Effects of diacetyl monoxime and cytochalasin D on ventricular fibrillation in swine right ventricles

Whether or not the excitation-contraction (E-C) uncoupler diacetyl monoxime (DAM) and cytochalacin D (Cyto D) alter the ventricular fibrillation (VF) activation patterns is unclear. We recorded single cell action potentials a nd performed optical mapping in isolated perfused swine right ventricles (R V) at different concentrations of DAM and Cyto D. Increasing the concentrat ion of DAM results in progressively shortened action potential duration (AP D) measured to 90% repolarization, reduced the slope of the APD restitition curve, decreased Kolmogorov-Sinai entropy, and reduced the number of VF wa ve fronts. In all RVs, 15-20 mmol/l DAM converted VF to ventricular tachyca rdia (VT). The VF could be reinduced after the DAM was washed out. In compa rison, Cyto D (10-40 mu mol/l) has no effects on APD restitution curve or t he dynamics of VF. The effects of DAM on VF are associated with a reduced n umber of wave fronts and dynamic complexities in VF. These results are comp atible with the restitution hypothesis of VF and suggest that DAM may be un suitable as an E-C uncoupler for optical mapping studies of VF in the swine RVs.