Author + information
- Received December 12, 2000
- Revision received March 19, 2001
- Accepted March 29, 2001
- Published online July 1, 2001.
- Mun K Hong, MD, FACC∗,* (, )
- Roxana Mehran, MD, FACC†,
- George Dangas, MD, PhD, FACC†,
- Gary S Mintz, MD, FACC†,
- Alexandra Lansky, MD, FACC†,
- Kenneth M Kent, MD, PhD, FACC‡,
- Augusto D Pichard, MD, FACC‡,
- Lowell F Satler, MD, FACC‡,
- Gregg W Stone, MD, FACC† and
- Martin B Leon, MD, FACC†
- ↵*Reprint requests and correspondence:
Dr. Mun K. Hong, Director, Cardiovascular Intervention and Research, Cornell University-New York Presbyterian Hospital, Starr Pavilion 4, 520 East 70th Street, New York, New York 10021
We sought to determine whether strategies to reduce procedural distal embolization and late repeat revascularization have resulted in more favorable outcomes after saphenous vein graft (SVG) angioplasty.
Angioplasty of SVG lesions has been associated with frequent procedural and late cardiac events. Therefore, evolving strategies have been attempted to improve outcomes after SVG angioplasty.
We compared our earlier experience (1990 to 1994) of 1,055 patients with 1,412 SVG lesions with a recent group (1995 to 1998) of 964 patients with 1,315 lesions.
Baseline characteristics were similar between the groups. However, there were significantly more unfavorable lesion characteristics (older, longer and significantly more degenerated SVGs) in the recent series. Between the two periods, there was decreased use of atheroablative devices, whereas stent use increased. The procedural success rates (96.6% vs. 96.1%) were similar. However, one-year outcome (event-free survival) was significantly improved in the more recent experience (70.7% vs. 59.1%, p < 0.0001), especially late mortality (6.1% vs. 11.3%, p < 0.0001). Multivariate analysis showed stent use to be the only protective variable for both periods.
This study shows that despite higher risk lesions, strategies to reduce distal embolization have maintained high procedural success. Late cardiac events, including mortality, have also been substantially reduced.
Conventional angioplasty of saphenous vein graft (SVG) stenosis has been associated with frequent procedural complications due to distal embolization (1), as well as adverse long-term outcomes due to high rates of target and nontarget lesion revascularization (2). Despite these limitations, SVG angioplasty cannot be abandoned because of the finite longevity of SVGs, as well as the increased risk and less symptomatic relief of repeat coronary artery bypass graft surgery in these patients (3–5). Therefore, over the past decade, we have adopted evolving strategies to minimize the risk of distal embolization during the initial procedure to improve the early outcome and reduce late restenosis, and possibly progression of disease, for better long-term results. Our initial hypothesis from 1990 to 1994 was that removal of the atherosclerotic and thrombotic material using the atherectomy devices (directional atherectomy and transluminal extraction atherectomy) might reduce distal embolization. However, from 1995 to 1998, we had to revise our strategy, as the bulky atherectomy devices did not reduce distal embolization. We hypothesized that minimizing the instrumentation within the diseased SVG and implanting stents wherever feasible might improve early and late outcomes. The objective of the current retrospective study was to determine whether these evolving strategies have resulted in more favorable outcomes after SVG angioplasty over the past decade.
We compared the baseline demographic data, lesion characteristics, angioplasty device use patterns, procedural results and one-year outcomes between the earlier experience (1990 to 1994) of 1,055 patients with 1,412 SVG lesions and the recent group (1995 to 1998) of 964 patients with 1,315 lesions treated at the Washington Hospital Center from 1990 to 1998. All patients gave written, informed consent, and the study was approved by the institutional Review Board before the procedures. Procedural success was defined as a final diameter stenosis <50% in the absence of in-hospital death, Q-wave myocardial infarction (MI) or emergency coronary artery bypass graft surgery. All patients had creatine kinase, MB isoenzyme (CK-MB) levels measured every 8 h after the procedure for at least 24 h in those with no elevation and until its peak in those with elevation. Non–Q-wave MI was defined as CK-MB greater than five times the upper limit of normal (defined as <4 mg/dl in our laboratory) in the absence of new Q waves on the post-intervention electrocardiogram.
