These investigations explore the impact of ischemia induced during the course of cardiopulmonary bypass on ventricular performance. Ischemic injury is quantitated by alterations in diastolic properties of the left and right ventricles as reflected by alterations in the pressure volume relationship (chamber stiffness) and alterations in stress-strain properties (muscle stiffness). Diastolic properties are derived from dimension measurements using pulse transit ultrasound to determine specific chamber axes and wall thickness. Similar dimension measurements combined with instantaneous pressure measurements are utilized on the minor axis and wall thickness at the equatorial minor axis in patients. Alterations in diastolic properties are correlated with the extent to which systolic performance is impaired as measured by contractile indices derived from the end-systolic pressure volume relationship. Specific studies planned involve comparisons of right ventricular as compared with left ventricular injury, particularly in studies of the hypertrophied right ventricle. These studies utilize canine models of valvular aortic stenosis to produce left ventricular hypertrophy and pulmonary stenosis to produce right ventricular hypertrophy. This is done in both experimental rat and dog models. Patterns of reperfusion following specific injury are assessed using radioactive microspheres to determine transmural blood flow and interventions are assessed for their effectiveness in reversing the deleterious effects of ischemia on hypertrophied as compared with nonhypertrophied ventricles. The influence of right ventricular dysfunction on left ventricular performance is assessed with both normal and abnormal levels of ventricular performance. The final extension of these studies assesses these same properties in patients undergoing cardiac surgical procedures subjected to varying ischemic periods or attempts made to preserve myocardial function. It is anticipated that these studies will provide significant new information that should provide safer techniques for dealing with hypertrophied hearts during cardiac reparative operations.
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