Percutaneous transluminal coronary angioplasty after previous coronary artery bypass surgery

Drug-Eluting Stents Versus Bare Metal Stents in Saphenous Vein Graft Intervention

Percutaneous coronary intervention (PCI) of saphenous vein graft (SVG) is associated with higher adverse event rates, lower procedural success, and inferior longterm patency rates compared with native vessel PCI. The ability to comply with dual antiplatelet therapy, and whether the patient will need an interruption in dual antiplatelet therapy, should be considered when deciding whether to implant a drug-eluting stent (DES) or bare metal stent (BMS) in an SVG. DES should be used for SVG PCI because they seem to reduce target vessel revascularization. This article reviews the evolution and contemporary evidence regarding use of DES versus BMS in SVG PCI.

Percutaneous coronary interventions in patients with prior coronary artery bypass surgery: changes in patient characteristics and outcome during two decades

PURPOSE

Patients who develop recurrent myocardial ischemia after coronary artery bypass graft (CABG) surgery are often referred for percutaneous coronary interventions. The objective of this study was to evaluate the changing demographic and clinical characteristics, and procedural and long-term outcomes, in patients with prior CABG referred for percutaneous coronary interventions during a 20-year period.

METHODS

We prospectively collected data on patients who underwent coronary interventional procedures following CABG surgery. We compared angiographic and procedural success, and long-term event-free survival, among patients who had procedures from 1979 to 1989 (n = 393), from 1990 to 1994 (n = 811), and from 1995 to 1998 (n = 937).

RESULTS

Patients in the 1995 to 1998 cohort were older, had a lower mean left ventricular ejection fraction, and were more likely to have diabetes, hypertension, and hyperlipidemia, but less likely to smoke. They were more likely to have treatment of complex lesions, including vein graft lesions, and had more prior CABG surgeries. More patients received intracoronary stents in 1995 to 1998. Both angiographic success rates (78% from 1979 to 1989, 88% from 1990 to 1994, and 91% from 1995 to 1998, P < 0.0001) and procedural success rates (78%, 86%, and 91%, P < 0.0001) improved with time. Long-term mortality was greater in the pre-1990 group (relative risk = 1.8, 95% confidence interval: 1.3 to 2.4) and 1990 to 1994 group (relative risk = 1.7, 95% confidence interval: 1.3 to 2.2) compared with the 1995 to 1998 group, as were the likelihoods of repeat revascularization and recurrent severe angina.

CONCLUSION

Although the demographic and clinical characteristics of patients who underwent percutaneous intervention following CABG surgery indicate that they are at increasingly greater risk of adverse cardiac events, success rates and long-term survival have improved with time. The rates of recurrent severe angina as well as of subsequent revascularization have also decreased, probably as a result of improvements in technique and greater use of stents and adjunctive medications.

Reperfusion therapy in patients with acute myocardial infarction and prior coronary artery bypass graft surgery (National Registry of Myocardial Infarction-2)

We reviewed data from the National Registry of Myocardial Infarction-2 to determine the differences in characteristics and outcomes in patients with acute myocardial infarction (AMI) who have undergone previous coronary artery bypass grafting (CABG), and those who have not, and between post-CABG patients who were treated with alteplase (recombinant tissue-type plasminogen activator [rt-PA]) and those who were treated with primary percutaneous transluminal coronary angioplasty (PTCA). Demographic, therapeutic, and outcome data from patients with AMI were collected at > 1,000 hospitals in the United States in collaboration with National Registry of Myocardial Infarction-2. Of the 45,925 patients receiving reperfusion therapy, 2,544 of the 39,574 treated with rt-PA (6.4%) had a history of CABG, and 375 of the 6,351 treated with primary PTCA (5.9%) had a history of CABG. Patients with a history of CABG were older, more likely to be men, and had more comorbidities, but prior CABG was still an independent predictor of mortality after multivariate regression analysis (odds ratio 1.23; 95% confidence interval 1.05 to 1.44). Among the post-CABG patients who received rT-PA or underwent PTCA, there was no significant difference in in-hospital mortality rate or the combined end point of death and nonfatal stroke. Thus, (1) prior CABG is an independent predictor of mortality, and (2) for post-CABG patients with AMI who are not in shock and who are lytic-eligible, reperfusion therapy with rt-PA and PTCA result in similar outcomes with regard to in-hospital mortality and the combined end point of death and nonfatal stroke.

Coronary artery and saphenous vein graft remodeling: a review of histologic findings after various interventional procedures--Part V

Catheter balloon angioplasty is a well accepted form of nonsurgical treatment of acutely and chronically obstructed coronary artery vessels. It is also the centerpiece for various new intervention techniques. Their morphologic effect on the site of obstruction has been termed "remodeling." Part V of this six-part series focuses on remodeling effects of balloon angioplasty on obstructed young (< or = 1 year) and old (> 1 year) saphenous vein bypass grafts.

Long-term clinical outcome after stent implantation in saphenous vein grafts

OBJECTIVES

We sought to determine the role of stent implantation in vein grafts by evaluating the long-term clinical outcome and estimated event-free survival at 5 years in 62 patients and by comparing our data with those of other treatment modalities previously reported.

BACKGROUND

Patients with recurrent angina after coronary artery bypass graft surgery pose a problem. Stent implantation has been advocated in an effort to avoid repeat operation and to address the limitations of balloon angioplasty.

METHODS

Patients undergoing stenting of a vein graft were entered into a dedicated data base. They were screened for death, infarction, bypass surgery and repeat angioplasty. Procedure-related events were included in the follow-up analysis. Survival and event-free survival curves were constructed by the Kaplan Meier method.

RESULTS

A total of 93 stents (84 Wallstent and 9 Palmaz-Shatz) were implanted in 62 patients. During the in-hospital period seven patients (11%) sustained a major cardiac event: two deaths (3%), two myocardial infarctions (3%) and three urgent bypass surgeries (5%). The clinical success rate, therefore, was 89%. During the follow-up period (median 2.5 years, range 0 to 5.9), another five patients (8%) died, 14 (23%) sustained a myocardial infarction, 12 (20%) underwent bypass surgery, and 14 (23%) underwent angioplasty. The estimated 5-year survival and event-free survival rates (free from infarction, repeat surgery and repeat angioplasty) were (mean +/- SD) 83 +/- 5% (95% confidence interval [CI] 73% to 93%) and 30 +/- 7% (95% CI 16% to 44%), respectively.

