained, and myocardial damage was avoided. Cardiopulmonary Assist During PTCA

The use of a cardiopulmonary bypass pump with an oxygenator as hemodynamic support during high-risk angioplasty has been a major advance allowing balloon angioplasty to be safely performed in patients who, otherwise, could not have tolerated the transient myocardial ischemia caused by balloon inflation. 75 This system includes a centrifugal pump and oxygenator and uses 18- to 21-Fr femoral arterial and venous cannulae. These cannulae may be placed percutaneously or by surgical cutdown. The cannulae will support 4 to 5 Llmin of flow, which, in our experience, adequately supports the poorest left ventricular function during the transient ischemia induced with balloon inflation. This femora-femoral cardiopulmonary bypass has two major applications. In patients with left ventricular failure in whom the dilated vessel supplies the only remaining viable myocardium, the patient is placed on cardiopulmonary bypass before the PTCA is begun. The bypass system supports the patient's hemodynamics and allows the PTCA to proceed under controlled conditions. The second application for cardiopulmonary bypass in the catheterization laboratory is when a patient with a failed angioplasty becomes hemodynamically unstable. This can be a very effective technique to stabilize the patient and allow further attempts at PTCA or the con trailed delivery of the patient for emergency coronary bypass surgery. The major drawbacks to using this technique are related to the insertion site, blood loss, hematomas, and the morbidity of wound healing. It is also recommended that patients not be supported by the machine for more than 4 hours owing to depletion of clotting factors and damage to the blood elements. NEW THERAPEUTIC DEVICES Laser Angioplasty

The use of laser energy for the recanalization of obstructed arteries has been of great interest. One potential advantage of using laser

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energy is the ability to vaporize tissue precisely within the blocked artery, thereby removing the atherosclerotic plaque. It is hoped that the laser would reduce the rate of restenosis following angioplasty and that more complex lesions and diffusely diseased arteries could be safely recanalized using this technique. A number of laser wavelengths have been investigated and applied to clinical laser angioplasty, including ultraviolet (excimer), visible, and infrared lasers. We have been very interested in the development of the midinfrared wavelengths of light for use in angioplasty. The potential advantages of the mid-infrared wavelengths include their selective absorption by water, which allows the efficient ablation or vaporization of tissue that has a very high water content, and their efficient transmission in optical fibers which is necessary when delivering the laser light through coronary catheters. These are pulsed lasers that deliver energy in very short bursts to minimize any thermal effects to surrounding tissues when the plaque is vaporized. Finally, the midinfrared lasers can remove calcified tissue. 41 The newest laser angioplasty system to begin clinical trials is the holmium:yttrium-aluminum-garnet (holmium:YAG) at a wavelength of 2.1 f.Lm. This laser is a solid-state device that allows compact storage. The prototype laser catheters (Trimedyne, Santa Ana, CA) are either 1.6 or 2.0 mm in diameter. The catheters contain multiple small optical fibers arranged in a concentric ring at the tip of the catheter, and the catheter has a central lumen for placement of a guidewire. The catheter follows the guidewire in the coronary artery lumen (analogous to conventional balloon angioplasty techniques), which decreases the possibility that the laser catheter will perforate the artery. Patients may be selected for the laser protocol if their coronary stenoses are considered unfavorable for routine angioplasty. Typically, the lesions are longer than angioplasty balloons (2: 2.0 cm), heavily calcified, or located in bypass grafts. We have successfully performed laser angioplasty in 16 of 17 (94%) lesions in 14 patients (Table 1). One of the stenoses was treated with the laser alone, nine required adjunctive balloon dilation, and six received directional atherectomy following laser angioplasty to reduce the stenosis further (Fig. 2). The major drawback to all current laser angioplasty systems is that the size of the recanalized lumen is too small, and, therefore, an adjunctive therapy such as balloon angioplasty is necessary to complete

Table 1. HOLMIUM:YAG CORONARY LASER ANGIOPLASTY RESULTS Lesions (n)

Prestenosis (%)

Post laser

(%)

After Final PTCA (%)

16

97.1 ± 4.9

38.8 ± 15.4*

8.3 ± 9.2t

Includes one lesion treated with laser alone, six lesions treated with adjunctive directional atherectomy, and nine lesions treated with adjunctive balloon dilation. *P 77 >81 69 0 72 95 >81 73

Therapy PTCA PTCA MED None MED CABG MED CABG

*If the ultrasound sheath was occlusive at the site of the lesion, the stenosis is given as the minimum value. Abbreviations: LM = left main; LAD = left anterior descending; LCX = left circumflex; MED = medical therapy; CABG = coronary bypass surgery; PTCA = coronary angioplasty; RCA = right coronary artery.

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In the six patients in whom angiography underestimated the severity of the coronary stenoses, two were referred for coronary artery bypass surgery, two underwent coronary balloon angioplasty, and two were treated with medical therapy for angina pectoris. We have demonstrated the clinical utility of intravascular ultrasound as an adjunctive diagnostic technique in patients with ambiguous findings on coronary arteriography. The results of the intravascular ultrasound study significantly affected the clinical management of our patients. The additional cost was justified because we avoided unnecessary angioplasty in two of the patients and were directed toward the appropriate therapy in the remaining six patients in whom angiography underestimated the severity of the coronary stenoses. Intracoronary Angioscopy

