Sirolimus-Eluting Stents for Treatment of Complex Bypass Graft Disease: Insights from the SECURE Registry

Treatment options for bypass graft disease, such as repeat CABG and percutaneous revascularization, are limited and provide disappointing outcomes.^1-4 Patients undergoing repeat CABG have over a four times greater rate of mortality compared to patients undergoing their first surgery.¹ The benefits of percutaneous revascularization with stent implantation, though superior to balloon angioplasty, are limited by a high incidence of procedural complications such as thrombosis and distal embolization, and unsatisfactory long-term reocclusion rates.^2-4 Large randomized trials have confirmed the long-term safety and efficacy of SES implanted in native coronary arteries.^5,6 However, SES have not been evaluated for the treatment of bypass graft disease. The aims of this study are to determine the feasibility and safety of using SES to treat high-risk patients with bypass graft disease. Methods The compassionate-use SES (SECURE) registry enrolled 252 patients and included the first series of patients with bypass graft disease treated with SES in the United States. This was a multicenter (5 U.S. sites) study involving the deployment of SES in patients with ischemic cardiac disease who had no acceptable revascularization alternatives available, as agreed upon by both cardiologist and surgeon. Six- and 12-month outcomes of patients with at least one graft treated with SES were compared with those of patients who had only native vessels treated. Target vessel failure (TVF) was defined as a composite of death, MI and TVR. Q-wave myocardial infarction (MI) was defined as the development of new, pathological Q-waves in e2 leads, with CK twice the upper limit of normal (7 Statistical analysis. Continuous variables were expressed as mean ± standard deviation. Categorical variables were expressed as percentages. Continuous variables were compared by means of an unpaired Student’s t-test. Categorical variables were compared by means of the chi-square test. A two-tailed value of p Results Baseline demographics are described in Table 1. Bypass graft disease was present in 76 patients, with a total of 94 lesions treated (71 vein and 23 arterial grafts); 90.4% were ISR and 67.1% had previous brachytherapy. A total of 176 patients (n = 311 lesions) were treated with SES exclusively in native vessels. Of these, 83.0% were in-stent restenosis (ISR) and 72.2% had undergone previous brachytherapy. Angiographic data are provided in Table 2. Procedural success was achieved in all but 8 lesions (5 native and 3 graft lesions). Follow-up data. There were 3 in-hospital deaths (2 in the native vessel group and 1 in the graft group). In the native vessel group, one death was secondary to stent thrombosis. Stent thrombosis was not documented in the other 2 patients who died of sudden cardiac death. All other patients were discharged without any complications. At 6 months, TVR rates were 18.1% in the native vessel population versus 16.7% in the graft population (p = 0.82), and the incidence of MI was 3.8% versus 3.3%, respectively. The cumulative 12-month outcomes are described in Table 3. The incidence of target vessel failure (primary endpoint) including death, MI, and TVR at 12 months in the bypass graft group (55.3%) was similar to that observed in the native vessel group (45.5%, p = 0.17). There were no differences comparing outcomes of patients with arterial or venous grafts treated with SES. Furthermore, clinical outcomes of patients with bypass grafts were not influenced by previous intravascular radiation therapy. However, TVR rates were higher in the native vessel brachytherapy treated population as compared with patients without previous brachytherapy (46.5% versus 25%, respectively; p = 0.023). IVUS data were available in 14 bypass grafts treated with SES. The volume of IH was 19.9 ± 25.5 mm3 in a total length of 26.4 ± 9.8 mm. Percent IH was 11.8 ± 16.5% and was virtually absent (Discussion This study suggests the feasibility of using SES to treat high-risk patients with bypass graft disease. At one year, patients with bypass graft treatment had similar outcomes compared to patients treated for native vessel disease. The treatment of diseased bypass grafts has been a challenge for both interventional cardiologists and cardiac surgeons. Unfortunately, up to 20% of vein grafts are occluded within the first year following CABG and many more develop significant disease within 10 years.⁸ Repeat operations are technically more difficult and are associated with high surgical morbidity and mortality rates.¹ Similarly, percutaneous revascularization strategies have provided unsatisfactory outcomes, with a high incidence of restenosis.^2–4 The high-risk profile of the present population limits comparison with previous studies involving less complex patients with bypass graft disease. Radiation therapy studies in patients treated for ISR in bypass grafts reported a 48% incidence of MACE at 12-month follow-up.9 In the SVG-WRIST trial (Washington Radiation for In-Stent restenosis Trial), TVR rates were 28% and 62% in patients with vein grafts treated with gamma radiation versus placebo, respectively.¹⁰ These findings compare favorably with the long-term results observed in the present study, which included patients who were refractory to other treatment modalities, including radiation therapy. It is nevertheless important to note that conventional percutaneous revascularization of patients with failed radiation therapy has been associated with 6% mortality and 32% TVR rates 6 months after the procedure.¹¹ The limited inventory available in this early study handcuffed operators when selecting appropriate stent sizes. Mean reference vessel diameter (Table 2) was relatively small as measured by QCA, which reflects the diffuse characteristics of the lesions and the lack of a “normal” reference vessel segment. Further, the initial concerns with the use of multiple DES in a single target vessel may have limited adequate lesion coverage. These factors may explain the 12 Fifty percent of the segments had virtually no intimal proliferation along the entire stented segment. These encouraging findings in this high-risk group warrant further randomized investigations to confirm whether percutaneous revascularization using SES is an effective treatment for patients with bypass graft disease. Study limitations. The study sample may not be representative of the general population, given their high-risk status. In addition, the comparison group may not be ideal, as it is composed of patients with native vessel disease. Nevertheless, the outcomes of this first series of patients with bypass graft disease treated with SES in the U.S. are extremely relevant for an increasing number of high-risk patients treated percutaneously in everyday practice. Therapeutic decisions for these patients cannot be supported by classic randomized studies. The ongoing Cypher™ Stent Post-Market Surveillance registry, which had no exclusionary criteria and represents routine clinical practice in the U.S., features 69% of patients who had previous stenting, 32.7% CABG and 7.5% brachytherapy — all common features of the present population. The favorable results observed in the present report provide important information regarding the feasibility of SES in bypass graft disease. Certainly, such findings require confirmation in well-designed prospective randomized trials which have not yet been developed. Email: dominick.angiolillo@jax.ufl.edu

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