Temporal changes in collateral coronary blood flow in ischemic myocardium during intra aortic balloon pumping

The effectiveness of intra aortic balloon pumping in augmenting collateral coronary blood flow was determined relative to the onset of myocardial ischemia produced by reversibly ligating the proximal 1/3 of the canine left anterior descending coronary artery (LAD). The right heart bypass preparation was used to maintain cardiac output, heart rate, and mean aortic pressure constant. Left ventricle end diastolic pressure and contractile state (maximum left ventricle dp/dt) were unchanged by balloon pumping. Therefore, alterations in regional myocardial blood flow were directly related to balloon pumping and not to a change in cardiac function. Regional myocardial blood flow was measured with radioactive microspheres. In 8 'time related' control animals there was no statistical change in regional myocardial blood flow during 2 consecutive reversible ligations of the LAD without balloon pumping. In 8 animals balloon pumping began 10 min before ligating the LAD significantly increased collateral coronary blood flow in ischemic myocardium 33 ± 14% (P < 0.05). Regional blood flow was also significantly increased in the nonischemic region of the left ventricle and ventricular septum. Total coronary blood flow was significantly increased 20.4 ± 6.3% (P < 0.02) by balloon pumping begun 10 min before LAD ligation. When balloon pumping was begun immediately after ligating the LAD (8 animals), collateral coronary blood flow increased significantly 20.4 ± 8.4% (P < 0.05) in ischemic myocardium while coronary blood flow remained unchanged in nonischemic myocardium and the ventricular septum. When balloon pumping was delayed 20 min after ligation of the LAD, collateral coronary blood flow was unchanged in ischemic myocardium. These results suggest that the increases in collateral coronary blood flow in ischemic myocardium observed with balloon pumping are dependent on the duration of ischemia prior to the initiation of balloon pumping.