Uncoupling of Muscle Shortening from Contractile Force in Intact Heart

摘要

It is well accepted that myocardial segment shortening is preceded by, and dependent upon, development of isometric force. In other words, muscle shortening is coupled in both time and amplitude to force; therefore it is assumed that dysfunctional contraction (e.g., in stunned myocardium) must be due to depressed contractility. However, it is also possible that dysfunctional shortening would result from poor coupling between force and shortening. This study was designed to test this hypothesis, and to show that it is possible to reversibly dissociate shortening from force development under certain conditions. In open-chest anesthetized dogs, 2,3-butanedione monoxime (BDM), acetylcholine and dobu-tamine were each injected directly into the left anterior descending coronary artery (LAD). The LAD was then lig-ated for 10 min to produce local myocardial ischemia, followed by reperfusion. In addition to global hemodynam-ics, regional myocardial force and segment shortening were measured in both the LAD-perfused area and that perfused by the circumflex coronary artery which served as a control area.