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Experimental studies demonstrate that short-term regional perfusion-contraction matching, in which the energy demands of regional myocardial contraction are reduced to match the diminished myocardial substrate supply, occurs during states of low coronary blood flow under resting conditions and during exercise-induced ischemia. This phenomenon is rapidly reversible and appears to occur in several clinical settings. Sustained perfusion-contraction matching is observed in states of partial experimental ischemia of intermediate duration lasting several hours. This condition might be called short-term hibernation and resembles clinical conditions such as unstable angina pectoris or myocardial infarction with some residual perfusion in which the contractile defect can be improved by reperfusion provided the ischemia is not severe enough to cause transmural necrosis. Such experimental and clinical observations may or may not relate to the setting of regional dysfunction at rest in patients with chronic coronary heart disease, in whom manifestations of acute ischemia may be absent but improvement of wall motion abnormalities occurs after CABG or balloon angioplasty. This condition may constitute the hypothetical state of chronic myocardial hibernation, for which tentative evidence exists from metabolic and perfusion studies using PET. Whether such a condition of prolonged perfusion-contraction matching might be associated with adaptive processes that could allow its persistence for long periods without manifest ischemia remains to be investigated.
J Ross (Fri,) studied this question.