Comparison of the coronary collateral circulation in dogs and baboons after coronary occlusion

The relevance to man of experimental observations on coronary collateral blood flow (CCBF) in dogs has been questioned. The effect of 2 to 3 hour coronary occlusions in the anesthetized dog and a primate, the baboon, were therefore compared, with CCBF measured by injections of 85Kr distal to occlusion with precordial counting. Before killing, additional isotope was infused to compare inner/outer wall flow distribution and myocardial tissue samples were analyzed for electrolyte content. Effects of nitrates on hemodynamics and metabolism were also compared in dog and baboon. Similar values for CCBF and resistance following occlusions were found in dog and baboon (flow approximately 25 per cent control, calculated resistance increase four- to sevenfold). Greater subendocardial ischemia in both species was indicated by isotope distribution less to the inner wall, but electrolyte changes (k+ less and Na+ greater in the ischemic area compared to nonischemic) were similar transmurally in both species. Hemodynamic responses to nitrate infusion (isosorbide dinitrate) were similar, with increase in CCBF and decrease in resistance. In neither group were inner/outer wall isotope distribution or electrolyte changes influenced by nitrate. The coronary collateral response to occlusion is similar in dog and baboon in terms of both hemodynamics and metabolic changes. After 2 to 3 hours of coronary occlusion some hemodynamic benefit may be demonstrated with nitrates but no metabolic advantage, at least in the central area of ischemia.