The ability to view the inner lumen of the coronary arteries directly through a percutaneous catheter during cardiac catheterization is afforded by the coronary angioscopeY' 78 The coronary angioscope (Advanced Cardiovascular Systems, Santa Clara, CA) is a 4.3-Fr polyethylene catheter that externally closely resembles a balloon angioplasty catheter. The angioscope has four channels: one to inflate/deflate the distal occlusion balloon, one for the 0.2-mm fiberoptic image bundle, one for the illumination fibers, and one used as a guide wire and distal flush lumen. The tip of the angioscope can be directed or steered into coaxial alignment with the vascular lumen in tortuous coronary arteries with a specially developed 0.014-in guidewire (Advanced Cardiovascular Systems, Santa Clara, CA). This wire has several sinusoidal bends placed over the distal several centimeters of the wire. By withdrawing these bends into the angioscope, the distal tip of the angioscope is passively deflected. The guidewire may also be rotated to allow circumferential viewing of the vascular lumen. The angioscope has two proximal connectors for coupling the illumination fibers to a "cold" halogen light source and the 2000element fiberoptic imaging bundle to a color television camera. The images are displayed on a color video monitor and archived on 0.7S-in videotape. We have performed intracoronary angioscopy before and after coronary angioplasty in ten patients with stable angina. 60 All had atherosclerotic plaque identified. Neither intracoronary thrombi nor plaque ulcerations were seen in any patient either by angiography or angioscopy. Intimal disruption or dissection was not detected by angiography or angioscopy in any of these stable angina patients prior to PTCA. Following balloon angioplasty, plaque fracture and dissections that had not been detected by angiography were seen in 3 of 10 (30%) stable angina patients. Percutaneous angioscopy was also performed in 18 patients with

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unstable angina before and after PTCA. 60 All of the patients had atherosclerotic plaque associated with their coronary lesions, which most commonly were yellow to yellow-brown in color. Before angioplasty, intracoronary thrombi were visualized angioscopically in 8 of 18 (44%) patients, of which only 2 (11%) were seen angiographically. Following coronary angioplasty, intracoronary thrombi were seen in 12 of 18 (66%) patients with the angioscopy, of which only two were identified with angiography (Table 3). These results confirm the intraoperative angioscopy study by Sherman et al65 in which they documented both a surprisingly high incidence of intracoronary thrombi in patients with unstable angina and the insensitivity of angiography in detecting these thrombi. Dissections were either delicate white fronds of tissue that appeared to be shallow intimal dissections or deep plaque fractures that extended deeply into the arterial wall and appeared to be medial dissections. Plaque ulcerations were seen in 5 of 18 (28%) unstable angina patients by angioscopy versus none being detected by angiography. Prior to angioplasty, no dissections were detected by angiography, but five patients were seen to have dissections by angioscopy. Following angioplasty, dissections were seen angioscopically in 18 of 18 unstable angina patients as opposed to angiographic detection of dissection in 3 of 18 (17%) (Table 3). This superior ability of the angioscope to detect intimal disruptions is due to the high-resolution optics that enable the operator to image subtle details of the surface morphology of the artery. The majority of the arterial dissections seen were very small, shallow tears that were not of sufficient magnitude to be detected by angiography. We have also performed angioscopy in five patients with angiographic restenosis following coronary balloon angioplasty. 7R Atherosclerotic plaque in this group of patients was distinctive in that in four of the five patients the lesions were white and had a fibrotic appearance. The white fibrotic appearance of the restenosis lesions is consistent with the hypothesis that restenosis is secondary to smooth muscle and fibrointimal proliferation. The single lesion that contained yellow pigmentation was from a patient who had early restenosis 6 weeks following balloon angioplasty. Angioscopically, there was evidence of a very large dissection that had healed in such a manner as to narrow the lumen of the coronary artery significantly. When compared with angiography, angioscopy offers a superior sensitivity and specificity for identifying these subtle changes in atherosclerotic plaque morphology. As with angiography, this is a percutaTable 3. A COMPARISON OF MORPHOLOGIC FINDINGS WITH ANGIOSCOPY VERSUS ANGIOGRAPHY IN UNSTABLE ANGINA (n = 18) Pre-PTCA

Thrombus Dissection

Post-PTCA

Angioscopy (%)

Angiography (%)

Angioscopy (%)

Angiog ,phy (%)

8/18 (44) 5/18 (28)

2/18 (11) 0

12/18 (66) 18/18 (100)

2/18 (11) 3118 (17)

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neous technique that can be used during diagnostic angiography to examine suspicious regions or lesions more closely and, it is hoped, provide more precise data concerning the progression of coronary disease. Angioscopy allows the in vivo examination of the surface pathology of a coronary artery. Our early studies suggest that angioscopy will help to improve our understanding of coronary artery lesion morphology. PERCUTANEOUS PERIPHERAL VASCULAR INTERVENTION

As with PTCA for coronary artery disease, percutaneous transluminal angioplasty (PTA) is recognized as a safe and effective alternative to surgery for selected patients with peripheral vascular disease. Since its first description by Charles Dotter in 1964, and subsequent development of inflatable balloon catheters in 1974, the procedure has gained broad acceptance among vascular surgeons, cardiologists, and interventional radiologists. IS, 28 In addition to its efficacy, which is roughly comparable to that of bypass surgery for certain types of lesions, angioplasty offers several distinct advantages over surgery,31, 51 It is performed under local anesthesia, making it feasible to treat patients who are at high risk for general anesthesia, When compared with surgical revascularization, the morbidity from angioplasty is low, generally related to problems with the vascular access site, and mortality is extremely rare. Unlike vascular surgery, there is no recovery period after angioplasty and most patients can return to normal activity within 24 to 48 hours of an uncomplicated procedure, Finally, angioplasty can be repeated, if necessary, and does not preclude surgery as adjunctive or definitive therapy. TECHNIQUE OF ANGIOPLASTY

For coronary angioplasty, percutaneous retrograde femoral access is commonly preferred, and a knowledge of how to handle the coronary guiding catheter is critical to the success of the procedure,9 In contrast, arterial access is the key to a successful procedure in peripheral angioplasty. Based on clinical and angiographic evaluation, vascular access is planned to allow visualization of the lesions during the procedure and to enable the operator to cross and dilate stenoses and occlusions successfully, At the Ochsner Clinic, depending on the circumstances, the ipsilateral femoral artery (retrograde or anterograde), brachial artery, or popliteal artery is cannulated with a percutaneous sheath using the modified Seldinger technique. The contralateral femoral artery is cannulated in certain circumstances, such as when there are lesions in the

