Coronary Artery Plaque Phenotype and 5-Year Clinical Outcomes in Older Patients with Non-ST Elevation Acute Coronary Syndrome

Background: Lesions with thin-cap fibroatheroma (TCFA), small luminal area and large plaque burden (PB) have been considered at high risk of cardiovascular events. Older patients were not represented in studies which demonstrated correlation between clinical outcome and plaque characteristics. This study aims to investigate the prognostic role of high-risk plaque characteristics and long-term outcome in older patients presenting with non-ST elevation acute coronary syndrome (NSTEACS). Methods: This study recruited older patients aged ≥75 years with NSTEACS undergoing virtual-histology intravascular ultrasound (VH-IVUS) imaging from the Improve Clinical Outcomes in high-risk patieNts with acute coronary syndrome (ICON-1). Primary endpoint was the composite of major adverse cardiovascular events (MACE) consisting of all-cause mortality, myocardial infarction (MI), and any revascularisation. Every component of MACE and target vessel failure (TVF) including MI and any revascularisation were considered as secondary endpoints. Results: Eighty-six patients with 225 vessels undergoing VH-IVUS at baseline completed 5-year clinical follow-up. Patients with minimal lumen area (MLA) ≤4 mm2 demonstrated increased risk of MACE (hazard ratio [HR] 2.37, 95% confidence interval [CI] 1.00–5.59, p = 0.048) with a worse event-free survival (Log Rank 4.17, p = 0.041) than patients with MLA >4 mm2. Patients with combination of TCFA, MLA ≤4 mm2 and PB ≥70% showed high risk of MI (HR 5.23, 95% CI 1.05–25.9, p = 0.043). Lesions with MLA ≤4 mm2 had 6-fold risk of TVF (HR 6.16, 95% CI 1.24–30.5, p = 0.026). Conclusions: Small luminal area appears as the major prognostic factor in older patients with NSTEACS at long-term follow-up. Combination of TCFA, MLA ≤4 mm2 and PB ≥70% was associated with high risk of MI. Clinical Trial Registration: NCT01933581.