EFFECTS OF PROPRANOLOL ON REGIONAL O-2 SUPPLY AND O-2 CONSUMPTION IN REPERFUSED DOG MYOCARDIUM

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  • 1 July 1987
    • journal article
    • research article
    • Vol. 242  (1) , 102-107
Abstract
This study was designed to assess whether propranolol would improve the relationship between O2 supply and O2 consumption in the reperfused ischemic dog myocardium. In 14 dogs, the left anterior descending coronary artery was occluded for 2 hr, followed by a 4-hr period of reperfusion. In 7 of the 14 dogs, 1 mg/kg of propranol was administered 10 min before and again 2 hr after reperfusion. Small artery and vein O2 saturations obtained microspectrophotometrically were combined with regional blood flow measurements using radioactive microspheres to determine regional myocardial O2 consumption. In both groups, 2 hr of occlusion lowered the regional flow to a similar level. In the control group, 4 hr of reperfusion returned the blood flow toward normal levels, from 17 .+-. 20 ml/min/100 g (mean .+-. S.D.) at the end of occlusion to 60 .+-. 42 ml/min/100 g in the affected area compared with 84 .+-. 28 ml/min/100 g in the nonischemic area. In the propranolol-treated animals, the flow increase with reperfusion was not significant (25 .+-. 30 ml/min/100 g to 45 .+-. 26 ml/min/100 g). O2 extraction was greater in the ischemic than in the unaffected area in both groups. However, ischemic region O2 extraction was lower in the propranolol-treated group than in the control group. There were a greater number of arteries and veins with reduced O2 saturations in the control group reperfused area compared with the nonischemic area. Propranolol decreased the number of low O2 saturation vessels in the ischemic area. Reperfusion alone does not restore the ratio of O2 supply to O2 consumption to control values, whereas propranolol significantly improves this ratio. Thus, propranolol appears to better match the increased flow during reperfusion with microregional O2 consumption.