Complete global myocardial ischemia in dogs.

Area of Science:

• Cardiovascular Physiology
• Metabolic Biochemistry

Background:

• Complete global myocardial ischemia, characterized by zero coronary arterial flow, initiates a cascade of cellular events.
• The myocardium shifts from aerobic to anaerobic metabolism, producing specific metabolic byproducts.

Purpose of the Study:

• To elucidate the metabolic changes and cellular injury during complete global myocardial ischemia.
• To investigate the relationship between metabolic alterations, myocyte injury, and functional recovery upon reoxygenation.

Main Methods:

• Induction of complete global myocardial ischemia in a canine model.
• Monitoring of metabolic shifts from aerobic to anaerobic pathways.
• Assessment of intracellular accumulation of anaerobic metabolites.
• Measurement of high-energy phosphate (HEP) levels, including adenosine triphosphate (ATP).
• Evaluation of myocyte injury during ischemia and reoxygenation.

Main Results:

• Myocardial ischemia leads to intracellular accumulation of anaerobic metabolites like inorganic phosphate, H+, and creatine.
• Net adenosine triphosphate (ATP) levels decline significantly, approaching zero after 100 minutes of ischemia at 37°C.
• Irreversible myocyte injury occurs under sustained total ischemia.
• Post-ischemic contractile recovery is contingent upon the extent of metabolic changes and myocyte damage.

Conclusions:

• Sustained global myocardial ischemia induces profound metabolic derangements and cellular injury.
• The degree of metabolic compromise and myocyte damage during ischemia dictates the potential for functional recovery upon reperfusion.