Quantification of ischemic stress during repeated coronary artery occlusion in the dog a method for validation of therapeutic effects

Summary

In 9 open-chest mongrel dogs 4–6 intermittent 3-min occlusions of the LAD artery were performed with time intervals of about 45 min. Using a μ-computer, the following variables, were calculated online: energy demand according to the Bretschneider equation (E_t) from digitized hemodynamic data; myocardial oxygen consumption (M$\dot V$O₂) from fiberoptically measured coronary sinus oxygen saturation and coronary sinus blood flow. Coronary occlusion led to a decrease in M$\dot V$O₂ in comparison to E_t. The integral of the difference between M$\dot V$ ₂ and E₁ over the entire occlusion time yielded a total O₂-deficiency (DO₂) of 76 (±12%) μl O₂/g ischemic tissue and a correlation coefficient with the weights of the intravitally stained ischemic areas of r=0.96. Additional O₂-uptake in relation to E_t during the early perfusion period yielded a correlation to the size of the ischemic area of r=0.95 and an average O₂-repayment (RO₂) of 32 (±14%) μl O₂/g ischemic tissue. The determination of total myocardial O₂-deficiency during ischemic stress as well as determination of O₂-repayment during the early reperfusion period could be used to estimate the extent of ischemic stressed myocardium. Subsequently, the evaluation of pharmacological effects on myocardial ischemia should be possible.