Baseline demographic and procedural variables were recorded prospectively and entered in the Cardiology Research Foundation data base. All patients were serially interviewed by experienced research nurses at 1, 3, 6 and 12 months after their procedure. Although the follow-up data were collected beyond one year after the procedure, the long-term comparison was intentionally limited to one year in this study for fair comparison between the groups. The patients were questioned regarding the occurrence of cardiac events or the need for repeat coronary revascularization. For deceased patients, family members and primary care physicians were contacted to try to determine the cause of death. The cause of death and any cardiac event were adjudicated from objective documents, whenever possible.
Evolving strategies and rationale
The efforts to minimize distal embolization during 1990 to 1994 included atherectomy and extraction devices to remove the atherosclerotic and thrombotic material. However, this strategy did not improve the early results and did not address the late outcomes. Thus, starting in 1995, we adopted the following strategies: 1) avoidance of bulky atheroablative devices; 2) use of staged procedures in selected degenerated or thrombus-containing SVG lesions; 3) “direct stenting” without pre- or post-balloon dilation and avoidance of high pressure for stent implantation; and 4) judicious use of glycoprotein IIb/IIIa inhibitors. The rationale for these approaches is based on the empiric observations that the SVG lesions seem tenuous and tend to be easily dislodged. Thus, since 1995, we have attempted to minimize the device size, as well as the amount of instrumentation within the graft. In a small percentage (∼5% of those in the recent experience), we improved blood flow during the initial procedure and provided definitive therapy during the second, staged procedure six weeks later (6). More recently, glycoprotein IIb/IIIa inhibitors have been used both prophylactically in patients with mobile intragraft filling defects and in a “rescue” manner in patients with reduced Thrombolysis In Myocardial Infarction (TIMI) flow or other evidence of distal embolization during the procedure, although they were used in <10% of patients.
To reduce the need for late revascularization, we have used stents whenever feasible since 1995. We routinely evaluated “intermediate lesions” with intravascular ultrasound of the SVG being treated for severe lesions, and we implanted stents in these angiographically intermediate lesions if there was evidence of lumen compromise. We also used stents in distal anastomotic lesions if the distal vessel was >2.5 mm in diameter (7).
Quantitative and qualitative angiographic analyses
All cineangiograms at baseline and after angioplasty were analyzed in a blinded manner with regard to the late outcome, using the previously published definitions of the qualitative assessment of lesions (8). Quantitative analysis was performed using a previously published edge-detection algorithm (8)in the projection showing the most severe stenosis in an unforeshortened view, with the contrast-filled guiding catheter as the reference standard. Degenerated SVGs were defined as grafts with ectasia or lumen irregularities comprising ≥50% of the graft length (1).
All statistical analyses were performed using the SAS statistical software (SAS Institute, Cary, North Carolina). Continuous variables are presented as the mean value ± SD, and categorical variables as percentages. Comparisons between the two groups were made using the chi-square test or Fisher exact test to analyze differences in categorical variables, and the Student ttest for continuous variables. Clinical, morphologic and procedural variables that had demonstrated a statistically significant difference between the groups were included in the multivariate logistic regression analyses to identify factors associated with target lesion revascularization (TLR) or late cardiac events. A p value <0.05 was considered significant.
The two groups were similar at baseline (Table 1). They represent a typical high-risk angioplasty population, with the majority experiencing unstable angina before the intervention, a high prevalence of previous MI and a relatively high prevalence of diabetes.
In contrast, there were significantly more unfavorable lesion characteristics in the more recent group (Table 2). The grafts were older and the lesions were longer, and notably, there was a significantly greater percentage of degenerated SVGs in the recent series compared with the earlier experience. Angiographic thrombus, however, was less frequent in the recent group. Quantitative angiographic analysis showed larger reference and final lesion lumen diameters in the recent group.
