The main objective of this proposal is to assess the regional diastolic elastic properties of the left ventricular (LV) myocardium in vivo, using a finite element technique. The geometry of the ventricle will be defined in two ways: 1) using two-dimensional (2-D) echocardiography and a specially-designed articulated transducer arm to allow three-dimensional (3-D) reconstruction of the LV; and 2) using several, closely-spaced, parallel 2-D scans obtained with a new generation, rapid computed tomographic (fast CT) scanner. Simultaneous intracavitary pressure will be recorded using a catheter-tip transducer. The geometric and pressure data will be analyzed using the finite element technique, solving for the regional elastic properties of the LV myocardium. During the three years of requested funding, the specific aims to be achieved are: (1) Validation of the geometric LV reconstruction by both imaging techniques from in vitro dog heart specimens, in vivo dog experiments, and in vivo human studies from patients undergoing left ventriculography; (2) studies of regional elastic modulus of the in vivo LV using the finite element technique. These studies will be performed in vivo in dogs in control and post-coronary occlusion experiments using both imaging methods and will also be conducted using echo imaging in patients undergoing left ventriculography as part of an ongoing study of the efficacy of intracoronary streptokinase infusion during acute myocardial infarction. The overall hypothesis in this project is that the elastic properties defined using this approach will accurately discriminate between normal and acutely infarcted myocardium.
