The plaque hypothesis: understanding mechanisms of plaque progression and destabilization, and implications for clinical management

PURPOSE OF REVIEW: Major adverse cardiac events (MACE) typically arise from nonflow-limiting coronary artery disease and not from flow-limiting obstructions that cause ischemia. This review elaborates the current understanding of the mechanism(s) for plaque development, progression, and destabilization and how identification of these high-risk features can optimally inform clinical management. RECENT FINDINGS: Advanced invasive and noninvasive coronary imaging and computational postprocessing enhance an understanding of pathobiologic/pathophysiologic features of coronary artery plaques prone to destabilization and MACE. Early investigations of high-risk plaques focused on anatomic and biochemical characteristics (large plaque burden, severe luminal obstruction, thin cap fibroatheroma morphology, and large lipid pool), but more recent studies underscore that additional factors, particularly biomechanical factors [low endothelial shear stress (ESS), high ESS gradient, plaque structural stress, and axial plaque stress], provide the critical incremental stimulus acting on the anatomic substrate to provoke plaque destabilization. These destabilizing features are often located in areas distant from the flow-limiting obstruction or may exist in plaques without any flow limitation. Identification of these high-risk, synergistic plaque features enable identification of plaques prone to destabilize regardless of the presence or absence of a severe obstruction (Plaque Hypothesis). SUMMARY: Local plaque topography, hemodynamic patterns, and internal plaque constituents constitute high-risk features that may be located along the entire course of the coronary plaque, including both flow-limiting and nonflow-limiting regions. For coronary interventions to have optimal clinical impact, it will be critical to direct their application to the plaque area(s) at highest risk.