Cardiac Efficiency and Contractile Function of In Situ Canine Left Ventricle

This study tests the hypothesis that arterial vascular stiffening adversely influences in situ left ventricular contractile function and energetic efficiency. Ten reflex-blocked anesthetized dogs underwent a bypass operation in which a Dacron graft was sewn to the ascending aorta and connected to the infrarenal abdominal aorta via a plastic conduit. Flow was directed through either native aorta or plastic conduit by placement of vascular clamps. Arterial properties were measured from aortic pressure-flow data, and ventricular function was assessed by pressure-volume (PV) relations. Coronary sinus blood was drained via an extracorporeal circuit for direct measurement of myocardial 02 consumption (MVo2). Data at multiple steady-state preload volumes were combined to derive chamber function and energetics relations. Energetic efficiency was assessed by the inverse slope of the MVo2-PV area relation. Directing flow through plastic versus native aorta resulted in a 60-80% reduction in compliance but little change in