Myocardial function in areas of heterogeneous perfusion after coronary artery occlusion in conscious dogs.

Regional myocardial function and blood flow in endocardial layers were correlated in myocardial segments subtending severely ischemic and adjacent, normally perfused myocardium in conscious dogs 1--3 weeks after recovery from coronary artery occlusion. With coronary artery occlusion induced by a hydraulic occluder, endocardial blood flow (measured with radioactive microspheres) and function (determined with an ultrasonic dimension gauge) in homogeneously nonischemic segments increased slightly but not significantly. In homogeneously ischemic segments, blood flow and function decreased (p less than 0.01) by 96 +/- 1% and 98 +/- 4%, respectively. In segments subtending zones of unequal perfusion, endocardial blood flow increased nonsignificantly in the myocardium surrounding the nonischemic crystal, while decreasing by 93 +/- 2% (p less than 0.01) in myocardium surrounding the ischemic crystal. Surprisingly, these segments behaved like homogeneously ischemic segments, i.e., endocardial shortening decreased by 92 +/- 6% (p less than 0.01). Thus, the failure to detect shortening despite normal perfusion of the myocardium surrounding one of the transducers suggest a potential problem with interpretation of regional function measurements or an inability of the apparently nonischemic myocardium to contract.