CONCLUSIONS

The in-hospital outcome of patients who underwent stent implantation in a vein graft is acceptable, but the long-term clinical outcome is poor. It is unlikely that mechanical intervention alone will provide a satisfactory or definite answer for the patient with graft sclerosis over the long term.

Excimer laser angioplasty vs. balloon angioplasty in saphenous vein bypass grafts: quantitative angiographic comparison of matched lesions

Technologies which ablate or debulk tissue may result in better angiographic outcomes by altering the elastic properties of the vessel wall. Accordingly, the procedural outcomes of 88 vein graft lesions treated by either excimer laser angioplasty with adjunct balloon angioplasty (PELCA + PTCA, n = 44) (Spectranetics CVX-300, 1.4-, 1.7-, or 2.0-MM catheters) or balloon angioplasty alone (PTCA, n = 44) were analyzed by quantitative angiography (Cardiac Measurement System). Lesions were individually matched for vessel position, reference diameter (RD), and minimal luminal diameter (MLD). Matching was deemed adequate as the preprocedure MLD (PELCA + PTCA, 1.14 +/- 0.48 mm; PTCA, 1.20 +/- 0.47 mm) and RD (PELCA + PTCA, 3.23 +/- 0.56 mm; PTCA, 3.25 +/- 0.57 mm) were not significantly different. There were also no significant differences between PELCA + PTCA- and PTCA-treated lesions with respect to patient age, graft age, lesion length, symmetry, and plaque area. Balloon diameter at maximal inflation was 2.77 +/- 0.55 mm (PELCA + PTCA group) and 2.84 +/- 0.59 mm (PTCA group), P = NS. Final MLD postprocedure was 2.17 +/- 0.54 mm and 2.19 +/- 0.55 mm for PELCA + PTCA- and PTCA-treated lesions (P = NS), respectively. Vessel stretch [(balloon diameter - MLD pre)/RD], elastic recoil [(balloon diameter - MLD post)/RD], and acute gain [(MLD post - MLD pre)/RD] were calculated and normalized for vessel size (RD). Vessel stretch (PELCA + PTCA, 0.60 +/- 0.22; PTCA, 0.59 +/- 0.24; P = NS), elastic recoil (PELCA + PTCA, 0.28 +/- 0.18; PTCA, 0.26 +/- 0.16), and acute gain (PELCA + PTCA, 0.34 +/- 0.24; PTCA, 0.31 +/- 0.23; P = NS) were not significantly different between the two treatment groups. In a matched population of successfully treated vein graft lesions, PELCA + PTCA did not reduce elastic recoil or improve immediate angiographic outcome, as compared with PTCA alone.

Clinical markers, management, and long-term follow-up of early ischemia after coronary artery bypass grafting

In summary, the occurrence of angina or myocardial infarction within 1 year after coronary bypass is associated with a high incidence of significant angiographic abnormalities. Early angiography is necessary to identify high-risk patients who could undergo revascularization. Patients with other markers of ischemia should have a noninvasive approach (stress imaging test) as initial evaluation, before coronary angiography is considered. When technically feasible, coronary angioplasty can be performed safely and with a high success rate. Repeat coronary bypass in this group of patients is associated with higher in-hospital complications. Patients with less compromised coronary anatomy can be treated medically with a good long-term outcome.

Percutaneous revascularization of ostial saphenous vein graft stenoses

OBJECTIVES

This study sought to evaluate the short-term results and long-term outcome of percutaneous revascularization of ostial saphenous vein graft stenoses in a large patient series.

BACKGROUND

Previous studies have demonstrated that the results of balloon angioplasty for native coronary ostial stenoses are significantly worse than those for nonostial lesions. However, it is controversial whether interventions in patients with ostial saphenous vein grafts carry a similar prognosis.

METHODS

We identified 68 consecutive patients with ostial (group I) and 72 consecutive patients with proximal, nonostial (group II) saphenous vein graft stenoses who underwent percutaneous angioplasty or directional atherectomy for a single new stenosis at the Cleveland Clinic between 1986 and 1992.

RESULTS

Success was achieved in 61 patients (89.7%) in group I and 64 (88.9%) in group II (p = 0.88). There were no differences in major procedural complications (death, Q wave infarction and bypass surgery) between the two groups. At a mean (+/- SD) follow-up of 23 +/- 17 months, 36 patients (64%) in group I had one or more adverse events (death, infarction, repeat coronary revascularization or cardiac-related hospital admission) compared with 34 patients (58%) in group II (p = 0.87). Twenty-eight patients (50%) were angina free in group I compared with 33 (56%) in group II (p = 0.65). During the follow-up period in group I, 7 patients died (13%), 10 had a myocardial infarction (18%), 11 had repeat bypass surgery (20%), 8 had repeat percutaneous interventions (14%), and 30 had one or more cardiac-related hospital admissions (54%). The incidence of these events was similar in group II except for a slightly higher incidence of myocardial infarction: 6 patients died (10%), 3 had a myocardial infarction (5%), 12 had repeat bypass surgery (20%), 12 had repeat percutaneous interventions (20%), and 26 had one or more cardiac-related hospital admissions (44%).

CONCLUSIONS

Unlike ostial native coronary disease, the clinical, procedural and follow-up profile of ostial saphenous vein graft revascularization is not significantly worse than proximal nonostial disease. This finding may be related to the overall suboptimal results of percutaneous revascularization in saphenous vein grafts compared with native coronary arteries or to the unfavorable intrinsic properties of ostial native coronary arteries compared with ostial vein grafts.

Immediate results and late outcomes after stent implantation in saphenous vein graft lesions: the multicenter U.S. Palmaz-Schatz stent experience. The Palmaz-Schatz Stent Study Group

OBJECTIVES

This study reports the multicenter registry experience evaluating the safety and efficacy of the Palmaz-Schatz stent in the treatment of saphenous vein graft disease.

BACKGROUND

Saphenous vein graft angioplasty is associated with frequent periprocedural complications and a high frequency of restenosis. Stent implantation has been shown to reduce restenosis, with improved long-term outcomes in the treatment of native coronary artery disease. Preliminary experience with stent placement in the treatment of saphenous vein graft lesions has been favorable.

