Use of a beta adrenergic receptor blocking agent (propranolol) in the treatment of cardiac arrhythmias

Comparison of acebutolol and propranolol therapy for ventricular arrhythmias

The effects of acebutolol, a new investigational cardioselective beta blocker, and propranolol on ventricular arrhythmias were compared in 14 patients with more than 30 premature ventricular contractions (PVCs) per hour. Each patient served as their own control, receiving both drugs and placebo in random sequence and in double-blind fashion, with an intervening one-week, drug-free period. Each drug was given for a two-month period, the maximum acebutolol dosage reaching 600 mg tid and the maximum propranolol dosage 80 mg tid. Seventy-two-hour ambulatory electrocardiographic monitoring assessed arrhythmia frequency for each study period. Mean PVC counts did not significantly differ during the two control periods. Acebutolol decreased mean PVC count by 65% (P less than .02), with eight patients exhibiting a 70% or greater decrease. Only three patients exhibited a similar decline with propranolol. The incidence of PVCs was not significantly decreased by propranolol. Acebutolol reduced the number of couplets by 70% (P less than .04), whereas propranolol did not significantly affect couplets. At the dosage of 600 mg tid, acebutolol was well tolerated, effectively suppressed total PVCs and couplets, and appeared to be more effective than propranolol administered at 80 mg tid.

Comparison of the antiarrhythmic effects of acebutolol and propranolol in the treatment of ventricular arrhythmias

This study was designed to assess the relative antiarrhythmic activity of fixed doses of 2 beta-adrenergic blocking agents, propranolol and acebutolol, in a prospective double-blind crossover trial. Twenty-one patients who had at least 30 premature ventricular contractions (PVCs) per hour while receiving placebo were entered into the study. Ten patients were randomized to initially receive propranolol, 40 mg every 8 hours, and 11 were assigned to receive acebutolol, 300 mg every 8 hours. After 6 weeks of treatment, patients were weaned off medication for 1 week and then placed on placebo for 1 week. Eighteen patients were available and eligible for crossover to the alternative regimen for an additional 6 weeks. All 21 patients completed courses with propranolol and 17 completed courses with acebutolol. The mean number of PVCs per hour during placebo, propranolol and acebutolol treatment were 267, 87 and 119, respectively. Using paired t test statistics on observation differences, both propranolol and acebutolol significantly reduced the number of PVCs per hour compared with placebo, whereas similar analysis revealed no significant difference in the antiarrhythmic effect. However, with the current sample size the power of the test is too low for the latter conclusion to be stated with confidence. Side effects were mild and infrequent, requiring discontinuation of acebutolol in 2 patients and discontinuation of propranolol in 1. Thus, acebutolol is a safe and effective antiarrhythmic agent and compares favorably with propranolol.

Antiarrhythmic effects of acute betablockade with atenolol on supraventricular tachycardias at rest and during exercise

In a total of 18 patients, 7 females and 11 male patients with ages ranging from 23 to 70 years (mean: 45.5 +/- 14.5) diagnostic His bundle studies incorporating programmed atrial and ventricular pacing for the induction of tachycardias was performed before and after betablockade with the cardioselective betablocking agent atenolol, in a dose of 5 mg given iv. over 3 to 5 minutes. In 7 patients the pacing procedure could be repeated following ergometric exercise in order to evaluate the influence of a raised sympathetic tone on the conditions initiating paroxysmal tachycardias. At rest, atenolol prevented the pacing induced tachycardias (20 dysrhythmias in 18 patients) in 3/5 individuals with Wolff-Parkinson-White (WPW)-syndrome, in 4/6 cases with atrial tachycardias, in 4/6 patients presenting atrial flutter, in 2/2 cases developing AV-nodal tachycardias and in 1/1 individual with ventricular tachycardia. Thus, in 13 out of 19 (68%) supraventricular dysrhythmias patients benefitted from atenolol by preventing or controlling the tachycardia. Ergometric exercise changed the tachycardia or echo zone in 5/8 arrhythmias after betablockade when compared to the controls before administration of atenolol (3/5 improvement by narrowing of the tach- or echo zone, 1/5 prevention of tachycardia, 1/5 impairment due to widening of the tachycardia zone). Considering only the prevention of tachycardias, the antiarrhythmic potency of atenolol was improved in one patient with pacing induced flutter and impaired in one individual with a WPW syndrome, by ergometric exercise. These results suggest that atenolol seems to provide a good antiarrhythmic action, especially in supraventricular tachycardias, and that an increased sympathetic tone during exercise may modify the antidysrhythmic strength of betablockade.

