Effects of myocardial hypoxia on left ventricular performance

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Abstract
Paced, isovolu-metric, canine left ventricle preparations were subjected to hypoxia under conditions of constant coronary perfusion pressure (increasing flow) or constant coronary blood flow (decreasing pressure). Characteristically, under either condition, hypoxia elicited a biphasic response in terms of the changes in left ventricular systolic pressure. There was a significant stimulation of left ventricular contractile strength with moderate hypoxia, and a depression with severe hypoxia. The initial, facilitative response of the ventricle to hypoxia is attributed partly to the rise in the pH of the perfusing blood associated with the change in O2 saturation, and partly to other factors. The subsequent depression of ventricular performance is related to the curtailment of aerobic metabolism.