METHODS

Twenty U.S. investigator sites enrolled a total of 589 symptomatic patients (624 lesions) for treatment of focal vein graft stenoses between January 1990 and April 1992. Follow-up angiography was performed at 6 months, and the clinical course of all study patients was prospectively collected at regular intervals for up to 12 months.

RESULTS

Stent delivery was successful in 98.8% of cases, and the procedural success rate was 97.1%. The lesion diameter stenosis decreased from 82 +/- 12% (mean +/- SD) before to 6.6 +/- 10.2% after treatment. Major in-hospital complications occurred in 17 patients (2.9%); stent thrombosis was found in 8 (1.4%); and major vascular or bleeding complications were noted in 83 (14.3%). Six-month angiographic follow-up revealed an overall restenosis rate (> or = 50% diameter stenosis) of 29.7%. Multivariate logistic regression analysis indicated that 1) restenotic lesions, 2) smaller reference vessel size, 3) history of diabetes mellitus, and 4) higher percent poststent diameter stenosis were independent predictors of restenosis. The 12-month actuarial event-free survival was 76.3%.

CONCLUSIONS

Stent implantation in patients with focal saphenous vein graft lesions can be achieved with a high rate of procedural success, acceptable major complications, reduced angiographic restenosis and favorable late clinical outcome compared with historical balloon angioplasty control series. The rigorous anticoagulation regimen after stent placement results in more frequent vascular and other bleeding complications. Future randomized studies comparing standard balloon angioplasty with stent implantation are warranted to properly assess the full impact of stent placement in the treatment of saphenous vein graft lesions.

Predictors and sequelae of distal embolization during saphenous vein graft intervention from the CAVEAT-II trial. Coronary Angioplasty Versus Excisional Atherectomy Trial

BACKGROUND

The purpose of this study was to identify the predictors and sequelae of distal embolization from a multicenter, randomized trial of saphenous vein graft intervention. The CAVEAT-II trial demonstrated that saphenous vein graft directional coronary atherectomy (DCA) was associated with greater angiographic success and less need for repeat intervention compared with percutaneous transluminal coronary angioplasty (PTCA) but at the cost of more acute complications--notably distal embolization.

METHODS AND RESULTS

In CAVEAT-II, 305 patients were randomly assigned to DCA (149 patients) or PTCA (156 patients) for lesions with > 60% diameter stenosis in vein grafts > or = 3 mm in diameter. Distal embolization occurred in 20 patients (13.4%) assigned to DCA and 8 patients (5.1%) assigned to PTCA (P = .011). Independent predictors of distal embolization were use of DCA (71% in distal embolization patients versus 47% in patients without distal embolization, P = .011) and presence of thrombus (39% in distal embolization patients versus 14% in patients without distal embolization, P < .00). In-hospital adverse events were more frequent after distal embolization; 71% versus 20%, odds ratio plus (95% confidence intervals) 9.87 (4.65, 20.94). At 12-month follow-up, adverse event rates were also higher in patients with distal embolization (odds ratio, 3.05 [1.95, 4.76]).

CONCLUSIONS

In this first prospective multicenter trial of saphenous vein graft intervention, distal embolization was more common after DCA than PTCA and in lesions containing thrombus. It also was associated with worse in-hospital and 12-month outcomes. The risk and sequelae of distal embolization should be considered when choosing a treatment strategy for vein graft disease.

Early and late quantitative angiographic results of vein graft lesions treated by excimer laser with adjunctive balloon angioplasty

BACKGROUND

Percutaneous excimer laser coronary angioplasty (PELCA) has been approved for treatment of diseased saphenous vein bypass grafts. However, detailed and complete quantitative angiographic analysis of immediate procedural and late follow-up results has not been performed.

METHODS AND RESULTS

PELCA using the CVX-300 excimer laser system was performed in 125 bypass lesions (mean graft age, 96 +/- 53 months; range, 2 to 240 months) in 106 consecutive patients at eight centers. Quantitative analyses of the procedural and follow-up angiograms were done with the Cardiac Measurement System. Stand-alone PELCA was done in 21 lesions (17%). Lesions were located at the ostium (20%), body (67%), or distal anastomosis (13%). The graft reference diameter was 3.26 +/- 0.79 mm (mean +/- SD). Minimal lumen diameter increased from 1.09 +/- 0.52 mm before treatment to 1.61 +/- 0.69 mm after laser and 2.18 +/- 0.63 mm after adjunctive balloon dilation (P < .001) but had declined at follow-up to 1.40 +/- 1.17 mm. Dissections were evident in 45% of lesions after laser treatment (types A and B, 27%; types C through F, 18%), including 7% occlusions. Angiographic success (< or = 50% diameter stenosis [% DS]) was 54% after laser and 91% after adjunctive PTCA, with an overall clinical success rate of 89%. In-hospital complications were death, 0.9%; myocardial infarction (Q-wave and non-Q-wave), 4.5%; and bypass surgery, 0.9%. Independent predictors of % DS after laser were reference diameter, lesion length, and minimal lumen diameter before laser. At angiographic follow-up in 83% of eligible patients, the restenosis rate per lesion (DS > 50%) was 52%, including 23 occlusions (24%). The only independent predictor of increased % DS at follow-up was lesion symmetry. Logistic regression indicated that smaller reference diameter was an independent predictor of late occlusion. Overall 1-year mortality was 8.6%. Actuarial event-free survival (freedom from death, myocardial infarction, bypass surgery, or target vessel percutaneous transluminal coronary angioplasty) was 48.2% at 1 year.

CONCLUSIONS

Excimer laser angioplasty with adjunctive balloon angioplasty can be safely and successfully performed in diseased, old saphenous vein bypass graft lesions considered at high risk for reintervention. The extent of laser ablation remains limited by the diameter and effectiveness of the catheters. Late restenosis and, in particular, total occlusion mitigate the early benefits of the procedure. Other approaches such as the routine use of additional anticoagulation (eg, warfarin) should be considered to reduce the risk of late occlusions and restenosis after laser angioplasty of bypass grafts.

