AIM: To investigate the effect of β-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 ). CONCLUSION: These findings indicate that atenolol suppresses ischemia-induced increase in spatial dispersion of ventricular repolarization, which may explain the antiarrhythmic effect of β-blockers.
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