The proposed studies will precisely define, in man, the usual sequence of postoperative changes in left ventricular systolic dynamics, volumes, compliance, and regional wall motion that occur in the immediate procedures and postoperative therapeutic interventions on these dynamics and on myocardial oxygen consumption will be examined serially. The long-term effects of valve replacement on left ventricular dynamics and volumes will be characterized in patients with left ventricular dysfunction of diverse etiology. Measurements will be made using a reproducible, noninvasive method (developed in our laboratories) to measure serially left ventricular volumes, systolic dynamics and compliance by means of fluoroscopy of radiopaque tantalum markers which are surgically implanted in selected locations inthe myocardium. Measurements of instantaneous left ventricular volume and pressure enable us to construct and compare, for the first time in man, sequential left ventricular pressure-volume loops and to quantitatively determine how left ventricular systolic performance and diastolic compliance vary as a function of time. Together with simultaneously measured myocardial oxygen consumption we can characterize and compare the effects of cardioactive drugs on overall cardiac efficiency. The results of the proposed studies will lead to more intelligent patient management, will yield new insight into the effects of specific operative techniques on postoperative left ventricular function, will prompt more astute clinical decision-making, and will elucidate the effects of specific operative techniques on postoperative left ventricular function, will prompt more astute clinical decision-making, and will elucidate the effects of valve replacement on left ventricular function. These results should, in turn, help reduce cardiac surgical operative mortality and late postoperative attrition rates and enhance clinical benefits. Furthermore, these studies should contribute new and basic physiological and pharmacological information that will increase our fundamental understanding of normal cardiac function and the pathophysiology of heart disease.
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