Transluminal extraction catheter for the treatment of diseased saphenous vein grafts: a multicenter experience

To evaluate the efficacy, safety, and long-term results of atherectomy using the Transluminal Extraction catheter (TEC), patients with diseased saphenous vein grafts were enrolled in a prospective nonrandomized trial. Patients were followed to hospital discharge for acute complications and underwent routine 6-mo reevaluation with repeat cardiac catheterization to assess restenosis. Atherectomy was performed on 650 graft lesions in 538 consecutive patients (male 81%; mean age 66 yr; range 37-81). Mean graft age was 8.3 yr; (range 0.3-20) with 85% of grafts > 3 yr of age. Complex lesion morphology included thrombus (28%), ulceration (13%), and eccentricity (50%). Lesion success was achieved in 606 lesions (93%) with clinical success in 479 patients (89%). Lesion success was achieved in 90% of thrombus containing lesions, 97% of ulcerated lesions, and 97% of grafts > 3 yr. Complications included nonfatal myocardial infarction in 4 (0.7%) of patients, emergency bypass surgery in 2 (0.41%), and in-hospital death in 17 patients (3.2%). Angiographic follow-up at 6 mo was obtained from 268 lesions in 227 patients. The overall lesion angiographic restenosis rate was 60%. TEC atherectomy can be performed in patients with diseased saphenous vein grafts with high primary success and low complication rates. It is suitable for use in aged grafts, particularly in the presence of thrombus and ulcerations, and may be superior to balloon angioplasty alone in this group of patients.

Clinical and angiographic outcome following implantation of the new Less Shortening Wallstent in aortocoronary vein grafts: introduction of a second generation stent in the clinical arena

One of the factors felt to have contributed to the high rate of stent occlusion in the European registry of the coronary Wallstent in the 1980s was the frequent deployment of more than one stent to cover the target lesion. This resulted from a high degree of shortening of the Wallstent upon expansion. To overcome this limitation the design of the Wallstent was modified to reduce the degree of shortening. We report the results of a study of the first patients to undergo implantation of the new Less Shortening Wallstent. Thirty-five Wallstents were electively deployed in aortocoronary vein grafts in 29 patients. Stent deployment was successful in 35 of 36 attempts in 30 lesions. In five of the 30 lesions, a second stent was required to cover the proximal portion of the lesion. Angiographic success (< 50% residual diameter stenosis as determined by off-line quantitative coronary angiography) was achieved in all 29 patients. During the in-hospital phase, no major adverse cardiac event occurred (reintervention, re-CABG, myocardial infarction, or death) and five patients had hemorrhagic complications. Following hospital discharge, one patient had a subacute stent occlusion associated with symptoms and elevated cardiac enzymes at 11 days, another patient had symptoms and elevated cardiac enzymes (CK 300 U/I) at 22 days with a patent stent, five patients required balloon angioplasty within the 6 month follow-up period (four for restenosis and one for stent occlusion), one patient underwent re-CABG for a native artery stenosis distal to the anastomosis of the patent stented vein graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous transluminal coronary angioplasty in patients with prior coronary artery bypass grafting: ten years' experience

We evaluated the acute and long-term results of percutaneous transluminal coronary angioplasty in 140 patients with prior coronary artery bypass grafting treated over a 10-year period (1981-1991). Angioplasty was technically successful in 85% of 122 nonoccluded native vessels and in 86% of 50 saphenous vein grafts. Two patients (1.4%) had a myocardial infarction and there were three procedure-related deaths (2.1%). The cumulative probability of survival was 91.5% and 74.5% at 1 and 5 years, respectively. Survival free from myocardial infarction and repeat bypass grafting at 1 and 5 years was 77.3% and 53.9%, respectively. At census, 31% of the 117 survivors were asymptomatic, and 47% were improved by at least two angina grades. Coronary angioplasty provides an apparently safe and effective alternative method of revascularization in selected patients with prior coronary artery bypass grafting. This treatment strategy potentially avoids reoperation with its attendant risks.

Angiographic predictors of a rise in serum creatine kinase (distal embolization) after balloon angioplasty of saphenous vein coronary artery bypass grafts

Distal coronary embolization is thought to be increased in the balloon angioplasty of coronary by-pass vein grafts. One hundred fifty-five procedures of balloon angioplasty involving single vein graft dilatation were successfully performed. Distal coronary embolization was defined as an elevation of creatine phosphokinase greater than twice the preangioplasty value and positive MB fraction. Twenty procedures were found to have embolism by this definition. Forty preangioplasty angiograms were randomly selected from the remaining procedures and analyzed as a control group. Eight angiographic features were evaluated as possible risk factors for distal coronary embolization, i.e., diffusely diseased vein graft, presence of thrombus, ulcerated lesion surface, marked eccentricity, large plaque volume, lesion angulation, abrupt proximal face and ectasia. A diffusely diseased vein graft (p = 0.002), presence of thrombus (p = 0.006), irregular or ulcerated lesion surface (p = 0.007), large plaque volume (p = 0.02) and marked eccentricity (p = 0.03) were found to be important predictors by univariate analysis. A diffusely diseased vein graft and a large plaque volume were found to be important independent predictors by multivariate analysis. The presence of thrombus and an irregular or ulcerated lesion surface frequently coexist with a diffusely diseased vein graft. It is concluded that a diffusely diseased vein graft and a large plaque volume are important independent predictors of distal embolization, and thrombus and an ulcerated lesion surface are also important.

Balloon angioplasty for the treatment of lesions in saphenous vein bypass grafts

OBJECTIVES

The purpose of this review is to assess the value and limitations of balloon angioplasty for the treatment of saphenous vein bypass graft obstructions. The potential efficacy of new interventional techniques is discussed.

BACKGROUND

Treatment of ischemia due to saphenous vein bypass graft obstructions poses a difficult problem that will be encountered more often as the pool of surgically treated patients continues to accumulate. Reoperation is technically demanding and is associated with high mortality and morbidity rates. Balloon angioplasty may provide a suitable alternative.

METHODS

The review proposes a classification of patients with attempted saphenous vein graft angioplasty according to expected early and late outcome based on the data obtained from the relevant published data and personal experience.

RESULTS

Angioplasty of a nonocclusive obstruction in a saphenous vein bypass graft has an initial success rate of approximately 90% and is a safe procedure (procedural death rate < 1%, myocardial infarction rate < 4%). The overall average restenosis rate is 42%. Surgical standby is limited and technically difficult. Angioplasty of chronic total occlusions in old grafts is associated with poor initial and long-term results. The long-term clinical results are unfavorable because of the continuing progression of disease in nontreated vein graft segments and native coronary arteries, in addition to the high restenosis rate. New techniques, although promising, have shown neither better initial results nor reduction of restenosis. Stent placement may be useful in longer graft lesions containing friable material.

