Objective: To observe the effect of endothelin A receptor antagonist BQ610 on acute myocardial ischemic arrhythmia in cats and to study the role of endothelin in the development of acute ischemic arrhythmia. Methods: Acute myocardial ischemic arrhythmia was induced by the occlusion of the initial segment of left anterior descending part of the coronary artery. Arrhythmia during 30 min of the ischemia was observed and the effects of BQ610 on the arrhythmia was evaluated. Results: BQ610 dose-dependently antagonized the acute ischemic arrhythmia. Conclusion: Mediated by endothelin A receptor, endogenous endothelin may play an important role in the development of acute ischemic arrhythmia in cats.