Comparison of angiographically derived coronary radial wall strain and superficial wall stress for the characterization of plaque vulnerability

Background: Angiography-derived radial wall strain (RWS) estimates the radial coronary wall deformation caused by pulsatile blood pressure, whereas superficial wall stress (SWS) summarizes the comprehensive wall deformation caused by both blood pressure and cardiac motion. This study sought to investigate the difference between RWS and SWS for the association with plaque vulnerability and the impact of cardiac motion on RWS. Methods: Concurrent RWS, cardiac motion-induced bending angle change (Δ C BA), SWS, and optical coherence tomography image analyses were retrospectively performed in 49 eligible intermediate coronary lesions. Correlation and multivariate linear regression analyses were applied to investigate the difference in the correlations of RWS and SWS with plaque characteristics and the impact of Δ C BA on RWS assessment. Results: Lipid-to-cap ratio (LCR), a novel vulnerable plaque indicator, was found to be correlated with both maximum RWS (RWS max ) (r = 0.58, p < 0.001) and peak SWS (r = 0.29, p = 0.041). RWS max tended to be more relevant to LCR in comparison with peak SWS, albeit statistically nonsignificant (z = 1.75, p = 0.080). With multivariate linear regression, LCR was independently associated with both RWS max (normalized β = 0.49, p = 0.001) and peak SWS (normalized β = 0.34, p = 0.012), whereas Δ C BA could only affect peak SWS (normalized β = 0.29, p = 0.035). Peak time-averaged SWS showed similar results to peak SWS. Conclusions: RWS tended to be more relevant to plaque vulnerability and less affected by cyclic bending as compared with SWS.