CONCLUSIONS

Patients may be classified into three groups according to expected early and late outcome on the basis of 1) unfavorable graft anatomy, 2) risk of cardiogenic shock in event of acute graft closure, and 3) age of grafts. The three groups are 1) those with an initial high success, low procedural risk and low restenosis rate; 2) those with an initial high success but high procedural risk and moderate to high restenosis rate; and 3) those with a low success, high risk and high restenosis rate. Balloon angioplasty to treat lesions in venous bypass grafts should be considered a palliative procedure, not a long-term solution, for ongoing progression of coronary artery and vein graft disease. The induced high restenosis rate remains a significant problem.

Coronary angioplasty in patients with previous coronary artery bypass grafting

Between 1982 and 1990, in 134 patients with prior coronary artery bypass grafting and recurrent angina, repeat coronary angiography and balloon angioplasty of stenoses in grafts or native arteries were attempted. Mean age of grafts was 45.6 months, range three days to twelve years. At the time of angioplasty, 6 patients had one-vessel-disease, 33 had two-vessel-disease, and 95 had three-vessel-disease. A total of 182 lesions were dilated: 55 venous grafts, 3 internal mammary artery grafts, and 124 native vessels. Forty-nine of 55 (89%) venous grafts could be successfully dilated, and in 3 internal mammary artery grafts, a stenosis reduction greater than 50% was achieved. In 65 of 88 (74%) grafted native arteries, dilation success was achieved. Twenty-seven of 36 (75%) patients with prior bypass surgery to other arteries had successful angioplasty of nongrafted native arteries. Three patients underwent emergency bypass surgery after dissection and acute occlusion: one of them died in cardiogenic shock secondary to acute myocardial infarction. The angiographic success rate in grafts was slightly higher than in native arteries (90% vs 74%). These data indicate that percutaneous transluminal coronary angioplasty in patients after bypass surgery is possible at a low risk (3%) and constitutes an effective therapy in symptomatic patients.

Prolonged intravenous urokinase infusion: an alternative pharmacologic approach in the treatment of thrombus-containing saphenous vein graft stenoses

A subtotally occlusive saphenous vein graft stenosis resolved after rapid intracoronary and prolonged intravenous urokinase infusion. Additional therapy was unnecessary, avoiding the attendant risks of saphenous vein graft angioplasty. Combined intracoronary and intravenous urokinase infusion should be considered prior to coronary angioplasty of saphenous vein graft stenoses, particularly when diffuse degeneration is present or the risk of underlying thrombus is high.

Palmaz-Schatz stent implantation in stenosed saphenous vein grafts: clinical and angiographic follow-up

Balloon-expandable stents may reduce the restenosis rate following coronary angioplasty. To evaluate this potential in saphenous vein grafts, 26 patients with 30 discrete stenoses underwent conventional balloon dilation and successful Palmaz-Schatz stent implantation as part of a multicenter trial. All patients had resolution of their angina following the procedure. In a mean 5-month follow-up period, 14 patients (54%, 16 lesions) had repeat arteriography; two patients (14%) developed recurrent ischemia ascribed to their venous grafts from in-stent restenosis (2 of 16 lesions, 13%). Two asymptomatic patients (8%) died: one from cardiac arrest (stent patent) and one from stroke (no autopsy). The clinical recurrence rate (cardiac death, myocardial infarction, bypass surgery, repeat angioplasty, or symptom recurrence) was 15%. These preliminary results show trends toward an improved primary success rate with combined vein graft angioplasty/stenting and a lower restenosis rate in stented saphenous vein grafts, but continuing follow-up will be needed to verify these observations.

Stenting of venous bypass grafts: a new treatment modality for patients who are poor candidates for reintervention

During a 2-year period, 136 self-expanding Wallstents were implanted in saphenous vein bypass grafts in 69 patients with end-stage coronary artery disease. All patients had severe symptoms and the majority were poor candidates for either repeat surgery or conventional bypass coronary angioplasty because of unfavorable native anatomy, impaired left ventricular function, or a high-risk bypass lesion anatomy for coronary angioplasty. All procedures were technically successful without major complications and a need for emergency bypass surgery. However, during the hospital stay acute thrombotic complications occurred in seven patients (10%) resulting in one death and acute myocardial infarction in five patients and necessitating emergency repeat PTCA in two patients and repeat CABG in four. Twenty-three patients had serious hemorrhagic complications directly related to the rigorous anticoagulation schedule. Two patients died of fatal cerebral bleeding. During follow-up, another five patients died accounting for a total mortality rate of 12%. At late angiographic follow-up (4.9 +/- 3.4 months, n = 53), 25 patients (47%) had a restenosis (greater than or equal to 50% DS) within or immediately adjacent to the stent, necessitating reintervention in 19 patients (PTCA, n = 12; repeat CABG, n = 7). In the group without stent-related restenosis (n = 28), 15 patients had progression of disease in either the native or bypass vessels leading to recurrence of major anginal symptoms within 1 to 24 months. Ten of these patients required further intervention (stent, n = 6; PTCA, n = 3; repeat CABG, n = 1). Stenting in saphenous coronary bypass grafts can be performed safely with excellent immediate angiographic and clinical results.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term angiographic follow-up after angioplasty of venous coronary bypass grafts

From April 1981 to June 1987, 57 patients underwent venous coronary bypass graft percutaneous angioplasty and had a minimal follow-up of 18 months. The procedure was elective for 28 patients, urgent for 19, and was considered as an emergency for 10. A total of 64 grafts were dilated that had been bypassed 58 +/- 48 months previously (range 2 to 184 months); lesions were located on the aortic anastomosis in 12 grafts, on the body in 38, and on the coronary anastomosis in 14. Technical success was 95.3% (61 of 64) per lesion; clinical success was 84.4% (54 of 64) per lesion and 82.5% (47 of 57) per patient. Thrombotic complications with images of a lacunar defect occurred in 11 grafts (17.2%). Predictive factors for these complications were: age of grafts 38.5% for greater than 60 month grafts versus 2.6% for less than 60 month grafts (p less than 0.01); site of lesion, body lesion 28.9% versus anastomosis none (p less than 0.01); type of lesion, concentric and short 6% versus other 29% (p less than 0.05); and recent fibrinolysis in 66% versus 10.6% (p less than 0.05). Long-term follow-up is available in the 47 successful patients and the three limited non-Q wave myocardial infarction patients. Two patients died at 13 and 17 months. Long-term angiographic follow-up is available in 45 of 48 patients or 94%. At the end of the study, 35 of 57 (61.4%) venous bypass grafts in 32 patients (64%) were patent after one or more percutaneous transluminal angioplasties.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical factors affecting the immediate outcome of PTCA in patients with unstable angina and poor candidates for surgery