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distal external iliac, common femoral artery, or proximal superficial femoral artery. With certain patients, the best site for vascular access may be via the brachial or popliteal arteries, and these vessels will be used on occasion. Patients are routinely pretreated and maintained on aspirin, 80 to 325 mg orally each day, and 3000-5000 units of heparin is administered after arterial access is secured. Baseline angiography is performed, and the lesion or lesions are then crossed with a guidewire. For most stenoses, a soft-tipped, stiff-bodied straight wire is used, such as a Wholey wire (Advanced Cardiovascular Systems, Santa Clara, CA) or an Amplatz Extra Stiff Straight Wire (Cook, Bloomington, IN), to cross the lesion atraumatically and support the balloon catheter. For total occlusions, a hydrophilic guidewire (Glidewire, Meditech, Watertown, MA) is used to cross the lesion. Although we have used thermal and free-beam lasers in crossing total occlusions (primarily in experimental protocols), they are rarely needed. After the lesion is successfully crossed with a guidewire, a balloon catheter that is long enough to encompass the lesion and the same size or slightly smaller in diameter than the nondiseased vessel segment adjacent to the lesion is passed across the stenosis or occlusion and inflated to the minimum pressure required to achieve complete balloon inflation. After successful balloon dilatation, angiographic flow is confirmed by brief test injections through the tip of the balloon catheter or through the sheath. If an acceptable angiographic result is present, a final angiogram is performed and the sheath is subsequently removed. After the procedure, heparin is used only in those situations where intravascular thrombus is present angiographically after balloon inflation. Patients are kept at bed rest for 6 to 8 hours after sheath removal, and most are generally kept in the hospital overnight to monitor for complications such as contrast reactions, bleeding, distal embolization, and vessel occlusions. ANGIOPLASTY OF THE LOWER EXTREMITY

Peripheral angioplasty has been shown to be a safe and effective means of restoring blood flow in symptomatic patients with symptomatic lower leg ischemia. The long-term results of angioplasty for stenoses and occlusions of the lower extremity compare favorably with the surgical results, and the morbidity from angioplasty is less than that of surgical treatment. 31 The selection of patients for angioplasty should follow the same guidelines established for surgically treating patients with peripheral vascular disease. Accepted indications for performing angioplasty include lifestyle limiting or progressive claudication, ischemic pain at rest, nonhealing ischemic ulcerations, and gangrene. Before attempting angioplasty, patients should have angiographically demonstrated vascular lesions that are amenable to angioplasty.31 The primary success of the procedure is dependent on several

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factors. A favorable primary result is more likely with stenoses than with total occlusions; with aortoiliac than femoropopliteal or tibioperoneal disease; and with claudicators rather than limb salvage situations. 51, 72 In our initial experience with 164 patients undergoing peripheral angioplasty, the primary success rate, defined as less than 30% residual angiographic stenosis without a major complication, was more dependent on lesion characteristics than vessel location. With stenoses and total occlusions less than 3 cm in length, regardless of vessel location, the primary success rate was 99% versus a success rate of only 80% for stenoses and total occlusions longer than 3 cm. The long-term success of peripheral angioplasty is also determined by both clinical and anatomic variables. Restenosis rates tend to be lower in patients with claudication, aortoiliac disease, and good distal run-off. Conversely, restenosis is more likely to occur in patients with rest pain, femoropopliteal or tibioperoneal disease, and poor distal runoff.36 The indications for intervention and expected success rates for peripheral angioplasty will be reviewed by vessel location. Aortoiliac Disease

The primary success rate of angioplasty for aortoiliac stenoses ranges between 90% and 100%, with a 3-year patency rate of successfully dilated lesions between 70% and 90%. The primary success rate and long-term patency rates are lower for occlusions, which have a 33% to 85% primary success and 75% to 100% patency at 2 to 4 years. 78 These results compare favorably with the surgical results in patients undergoing aortoiliac and aortofemoral bypass, operations that have a 74% to 95% 5-year patency.45 In our institution, patients with isolated aortoiliac stenoses and short occlusions are generally offered angioplasty as an alternative to surgical revascularization (Fig. 5), and surgery is reserved for those patients who have a "shaggy" aorta, aneurysmal

Figure 5. A. High-grade right common iliac stenosis in a patient with severe, symptomlimiting claudication of the right leg. S, Simultaneous balloon inflation in both common iliacs, known as the "kissing balloon" angioplasty technique. C, Final angiographic result.

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disease, long total occlusions that do not appear to be amenable to angioplasty, or lesions that do not respond well to balloon angioplasty. Femoropopliteal Disease

Percutaneous angioplasty has a primary success rate between 70% and 97% for femoropopliteal atherosclerosis, with the success rate again being higher for stenoses than for total occlusions. In our initial experience with femoropopliteal angioplasty in 81 patients, the primary success rate was 91 %. The procedural success rate was higher in patients with stenoses (100%) than in those with total occlusions (75%). Patency rates for successfully dilated femoropopliteallesions range between 50% and 70% at 3 to 5 years. 79 As with aortoiliac disease, these results compare favorably with the results of infrainguinal surgical bypass. In patients with autogenous vein femoropopliteal bypass surgery, the 5-year cumulative patency is 78%. The 5-year patency is only 52% for Gore-Tex femoropopliteal grafts. 45 The long-term patency of aortoiliac and femoropopliteal angioplasty depends on both clinical and technical factors.8, 35 Clinical factors that negatively impact on a good long-term result include diabetes and the presence of rest pain or threatened limb loss. Technical factors that correlate with long-term failure of angioplasty include lesion length, lesion eccentricity, and poor angiographic appearance postangioplasty. 8 The status of the distal run-off in the tibial vessels also impacts on the long-term success of PT A. In one study of 370 patients undergoing angioplasty for lower limb ischemia, patients with greater than or equal to one vessel run-off had a 3-year patency of only 25% compared with 78% in patients with two- or three-vessel run-off. 35 In certain patients, a combined approach using angioplasty and surgery can be a safe and effective method of revascularization. In a recent report of 46 patients with severe ischemia, including 41 with rest pain or tissue necrosis, iliac angioplasty and infrainguinal surgical bypass were performed with a 93% five-year limb salvage rate and 72% five-year angioplasty patency rate. 54 These results are comparable with previously published results from surgical series for limb salvage procedures. 38, 58 Our approach to symptomatic patients with multilevel atherosclerosis of the lower extremity is to plan a strategy that will relieve the patient's symptoms with the lowest morbidity. This includes involvement by both the vascular surgeon and the interventional cardiologist; a combined approach is used if indicated. Tibioperoneal Disease

