Abstract: This study was designed to evaluate whether VBt has beneficial effect on action potential of rabbit left ventricular muscle cells in situ during myocardial ischemia.Coronary occlusion resulted in significant diminution in amplitude of action potential (APA) and maximal depolarization rate of phase O (dv/dt), and decrease in action potential duration at 50% repolarization (APD₅₀) and 90% repolarization (APD₉₀). VBt lengthened the duration of action potential of ventricular muscle cell and greatly reduced the ischemic shortening changes of APD₅₀ and APD₉₀ (P<0.001), but exerted no significant effects on APA and dv/dt. These findings suggest that VBt may have some antiarrhythmic actions owing to its beneficial effect on APD₅₀ during myocardial ischemia.