Percutaneous Transluminal Coronary Angioplasty (PTCA) has been successfully applied in unstable angina to carefully selected patients. In this study, PTCA was performed in 277 consecutive patients suffering from unstable angina and for whom bypass surgery was not a valid alternative because either of inoperable conditions or of emergency, or because surgery was not the best option. All patients were admitted first to the intensive care unit where an attempt was made to control unstable angina under conventional medical therapy using at least iv nitroderivative, heparin, and calcium blockers. After a standardized preparation PTCA was performed either as an emergency procedure in medically refractory unstable angina (107 cases) or as an elective procedure in controlled situations after a 7 to 10 days symptom-free period. Three hundred fifty-three coronary vessels were attempted. Results of this group are compared with those of a control group made of 670 consecutive stable patients recruited during the same period, and clinical characteristics are envisaged as potential predictive factors. Unstable angina is undoubtedly associated with a higher overall complication rate, but the immediate outcome is strongly affected by the clinical context. As an example, respective success and mortality rates are: 93% and 0% when a full revascularization is attempted; 91% and 0% in elective procedures in patients under 60; 87% and 1.2% in elective PTCA for multiple vessel disease; 80% and 6.5% in emergency PTCA; 80% and 11% in the overall triple vessel disease; 84% and 16% in patients with deeply altered ejection fraction; and 58% and 26% in triple vessel disease with 2 previously occluded coronary arteries.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous transluminal angioplasty of aortocoronary venous bypass grafts and effect of the caliber of the grafted coronary artery on graft stenosis

The influence of morphologic parameters on the recurrence of stenosis after percutaneous transluminal coronary angioplasty of 49 stenoses in aortocoronary venous bypass grafts of 41 patients was investigated. Vessel dimensions were measured quantitatively. Angioplasty was successful in 46 stenoses (94%) of 38 patients (93%). In 35 patients (92% of successfully treated patients) with 42 stenoses, control angiography was performed after a mean interval of 189 +/- 186 days. In 9 patients (26%), 9 stenoses (21%) had recurred. The diameter of the grafted coronary artery distal to the anastomosis was significantly smaller in grafted arteries with than without recurrent stenoses (1.92 +/- 0.52 vs 2.45 +/- 0.50 mm; p less than 0.01). Recurrence also correlated with the ratio between graft diameter and coronary artery diameter greater than 1.35 (p less than 0.02) and with the stenosis length greater than 10 mm before angioplasty (p less than 0.01). Graft age, graft diameter and stenosis location in the graft had no significant influence on recurrence. Thus, the diameter of the grafted coronary artery and the length of the critical stenosis are parameters for recurrence after angioplasty of graft stenoses and should be considered in the selection of patients for this intervention.

Diffuse embolization following percutaneous transluminal coronary angioplasty of occluded vein grafts: the blush phenomenon

Percutaneous transluminal coronary angioplasty (PTCA) was performed on 146 saphenous vein grafts in 116 patients. In 29 patients, 31 grafts were totally occluded. Myocardial staining lasting over 5 minutes--"the blush phenomenon"--followed the opening of the occluded grafts in 9 of these patients. In 5 of these 9, enzyme release suggested infarction. A sixth patient died within a few hours of PTCA, with suspected infarction. Autopsy demonstrated diffuse and extensive distal coronary arterial embolization of grumous material, including cholesterol crystals, platelets, and fibrin. The blush phenomenon was not seen following PTCA in the remaining 20 patients with total occlusions, nor in any of the 87 patients with stenosed grafts. We have not observed the blush phenomenon following PTCA of more than 3300 coronary arteries. Of the 9 patients demonstrating the blush phenomenon, 6 had a recent history of myocardial infarction or unstable angina pectoris, compared with 4 of the remaining 20 patients with occluded grafts. We now approach occluded grafts with injection of intragraft thrombolytic agents or with atherectomy prior to PTCA. Future approaches may include atherectomy or laser angioplasty.

The Dutch experience in percutaneous transluminal angioplasty of narrowed saphenous veins used for aortocoronary arterial bypass

Of 19,994 percutaneous transluminal coronary angioplasty procedures performed in The Netherlands between April 1980 and January 1989, the long-term follow-up of 454 patients who underwent angioplasty of greater than or equal to 1 saphenous vein bypass graft was reviewed. In 46% of patients single graft angioplasty was attempted, and in 54% of patients sequential graft angioplasty was attempted. The clinical primary success rate was 90%. In-hospital mortality was 0.7%, 2.8% of patients sustained a procedural myocardial infarction, and 1.3% of patients underwent emergency bypass surgery. After a follow-up period of 5 years, 74% of patients were alive, and 26% were alive and event-free (no myocardial infarction, no repeat bypass surgery or repeat angioplasty). In patients in whom the initial angioplasty attempt was unsuccessful, only 3% were event-free at 5 years, versus 27% of successfully dilated patients. The time interval between the angioplasty attempt and previous surgery was a significant predictor for 5-year event-free survival. The event-free survival rates for patients who had bypass surgery 1 year before, between 1 and 5 years, and 5 years before angioplasty, were 45, 25 and 19%, respectively. Less than one-third of patients with previous bypass surgery who had angioplasty of the graft remained event-free after 5 years. In patients needing angioplasty within 1 year after bypass surgery, better long-term results were achieved.