Angioplasty of the distal vessels in the leg has been performed in the past only in cases of threatened limb loss because of technical difficulty using standard peripheral angioplasty equipment. Salvage

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surgery for failed angioplasty below the knee also has an increased failure rate compared with iliofemoral revascularization. Although published experience is limited the earlier primary success rates for tibioperoneal angioplasty are about 85% and 1- to 2-year patency rates range between 40% and 85%.10, 61, 64, 79 The surgical results using saphenous vein bypass with 50% to 60% graft patency at 5 years are similar to long-term angioplasty results; however, no controlled study has been undertaken. The use of smaller, more flexible balloon catheters over steerable guidewires based on the design of coronary balloon angioplasty systems has yielded better angioplasty results. 13 In 111 patients with tibioperoneal angioplasty for claudication (47%), tissue loss (27%), or rest pain (26%), Dorros and his co-workersl6a had a primary success rate of 90% for all lesions, 99% for stenoses, and 65% for occlusions. At the time of hospital discharge, 95% of patients were symptomatically improved. These excellent results as well as our own experience support other authors' contentions that angioplasty of the tibioperoneal vessels should not be reserved only for limb salvage situationslO, 64; however, we feel that caution is still advised in patient selection because the surgical options are limited if angioplasty fails. THROMBOLYSIS FOR ACUTE AND CHRONIC EXTREMITY ISCHEMIA

Twenty-three years ago, Poliwoda and colleagues 57 described the first use of peripheral intravenous infusions of streptokinase for chronic arterial occlusions. A number of other reports followed, proving that treatment of chronic arterial occlusions with intravenous streptokinase had a disappointingly low success rate and a high complication rate. In 1972, Dotterl9,20 proposed that direct intra-arterial infusion might have a higher efficacy and lower complication rate, but even his own trials failed to support this contention. More aggressive infusion techniques, together with the use of newer thrombolytic agents such as urokinase and tissue plasminogen activator, have resulted in an improvement in the clinical results of intra-arterial thrombolysis and decreased complication rates. 23 The technique of direct intra-arterial infusion of thrombolytic agents has been used with increasing success in both chronic symptomatic occlusions and acute ischemia with threatened limb 10ss.23, 29, 37, 47-49, 70 Thrombolysis is proving to be a useful adjunct to percutaneous angioplasty for thrombotic native vessel occlusions as well as for occlusions of bypass grafts in both the lower and upper extremities,So McNamara et a147 reported results in patients with acute ischemia, defined as sudden onset of symptoms within 7 days, administering 4000 IU/min urokinase by direct intra-arterial infusion through a catheter imbedded in the thrombus and advanced serially during the infusion to remain in direct contact with the clot Overall success was obtained

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in 85%, with an 82% success rate for thrombosed vessels and 94% success rate for embolic occlusions. Success rates were similar in native vessels (88%) and occluded grafts (80%). Thrombolysis was used alone in 36%, in combination with angioplasty in 51 %, in combination with surgery in 5%, and in combination with both angioplasty and surgery in 8%. Newer, clot-specific agents have been used in an attempt to improve efficacy and reduce complication rates. Graor et aF6 and Verstraete 74 have reported success rates of 76% to 88% using tissue plasminogen activator (t-PA) with bleeding complications in up to 20% of patients. One randomized trial of thrombolysis comparing urokinase to tissue plasminogen activator failed to show a significant difference in successful thrombolysis or in clinical outcome; however, this study did note lower fibrinogen levels and increased speed of clot lysis in the patients given t-P A. 48 Although uncertainty exists regarding the optimal agent and dosage regimen, it is clear that intra-arterial thrombolysis has a growing role in the treatment of acute and recent thrombotic and embolic occlusions. In our institution, angiography is performed when patients present with acute ischemic symptoms. Thrombolytic therapy is administered only if the tip of the catheter can be imbedded in the thrombus (Fig. 6) and there are no contraindications to thrombolysis. In most cases, a coaxial infusion is used, which insures a high concentration of the lytic drug in the thrombotic occlusion. Angiography is repeated every 4 to 8 hours, and the catheters are advanced as needed to maintain contact with the thrombus. The infusion is continued until

Figure 6. Superficial femoral artery occlusion in a patient with abrupt onset of a cold,

painful left lower extremity. A, Total pcclusion of the mid superficial femoral artery with an abrupt cut-off and filling defect suggesting thrombus. S, Four hours after continuous urokinase infusion, partial recanalization is seen; however, there are persistent intraluminal filling defects. C, Complete recanalization without concomitant balloon angioplasty.

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clinical success is achieved, no further progress can be seen, or complications ensue. A decision whether and when to perform adjunctive surgery or angioplasty is made jointly by the vascular surgeon and angiographer. We have reviewed the results of 45 consecutive patients treated in our catheterization laboratory for peripheral arterial occlusion. Twentythree (51 %) bypass grafts and 22 (49%) native arteries were treated with an intra-arterial infusion of urokinase. The majority of the patients were treated with a coaxial infusion system. The average dose of urokinase was 418,550 ± 273,250 U (range, 96,000 to 1.25 million U). The mean duration of the infusion was 20.4 ± 13.1 hours (range, 0.5 to 50 hours). We successfully recanalized 37 of 45 (82%) patients. After recanalization, the ankle brachial indices rose from 0.37 to 0.94 (P < 0.01). There was no difference in success rates between the native arteries and bypass grafts. Our experience confirms that the majority of patients with limbthreatening ischemia due to peripheral arterial occlusion can be treated successfully with a local infusion of the thrombolytic agents and then receive definitive percutaneous or surgical therapy. SUBCLAVIAN AND VERTEBROBASILAR ARTERY ANGIOPLASTY

