Percutaneous Intervention of Acutely Occluded Saphenous Vein Grafts: Contemporary Techniques and Outcomes

   ABSTRACT: Objectives. To examine the contemporary acute and long-term outcomes after percutaneous coronary interventions (PCI) of acutely occluded saphenous vein grafts (SVGs). Background. PCI of acutely thrombosed SVGs carries low success rates. It is unknown whether outcomes have improved with contemporary PCI techniques. Methods. We reviewed the acute and long-term outcomes of 34 consecutive patients who underwent PCI of 36 acutely occluded SVGs at our institution between 2003 and 2009. Results. Mean patient age was 70 ± 10 years and 39% had stent thrombosis. Mean SVG age was 14 ± 6 years. SVG PCI was successful in 81%. In 3 patients, PCI of the target vessel native chronic total occlusion (CTO) was attempted after SVG PCI failed and was successful in 2, increasing the overall target myocardial territory revascularization success rate to 86%. Adjunctive PCI techniques were used as follows: mechanical thrombectomy (69%), rheolytic thrombectomy (39%), embolic protection devices (25%) and laser (14%). Stents (61% drug-eluting) were implanted in 78% of the treated lesions. Mean follow up was 2.3 ± 1.9 years. At 1 and 3 years, mortality was 8% and 42%, an acute coronary syndrome occurred in 15% and 41% and repeat coronary revascularization was required in 28% and 38%, respectively. Conclusions. In this particular population of thrombosed SVG PCIs, a high incidence of stent thrombosis was observed and procedural success rate was 81% with an additional 5% undergoing successful native coronary artery CTO PCI. Patients presenting with thrombosed SVGs were at high risk for recurrent events.    Acute saphenous vein graft (SVG) thrombosis is challenging to treat due to large thrombus burden and high recurrent SVG failure rates.^1–16 Even if acute percutaneous coronary interventions (PCI) are successful, long-term SVG patency is low. Alternative revascularization approaches, such as PCI of a native coronary artery chronic total occlusion (CTO) have been recently proposed for this patient population.¹⁷ Whether the availability of novel equipment and techniques (such as embolic protection devices, improved thrombectomy devices, drug-eluting stents (DES) and advanced chronic total occlu- sion PCI techniques) has improved acute and long-term outcomes, has received limited study.    The goal of this study was to review the acute and long-term outcomes after PCI of acutely thrombosed SVGs in a contemporary patient cohort.

Methods

    Study population. We identified all patients with prior coronary artery bypass graft (CABG) surgery who underwent PCI of an acutely occluded SVG at our institution between 2003 and 2009. Patients were included if they presented with an acute coronary syndrome (ACS) due to a SVG with throm- bolysis in myocardial infarction (TIMI) 0 flow and intragraft thrombus on which PCI was attempted. During the study period, 34 consecutive patients underwent PCI for 36 acutely occluded SVGs. The medical records and coronary angiograms of those patients were reviewed to determine the acute procedural success and long-term clinical outcomes. An acute myocardial infarction (AMI) was diagnosed if a patient had evidence of my- ocardial injury (CK-MB > 3 times the upper limit of normal) with either symptoms suggestive of ischemia or ischemic elec- trocardiographic (ECG) changes.    Percutaneous coronary intervention. Procedural success was defined as the achievement of residual in-stent stenosis of 18 All cases were performed via femoral access using 6–8 French (Fr) guiding catheters. The choice of procedural strategies, equipment utilization and anticoagulation/ antiplatelet regimen was at the discretion of the interventional cardiologist performing the procedure.    Statistical analyses. Continuous parameters were reported as mean ± standard deviation and compared using the t-test or the Wilcoxon rank-sum test, as appropriate. Discrete parameters were reported as % and compared using the chi-square or Fisher’s exact test, as appropriate. The incidence of major adverse cardiovascular events (MACE) and death was calculated using the Kaplan-Meier method. All analyses were performed using JMP 8 (SAS Institute, Inc., Cary, North Carolina). The study was approved by our institutional review board.

