Local Mitochondrial Enzyme Activity Correlates with Myocardial Blood Flow at Basal Workloads

Myocardial O2consumption in porcine left ventricle is heterogeneously distributed in parallel to heterogeneous O2delivery

“…However, blood flow values were similar as those found in earlier experiments without cannulation of a coronary artery (3,5,9), indicating no hyperemic response.…”

“…In any case, the existence of other biological factors besides V O 2 means that O 2 extraction is not perfectly regulated and shows local variation. The relation between succinate dehydrogenase activity, a marker enzyme of the mitochondria, and blood flow explained merely 22% of blood flow variance (9). Thus it appears that blood flow is much more strongly related to the actual aerobic metabolic flux than to local aerobic capacity.…”

“…Correcting for the measurement errors, the contribution of the linear relation between blood flow and V O 2 to the variance of blood flow was therefore 43%. In a separate study, the contribution of succinate dehydrogenase, a TCA cycle enzyme, was found to be 22% (9). It is highly likely that the effects of succinate dehydrogenase and V O 2 are not additive but strongly overlapping.…”

“…Heterogeneity in oxygen consumption (V O 2 ) between different areas of the left ventricle may explain at least part of the heterogeneity of myocardial blood flow. Indeed, it has been shown in previous studies (9,19) that indirect indicators of local aerobic metabolism show heterogeneity. For instance, a correlation between local blood flow and fatty acid uptake has been shown (24).…”

“…We calculate that, in the heart at normal workload, the variance of left ventricular oxygen delivery at submilliliter resolution is explained for 43% by heterogeneity in oxygen demand. regional blood flow; metabolism; myocardium; magnetic resonance spectroscopy MYOCARDIAL BLOOD FLOW is highly heterogeneous, as demonstrated in many different species, with various methods (radioactive, colored and fluorescent microspheres, molecular tracers, MRI, and PET), and under different experimental circumstances, such as open-versus closed-chest and anesthetized versus awake animals (5,9,19,22,26,27). Myocardial perfusion shows similar heterogeneity in the human heart (47).…”