Experience with angioplasty of the upper extremity and head and neck vessels is very limited compared with the rather extensive data that have been compiled on angioplasty of the lower extremities. Because of the limited data available regarding the safety and efficacy of angioplasty in the subclavian and vertebral arteries, its use is considered to be investigational. 5 Preliminary results, however, are encouraging. 12, 16, 24, 50, 71, 73 The conventional treatment for severely limiting symptoms of subclavian steal refractory to medical therapy is carotid to subclavian artery bypassY The clinical success with surgical revascularization is about 75%; however, complication rates (15% to 33%) and mortality (5% to 8%) are relatively high. 5 , 22 One recent report suggests that angioplasty may be preferable to surgery in patients with symptomatic subclavian and innominate stenosis. 16 In 27 patients with arm claudication (37%), neurologic symptoms (26%), need for vascular access for PTCA or PTA (30%), or coronary ischemia due to internal mammary to coronary artery bypass grafting, the primary success rate of angioplasty was 100% with no complications. Two patients developed symptomatic restenosis and were successfully redilated. Follow-up data were obtained on 22 of 27 patients, 95% of whom were asymptomatic or improved at 28 months (range, 2-73 months). Surgical intervention in patients with vertebral and basilar artery disease is not commonly performed, and its efficacy has been questioned. 42 Most patients with symptomatic vertebral and basilar artery stenosis also have associated carotid disease, and their vertebral symp-

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toms are usually relieved by carotid endarterectomy. There is a small group of patients who are candidates for vertebral or basilar artery revascularization because they have no associated carotid stenosis or because their symptoms do not respond to carotid endarterectomy. Experience with angioplasty in these patients is limited to case reports SO ,72 and small series, 12,73 and although the results are promising, it is too early to recommend angioplasty outside of investigational protocols. RENAL ARTERY ANGIOPLASTY

Renovascular hypertension is probably the most common cause of remediable secondary hypertension, and incidence figures as high as 32% have been reported in patients with severe or accelerated hypertension. s1 Renal artery stenosis due to fibromuscular dysplasia should be suspected in any young patient with severe hypertension. Among elderly patients most likely to have renovascular hypertension are those with known atherosclerosis who also have accelerated or malignant hypertension, sudden worsening of previously stable hypertension, hypertension with concomitant renal failure, hypertension refractory to usual medical therapy, or decline in renal function in response to angiotensin-converting enzyme inhibitors. There should be a strong suspicion of renovascular hypertension in any patient who has a unilateral small kidney or flank bruit. New antihypertensive drugs, especially the angiotensin-converting enzyme inhibitors, have dramatically improved the ability to control the blood pressure in patients with renovascular hypertension, but these drugs do not ensure preservation of renal function. s1 Renal artery angioplasty has become an alternative to surgical revascularization for controlling hypertension and preserving renal function in both young patients with fibromuscular dysplasia and in elderly patients with atherosclerotic renal artery stenosis. The immediate and long-term results of unilateral angioplasty for nonostial atheromas have been recently reviewed. 68 Primary success rates range between 75% and 100%. Hypertension can be cured in roughly 25% of patients, with improvement in blood pressure control in an additional 30% to 60% by angioplasty in patients followed for 3 or 4 years after angioplasty in different series. We have developed a renal artery angioplasty system based on the design of coronary artery devices that allows hemodynamic as well as angiographic assessment during renal artery angioplasty and that has resulted in concurrent high-success and low-complication rates in a small series of patients. 77 Some investigators are now also exploring the use of atherectomy, stenting, and lasers for percutaneous renal artery revascularization. With improvements in technology and experience, angioplasty will probably continue to play an expanding role in the treatment of renal artery stenosis.

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DIAL VSIS ACCESS ANGIOPLASTV

The most common cause of dialysis access failure is stenosis in the access itself or its venous drainage, resulting in inadequate dialysis or thrombosis. Angioplasty is an accepted technique for prolonging the life of dialysis access sites and the short- and long-term results have been quite good. 25 , 46, 62 We have successfully performed PTA in one or more lesions in 51 patients, including 10 with endogenous arteriovenous fistulas and 41 with Gore-Tex grafts. 59 The stenoses were most commonly located in the venous anastomosis, venous drainage, or the Gore-Tex graft itself (74%); however, stenoses were also found in subclavian veins (16%) and proximal anastomoses (9%) in a small number of patients (Fig. 7). Angiographic success was obtained in 48 of 51 (96%) procedures. Restenosis occurred in 10 patients (20%), and 80% of these were successfully treated with repeat PTA. At 8 months, 48 of 51 fistulas remained patent and only 3 (6%) required surgical revision. These excellent results have made PT A the treatment of choice for failing dialysis access in our institution. NEW TECHNOLOGIES

As with coronary angioplasty, there has been an explosion of new devices developed for percutaneous angioplasty of peripheral vessels. These new techniques are intended to improve the immediate and

Figure 7. A, Subtotal occlusion of the brachial vein in a patient with a Gore-Tex dialysis shunt in his upper arm. B, Angiographic result after balloon angioplasty,

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long-term results of percutaneous intervention, including atherectomy, intravascular stenting, and laser angioplasty. Atherectomy

Atherectomy is defined as the removal of atheroma. Transluminal atherectomy can be performed by a number of devices; however, our discussion will be limited to the two techniques that have been investigated most thoroughly: directional atherectomy and rotational atherectomy. Transluminal atherectomy using the Simpson AtheroCath (Devices for Vascular Intervention, Palo Alto, CA) is well described in the literature. 2, 14, 15, 17, 27, 67, 76 It has been demonstrated to be a safe and effective method of treating stenoses in the lower extremities (Fig. 8). The primary success rate in various studies is between 87% and 100%, and the restenosis rate ranges between 14% and 52% .14,27,67 Directional atherectomy is ideally suited for eccentric, noncalcified lesions that are not easily dilated by balloon angioplasty; however, it is not well suited for the treatment of total occlusions or heavily calcified vessels. Rotational atherectomy uses a diamond-studded burr (Rotablator, Heart Technology, Bellevue, WA) that spins at more than 120,000 rpm over a guidewire and opens stenoses and occlusions by fine particle

A

Figure 8. Directional atherectomy. A, Subtotal occlusion of the superficial femoral artery with eccentric and complex morphology (arrow). B, Smooth angiographic result after directional atherectomy. Note lack of dissection.

