Correlation between heterogeneous myocardial flow and oxidative metabolismin normoxic and stunned myocardium

Myocardial blood flow exhibits considerable heterogeneity. Consequently, ox ygen supply to the myocardium is also heterogeneous, as is myocardial metab olism. Many lines of evidence show a close correlation between local flow a nd local metabolism in the normoxic myocardium. So far, myocardial metaboli sm has predominantly been assessed indirectly by using labeled substrates. We used the O-18 isotope, permitting analytical separation of (H2O)-O-18 fr om the O-18 isotope, as well as quantification of regional oxidative metabo lism by measuring the tissue residue of oxidation water in the rabbit myoca rdium. Correlation of local flow with oxidative metabolism was significant in the normoxic myocardium. This correlation was lost in the postischemic/r eperfused myocardium. Apart from the established mechanisms underlying myoc ardial stunning, a mismatch between local flow and oxidative metabolism mig ht thus also contribute to the postischemic dysfunction. In the normoxic myocardium, function should correlate with metabolism and b lood flow. For technical reasons, function has not been assessed on a very local scale. Nevertheless, some considerations are presented on the heterog eneity of function as well as on the scale on which heterogeneity should be investigated to convey physiologically meaningful information on regulator y cardiac mechanisms.