Myocardial Oxygen Utilization During Left Heart Bypass

Myocardial oxygen utilization during left heart bypass was studied in a preparation where a mean aortic pressure of 75 mm Hg and a heart rate of 100 beats per minute were kept constant. The relationship of reduction of myocardial oxygen consumption (MVO2) as bypass increased was nonlinear. A partial bypass flow as high as 80% produced a decrease in MVO2of only 15% from controls. Thereafter, MVO2decreased rapidly to a maximum reduction of 50% from controls with complete left ventricular bypass with left ventricular decompression. This study indicates that the maximum benefit in salvaging marginal ischemic muscle with the use of left ventricular bypass would be expected to occur with complete left ventricular bypass and left ventricular decompression.