O2 Uptake, Exercise & Cor. Circ., Dr. D. Penney



The Heart's Dilemma:

It normally operates with a large A-V O2 difference, ie. high oxygen extraction ratio. Increased oxygen delivery can only be achieved through vasodilation, i.e. increased blood flow. This ability decreases with age and pathology.

Myocardial ischemia is indicated by the following:

  • Acute change in the T-wave
  • Acute alteration in height of the ST segment
  • Release of enzyme (LDH, CPK) into the coronary venous blood
  • Increased coronary arteriovenous oxygen concentration difference
  • Higher lactate concentration in the coronary sinus than in a coronary artery

    Treatment options:

  • vasodilators, e.g. nitrates
  • decrease O2 consumption, e.g. beta-blockers.
  • decrease blood volume e.g. diuretics



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