Effective treatment of supraventricular arrhythmias with acebutolol

To evaluate the antiarrhythmic efficacy of the new beta adrenergic blocking agent acebutolol, 15 monitored patients with supraventricular arrhythmias received, in double-blind fashion, an intravenous infusion of either acebutolol or saline solution after a control period. Patients treated with saline solution demonstrated no change (P greater than 0.05) in heart rate or arterial blood pressure or conversion to sinus rhythm. After administration of acebutolol, significant (P less than 0.05) reductions in heart rate were noted at 5 minutes. Peak reduction occurred at 10 to 30 minutes and correlated with maximal acebutolol plasma concentrations, antiarrhythmic activity persisted for 24 hours. Mild reductions in systolic blood pressure were observed in the majority of patients. Two patients with atrial fibrillation and one with multifocal atrial tachycardia had conversion to sinus rhythm. Frequent premature atrial complexes noted in one patient were greatly suppressed after administration of the drug. In the nine patients with clinical evidence of chronic obstructive lung disease acebutolol was well tolerated. Adverse reactions were limited to transient dyspnea in one patient with prior heart failure and a decrease in systolic blood pressure to less than 90 mm Hg in three patients who remained asymptomatic. In the patients studied, acebutolol was an effective agent for the treatment of supraventricular arrhythmias and appeared to be of special value in those with chronic obstructive lung disease.

Treatment of premature ventricular complexes with acebutolol

The effect of intravenous acebutolol versus saline solution on frequent premature ventricular complexes was evaluated in a double-blind, randomized study in 20 patients, including 3 with chronic obstructive pulmonary disease. Frequent premature ventricular complexes were abolished or reduced by 75% or more in none of 12 patients given saline solution but in 18 of 20 patients (90%) given acebutolol (P less than 0.001). This therapeutic effect of acebutolol persisted for at least 2.5 hours in 17 of 20 patients (85%), for at least 3.5 hours in 14 (70%) and for at least 4 hours in 8 (40%). Acebutolol was well tolerated by the three patients with chronic obstructive pulmonary disease. These data indicate that intravenous acebutolol is useful in the treatment of premature ventricular complexes.

Effect of -adrenoceptor blocking agents on poststimulatory atrial flutter in the dog, with observations on the participation of adrenergic mechanisms in this experimental arrhythmia

1. Four beta-adrenoceptor antagonists, viz. (+/-) propranolol (0.5 mg/kg), (-) alprenolol (0.25 mg/kg), practolol (5 mg/kg) and USVC 6524 (20 mug/kg), were tested for their effects on atrial flutter produced by electrical stimulation of the right atrium around the crushed inter-venae-caval bridge in anaesthetized dogs.2. All the drugs reduced atrial and ventricular rates; this was followed by the abrupt termination of flutter and restoration to normal sinus rhythm.3. Since all the drugs (including practolol, which is devoid of local anaesthetic activity) were given in doses just sufficient to block beta-adrenoceptors, it indicated that beta-adrenoceptor blockade was responsible for their antiarrhythmic property in this test procedure.4. Further evidences in support of participation of the sympathetic nervous system in poststimulatory flutter were: (i) flutter could not be produced in nine out of ten dogs whose catecholamine stores were depleted by pretreatment with reserpine; (ii) infusion of adrenaline in these animals resulted in the production of flutter; (iii) duration of flutter after termination of exposure to adrenaline was a few minutes, which is similar to the brief time previously reported to be taken for the disappearance of catecholamines from the hearts of reserpinized animals.5. The clinical significance of the above findings is discussed.

Use of oxprenolol in cardiac arrhythmias associated with acute myocardial ischaemia

Oxprenolol, a new beta-receptor blocking drug with intrinsic sympathomimetic activity, was used to treat 63 episodes of cardiac arrhythmia occurring in 43 patients with acute myocardial infarction or myocardial ischaemia. The drug was most effective in abolishing ventricular ectopic beats and supraventricular tachycardia. The best method of administration was by continuous intravenous infusion and the most satisfactory bolus does was 6 mg. The main side effect was hypotension, which occurred in 59% of episodes of arrhythmia that had responded previously to intravenous administration. Oxprenolol was often effective in lignocaine-resistant arrhythmia. The two main advantages of oxprenolol over propranolol are the reduced likelihood of adversely affecting myocardial function and the diminished tendency to produce bronchospasm.