Cardiac surgery for the treatment of acquired and congenital defects has become a common and relatively safe procedure as the instances of technical and mechanical complications have diminished. A significant morbidity and mortality remains, however, due to preoperative and postoperative derangements of the performance characteristics of the left ventricle. It is proposed to utilize techniques we have previously developed and validated in this laboratory to evaluate the relative contributions of preoperative and intraoperative factors to the ultimate incidence of left ventricular dysfunction in canine models of heart disease. The effects will be studied of acutely and chronically altered loading states, as seen in congenital and valvar heart disease, and of regional myocardial dysfunction, as seen in ischemic heart disease, on left ventricular mechanics using chronically implanted sonomicrometry and solid state micromanometry. These techniques will allow direct measurement of ventricular geometry and pressure in conscious animals and permit quantification of geometric adaptation, the diastolic properties, and certain determinants of systolic performance in the intact heart in response to altered loading states. The manner in which the coronary circulation responds to altered loading states and chronic hypertrophy will be studied by radionucleotide microsphere techniques in order to measure to regional left ventricular distribution of coronary blood flow under basal and stress conditions. These studies are aimed at clarifying the relationship between coronary blood flow and myocardial function. Additional goals will be to develop and validate echocardiographic and angiographic methods of evaluating myocardial mechanics in the intact heart and to determine the effects of cardiopulmonary-bypass on cardiac mechanics and coronary circulation in both normal and hypertrophied ventricles.
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