Regional O2 consumption and coronary flow during beta adrenoceptor stimulation in reperfused canine myocardium

This study was performed to assess the ability of a reperfused region to increase its flow and O2 consumption upon inotropic stimulation. Isoproterenol (5 micrograms/kg/min) was infused i.v. during the reperfusion phase (4 hr) after 2 hr of the left anterior descending coronary artery occlusion in anesthetized open chest dogs (n = 7). The response was compared to a similar untreated reperfused group (n = 8). Coronary blood flow was obtained with labeled microspheres. Arterial and venous O2 saturations were determined microspectrophotometrically. During reperfusion and isoproterenol infusion, significantly higher heart rate (226 +/- 48 beats/min), maximum positive derivative of left ventricular pressure (3132 +/- 838 mm Hg/sec) and systolic aortic blood pressure (162 +/- 16 mm Hg) were recorded compared to reperfusion in the control group (133 +/- 22, 1615 +/- 184 and 124 +/- 30, respectively). In the control group, coronary blood flow to the reperfused areas decreased from preocclusion values of 85 +/- 22 and 95 +/- 43 to 63 +/- 45 and 47 +/- 31 ml/min/100 g for the subepicardium and subendocardium, respectively. O2 extraction was increased significantly in the reperfused region and O2 consumption was similar to that in the nonoccluded area. The corresponding flow values in the treated group at the end of the reperfusion period were 272 +/- 142 and 183 +/- 150 ml/min/100 g, respectively. With isoproterenol, the O2 extraction was not greater than in the nonoccluded area and the O2 consumption increased about 3-fold in comparison to the control group, although the increase in the reperfused subendocardium was less.(ABSTRACT TRUNCATED AT 250 WORDS)