After administration of isoproterenol under Ca(2+) loading, fatal VA frequently occurred in the vehicle (9 of 10 animals, 90%) and diltiazem (8 of 10, 80%) groups, and K201 significantly suppressed the incidences of arrhythmia and mortality (2 of 10, 20%). In the reperfusion study, the incidence and the time until occurrence of reperfusion-induced VA and mortality were significantly suppressed in the K201 (2 of 15 animals, 13%) and diltiazem (1 of 9 animals, 11%) groups compared to the vehicle group (8 of 14 animals, 57%).