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ablation. In preliminary reports, the procedural success rate is high and the complication rate is low; however, no follow-up data have been published regarding restenosis rates. IS, 82 It appears to be most useful in certain lesions that are not ideal for standard balloon angioplasty, namely ostial stenoses and short, heavily calcified lesions; however, published reports give only preliminary data and more data are required regarding long-term efficacy. Intravascular Stents

Another new type of device designed to improve the initial and long-term benefit of percutaneous revascularization is the intravascular stent. Stenting has been proposed as a method of dealing with both dissection and elastic recoil, which are thought to be the most common causes of primary angioplasty failure. Stent implantation may also reduce the incidence of late failure, or restenosis, due to neointimal hyperplasia by maintaining a wider neolumen than balloon angioplasty alone. 3 To test these hypotheses, a variety of different stents have been evaluated in clinical trials. 4 , ,10, 66, 69,82 Although experience with stenting is still limited, it is clear that iliac stenting with the Palmaz stent (Johnson & Johnson Interventional Systems, Warren, NJ) is very effective in treating abrupt reocclusion or dissection without surgery, and that the I-year patency for iliac stents exceeds 90%.4, 83 A prospective trial comparing stenting to conventional balloon angioplasty for iliac stenosis still needs to be done. In femoropopliteal stenoses, the abrupt reocclusion rates and restenosis rates are not improved by stenting,3, 83 limiting the application of stents in these vessels. Laser Angioplasty

The role of laser technology in the management of peripheral vascular disease remains uncertain at present. Clearly, one useful application of this technology would be in crossing totally occluded lesions not able to be crossed with a guidewire. 55 The utility of the laser in this situation is in allowing a percutaneous procedure to be performed in a patient who would otherwise require surgical revascularization. In 12 patients in whom a conventional angioplasty guidewire would not cross an occlusive lesion, we used laser-assisted balloon angioplasty with a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser and silica ball-tip laser fiber. We were able to obtain a successful result in 11 of 12 patients. Although the adjunctive use of lasers with other angioplasty devices has been associated with an initially high success rate, there has been no evidence that the incidence of restenosis has been reduced or the long-term result enhanced. The full potential of the percutaneous

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laser ablation of atheromatous tissue has been hampered by the inability to create a large enough neolumen to sustain vessel patency without adjunctive balloon angioplasty. SUMMARY

Angioplasty has become an established treatment for both coronary and peripheral atherosclerosis, and a number of new techniques and devices promise to improve the results of percutaneous intervention during the coming decades. It is likely that balloon angioplasty will remain the percutaneous treatment of choice for both coronary and peripheral intervention; however, we look with hope toward the development of new devices that will expand the role of percutaneous angioplasty and improve the long-term success of these procedures. As technical expertise grows with the new procedures, prospective randomized trials comparing them with standard PICA will be required to enable physicians to judge their clinical utility. References 1. Arnett EN, Isner JM, Redwood CR, et al: Coronary artery narrowing in coronary heart disease: Comparison of cineangiographic and necropsy findings. Ann Intern Med 91:350, 1979 2. Bates ER, O'Neill WW, Topol EJ: Percutaneous atherectomy catheters. Cardiol Clin 6:373, 1988 3. Becker GJ: Intravascular stents: General principles and status of lower-extremity arterial applications. Circulation 83(Suppl 1):122, 1991 4. Becker GJ, Palmaz le, Rees CR, et al: Angioplasty-induced dissections in human iliac arteries: Management with Palmaz balloon-expandable intraluminal stents. Radiology 176:31, 1990 5. Beebe HG, Stark R, Johnson ML, et al: Choices of operation for subclavian vertebral arterial disease. Am J Surg 139:616, 1980 6. Block pe, Myler RK, Stertzer 5, et al: Morphology after transluminal angioplasty in human beings. N Engl J Med 305:382, 1981 7. Brenner AS, Browne KF: Five-hour balloon inflation to resolve recurrent reocclusion during coronary angioplasty. Cathet Cardiovasc Diagn 22:107, 1991 8. Capek P, McLean GK, Berkowitz HO: Femoropopliteal angioplasty: Factors influencing long-term success. Circulation 83(Suppl 1):70, 1991 9. Carr ML: The use of the guiding catheter in coronary angioplasty: The technique of manipulating catheters to obtain the necessary power to cross tight coronary stenoses. Cathet Cardiovasc Diagn 12:189, 1986 10. Casarella WJ: Percutaneous transluminal angioplasty below the knee: New techniques, excellent results. Radiology 169:271, 1988 11. Chapekis A, George B, Candela R: Rapid thrombus dissolution by continuous infusion of urokinase through an intracoronary perfusion wire prior to and following PTCA: Results in native coronaries and patent saphenous vein grafts. Cathet Cardiovasc Oiagn 23:89, 1991 12. Courtheoux P, Tornade A, Theron J, et al: Transcutaneous angioplasty of vertebral artery atheromatous ostial stricture. Neuroradiology 27:259, 1985 13. Oavis RK, Bosher EP, Brown PW: Critical elements in successful tibial artery reconstruction based on a 10-year experience with reversed vein grafts. In Veith FJ