Results

   Patient characteristics. During the study period, 34 prior CABG patients underwent 36 PCIs for acutely occluded SVGs. PCI was performed in 1 SVG during each PCI attempt. The baseline characteristics of the study population are shown in Table 1. All patients were white males and they all presented with an ACS as follows: non-ST-segment AMI in 58.4%, ST- segment elevation AMI in 22.2% and unstable angina in 19.4%. The maximal CK-MB and troponin (I or T) levels were 94 ± 118 ng/ml and 5.7 ± 16.6 ng/ml, respectively.    Procedural outcomes. The angiographic findings, trea- ment modalities and acute procedural results are summarized in Table 2. Mean SVG age was 14 ± 6 years. The occluded SVG supplied the obtuse marginal (53%), right coronary artery (33%), left anterior descending artery (8%) or diagonal branch (6%). SVG occlusion was due to stent thrombosis in 14 (39%) patients. The thrombosed stent was bare-metal in 8 patients, drug-eluting in 5 patients and of unknown type in 1 patient. Three patients had stent thrombosis twice: 1 patient had stent thrombosis of the same SVG, 1 patient had stent thrombosis of two different SVGs (one to the obtuse marginal and one to the right coronary artery), and a third patient had subtotal SVG stent thrombosis (not included in the current analysis) 4 years prior to presenting with complete SVG occlusion (included in the current analysis). The mean time to stent thrombosis was 2.7 ± 2.6 years. One patient had acute stent thrombosis on the same day as stent implantation, and the other 13 had very late stent thrombosis.    Overall, SVG PCI was successful in 81% and PCI of a native coronary artery CTO was successful in another 2 patients, bringing the overall target myocardial territory revascularization success rate to 86% (Figure 1). Mechanical thrombectomy and embolic protection devices (proximal embolic protection in all cases) were frequently used (Table 2). SVG PCI was successful in 19 of 25 (76%) lesions in which mechanical thrombectomy was used, in 11 of 14 (79%) lesions in which rheolytic thrombectomy was used; in 8 of 9 (89%) lesions in which proximal embolic protection was used; in 11 of 13 (85%) lesions in which a glycoprotein (GP) IIb/IIIa inhibitor was used; and in 3 of 5 (60%) lesions in which a laser was used. Stents (59% DES) were used in 27 of the 29 successfully recanalized SVGs. Two patients did not receive a stent, one because he had an aneurysmal and diffusely degenerated SVG and one because he had a distal anastomotic lesion that responded well to thrombectomy and balloon angioplasty alone. In another patient, antegrade SVG flow could not be established in spite of stent implantation. Both patients who underwent successful native CTO PCI received DES.    Follow up. Follow up was available for all study patients. During a mean follow-up period of 2.3 ± 1.9 years, 10 patients (29%) died, 11(32%) presented with an ACS and 9 (26%) required target vessel revascularization (TVR) (Figure 4). At 1 and 3 years, mortality was 8% and 42%, respectively, the incidence of ACS was 15% and 41%, respectively, and repeat coro- nary revascularization was required in 24% and 34%, respectively.    Of the 11 patients who developed an ACS, 5 presented with an AMI (non-ST segment elevation in 4 patients and ST-segment elevation in 1 patient), and 6 patients presented with un- stable angina. Two patients had a recurrent ACS (one had ST-segment elevation MI and another had unstable angina).    Repeat coronary revascularization was achieved by PCI in 8 patients and repeat CABG in 1 patient. Of the 9 patients who required repeat coronary revascularization, 4 required TVR (only one of which was target lesion revascularization [TLR]), and 5 required revascularization of a non-target vessel. Four patients underwent a second coronary revascularization procedure (TLR in 2) and 1 patient required a third coronary revascularization procedure (TLR).