Early postoperative balloon coronary angioplasty for failed coronary artery bypass grafting

In a small number of patients, coronary artery bypass grafting (CABG) fails to relieve anginal symptoms. The usefulness of coronary angioplasty for the treatment of early (less than or equal to 90 days) recurrent ischemia after CABG was examined. Forty-five patients were treated from 2 to 90 days after CABG, including 8 patients studied emergently for prolonged ischemic symptoms. One-, 2- and 3-vessel native disease was found in 4, 10 and 31 patients, respectively. At the time of postoperative angiography, the major anatomic mechanism of recurrent ischemia was complete vein graft occlusion in 12 patients (27%), internal mammary artery occlusion in 3 (7%), vein graft stenoses in 13 (29%), internal mammary artery stenoses in 10 (22%), unbypassed disease in 4 (8%) and disease distal to the graft insertion site in 3 (7%). Angioplasty was successful at 91 of 98 sites (93%), including 95% of 41 lesions in native arteries, 89% of 46 lesions in vein grafts and 100% of 11 internal mammary artery lesions attempted. Complete revascularization was achieved in 84% of patients. There were 2 in-hospital deaths and 2 myocardial infarctions. Two additional patients underwent repeat CABG before discharge after uncomplicated but unsuccessful angioplasty. At late follow-up of the 43 survivors (mean 44 months), there were 4 deaths, 2 of which were noncardiac. Repeat CABG was required in only 3 patients and repeat angioplasty was performed in 10. Angina was absent or minimal in 35 patients; 17 patients were employed full time. Thus, percutaneous transluminal coronary angioplasty can relieve myocardial ischemia after unsuccessful CABG in the majority of patients.

Coronary angioplasty after coronary bypass surgery: initial results and late outcome in 422 patients

From 1978 to 1988, coronary angioplasty was performed in 422 patients with prior coronary artery bypass surgery (264 patients with native coronary artery angioplasty and 158 patients with graft angioplasty). Angioplasty was successful in 84%, unsuccessful but uncomplicated in 11% and complicated by one or more major cardiac events in 5% (myocardial infarction 5%, emergency bypass surgery 2% and death 0.2%). Follow-up data were obtained in 99% of 356 patients with successful angioplasty. At a mean of 33 +/- 26 months, 92% were alive, 73% had improvement in angina and 61% were free of angina. One or more of the following late events occurred in 67 patients (19%): myocardial infarction (6%), elective reoperation (13%) and cardiac death (6%). Repeat angioplasty was performed in 27%, with a success rate of 89% and no deaths. Initial success rates were equal in native vessel versus graft angioplasty, but late outcome was less favorable with the latter because of a higher rate of infarction (11% versus 4%, p less than 0.05) and need for reoperation (19% versus 10%, p less than 0.05). The initial success rate was higher in vein grafts less than 1 year old compared with grafts 1 to 4 years or greater than 4 years after operation (92% versus 85% versus 83%, respectively) and adverse late events were less frequent after angioplasty in recent vein grafts (less than 1 year 13%, 1 to 4 years 35%, greater than 4 years 29%; less than 1 versus greater than 1 year, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary angioplasty in patients with prior coronary artery bypass grafting

We studied the clinical and angiographic outcome of patients with prior coronary arterial bypass grafting who underwent percutaneous transluminal coronary angioplasty at the Royal Infirmary of Edinburgh. Over a 4 year period, 47 patients with prior bypass surgery underwent angioplasty of 23 stenotic graft sites and 37 stenotic sites of native vessels. The procedure was performed a mean of 31.3 months after surgery for recurrence of symptoms refractory to maximal medical treatment. Satisfactory angiographic results were achieved in 42 patients (58 stenotic grafts or native vessels). At a median follow up period of 18 months, 20 patients were symptomatically improved, but 22 patients experienced recurrence of symptoms a mean of 4.7 months after angioplasty, despite a good initial angiographic result. Overall, 4 patients had a repeat bypass grafting and 9 patients had a repeat angioplasty. Angioplasty can be used as an alternative to a repeat operation in patients with prior bypass grafting who experience recurrence of symptoms. Initial success rates are high and complication rates low. Restenosis or development of new lesions in the native circulation, and/or in the grafts, remain significant problems. Patients with a long asymptomatic interval (greater than 6 months) between the bypass operation and recurrence of symptoms are more likely to have better long-term results after successful angioplasty, perhaps because of slower progression of atherosclerotic heart disease.

Percutaneous transluminal angioplasty in patients greater than or equal to 5 years after their last coronary bypass graft surgery

Angioplasty (PTCA) was successfully performed in 257 of 304 patients (85%) greater than or equal to 5 years after their last bypass surgery. A lesion was successfully dilated in 496 of 566 vessels attempted (88%): 332/386 coronary arteries (86%) and 164/180 vein grafts (91%). Significant complications included: 8 (2.6%) mortalities, 4 (1.3%) emergency surgeries, 13 (4.3%) Q-wave myocardial infarctions, and 14 (4.6%) distal embolizations. Distal embolization occurred in 13/180 (7%) vein graft lesions dilated and usually resulted in a non-Q-wave infarction (4/13 distal embolizations). A second PTCA was performed on 89 (35%) patients: 44% of them had lesion recurrence; 20% a new lesion requiring dilatation; and 30% both recurrence and new lesion. Follow-up (mean 3.7 years) revealed 78% of patients having an improved anginal status, and 58% no angina. The cumulative probability of survival at 60 months was 88 +/- 3%. Angioplasty can be effectively employed in patients greater than or equal to 5 years remote from their last bypass surgery in native arteries or saphenous vein grafts with good procedural and long-term success. Vein graft age inherently does not appear to be a contraindication to angioplasty.

Internal mammary angiography: a review of technical issues and newer methods

Up to 90% of coronary bypass operations in some centers now include at least one IMA graft. In parallel with the increased use of IMA grafts, our catheterization laboratory records for 1986-7-8 demonstrate a progressive increase in IMA angiography, both absolutely (11, 28, 48 cases/yr) and as a percent of restudy procedures performed after prior bypass (14, 25, 43%). Unfortunately, these records also show that cannulation of the right and left IMAs may involve substantial technical hurdles, resulting in a mean time of 19 +/- 19 min from catheter insertion to selective IMA angiography. Based on this experience, we review a standard technique for IMA angiography using preformed catheters, and describe alternative methods (including use of PTCA guidewires with or without super-selective catheters, and non-selective angiography utilizing a specially designed balloon occlusion catheter).

