The ICONIC study is a retrospective, international, multicenter, nested case-control study based on propensity scoring methods to match patients with (Cases) and without (Controls) an acute coronary syndrome (ACS). Our objective is to identify atherosclerotic plaque characteristics (APCs) that may be implicated in future ACS and compare gender-specific disparities, if any, in coronary plaques among women and men who subsequently experience a future ACS. The primary outcome is an ACS comprised of ST elevation myocardial infarction (STEMI), non-ST elevation MI (NSTEMI), or unstable angina, and the secondary outcome of MI includes STEMI and NSTEMI only.