Safety of beta-blocker therapy with and without thrombolysis:A comparison of bisoprolol and atenolol in acute myocardial infarction

In the current era of widely used thrombolytic therapy, the new betablocker bisoprolol was compared with the well-established betablocker atenolol in the treatment of acute myocardial infarction (AMI), A total of 334 patients were enrolled in this international, multicenter, randomized, double-masked, controlled study of 7 days' duration in two parallel groups, The purpose of the study was to compare the tolerability and safety of the two beta-blockers given to patients with AMIs who either were (281 patients) or were not (53) given concurrent thrombolytic agents, A statistically significant decrease in heart rate was seen with both bisoprolol and atenolol, Beta-blocker therapy had to be interrupted in 70 patients, 36 receiving bisoprolol and 34 atenolol, because of serious adverse effects, The difference in incidence of adverse events between groups was not significant, A logistic regression analysis based on conditions at admission predicted an increase in the risk of critical events occurring during the first week after an AMI for patients with a positive family history of AMI, a moderate-sized myocardial infarction, or a heart rate >70 beats/min, and for patients pretreated with dihydropyridine calcium antagonists, Bisoprolol was found to be as effective as atenolol in reducing heart rate, an important goal of intervention in AMI. Furthermore, some characteristics that might influence the decision to use beta-blockers in addition to thrombolytic agents were identified

Effects of beta-blockade on atrial and atrioventricular nodal refractoriness, and atrial fibrillatory rate during atrial fibrillation in pigs

Despite their widespread use in atrial fibrillation, the effects of beta-adrenoceptor blockers on atrial and atrioventricular (AV) nodal refractoriness, and atrial fibrillatory rate during atrial fibrillation have been incompletely characterised. In particular, it is unknown whether additional sodium channel (class I) blocking effects play a role. Effects of bisoprolol (no class I effect) and metoprolol (mild class I effect) were therefore compared in 12 open-chest pigs. Atrial and AV-nodal effective refractory periods were determined at pacing cycle length 500 ms and 300 ms. Atrial fibrillation was then induced by premature stimulation and topical application of metacholine, and atrial fibrillatory intervals and ventricular intervals were recorded. After resumption of sinus rhythm, bisoprolol 0.1 mg/kg or metoprolol 0.3 mg/kg was administered, and measurements were repeated. Also, effects on plasma catecholamines and signal-averaged QRS duration were determined. Both bisoprolol and metoprolol prolonged atrial and AV-nodal effective refractory periods at both pacing cycle lengths, however, no differences were noted between the two drugs. No significant effects were observed on atrial and ventricular intervals during atrial fibrillation. Plasma catecholamines were low and unaffected by either drug, as was the QRS duration. It is concluded that the mild class I effect of metoprolol does not play a role in atrial fibrillation. Also, the results confirm the clinical notion that beta-blockers exert insignificant effects during atrial fibrillation in the setting of low sympathetic tone