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Reduction of heart rate by chronic β1-adrenoceptor blockade promotes growth of arterioles and preserves coronary perfusion reserve in postinfarcted heart.
American Journal of Physiology-Heart and Circulatory Physiology (2005)
  • Eduard I. Dedkov, University of Iowa Carver College of Medicine
  • Lance P. Christensen, University of Iowa Carver College of Medicine
  • Robert M. Weiss, University of Iowa Carver College of Medicine
  • Robert J. Tomanek, University of Iowa Carver College of Medicine
Abstract
Adequate growth of coronary vasculature in the remaining left ventricular (LV) myocardium after myocardial infarction (post-MI) is a crucial factor for myocyte survival and performance. We previously demonstrated that post-MI coronary angiogenesis can be stimulated by bradycardia induced with the ATP-sensitive K+ channel antagonist alinidine. In this study, we tested the hypothesis that heart rate reduction with β-blockade may also induce coronary growth in the post-MI heart. Transmural MI was induced in 12-mo-old male Sprague-Dawley rats by occlusion of the left anterior descending coronary artery. Bradycardia was induced by administration of the β-adrenoceptor blocker atenolol (AT) via drinking water (30 mg/day). Three groups of rats were compared: 1) control/sham (C/SH), 2) MI, and 3) MI + AT. In the MI + AT rats, heart rate was consistently reduced by 25–28% compared with C/SH rats. At 4 wk after left anterior descending coronary ligation, infarct size was similar in MI and MI + AT rats (67.1 and 61.5%, respectively), whereas a greater ventricular hypertrophy occurred in bradycardic rats, as indicated by a higher ventricular weight-to-body weight ratio (3.4 ± 0.1 vs. 2.8 ± 0.1 mg/g in MI rats). Analysis of LV function revealed a smaller drop in ejection fraction in the MI + AT than in the MI group (∼24 vs. ∼35%). Furthermore, in MI + AT rats, maximal coronary conductance and coronary perfusion reserve were significantly improved compared with the MI group. The better myocardial perfusion indexes in MI + AT rats were associated with a greater increase in arteriolar length density than in the MI group. Thus chronic reduction of heart rate induced with β-selective blockade promotes growth of coronary arterioles and, thereby, facilitates regional myocardial perfusion in post-MI hearts.
Keywords
  • myocardial infarction,
  • angiogenesis,
  • coronary circulation,
  • resistance vessels,
  • capillaries
Publication Date
June 1, 2005
DOI
10.1152/ajpheart.01047.2004
Citation Information
Eduard I. Dedkov, Lance P. Christensen, Robert M. Weiss and Robert J. Tomanek. "Reduction of heart rate by chronic β1-adrenoceptor blockade promotes growth of arterioles and preserves coronary perfusion reserve in postinfarcted heart." American Journal of Physiology-Heart and Circulatory Physiology Vol. 288 Iss. 6 (2005) p. H2684 - H2693
Available at: http://works.bepress.com/edward-dedkov/55/