Development of regional myocardial ischemia distal to a critical coronary stenosis during cardiopulmonary bypass: comparison of the fibrillating vs. the beating nonworking states
Schaff, H.V.; Ciardullo, R.C.; Flaherty, J.T.; Gott, V.L.
Surgery 83(1): 57-66
1978
ISSN/ISBN: 0039-6060 PMID: 619472 Document Number: 136180
The present study was designed to determine whether conversion to the beating, nonworking (BNW) heart would diminish fibrillation-induced regional ischemia distal to a critical coronary stenosis. Ten mongrel dogs were placed on total cardiopulmonary bypass with a critical stenosis applied to the left anterior descending coronary artery (LAD). The time on total bypass was divided into 3 equal 50 min periods during which the hearts were maintained alternately in sinus rhythm or ventricular fibrillation. When BNW hearts were fibrillated, intramyocardial CO2 tension (PmCO2) in the LAD supplied subendocardium rose from 73 .+-. 7 (.+-. SEM ) to 120 .+-. 14 mm Hg (P < 0.001), and intramyocardial O2 tension (PmO2) fell from 24 .+-. 4 to 10 .+-. 2 mm Hg (P < 0.005). Regional arterial-coronary venous lactate difference (A-CV lac) fell from 13.8 .+-. 3.8 mg% (extraction) to -10.8 .+-. 3.2 mg% (production) (P < 0.005). When fibrillating hearts were converted to the BNW state, PmO2 rose from 12 .+-. 2 to 19 .+-. 4 mm Hg and PmCO2 decreased from 101 .+-. 9 to 85 .+-. 4 mm Hg. A-CV lac rose from -6.5 .+-. 2.6 mg% (production) to 10.4 .+-. 4.8 mg% (extraction) (P < 0.01). In a region of myocardium distal to a critical stenosis, ventricular fibrillation during bypass results in regional myocardial ischemia whereas the BNW state does not. This ischemia likely is due to the inability of flow in the stenosed coronary artery to increase in response to the increased O2 demand of fibrillation. Conversion to the BNW state can reverse the ischemia which develops in the fibrillating state.