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(ed): Critical Problems in Vascular Surgery. St. Louis, Quality Medical Publishing, 1989 14. Dorros G, Iyer S, Lewin R, et al: Angiographic follow-up and clinical outcome of 126 patients after percutaneous directional atherectomy (Simpson Atherocath) for occlusive peripheral vascular disease. Cathet Cardiovasc Diagn 22:79, 1991 15. Dorros G, Iyer S, Zaitoun R, et al: Acute angiographic and clinical outcome of highspeed percutaneous rotational atherectomy (Rotablator®). Cathet Cardiovasc Diagn 22:157, 1991 16. Dorros G, Lewin RF, Jamnadas P, et a1: Peripheral transluminal angioplasty of the subclavian and innominate arteries utilizing the brachial approach: Acute outcome and follow-up. Cathet Cardiovasc Diagn 19:71, 1990 16a. Dorros G, Lewin RF, Jamnadas P, et a1: Below-the-knee angioplasty: Tibioperoneal vessels, the acute outcome. Cathet Cardiovasc Diagn 19:170, 1990 17. Dorros G, Lewin EF, Sachdev N, et al: Percutaneous atherectomy of occlusive peripheral vascular disease: Stenoses and/or occlusions. Cathet Cardiovasc Diagn 18:1, 1989 18. Dotter CT, Judkins MP: Transluminal treatment of arteriosclerotic obstruction: Description of a new technique and a preliminary report of its application. Circulation 30:654, 1964 19. Dotter CT, Rosch I, Seaman AJ: Selective clot lysis with low-dose streptokinase. Radiology 111:31, 1974 20. Dotter CT, Rosch I, Seaman AI, et al: Streptokinase treatment of thromboembolic disease. Radiology lO2:283, 1972 21. Duber e, Jungbluth A, RumpeJt H, et al: Morphology of the coronary arteries after combined thrombolysis and percutaneous transluminal coronary angioplasty for acute myocardial infarction. Am J Cardiol 58:698, 1986 22. Fields WS, Lemak NA: Joint study of extracranial arterial occlusions. JAMA 222:1139, 1972 23. Gardiner GA, Rao AK: Thrombolysis for peripheral arterial occlusions. Radiology 175:34, 1990 24. Gershony G, Basta L, Hagan AD: Correction of subclavian artery stenosis by percutaneous angioplasty. Cathet Cardiovasc Diagn 21:165, 1990 25. Gordon OH, Glanz S, Butt KM, et al: Treatment of stenotic lesions in dialysis access fistulas and shunts by transluminal angioplasty. Radiology 143:53, 1982 26. Graor RA, Risius B, Lucas V, et a1: Thrombolysis with recombinant human tissuetype plasminogen activator in patients with peripheral artery and bypass graft occlusions. Circulation 74(suppl 1):1, 1986 27. Graor RA, Whitlow PL: Transluminal atherectomy for occlusive peripheral vascular disease. JAm Coll Cardiol 15:1551, 1990 28. Gruntzig A, Hopff H: Perkutane rekanalisation chronischer arterieller verschlusse mit einem neuen dilatationskatehetr: modifikation der Dotter-Technik. Dtsch Med Wochenschr 99:2502, 1974 29. Hargrove We, Barker CF, Berkowitz HO, et al: Treatment of acute peripheral arterial and graft thromboses with low-dose streptokinase. Surgery 92:981, 1982 30. Hartman I, McKeever L, Teran I, et a1: Prolonged infusion of urokinase for chronically occluded aortocoronary bypass grafts. Am J Card 61:189, 1986 31. Health and Public Policy Committee, American College of Physicians: Percutaneous transluminal angioplasty. Ann Intern Med 99:864, 1983 32. Holmes OR, Vlietstra RE, Smith He, et al: Restenosis after percutaneous transluminal coronary angioplasty (PTCA): A report from the PTCA registry of the National Heart, Lung, and Blood Institute. Am J Cardiol 53:77c, 1984 33. Isner JM, Kishel J, Kent KM, et a1: Accuracy of angiographic determination of left main coronary arterial narrowing: Angiographic-histologic correlative analysis in 28 patients. Circulation 63:1056, 1981 34. Isner JM, Rosenfield K, Losordo DW, et al: Percutaneous intravascular US as adjunct to catheter-based interventions: Preliminary experience in patients with peripheral vascular disease. Radiology 175:61, 1990 35. Jens WO, Armstrong S, Cole SEA, et a1: Fate of patients undergoing transluminal angioplasty for lower-limb ischemia. Radiology 177:559, 1990

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36. Johnston KW: Balloon angioplasty: Predictive factors for long-term success. Semin Vasc Surg 3:117, 1989 37. Juhan e, Haupert S, Miltgen C, et al: A new intra arterial rt-PA dosage regimen in peripheral arterial occlusion: Bolus followed by continuous infusion. Thromb Haemost 65:635, 1991 38. Kalman PC, Hosang M, Johnston KW, et al: The current role for femorofemoral bypass. J Vasc Surg 6:71, 1987 39. Kereiakes 0, Stack R: Perfusion angioplasty. In Topol EJ (eds): Interventional Cardiology. Philadelphia, WB Saunders, 1990, pp 452-466 40. Kichikawa K, Uchida H, Yoshioka T, et al: Iliac artery stenosis and occlusion: Preliminary results of treatment with Cianturco expandable metallic stents. Radiology 177:799, 1990 41. Kopchok CE, White RA, Tabbara M, et al: Holmium:YAC laser ablation of vascular tissue. Lasers Surg Med 10:405, 1990 42. Lee NS, Jones HR: Extracranial cerebrovascular disease. Cardiol Clin 9:523, 1991 43. Leimgruber PP, Roubin CS, Hollman L et al: Restenosis after successful coronary angioplasty in patients with single vessel disease. Circulation 73:710, 1986 44. Mallery JA, Tobis JM, Cessert L et al: Evaluation of an intravascular ultrasound imaging catheter in porcine peripheral and coronary arteries in vivo. Circulation 78:11, 1988 45. Manic JA, Brewster DC: Common Problems in Vascular Surgery. Chicago, Year Book Medical Publishing, 1989, p 234 46. Martin Ee, Diamond NC, Casarella WJ: Percutaneous transluminal angioplasty in nonatherosclerotic disease. Radiology 135:27, 1980 47. McNamara TO, Bomberger RA, Merchant RF: Intra-arterial urokinase as the initial therapy for acutely ischemic lower limbs. Circulation 83:106, 1991 48. Meyerovitz MF, Coldhaber SZ, Reagan K, et al: Recominant tissue-type plasminogen activator versus urokinase in peripheral arterial graft occlusions: A randomized trial. Radiology 175:75, 1990 49. Motarjeme A: Thrombolytic therapy in arterial occlusion and graft thrombosis. Sem Vasc Surg 2:155, 1989 50. Motarjeme A, Keifer JW, Zuska AJ: Percutaneous transluminal angioplasty of the vertebral arteries. Radiology 139:715, 1981 51. O'Keeffe ST, Woods BO, Beckmann CF: Percutaneous transluminal angioplasty of the peripheral arteries. Cardiol Clin 9:515, 1991 52. Pandian N, Kreis A, Desnoyers M, et al: In vivo ultrasound angioscopy in humans and animals: Intraluminal imaging of blood vessels using a new catheter-based high resolution ultrasound probe [abstractJ. Circulation 78(Suppl 11):22, 1988 53. Pepine CJ, Feldman RL, Nichols WW, et al: Coronary arteriography: Potentially serious sources of error in interpretation. Cardiovascular Med 2:747, 1977 54. Peterkin CA, Belkin M, Canttelmo NL, et al: Combined transluminal angioplasty and infrainguinal reconstruction in multilevel atherosclerotic disease. Am J Surg 160:277, 1990 55. Pilger E, Lammer J, Bertuch H, et al: Nd:YAC laser with sapphire tip combined with balloon angioplasty in peripheral arterial occlusions: Long-term results. Circulation 83:141, 1991 56. Platko WP, Hollman J, Whitlow PL, et al: Percutaneous transluminal angioplasty of saphenous vein graft stenosis: Long-term follow-up. J Am Coli Cardiol 14:1645, 1989 57. Poliwoda H, Alexander K, Buhl V, et al: Treatment of chronic arterial occlusions with streptokinase. N Engl J Med 280:689, 1969 58. Rafferty TO, Avellone Je, Farrell CL et al: A metropolitan experience with infrainguinal revascularization: Operative risk and late results in northeastern Ohio. J Vasc Surg 6:365, 1987 59. Ramee SR, Rees AJ, Husserl FE, et al: Percutaneous angioplasty for preservation of dialysis access: Immediate results and follow-up [abstract]. Circulation 84(Suppl 11):292, 1991 60. Ramee SR, White CJ, Collins TJ, et al: Percutaneous angioscopy during coronary angioplasty using a steerable microangioscope. J Am Coli Cardiol 17:100, 1991 61. Ratner SW, Reilly CH, Cudas CJ: Percutaneous transluminal angioplasty in the treatment of ischemic disease of the lower extremity. J Foot Surg 22:86, 1983

