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The pathophysiology of myocardial hibernation: current controversies and future directions
J L Vanoverschelde1, J A Melin
1Divisions of Cardiology, Université Catholique de Louvain, Brussels, Belgium.
Insights
Chronic stunning and hibernation are reversible causes of left ventricular dysfunction in coronary artery disease. Early stunning allows rapid recovery after revascularization, while advanced hibernation leads to delayed, incomplete recovery.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Chronic ischemic dysfunction in coronary artery disease can be reversible.
- This dysfunction is a complex, progressive phenomenon with distinct stages.
Purpose of the Study:
- To differentiate between chronic stunning and chronic hibernation in left ventricular dysfunction.
- To predict functional recovery after revascularization based on the stage of dysfunction.
Main Methods:
- Characterization of myocardial dysfunction based on perfusion, myocyte alterations, membrane integrity, and response to inotropic stimuli.
- Assessment of tissue fibrosis and functional recovery post-revascularization.
Main Results:
- Chronic stunning: normal resting perfusion, reduced flow reserve, mild myocyte changes, preserved membrane function and inotropic response. Rapid recovery post-revascularization.
- Chronic hibernation: reduced resting perfusion, more severe myocyte alterations, increased fibrosis, decreased inotropic response. Delayed and incomplete recovery post-revascularization.
Conclusions:
- Distinguishing between chronic stunning and hibernation is crucial for predicting recovery of left ventricular function.
- Early-stage dysfunction (stunning) shows high potential for complete recovery, whereas advanced stages (hibernation) have limited recovery potential.
Abstract:
It is now widely accepted that patients with chronic coronary artery disease can experience prolonged regional ischemic dysfunction that does not necessarily arise from irreversible tissue damage and, to some extent, can be reversed by restoration of blood flow. Recent clinical and experimental data suggest that this form of chronic but reversible left ventricular dysfunction represents a complex, progressive, and dynamic phenomenon. The initial stages of dysfunction are probably caused by chronic stunning. They are characterized by normal resting perfusion but reduced flow reserve, mild myocyte alterations, maintained membrane integrity (allowing the transport of both thallium and glucose), preserved capacity to respond to an inotropic stimulus, and no or little tissue fibrosis. After revascularization, functional recovery will probably be rapid and complete. On the other hand, the more advanced stages of dysfunction likely correspond to chronic hibernation. They usually are associated with reduced rest perfusion; increased tissue fibrosis; more severe myocyte alterations (degeneration[?], apoptosis); and a decreased ability to respond to inotropic stimuli. Nonetheless, membrane function and glucose metabolism may long remain preserved. After revascularization, functional recovery, if any, will probably be quite delayed and mostly incomplete.