EFFECTS OF CORONARY PERFUSION DURING MYOCARDIAL HYPOXIA - COMPARISON OF METABOLIC AND HEMODYNAMIC EVENTS WITH GLOBAL ISCHEMIA AND HYPOXEMIA

  • 1 January 1976
    • journal article
    • research article
    • Vol. 71  (5) , 726-736
Abstract
The effects of metabolic accumulation on myocardial metabolism during global heart O2 deprivation were evaluated in a working in situ swine heart preparation with controlled total coronary blood flow. Myocardial O2 consumption was depressed to a similar extent by either reducing total coronary flow 60% (ischemia, low coronary perfusion) in 10 swine or by decreasing coronary perfusate PO2 [O2 pressure] to 30 mm Hg at normal coronary flows (hypoxemia, high coronary perfusion) in 13 swine. Compared with findings in 13 control hearts, ischemia significantly (P < 0.05) decreased myocardial O2 consumption (640-390 .mu.mol/h per g), glucose uptake (185-16 .mu.mol/h per g) and free fatty acid consumption (32-17 .mu.mol/h per g). Tissue levels of glycogen, creatine phosphate and ATP were significantly reduced (P < 0.005), and tissue lactate, ADP and AMP were increased (P < 0.001). During hypoxemia, glucose uptake was increased (240 .mu.mol/h per g) and free fatty acid consumption was somewhat less depressed (19 .mu.mol/h per g). Creatine phosphate and ATP were higher than with ischemia (P < 0.01), and lactate, ADP and AMP accumulations were less (P < 0.01). Thus, in the period immediately following myocardial O2 deprivation, inadequate coronary perfusion caused greater metabolic buildup which inhibited myocardial substrate utilization and energy production. High coronary perfusion, even though the perfusate was unoxygenated, was associated with greater preservation of substrate utilization, higher levels of high-energy phosphates, less accumulation of metabolic products and a longer survival. A critical role of coronary perfusion exists in protecting myocardial metabolism in the immediate period following global heart hypoxia.