The overall goal of the project is to provide a better understanding of the pathophysiology of the chronically, overloaded and failing ventricle. Toward this end we have the following specific, yearly objectives: a) to describe the mechanical and dimensional characteristics of ventricular contraction in the isolated servoregulated, canine heart; b) an equivalent description in the instrumented conscious animal during the developmental stages of volume or pressure cardiac overload; and c) to document these responses during regressional phases of following correction of overloaded state.