The effect of beta-adrenergic blockade on infarct size following experimental coronary occlusion.

The effect of Pindolol on myocardial infarct size was studied in 10 open chest dogs. In each animal a sequential occlusion and reperfusion of 2 medium-sized branches of the left coronary artery was performed in the same heart. After occlusion and reperfusion of the control artery the initial dose of Pindolol (0.25 mg/kg body weight) was administered. Thereafter the test artery was occluded, followed by a maintenance dose of Pindolol (0.3 mg/kg body weight). The drug caused a significant decrease in LVP and LV-dp/dt but no change in heart rate. MVO2 also decreased significantly. Regional myocardial blood flow was measured with the tracer microsphere method. Collateral flow in the perfusion area of the control artery was 11.2 +/- 5.9% and in the area of the test artery 10.0 +/- 4.4% of normal. No change in the endo/epi ratio as a result of treatment was observed. The area of infarction (p-nitroblue tetrazolium-reaction) was divided by the area of perfusion (angiography). Infarct size, expressed as the percentage of the perfusion area, was 48.2 +/- 22.2% in the region of the control artery and 43.0 +/- 23.9% in the region of the test artery. The difference was statistically not significant.