Hemodynamics of coronary artery with systolic luminal narrowing

Myocardial bridging (MB), a congenital coronary anomaly with systolic luminal narrowing of arteries, may lead to serious cardiovascular events. However, the biomechanical effects of MB remain poorly understood. In this paper, computational and theoretical efforts are combined to investigate the morpho-hemodynamics of MB. A fluid mechanics model, validated by fluid dynamics analysis, is developed to predict the luminal pressure distributions in branched, slender tubular structures with non-uniform curvatures and varying cross-sections. An elastic mechanics model is proposed to predict the stress concentrations in perforated soft tissues with an anisotropic constitutive relation and arbitrarily shaped holes. The results show that increasing the compression ratio, the narrowed arterial length, and the embedded depth leads to a higher relative pressure drop (RPD) across the tunneled segment and a lower major outlet flow rate. The dependence of RPD on the bridge location is indistinct. Due to myocardial contractility, the maximum von Mises stress in the arterial wall increases significantly, which may cause endothelial dysfunction. Further, a risk classification model, supported by clinical results, is proposed. By combining the compression ratio of MB and the length of the narrowed section, this model exhibits excellent discriminant ability in assessing the severity of MB. This work helps understand the biomechanical effects of MB in coronary arteries, and provides a theoretical basis for the prognostic predictions and clinical interventions of MB patients.