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 mat erial properties cannot be measured directly in intact myocardium, understa nding how regional alterations in myocardial strain or segment function are related to underlying cellular dysfunction must be deduced from theoretica l models. Here, we describe how anatomically detailed, three-dimensional co mputational models can be used in conjunction with experimental or clinical studies to elucidate the structural basis of regional dysfunction in acute ly ischemic and ischemic-reperfused ("stunned") myocardium in vivo. Integra tive experimental and computational analysis shows that: (1) in acutely isc hemic myocardium, the transition from abnormal systolic strain in the ische mic region to normal shortening in adjacent, normally perfused tissue is go verned primarily by systolic blood pressure and regional fiber orientation rather than the geometry of the perfusion boundary; and (2) in stunned myoc ardium, the degree of reperfusion injury to the contractile apparatus may b e 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. (C) 2000 Biomedical Engineeri ng Society. [S0090-6964(00)01208-X].