Angiography-derived radial wall strain as a predictor of myocardial ischemia, high-risk plaque, and outcomes

Abstract Background Angiography-derived radial wall strain (RWS) is a novel method to assess the biomechanical characteristics of the underlying plaque. There is limited data regarding how the biomechanical attributes of atherosclerotic lesions relate to their physiologic and morphological attributes. Purpose This study aimed to investigate the association of RWS with myocardial ischemia and high-risk plaque, and their prognostic implication. Methods From the international CCTA-FFR registry, 484 deferred vessels underwent RWS analysis. Angiography-derived RWS was defined as relative changes of lumen diameter within the cardiac cycle, expressed as a percentage of the largest lumen diameter. Plaque characteristics were assessed in a coronary CT angiography core laboratory and high-risk plaque was defined as 3 or more high-risk plaque characteristics (HRPC) including minimum lumen area <4.0 mm2, plaque burden ≥70%, low-attenuation plaque, and positive remodeling. Functional significance of coronary lesion was assessed by invasively measured fractional flow reserve (FFR). The primary outcome was vessel-oriented composite outcome (VOCO), a composite of cardiac death, target vessel myocardial infarction, or target vessel revascularization at 5 years. All clinical outcomes were adjudicated by an independent clinical event committee. Results The mean FFR was 0.89±0.07, and that for maximum RWS (RWSmax) was 11.2±2.5%. RWS proportionally increased along with the decrease in FFR values, and the increase in the number of HRPC (Both p-for-trend <0.001). The proportion of vessels with FFR ≤0.80 and that of vessels with high-risk plaque increased in the order of RWSmax quartile group (Both p-for-trend <0.001) and these associations maintained after the adjustment of clinical characteristics (adjusted odds ratio [OR] 1.31, p value <0.001 for FFR ≤0.80; adjusted OR 1.24, p value <0.001 for high-risk plaque) and angiographic parameters (adjusted OR 1.24, p value <0.001 for FFR ≤0.80; adjusted OR 1.14, p value 0.012 for high-risk plaque). High RWSmax (>14.2%, optimal cut-off value for VOCO) was an independent predictor for VOCO after adjusting for diabetes and % diameter stenosis, FFR ≤0.8, or high-risk plaque (Figure 1). In a mediation analysis, RWS showed an independent effect from lesion-specific ischemia or high-risk morphological attributes in defining prognosis (Figure 2). Conclusion(s) Angiography-derived RWS was closely related to coronary physiologic and plaque morphological attributes, but was an independent predictor of clinical events. This novel index can provide additional prognostic implications over physiological severity or plaque characteristics in patients with coronary artery disease.Prognostic implications of high RWSMediation analysis