Chronic hibernating myocardium: Concepts and controversies

Since the introduction of the term 'hibernating myocardium' by Rahimtoola in 1985, a variety of clinical studies have confirmed the existence of dysfunctional but viable myocardium, with the ability to recover following successful revascularization. There is no question that only complete restoration of coronary blood flow by surgical or interventional revascularization can prevent myocardial tissue from further degeneration and cell death, and thus represents the ultimate therapy for hibernating myocardium. However, the pathophysiologic mechanisms leading to an adaptive down regulation of contractile function in order to preserve structural integrity are not yet fully understood, mainly due to the absence of an appropriate chronic animal model. In the clinical setting, controversy still exists concerning the role of coronary flow, which was thought to be persistently reduced in hibernating myocardium. Some studies, however, showed normal flow in dysfunctional viable myocardium, contributing to the concept of repetitive stunning rather than the classical concept of hibernation. These concepts and controversies, the diagnostic detection, clinical and structural manifestations, and therapeutical interventions of the hibernating myocardium form the focus of this review.