Prolonged Myocardial Hibernation Exacerbates Cardiomyocyte Degeneration and Impairs Recovery of Function After Revascularization

Abstract

Objectives. We sought to define the effects of time on contractile function, morphology and functional recovery after coronary revascularization in patients with dysfunctional but viable (hibernating) myocardium.Background. Functional recovery after coronary artery bypass graft surgery in patients with chronic myocardial hibernation is incomplete or delayed. The proposed cause is a progressive temporal degeneration of cardiomyocytes.Methods. In 32 patients with multivessel coronary disease, regional wall motion analysis was performed in hypoperfused but metabolically active areas before and 6 months after bypass surgery. During bypass surgery, transmural biopsy samples were obtained from the center of the hypokinetic zone for light and electron microscopic analyses. The proposed duration of myocardial hibernation was retrospectively assessed.Results. Patients with a subacute hibernating condition (<50 days) demonstrated a higher preoperative ejection fraction (EF, 50 ± 8%), and a better preserved wall motion (WM) in the supraapical wall (−1.4 ± 0.4) than did patients with intermediate-term (>50 days, EF 37 ± 9%, p < 0.05; WM −2.4 ± 1.5, p = 0.08) or chronic (>6 months, EF 40 ± 14%, WM −2.7 ± 0.9, p < 0.005) ischemia. Structural degeneration correlated with the duration of ischemia (r = 0.56, p < 0.05). Postoperative recovery of function was enhanced in patients with a short history of hibernation compared with patients with an intermediate-term or chronic condition (EF 60 ± 10% vs. 40 ± 10%, p < 0.001, and vs. 47 ± 14%, p < 0.05).Conclusions. Hibernating myocardium exhibits time-dependent deterioration due to progressive structural degeneration with enhanced fibrosis. Early revascularization should be attempted to salvage the jeopardized tissue and improve postoperative outcome.