Angioplasty devices and pharmacology
The percentage of stand-alone balloon procedures was relatively unchanged between the groups (Table 3). This procedure was reserved mainly for the distal anastomotic lesions. In contrast, the use of atheroablative devices, in general, was significantly reduced between the two periods. The only exception was the Excimer laser (Spectranetics, Colorado Springs, Colorado), which was used more frequently in the recent group, with the hope of reducing distal embolization from the front-end ablation, owing to the lower profile of the device compared with other atherectomy devices. Stent use has increased significantly. In fact, the stent has become the device of choice in the majority of lesions, excluding the distal anastomotic site. In the early group, the patients mainly received heparin during the procedure and crossed over to warfarin with stent use. In the recent group, the patients received either ticlopidine or clopidogrel after stent implantation and no warfarin therapy. Abciximab use was limited to the recent group in a minority of patients (8.7%). Distal protection device was not used in either group.
Procedural success was high in both groups and did not differ much. The major in-hospital complications, as well as the rates of non–Q-wave MI and no reflow phenomenon, were similar between the groups (Table 4).
Late clinical outcomes
One-year outcome was significantly improved in the more recent experience (Table 5). Event-free survival was markedly better, mainly because of significantly reduced late mortality and TLR. There was an absolute reduction of almost 5% in late mortality and 7% absolute reduction in late TLR. The majority (>70%) of late mortalities in both groups were cardiac in origin, including sudden out-of-hospital death and uncompensated heart failure. In contrast, the incidence of non-TLR and nonfatal Q-wave MI was not significantly different between the two groups.
Multivariate predictors of late cardiac events
For both groups, unstable angina was a predictor of late cardiac events (Table 6). Diabetes was also a negative predictor in the early group, whereas ostial location was a negative predictor in the recent group. Stent use was the only protective variable for both groups.
Multivariate predictors of TLR
For both groups, ostial location was a negative predictor of TLR (Table 7).
For the early group, age and final minimal lumen diameter were inversely associated with TLR. Stent use was associated with reduced TLR only for the recent group.
This study shows that the evolving strategies to treat SVG lesions have maintained high procedural success, despite high-risk lesions, and have resulted in substantially improved late outcomes, including late mortality and TLR. Although this is a retrospective study without randomization between the strategies and the results do not provide mechanistic insights for the results, the findings suggest that high-risk SVG lesions may still be approached with minimal instrumentation and liberal use of stents for better long-term results.
Initial experience with angioplasty of SVG lesions was discouraging, mainly because of frequent distal embolization and the high incidence of major ischemic complications associated with distal embolization (1,2). Even new angioplasty devices were not helpful, and some were actually associated with greater procedural complication rates (9). Furthermore, abciximab was initially reported to improve procedural outcomes in a small subgroup study of the Evaluation of IIb/IIIa platelet receptor antagonist 7E3 in Preventing Ischemic Complications (EPIC) trial (10). However, there has been no large randomized series conclusively showing a benefit with this potent pharmacologic agent in SVGs.
The only reports showing consistently improved results, compared with conventional SVG angioplasty, have been stent experiences (11,12). Wong et al. (11)showed that Palmaz-Schatz stents could successfully treat 97% of focal SVG lesions and result in a restenosis rate of ∼30% at six months. Randomized stenting of focal SVG lesions (12)also showed significantly improved procedural results compared with balloon angioplasty (97% vs. 86%), as well as reduced restenosis rates (37% vs. 46%).
Evolving strategies at the Washington Hospital Center
Because of the discouraging results with balloon angioplasty of SVG lesions, we initially tested the hypothesis that removal of the lesion components with atherectomy and extraction devices might reduce the risk of distal embolization. However, in agreement with the histologic finding that SVG lesions are tenuous, we observed that the risk of distal embolization appeared to increase with more instrumentation within the graft, especially with bulky devices. Thus, we revised our hypothesis and strategy starting in 1995, when we essentially eliminated the use of bulky atheroablative devices, except for selective use of the Excimer laser in degenerated SVGs and increased stent use, especially “direct” stenting without pre- or post-stent balloon angioplasty. Furthermore, we have limited the stent implantation pressure to <10 atm to reduce the risk of distal embolization from plaque material squeezed through the stent struts, except for fibrotic lesions requiring higher pressure for complete stent expansion. In a small percentage of patients (∼5%) who could not tolerate any further ischemic insult, as judged by the operators, we adopted the “staged” procedure (6). These patients underwent the initial procedure with transluminal extraction catheter to create a 2.0- to 2.5-mm channel (with 50% residual stenosis in 4- to 5-mm SVGs). Then, the patients were discharged home on warfarin (Coumadin) therapy and returned for more definitive procedure with stents six weeks later. This approach did result in avoidance of distal embolization during the initial procedure (6). More recently, glycoprotein IIb/IIIa inhibitors have been used (8.7%), with one-third prophylactic use and two-thirds use in “rescue” situations when there was a procedural complication. We cannot definitively conclude whether these strategies have reduced procedural complications, as no large-scale randomized study has been performed in SVGs. However, considering the fact that the recent group had significantly more unfavorable lesion characteristics, especially a higher incidence of graft degeneration, compared with the earlier group (60.2% vs. 36.5%), the comparable procedural results should be viewed as encouraging.
