Improvement in the relationship between flow to ischemic myocardium and the extent of necrosis with glycolytic intermediates that decrease blood oxygen affinity in dogs

Reducing blood oxygen affinity may enhance myocardial oxygen delivery during ischemia. We evaluated this hypothesis in awake, preveiously instrumented dogs that received a 20 ml/kg infusion of a solution of dihydroxyacetone, phosphate, and pyruvate after acute occlusion of either the left anterior descending of circumflex coronary artery. This infusion reduced blood oxygen affinity (↓BOA) after 2 hours; the P₅₀ increased from 29.9 ± 0.7 torr (mean ± SD) to 32.1 ± 0.6 torr; P < 0.01 (BOA group). Four dogs received 20 ml/kg of phosphate and pyruvate solution to assess volume effects (V group), and five dogs were controls (C group). The 2-hour P₅₀ values in V and C were unchanged. Regional flow (15-μm spheres) reduction 2 hours postocclusion was compared to the percent tissue infarcted determined by histology 7-9 days after occlusion for multiple samples from the endocardial layer of the left ventricle. When flow was less than 40% of normal, V and C had 55% infarction while ↓BOA had 37% (P < 0.05); at flow less than 20% of normal, V and C had 79% infarction while ↓BOA had 38% (P < 0.001); and at less than 10% of normal, V and C had 87% and 94% infarction, respectively, while ↓BOA had 56% (P < 0.001). Reducing blood oxygen affinity after coronary artery occlusion significantly decreased the extent of myocardial necrosis for the same degree of ischemia. Reducing BOA may increase oxygen delivery to ischemic myocardium when flow is restricted.