Percutaneous transluminal angioplasty of saphenous vein graft stenosis: long-term follow-up

Percutaneous transluminal angioplasty was used to treat 101 patients with saphenous vein bypass graft stenosis at a mean of 50.1 months (range 2 to 196) after coronary artery bypass surgery. The patients presented between March 1981 and April 1987. A total of 107 saphenous vein grafts were dilated at 117 sites. The primary success rate was 91.8%. The incidence of cardiac complications was 7.1%. There were no cardiac complications in 53 patients with grafts implanted less than 36 months before angioplasty (Group 1). The 48 patients with grafts implanted for greater than 36 months (Group 2) had a 12.5% incidence rate of myocardial infarction, a 4% incidence rate of emergent bypass surgery and a 4% incidence rate of death for an overall cardiac complication rate of 14.9% (p less than 0.01). Follow-up was obtained at a mean of 16.8 +/- 13.9 months (range 1 to 54) in 87 patients (97% of successful cases). Repeat coronary angiography was performed in 49 patients and revealed restenosis in 30 patients (61.2%), with no difference in recurrence rates for proximal, mid or distal graft sites. Clinical recurrence (defined as recurrence of symptoms, myocardial infarction, repeat angioplasty, surgery or death) was 33.1% for Group 1 patients and 64.1% for Group 2 patients (p less than 0.01). The complication and recurrence rates of saphenous vein graft angiography are significantly higher when performed for late (greater than 36 months) vein graft failure. All therapeutic options should be carefully examined before proceeding with angioplasty for saphenous vein graft stenosis in this type of patient.

Role of angioplasty in patients with previous coronary artery bypass surgery

Fifty-nine patients with previous coronary artery bypass surgery (CABG) underwent coronary artery or vein graft angioplasty following a recurrence of symptoms, 141 lesions were attempted in 70 procedures. The overall angiographic success rate was 77%. Some angiographic success was achieved in 83% of patients. Complications included myocardial infarction in three (4.3%), death in one (1.4%), and iliac artery thrombosis in one (1.4%). No patients were referred for urgent surgery. Twenty-eight patients have undergone repeat coronary arteriography after 7.5 +/- 2.6 months (mean +/- SD), and 31% of lesions have recurred. Fifty-eight percent of patients without recurrence at follow-up continue to have improved symptoms. Treadmill exercise time was significantly prolonged in patients in whom all attempted lesions had been successfully dilated and in those in whom only some lesions were dilated. Our experience suggests that approximately 29% of patients with recurrence of angina following CABG may be suitable for angioplasty.

The clinical efficacy and scintigraphic evaluation of post-coronary bypass patients undergoing percutaneous transluminal coronary angioplasty for recurrent angina pectoris

The efficacy of percutaneous transluminal angioplasty in improving recurrent anginal symptoms and myocardial perfusion after coronary artery bypass graft surgery was assessed prospectively in 55 patients, of whom 50 had an initial angiographic and clinical success. Although 80% of those successfully dilated were initially free of angina at 23 +/- 11 months of follow-up, one half of these patients had recurrent angina. Although only 48% of the patient cohort had complete relief of angina, 94% had less angina than before dilatation and 86% were able to decrease antianginal medications. Fifteen patients with persistent or recurrent angina had from one to five repeat dilatations. After angioplasty, lung thallium uptake, the extent of abnormal scan segments, and the magnitude of redistribution in dilated lesions were significantly reduced (n = 24 patients). Redistribution defects were seen in 38% of patients on postangioplasty scans. All were associated with subsequent angina. Of various clinical, angiographic, exercise, and thallium-201 scan variables, only the presence of delayed redistribution was an independent predictor of recurrent angina. Restenosis was the most common underlying cause for this exercise-induced perfusion defect. Thus percutaneous coronary angioplasty performed as primary therapy for recurrent angina after bypass surgery is moderately successful in long-term follow-up for the amelioration of symptoms and enhancement of regional myocardial perfusion.

Balloon angioplasty of aortocoronary saphenous vein bypass grafts: a histopathologic study of six grafts from five patients, with emphasis on restenosis and embolic complications

Among 103 patients undergoing percutaneous transluminal balloon angioplasty of obstructed aortocoronary saphenous vein bypass grafts at the Mayo Clinic, six grafts from 5 patients were available for histopathologic examination. The interval from graft insertion to angioplasty ranged from 5 to 105 months and that from angioplasty to graft excision ranged from 6 h to 24 months. Angioplasty produced intimal fissures in three grafts initially obstructed by intimal fibromuscular proliferation. Healing and restenosis resulted from filling of lacerations with fibrocellular tissue and apparently also from restitution of muscular tone. In two of three grafts initially narrowed by atherosclerosis, balloon angioplasty cause extensive plaque rupture and restenosis resulted from extrusion of plaque debris and secondary luminal thrombosis. In the third graft, angioplasty produced no distinct lesions and late restenosis was due to progressive atherosclerosis of the vein graft. Atheroembolization was observed in both patients with plaque rupture and was associated with reoperation in one and death in the other. In conclusion, the results derived from six saphenous vein bypass grafts subjected to balloon angioplasty indicate that restenosis may result from intimal fibrocellular proliferation, thrombosis, restitution of muscular tone and progressive atherosclerosis. Symptomatic atheroembolization may occur in grafts greater than 1 year old.

Percutaneous transluminal angioplasty in patients with prior myocardial revascularization surgery

Direct myocardial revascularization surgery using either the saphenous vein or internal mammary artery has become the definitive surgical treatment for coronary artery occlusive disease. Certain patients who have undergone these procedures, however, have recurrent myocardial ischemia due to progression of disease in unbypassed vessels, to obstruction in the arteries distal to the insertion of the bypass conduit, or to disease of the conduit itself. Balloon angioplasty may be used to relieve myocardial ischemia in these situations; however, initial studies suggested a low primary success rate coupled with excessive mortality and morbidity. Improvements in patient selection, equipment and technical expertise now allow angioplasty to be performed in this patient population with results comparable to that in the general coronary angioplasty population. Of the 3,016 angioplasty procedures performed between September 1980 and June 1987, 236 patients had previously undergone revascularization surgery. The primary success rate was 93% (390 of 419 stenoses successfully dilated). Overall, clinical restenosis was observed in 39%, including a 43% restenosis rate in patients undergoing only saphenous vein graft angioplasty. This did not differ appreciably from the restenosis rate in postbypass patients undergoing angioplasty of only native vessels (37%) or internal mammary arteries (42%). Emergency revascularization surgery was required in 7 of 236 patients (3%), each of whom had myocardial infarction. One of 236 patients (0.4%) died. Thus, angioplasty may be used to relieve recurrent myocardial ischemia in patients with prior direct myocardial revascularization procedures with a high initial success rate and acceptable risk. Early (less than 6 months) restenosis is not infrequent and remains the largest obstacle to a satisfactory clinical outcome.(ABSTRACT TRUNCATED AT 250 WORDS)