The other discouraging fact, even after initially successful SVG angioplasty, has been the high incidence of late cardiac events, including high late mortality rate (approaching 10% within one year after SVG angioplasty). The potential reasons for this observation include more comorbid conditions in these patients (e.g., higher prevalence of previous MI and lower ejection fraction), high restenosis rates and rapid progression of nontarget lesions. On the basis of previous registry findings (11)and the only randomized study comparing balloon and stent use in SVGs (12), we have attempted to implant stents whenever feasible since 1995. This approach has included angiographically borderline lesions in the SVG being treated (13), as well as in selected distal anastomotic lesions (7). The results of the current study show that this approach may reduce late mortality and the need for TLR.
Predictors of late cardiac events and TLR
Multivariate analysis showed that certain factors were predictive of late cardiac events during both periods, with unstable angina negatively associated with late events and stent use conferring protection. Although diabetes mellitus was predictive of late cardiac events in the early group, it was no longer a predictor in the recent group, possibly due to the “neutralizing” effects of stents. Ostial location was a negative predictor in the recent group, suggesting that even stents do not prevent late adverse sequelae at this location.
Indeed, ostial location was the only consistent predictor of TLR in both groups. In the early period, age was a weak negative predictor of TLR, possibly because of reluctance of the cardiologists to recommend repeat procedures in elderly patients. Final minimal lumen diameter was an inverse predictor of TLR in the early period, probably because of less than optimal stent implantation techniques. The suboptimal stent implantation techniques, as well as the use of articulated coronary stents in the early period, may explain why stents were not a predictor of reduced TLR. In the recent group, stent use without central articulation provided strong protection against TLR.
Clinical implications and future directions
The present study shows that despite more unfavorable lesion characteristics, we can treat SVG lesions with comparable early results and improved long-term outcomes, mainly by deploying stents in all suitable SVG lesions. Aorto-ostial lesions still present a difficult subset of lesions associated with high restenosis rates, despite stenting. Promising results with radiation therapy (14)may further improve late outcomes in this unfavorable lesion subset. Future efforts with distal protection device (15)may also improve the procedural and late outcomes in these challenging lesions. Finally, at present, stents are without question the treatment of choice in SVG lesions.
The main limitation of this study is that it is a retrospective comparison of the two periods and does not include any randomization of different treatment strategies. Furthermore, there was no prospective, consistent strategy adopted during any period. Thus, it is difficult to determine which, if any, of the evolving treatment options contributed to the favorable results. For these reasons, it is impossible to recommend the adoption of these strategies to the interventional cardiology community. Finally, these results were obtained before the exciting recent developments of brachytherapy and distal protection devices. It is conceivable that the results can be even further improved with these treatment options.
This study shows that continuing efforts to prevent distal embolization and reduce late cardiac events with stents may provide acceptable procedural and long-term outcomes in patients with SVG disease. Future efforts to address high-risk subsets, such as those with unstable angina or ostial lesions, may further improve results in SVG population.
☆ This research was supported by a grant from the Cardiovascular Research Foundation.
- creatine kinase-MB isoenzyme
- myocardial infarction
- saphenous vein graft
- target lesion revascularization
- Received December 12, 2000.
- Revision received March 19, 2001.
- Accepted March 29, 2001.
- American College of Cardiology
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