Discussion

   Our study demonstrates that in the population of patients in whom PCI of thrombosed SVGs was attempted, stent thrombosis was highly prevalent (39%) and the SVG PCI success rate was high (81%), although the risk for subsequent cardiovascular events was also high. PCI of a native coronary artery CTO might offer an alternative treatment option if SVG PCI fails and the patient continues to have symptoms of ongoing myocardial ischemia.    De Feyter et al first reported PCI of an acutely occluded SVG in 2 patients.¹ In spite of initial success, both SVGs reoccluded within a year, leading the authors to state that “angioplasty of totally occluded vein grafts is a challenge to be resisted.” Several studies have since reported acute success rates ranging between 27% and 100%, however, some studies have provided composite outcomes for PCI of totally and subtotally occluded SVGs.^2–6 The long-term outcomes after thrombotic SVG PCI are also poor, with 1-year mortality rates between 19–30%.^12,13,15 Nguyen et al reported a 1-year reinfarction rate of 8% and a TVR rate of 8%.¹³ Al-suwaidi et al reported 1- year rates of 26% for MI, 20% for repeat PCI, and 15% for re-do CABG 15%.¹²     Several reasons may account for the low acute and long-term success of treating acutely occluded SVGs. First, those SVGs often have diffuse degeneration leading to recurrent events (the mean SVG age in our cohort was 14 years, suggesting that diffuse disease was likely present in most SVGs). Second, occluded SVGs have a large amount of thrombus (Figures 2 and 3), removal of which may not be feasible despite using multiple types of thrombectomy and embolic protection devices and aggressive use of antiplatelet and anticoagulation medication.^17,19 The large thrombus burden may also make SVG wiring challenging, especially in the absence of filling of the target native coronary artery by collaterals. Third, myocardial necrosis of the territory supplied by the SVG can lead to reduced antegrade flow and predispose the SVG to recurrent occlusion. Fourth, a large SVG segment (occasionally the entire SVG) may require stenting to restore antegrade flow with high subsequent rates of restenosis, especially if bare-metal stents are used.^2,9,20 Indeed, the mean SVG stent length in our series was 65 mm. Finally, in 39% of the patients included in our study, SVG occlusion was due to stent thrombosis, and those patients may be more likely to de- velop recurrent stent thrombosis.    In our patient population, the success rate in recanalizing thrombosed SVGs was 81%. This relatively high success rate might in part be due to the high frequency of stent thrombosis that may be easier to treat than diffuse SVG degeneration. How could these rates further improve? First, PCI of thrombotic SVGs is a challenging procedure that may best be performed by experienced, high-volume operators who are familiar with the many types of equipment (such as embolic protection and thrombectomy devices and lasers) required to enhance procedural success in these challenging lesions. Aggressive thrombectomy can allow localization of the culprit lesion and minimize the SVG length that requires stenting (Figure 2). Whereas use of embolic protection devices has not been studied in this setting, it could prevent further distal embolization when used in combination with thrombectomy devices and stent implantation.^3,4,21 Intragraft GP IIb/IIIa inhibitor or thrombolytic administration may also reduce thrombus burden, although it can increase the risk of significant bleeding.⁵ Rarely, spontaneous thrombolysis of an occluded SVG may occur.^6,22 Use of DES may reduce in-stent restenosis rates and the need for repeat revascularization or recurrent SVG occlusion,² although large definitive studies are currently underway.^23,24 PCI of the native coronary artery lesion (subtotal or total) that supplies the occluded SVG target territory is another alternative strategy if SVG PCI fails.^17,25 PCI of a native coronary artery CTO was successful in 2 of 3 patients in whom it was attempted in the present series, and may become an increasingly utilized (or possibly preferred) treatment option as CTO angioplasty techniques and success rates continue to improve. However, this approach should be used as a last resort attempt at reperfusion after SVG PCI fails and the patient continues to experience angina. Although CTO interventions can be lengthy and therefore significant myocardial damage may still occur, CTO PCI may occasionally be the only feasible approach (apart from medical therapy alone) to limit myocardial injury after SVG PCI attempts fail and the patient continues to have symptoms of ongoing myocardial ischemia. Emergency repeat CABG may not be feasible or desirable in many SVG thrombosis patients in whom SVG PCI fails.    Part of the increased risk of thrombosed SVG PCI patients may be unrelated to the risk of SVG-related recurrent events, as shown in a recent study that found similar intermediate-term clinical outcomes of prior CABG patients who underwent PCI of a SVG or a native coronary artery.²⁵ Both cardiac and noncardiac comorbidities and advanced age likely contributed to the high event rates of those patients. Aggressive medical therapy with lipid-lowering and antiplatelet therapies and risk-factor control might improve their cardiovascular and overall outcomes.^26,27   Study limitations. Our study is limited by its observational retrospective design and relatively small sample size, although it is one of the largest single-center series to report on the outcomes after PCI of acutely occluded SVGs. Another major limitation is selection bias: one cannot draw conclusions regarding the success rate of SVG PCI for occluded grafts when the op- erator determined when and if to intervene, especially since no data were available regarding patients who did not undergo intervention and the reasons behind this decision. The success rate of 81% may reflect good judgment by the operators at our institution concerning which SVGs to treat, but may not be representative of the success rate for SVG PCI in the entire spectrum of acutely occluded grafts. Decisions about equipment utilization and procedural strategies were not standardized, but remained at the discretion of the operator. No routine angiographic follow up was done in our study, although clinical follow up is the standard of care for these patients. Patients in whom PCI of an occluded SVG was not attempted were not included in this study.

Conclusion

   In summary, using contemporary PCI techniques, angiographic success was achieved in most acutely thrombotic SVGs that underwent PCI attempts at our institution, yet subsequent clinical outcomes remained poor. PCI of a chronically occluded native coronary artery that supplies the thrombotic SVG target territory may be an alternative therapeutic option if SVG PCI fails.

_________________________________________________ From the Veteran Affairs North Texas Healthcare System, Dallas, Texas and University of Texas Southwestern Medical Center, Dallas, Texas. Disclosures: Subhash Banerjee: received speaker honoraria from St. Jude Medical, Medtronic and Cordis and research support from Boston Scientific and The Medicines Company. Emmanouil Brilakis: received speaker honoraria from St. Jude Medical, consulting fees from Medicure, research support from Abbott Vascular and The Medicines Company. Manuscript submitted November 11, 2009, provisional acceptance given December 14, 2009, final version accepted January 18, 2010. Address for correspondence: Emmanouil S. Brilakis, MD, PhD, VA North Texas Healthcare System, Division of Cardiology (111A), 4500 South Lancaster Road, Dallas, TX 75216. E-mail: esbrilakis@yahoo.com

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