Effect of beta-blocker atenolol on spatial dispersion of ventricular repolarization of sheep following acute myocardial ischemia.
OBJECTIVE
To investigate the effect of beta-blockers on spatial dispersion of ventricular repolarization following acute myocardial ischemia.


METHODS
Twenty sheep were randomized into control (normal saline,iv) and atenolol (1.5 mg/kg,iv) group. Acute myocardial ischemia was induced by occlusion of the obtuse marginal coronary artery. Unipolar ECG was simultaneously acquired from 64 epicardial sites in both ischemic and non-ischemic regions. Activation-recovery intervals (ARI), an index of ventricular repolarization, was determined from the epicardial ECG. The difference between the longest and shortest ARI was defined as ARI dispersion.


RESULTS
Ischemic zone in atenolol group was less than that of control group (13 %+/-2 % vs 19 %+/-3 %, P=0.04). In the control group, pooled ARI dispersion was increased by (18+/-21), (27+/-21), and (16+/-10) ms at 30, 60, and 90 min of coronary artery occlusion respectively (P <0.01), whereas in the atenolol group, ARI dispersion was only increased by (6+/-4), (6+/-7), and (2+/-7) ms respectively (P >0.05).


CONCLUSIONS
These findings indicate that atenolol suppresses ischemia-induced increase in spatial dispersion of ventricular repolarization, which may explain the antiarrhythmic effect of beta-blockers.
Wang
Le-Xin
LX
School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia. lwang@csu.edu.au
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001262:Atenolol / Q000494:pharmacology*; D004562:Electrocardiography; D006352:Heart Ventricles / Q000503:physiopathology; D017202:Myocardial Ischemia / Q000188:drug therapy / Q000503:physiopathology*; D012756:Sheep; D016276:Ventricular Function / Q000187:drug effects* / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D001262:Atenolol