Incident COronary EveNts Identified by Computed Tomography

Acute myocardial infarctions resulting from unstable plaque in patients with coronary artery disease (CAD) account for a significant portion of cardiovascular morbidity and mortality. Although prediction models that incorporate traditional risk factors have been developed in order to risk stratify patients at highest risk for development of subsequent cardiovascular events, such models lack precision and are often found to over or under-estimate risk. Moreover, current clinical practice has focused on stenosis severity as a predictor of future plaque erosion and/or rupture, in spite of the fact that evidence from intravascular ultrasound (IVUS) studies, such as the PROSPECT trial, demonstrate that ACS events are more likely to occur in less than severely stenotic lesions. Furthermore, there is incomplete understanding of the influence of gender on atherosclerotic plaque composition and downstream coronary events, given the chronologic and prognostic differences between men and women in atherosclerotic cardiovascular disease.

Several studies have attempted elucidating characteristics of vulnerable plaque using invasive imaging modalities such as IVUS. However, such studies have several limitations, most significantly is the fact that plaque characterization was performed after an acute coronary event, which limits the ability to isolate baseline plaque characteristics from changes following the acute event. Noninvasive evaluation of atherosclerotic coronary disease using coronary computed tomographic angiography (CCTA) has been established as an accurate and readily available imaging modality in clinical practice. In addition to the evaluation of diameter stenosis, CCTA is capable of evaluation plaque composition as well as arterial remodeling, in a similar fashion to IVUS. The agreement between plaque characterization using IVUS and CCTA has been demonstrated in several large-scale trials. Nevertheless, there are several key aspects that have yet to be addressed, including the utility of plaque characterization by CCTA for determination of future cardiovascular events, and gender-based differences in atherosclerotic plaque composition in patients with stable and unstable coronary artery disease.

The ICONIC trial was designed as a nested case-control study based on the previously published CONFIRM registry, evaluating demographic, clinical as well as baseline CCTA-determined plaque composition in 238 patients with subsequent ACS events and 238 matched patients without ACS events. As previously described, ICONIC utilizes CCTA to comprehensively assess plaque morphology and characteristics, in addition to arterial wall changes in order to determine characteristics implicated in future adverse events, beyond what has been traditionally described using invasive imaging modalities. The primary goal is to investigate differences in atherosclerotic plaque composition in patients with ACS, compared to patients with stable coronary disease. The secondary goal is to determine gender-specific differences in plaque composition in both stable and unstable coronary artery disease.