Myocardial Lactate Release During Ischemia in Swine Relation to Regional Blood Flow

To determine the relation between regional myocardial blood flow, contractile function, and myocardial lactate release during mild-to-moderate regional myocardial ischemia, nine open-chest swine were instrumented for measurement of regional myocardial blood flow (micro-sphere method), contractile function (sonomicrometry), and hemodynamics. L-[1-14C]Lactate or L- [U-3C]lactate was infused intravenously using a primed continuous infusion technique to quantify regional myocardial lactate release. D-[U-_3C]glucose or D-[6-`4C1glucose was simul-taneously infused to determine the contribution of exogenous glucose to lactate release. Graded coronary ischemia (two to three levels) was created in the left anterior descending coronary arterial distribution by mechanically constricting the artery in five animals or by decreasing flow through a cannulated left anterior descending artery in four animals. In all nine animals, subendocardial blood flow was 0.99 ± 0.21 (ml/min)/g during control and 0.34±0.14 (ml/min)/g during the most severe grade of underperfusion (p<0.001) in the left anterior descending coronary arterial distribution. Regional myocardial lactate release was 0.15±0.09 and 1.19+0.75,mol/ml, respectively (p<0.003). A highly significant inverse correlation was observed between subendocardial blood flow and myocardial lactate release during the grade