Integrative models for understanding the structural basis of regional mechanical dysfunction in ischemic myocardium

Myocardial ischemia and many other cardiac pathologies are associated with regional ventricular dysfunction. Since the distributions of stress and material properties cannot be measured directly in intact myocardium, understanding how regional alterations in myocardial strain or segment function are related to underlying cellular dysfunction must be deduced from theoretical models. Here, we describe how anatomically detailed, three-dimensional computational models can be used in conjunction with experimental or clinical studies to elucidate the structural basis of regional dysfunction in acutely ischemic and ischemic-reperfused ("stunned") myocardium in vivo. Integrative experimental and computational analysis shows that: (1) in acutely ischemic myocardium, the transition from abnormal systolic strain in the ischemic region to normal shortening in adjacent, normally perfused tissue is governed primarily by systolic blood pressure and regional fiber orientation rather than the geometry of the perfusion boundary; and (2) in stunned myocardium, the degree of reperfusion injury to the contractile apparatus may be uniform across the wall thickness despite observations that the extent of ischemia and the impairment of regional strain during reperfusion are both significantly greater in the subendocardium.