Ultrastructural evidence of increased tolerance of hibernating myocardium to cardioplegic ischemia-reperfusion injury

J Am Coll Cardiol. 2004 Jun 16;43(12):2329-36. doi: 10.1016/j.jacc.2004.01.049.

Abstract

Objectives: The goal of this study was to investigate the effects of ischemia-reperfusion on myocardial ultrastructure in patients with and without hibernating myocardium.

Background: It is generally accepted that chronically dysfunctional, hibernating myocardium may remain nonetheless viable for a long time. It has been postulated that hibernating myocytes may survive, despite being subtended by a severe coronary artery stenosis, as they might be less susceptible to ischemic insults. However, whether hibernating myocardium is indeed more resistant to ischemia has never been investigated.

Methods: Myocardial biopsies were taken before cardiac arrest and after reperfusion from the anterior wall of the left ventricle in patients undergoing coronary artery bypass surgery, divided according to presence (n = 7) or absence (n = 7) of hibernating myocardium. Ultrastructural changes were studied by electron microscopy. Because ischemia-reperfusion injury is related to oxidative stress, we also evaluated coronary sinus concentration of the antioxidants alpha-tocopherol, beta-carotene, and ubiquinol, and of lipid peroxidation products pre-ischemia and after reperfusion.

Results: Both groups were similar with respect to length of ischemia and changes in the various indexes of oxidative stress. In normally contracting myocardium, ischemia/reperfusion induced moderate overall ultrastructural changes, and marked alterations at the mitochondrial level. In contrast, post-reperfusion biopsies of hibernating myocardium displayed only minor overall ultrastructural changes, and scored significantly better on mitochondrial damage.

Conclusions: Despite similar severity of ischemia/reperfusion, hibernating myocardium showed significantly less ultrastructural evidence of cell injury compared with normally contracting myocardium. These data indicate that human hibernating myocardium is intrinsically more resistant to ischemia/reperfusion injury.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Antioxidants / metabolism
  • Biomarkers / blood
  • Biopsy
  • Coronary Artery Bypass
  • Coronary Artery Disease / physiopathology
  • Coronary Artery Disease / surgery
  • Follow-Up Studies
  • Humans
  • Lipid Peroxidation / physiology
  • Microscopy, Electron
  • Middle Aged
  • Myocardial Contraction / physiology
  • Myocardial Stunning / physiopathology*
  • Myocardium / metabolism
  • Myocardium / pathology
  • Myocardium / ultrastructure
  • Myocytes, Cardiac / metabolism
  • Myocytes, Cardiac / pathology
  • Myocytes, Cardiac / ultrastructure
  • Oxidative Stress / physiology
  • Postoperative Complications / etiology
  • Postoperative Complications / metabolism
  • Postoperative Complications / physiopathology
  • Reperfusion Injury / pathology
  • Reperfusion Injury / physiopathology*
  • Stroke Volume / physiology
  • Treatment Outcome
  • Ultrasonography, Interventional*
  • Ventricular Dysfunction, Left / pathology
  • Ventricular Dysfunction, Left / physiopathology
  • Ventricular Dysfunction, Left / surgery

Substances

  • Antioxidants
  • Biomarkers