Myocardial segment motion during regional ischemia--regional contraction and relaxation.

Several aspects of regional ischemic myocardial function determined by segment motion are discussed, based on our studies. Although global left ventricular function decreased progressively as the global severity of myocardial ischemia increased, there are several possible factors which may modify this relationship. As for the site of the ischemic area, occlusion of the left anterior descending artery resulted in a greater decrease in the left ventricular ejection fraction than occlusion of the left circumflex artery. Interaction between the ischemic myocardium and the non-ischemic myocardium may be a multifactorial phenomenon rather than simple tandem stretching. The segment length motion during acute ischemia appears to be complicated. The segment motion of the severe ischemic myocardium during systole and diastole was explained for the most part by a uniform tension-length curve which was independent of changes in the loading condition. This non-linear elastic property was fundamental to the production of segment motion asynchrony. The wall motion of the hypokinetic segment might be explained by a combination of the active change in myocardial stiffness and the non-linear elastic property of the myocardium.