Short-term hibernating myocardium: circulation, function and metabolism in sustained regional myocardial ischemia

Abstract

During moderate prolonged myocardial ischemia, the myocardium is dysfuctional but can remain viable. In such ischemic and dysfunctional myocardium, contractile function is reduced in proportion to the reduction in regional myocardial blood flow, i.e., a state of "perfusion-contraction matching" exists. The metabolic status of such myocardium improves over the first few hours, as myocardial lactate production is attenuated and creatine phosphate, after an initial reduction, returns to control values. Ischemic myocardium, characterized by perfusion-contraction matching, metabolic recovery and lack of necrosis, has been termed "short-term hibernating myocardium". "Short-term hibernating" myocardium can respond to an inotropic stimulation with increased contractile function, however, at the expense of a renewed worsening of the metabolic status. A role for endogenous adenosine in the development of hibernation has been excluded, since neither contractile function, metabolic parameters, nor viability are altered by increased catabolism of endogenous adenosine by infusion of adenosine deaminase. Also activation of ATP-dependent potassium channels is not responsible for "short-term hibernation". "Short-term hibernating" myocardium has, however, reduced calcium responsiveness.