The Journal of Thoracic and Cardiovascular Surgery, Vol 71, 726-735, Copyright © 1976 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Effects of coronary perfusion during myocardial hypoxia. Comparison of metabolic and hemodynamic events with global ischemia and hypoxemia
AJ Liedtke
The effects of metabolic accumulation on myocardial metabolism during
global heart oxygen deprivation were evaluated in a working in situ swine
heart preparation with controlled total coronary blood flow. Myocardial
oxygen consumption was depressed to a similar extent by either reducing
total coronary flow 60 per cent (ischemia, low coronary perfusion) in 10
swine or by decreasing coronary perfusate PO2 to 30 mm. Hg at normal flows
(hypoxemia, high coronary perfusion) in 13 swine. Compared with findings in
13 control hearts, ischemia significantly (p less than 0.05) decreased
myocardial oxygen consumption (640 to 390 mumole per hour per gram),
glucose uptake (185 to 16 mumole per hour per gram), and free fatty acid
consumption (32 to 17 mumole per hour per gram). ttissue levels of
glycogen, creatine phosphate, and adenosine triphosphate (tatp) were
significantly reduced (p less than 0.005), and tissue lactate, adenosine
diphosphate (ADP), and adenosine monophosphate (AMP) were increased (p less
than 0.001). During hypoxemia, glucose uptake was increased (240 mumole per
hour per gram) and free fatty acid consumption was somewhat less depressed
(19 mumole per hour per gram). Creatine phosphate and ATP were higher than
with ischemia (p less than 0.01), and lactate, ADP, and AMP accumulations
were less (p less than 0.01). Thus, in the period immediately following
myocardial oxygen 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. These data suggest a critical
role of coronary perfusion in protecting myocardial metabolism in the
immediate period following global heart hypoxia.
