Approximately 500,000 arrhythmia-related sudden deaths occur annually in the United States. Surgical approaches are feasible for control of many such arrhythmias, yet the hemodynamic effects of these procedures are not well understood. Accordingly, laboratory and clinical studies are proposed to define the hemodynamic effects of left ventricular aneurysm (LVA) repair, surgical electrophysiologic (EP) testing, automatic implantable cardiovertor-defibrillator (AICD) insertion, and surgery for the Wolff-Parkinson-White (WPW) syndrome. Studies will be based on current methods for analysis of systolic and diastolic mechanics of the left ventricle (LV). Measuring techniques will include two-dimensional echacardiography, impedance ventriculography, and sonomicrometry. Segmental function, including changes in local wall thickening and wall motion, will also be assessed, with echo and computer analysis. LVA will be studies with emphasis on cardiac geometry. A technique for inducing chronic LVA in animals will be developed and the model used for study of LVA repair. The effects of standard aneurysmectomy and patch reconstruction on global and segmental function will be compared. Plans include the development of an adjustable patch that will allow surgeons to optimize LV repair by balancing geometric-dependent variables such as wall tension and stroke volume. The effects of chronically-implanted AICD patch electrodes on diastolic and systolic LV properties will be investigated. The effects of intra- and extra-pericardial lead placement will be defined, and new surgical methods, including thoracoscopic insertion, aimed at minimizing both surgical trauma and compliance changes, will be evaluated. The effects of EP testing on LV function will be studied and interventions, including hypothermia, allopurinol and nitrates, will be investigated in an effort to minimize injury. Finally, the differential effects on hemodynamics of epicardial vs. endocardial WPW ablation will be investigated. As a result of this research, understanding of difficulties associated with these procedures will be increased, morbidity and mortality will be minimized, and salutary effects will be maximized.