The effect of timolol given five minutes after coronary occlusion on plasma catecholamines.

The reported study determined whether timolol would afford a protective effect by preventing the coronary occlusion-induced arrhythmias associated with the increase in plasma norepinephrine (NE) and epinephrine (E). Ten anesthetized cats received saline or timolol (5 mg/kg, IV) five minutes after coronary occlusion of the left anterior descending coronary artery 10 to 14 mm below its origin. Coronary occlusion produced arrhythmia in three of the cats that received saline and in four of the cats that received timolol. Three of the saline-treated cats died in cardiogenic shock; two were sacrificed six hours postocclusion. Four of the timolol-treated cats died in congestive heart failure postcoronary occlusion. There was a gradual increase in NE (P greater than .05) and E (P less than .05) in both groups after coronary occlusion. Death produced a significant increase in NE and E levels. Timolol did not modify the occurrence of arrhythmias and the associated increase in plasma NE and E that developed after coronary occlusion and at death.