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62. Saeed M, Newman GE, McCann RL, et al: Stenoses in dialysis fistulas: Treatment with percutaneous angioplasty. Radiology 164:693, 1987 63. Schieman G, Cohen BM, Kozina J, et al: Intracoronary urokinase for intracoronary thrombus accumulation complicating percutaneous transluminal coronary angioplasty in acute ischemic syndromes. Circulation 82:2052, 1990 64. Schwarten DE, Cutliff WB: Arterial occlusive disease below the knee: Treatment with percutaneous transluminal angioplasty performed with low-profile catheters and steerable guide wires. Radiology 169:71, 1988 65. Sherman CT, Litvack F, Grundfest W, et al: Coronary angioscopy in patients with unstable angina pectoris. N Engl J Med 315:912, 1986 66. Sigwart U, Puel J, Mirkovitch V, et al: Intravascular stents to prevent occlusion and restenosis after transluminal angioplasty. N Engl J Med 316:701, 1987 67. Simpson JB, Selmon MMR, Robertson GC: Transluminal atherectomy for occlusive peripheral vascular disease. Am J Cardiol 61:96G, 1988 68. Sos TA: Angioplasty for the treatment of azotemia and renovascular hypertension in atherosclerotic renal artery disease. Circulation 83(Suppl 1):162, 1991 69. Strecker EP, Liermann DD, Barth KH, et al: Expandable tubular tantalum stents for treatment of arterial occlusive disease with special reference to iliac arteries. Radiology 173:268, 1989 70. Sullivan KL, Gardiner GA, Kandarpa K, et al: Efficacy of thrombolysis in infrainguinal bypass grafts. Circulation 83(Suppl 1):99, 1991 71. Sundt TM, Smith He, Campbell JK, et al: Transluminal angioplasty for basilar artery stenosis. Mayo Clin Proc 55:673, 1980 72. Tegtmeyer CJ, Hartwell GO, Selby JB, et al: Results and complications of angioplasty in aortoiliac disease. Circulation 83(Suppl 1):53, 1991 73. Tournade A, Senglein JP, Braun JP, et al: Percutaneous transluminal angioplasty of the vertebral and subclavian arteries. J Neuroradiol 13:95, 1986 74. Verstraete M, Hess H, Mahler F, et al: Femoro-popliteal artery thrombolysis with intra-arterial infusion of recombinant tissue-type plasminogen activator: Report of a pilot trial. Eur J Vasc Surg 2:155, 1988 75. Vogel R, Shawl F, Tommaso e, et al: Initial report of the National Registry of Elective Cardiopulmonary Bypass-Supported Coronary Angioplasty. J Am Coli Cardiol 15:23, 1990 76. von Polnitz A, Nerlich A, Berger H, et al: Percutaneous peripheral atherectomy: Angiographic and clinical follow-up of 60 patients. J Am Coli Cardiol 15:682, 1990 77. White CJ, Ramee SR, Collins TJ, et al: Guiding catheter assisted renal artery angioplasty. Cathet Cardiovasc Diagn 23:10, 1991 78. White CJ, Ramee SR, Mesa J, Collins TJ: Percutaneous coronary angioscopy in patients with restenosis after coronary angioplasty. J Am Coli Cardiol 17:46B, 1991 79. Wildus OM, Osterman FA Jr: Evaluation and percutaneous management of atherosclerotic peripheral vascular disease. J Am CoIl Cardiol 21:3148, 1989 80. Widlus OM, Venbrux Ae, Benenati JF: Fibrinolytic therapy for upper-extremity arterial occlusions. Radiology 175:393, 1990 81. Working Group on Renovascular Hypertension, National Heart, Lung, and Blood Institute: Detection, evaluation and treatment of renovascular hypertension: Final Report. Arch Intern Med 147:820, 1987 82. Zacca NM, Raizner AE, Noon GP, et al: Treatment of symptomatic peripheral atherosclerotic disease with a rotational atherectomy device. Am J Cardiol 63:77, 1989 83. ZoIlikofer CL, Antonucci F, Pfyffer M, et al: Arterial stent placement with use of the wallstent: Midterm results of clinical experience. Radiology 179:449, 1991

Address reprint requests to Christopher J. White, MD Section on Cardiology Department of Medicine Ochsner Medical Institutions 1514 Jefferson Highway New Orleans, LA 70121