Clinical outcomes of drug-eluting stent use in patients with ST elevation myocardial infarction

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Abstract

Aim

Randomised trials using drug-eluting stents (DES) in ST elevation myocardial infarction (STEMI) have shown mixed results, and excluded patients at the highest risk of adverse outcomes. We aimed to determine the real world clinical outcomes of DES and compare these with bare-metal stents (BMS) in an unrestricted observational study of patients presenting with STEMI.

Methods

564 consecutive patients undergoing primary PCI for STEMI were prospectively enrolled in the Melbourne Interventional Group registry (August 2004 to May 2006). The choice of using DES was at the operator's discretion, yet restricted to patients considered at highest risk of restenosis [e.g. diabetes, long lesions (> 20 mm) and small target vessels (< 2.5 mm)]. Clinical, procedural, and 12-month outcomes of patients receiving DES were evaluated and compared to BMS.

Results

DES were used in 45% of patients presenting with STEMI. The rates of cardiogenic shock were similar in the DES and BMS groups (10.2 vs. 11%, p = 0.71). In-hospital outcomes were not significantly different with respect to death (4.7 vs. 7.2%, p = 0.23), major adverse cardiac events (MACE) (10.6 vs. 11.3%, p = 0.80) or stent thrombosis (1.7 vs. 0.3%, p = 0.71). At 12 months, target vessel revascularisation (TVR) in patients with DES was 10.2% vs. 7.2% in BMS (p = 0.22). On propensity score adjusted multivariate analyses, the only independent predictor of 12-month MACE was presentation with cardiogenic shock (OR 2.59, 95% C.I 1.04–6.45), and the only predictor of 12-month TVR was reference vessel diameter 2.5 mm (OR 2.16, 95% C.I 1.06–4.33). DES use was not independently predictive of lower TVR, MACE rates or mortality. Late stent thrombosis rates were similar (DES 3.2 vs. BMS 3.8%, p = 0.65).

Conclusions

Drug-eluting stents are frequently used in Australia in the high-risk setting of STEMI. While target vessel revascularisation rates were moderate in this high-risk group, there was no increased mortality, reinfarction or stent thrombosis compared to bare-metal stents.

Introduction

Percutaneous coronary intervention (PCI) is the preferred reperfusion method for patients with ST elevation myocardial infarction [STEMI, [1], [2]]. Bare-metal stents (BMS) are clearly superior to balloon angioplasty alone, however significant restenosis does occur and may be associated with adverse clinical outcomes [3].

Drug-eluting stent (DES) use has been shown to be associated with significantly reduced clinical and angiographic restenosis compared with BMS in various patient populations and lesion subsets [4], [5], [6], [7]. However, the early pivotal trials establishing the efficacy of DES compared with BMS excluded patients with STEMI. Recently, a number of randomised trials have compared the outcomes of patients with STEMI undergoing implantation of DES vs. BMS and confirm a favourable reduction in restenosis with DES [8], [9], [10]. However, these trials have generally excluded complex patients such as those in cardiogenic shock, rescue angioplasty and patients with complex lesions. Furthermore, there has been concern in the interventional community of using DES in patients presenting with STEMI, given concerns of delayed healing, lack of complete endothelialization, and the thrombogenic environment of the exposed culprit plaque necrotic core [11], [12]. The presence of a large thrombus burden, as is often the case during STEMI, has been shown to predict adverse events in patients treated with DES, with particular concern for late stent thrombosis [13], [14].

The aim of this study was to assess the clinical outcomes of consecutive patients undergoing PCI for STEMI based on stent type (DES vs. BMS) from a ‘real world’ interventional registry.

Section snippets

Patients and design

The study population consists of 564 consecutive STEMI patients treated with PCI with stent implantation from 1st August 2004 to 1st May 2006. Patients were prospectively enrolled in the Melbourne Interventional Group (MIG) registry. The DES group had ≥ 1 DES implanted and the BMS group had only BMS implanted.

The MIG registry is a voluntary, collaborative venture of interventional cardiologists practicing at 7 Australian tertiary referral hospitals, designed to record data pertaining to PCI and

Baseline characteristics

A total of 564 patients with STEMI were enrolled over the stated time period, and 528 patients (94%) had 12-month follow-up at the time of data analysis (Table 1). Baseline clinical characteristics were similar in patients receiving DES vs. BMS with respect to age (62.6 ± 12.5 vs. 62.2 ±  13.3 years, p = 0.71), male gender (79.2 vs. 74.3%, p = 0.19), prior myocardial infarction (14.2 vs. 11.6%, p = 0.52), rescue PCI (11.4 vs. 11.6%, p = 0.9) and cardiogenic shock (10.2 vs. 11.0%, p = 0.78). As would be

Discussion

Our study provides several important insights regarding the use of DES implantation in a “real world” STEMI population: (i) DES are commonly (44.7%) used for treatment of STEMI in Australia despite potential safety concerns raised recently; (ii) our registry suggests low and equivalent rates of 12-month late thrombosis in patients receiving DES compared to BMS in the presence of prolonged clopidogrel therapy for patients receiving DES; (iii) DES use in a higher risk cohort yields overall

Conclusions

The present study demonstrates that despite limited and conflicting evidence, DES are very frequently used in patients presenting with STEMI in contemporary cardiology centres in Australia. In our study population, the selective approach of DES for patients at highest risk of restenosis demonstrated equivalent outcomes in terms of TVR and mortality despite a higher risk profile. Further randomised trials including all high-risk patients are required before definitive conclusions can be made

Acknowledgements

The Melbourne Interventional Group acknowledges funding from Abbott Vascular, Astra-Zeneca, Biotronik, Boston-Scientific, Johnson & Johnson, Medtronic, Pfizer, Sanofi-Aventis, Schering-Plough, Servier, St Jude and Terumo. These companies do not have access to the data, and do not have the right to review articles before publication. Dr. Duffy's work is supported by a National Health and Medical Research Council of Australia Program Grant.

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