The primary purpose of this project is to develop and evaluate new instrumentation which uses ultrasonic principles. The instruments are directed towards the study of cardiovascular physiology both in animals and in humans. Two primary directions have been taken. One has been the development of a blood flow velocity detector, mounted on the tip of a Sones coronary catheter. The transducer utilizes the pulsed Doppler principle and has been successfully employed in both animals and humans. The second major direction has been the development of chronically instrumented animal models. The animals are implanted with ultrasonic segment length gauges capable of measuring regional myocardial function in three or four areas of the left ventricle, Doppler flow probes on left anterior and/or circumflex coronary arteries and high fidelity left ventricular pressure gauges plus a snare around the coronary artery capable of inducing varying degrees of coronary artery stenosis. Animals are allowed to heal following implantation surgery for one to three weeks and a variety of physiologic studies performed including the evaluation of reversible myocardial ischemia and the effects of various interventions on reversal of myocardial ischemia.