ULTRASONIC INSTRUMENTATION FOR CARDIOVASCULAR STUDIES

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The goal of this project is to develop, evaluate, and utilize several ultrasonic techniques in the measurement of blood flow, cardiac function and mechanics, and vascular dimensions in acute and chronically instrumented animal models of cardiovascular disease, in patients being diagnosed and treated for coronary artery disease, and in patients undergoing microvascular reconstruction. The specific projects are: 1) Continue the development of the single crystal Doppler displacement technique for measuring myocardial thickening by adding a range gate tracker to follow any desired layer. This and the original non-tracking device will be evaluated against the transit-time method using wire and sponge targets in-vitro and in normal and ischemic myocardium in acute and chronically instrumented dogs. 2) Utilize the Doppler displacement instrument to determine the regional variations in the transmural distribution of thickening in normal and ischemic myocardium both in animals and in patients during cardiac surgery. 3) Develop an easily removable pulsed Doppler probe to monitor the patency of reconstructive microvascular repairs post-operatively. 4) Develop a small, high resolution vessel diameter sensor using high frequency (10 or 20 MHz) transit-time crystals or a high frequency (20 MHz) Doppler displacement probe to be utilized in ongoing studies of vasomotion, factors affecting arterial growth, arteriolization of vein grafts, and regional responses to vasodilators. 5) Develop a miniature (1 mm), single-crystal pulse-echo catheter to sense arterial wall thickness (and composition) from within the vessel to be used to plan and assess dilatation with balloon and laser angioplasty procedures. 6) Develop a miniature (1 mm) 20 MHz pulsed Doppler catheter with a guide wire lumen for sensing flow velocity subselectively in the coronary arteries of man during coronary arteriography and angioplasty procedures. Applications include the assessment of vascular reserve (hyperemic response) through discrete lesions during diagnostic procedures and the evaluation of the effects of angioplasty on flow and vascular reserve.