Treatment of arrhythmias with tolamidol

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.

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.

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.

Efficacy of cardioselective beta adrenergic blockade with intravenously administered tolamolol in the treatment of cardiac arrhythmias

The efficacy of tolamolol, a cardioselective beta adrenergic blocking agent, was evaluated in the treatment of cardiac arrhythmias in 27 patients. Nineteen patients had supraventricular arrhythmias and eight had ventricular arrhythmias. Evaluation was by doulbe-blind randomized trial in 23 patients. Tolamolol was effective in reducing ventricular rate in 17 (85 percent) of 19 patients with supraventricular arrhythmias and resulted in conversion to sinus rhythm in 2 of the 17. The mean ventricular rate in 17 patients decreased from 135 to 102/min 10 minutes after initiation of administration of tolamolol and gradually decreased further to 93/min after 60 minutes. Reduction in ventricular rate was sustained for 2 hours of monitoring undergone by all patients and for 4 and 6 hours monitoring in two subgroups. Among the eight patients with ventricular ectopic beats, tolamolol reduced their frequency in four patients and had no effect in four. Six patients had chronic obstructive pulmonary disease and experienced no adverse clinical effects on respiratory function in association with administration to tolamolol. Untoward effects occurred in 10 patients, including hypotension in 3, 1 of whom required vasopressor therapy. Other side effects were sedation, nausea, dyspnea and warmth in the chest, all of which were mild and transient, requiring no treatment. Cardioselective beta adrenergic blockade with tolamolol was highly effective in controlling ventricular rate in supraventricular arrhythmias and reduced the frequency of ventricular ectopic beats in half of the small group of patients with this arrhythmia. It is particularly applicable in patients with obstructive pulmonary disease in whom cardiac beta adrenergic blockade is indicated. Hypotension is an important potential side effect.

Electrophysiologic effects of tolamolol on atrioventricular conduction in man

The electrophysiologic effects of tolamolol (UK-6558-01), a beta-adrenergic blocking agent, were studied in 13 patients by means of intracardiac electrograms and the extrastimulus method. Tolamolol (4 to 30 mg. intravenously) resulted in : (1) prolongation of sinus cycle length (SCL) in all patients (p less than 0.01); (2) prolongation of sinus escape time (SET) in 11 of 13 patients (p less than 0.001); (3) prolongation of A-V nodal conduction time during sinus rhythm in 1i of 13 patients (p less than 0.001); (4) onset of A-V nodal Wenckebach block at longer paced cycle lengths in 10 of 11 patients (p less than 0.001); (5) prolongation of the functional refractory period (FRP) of the A-V node in 11 of 11 patients (p less than 0.001); and (6) prolongation of the effective refractory period (ERP) of the A-V node in 10 of 10 patients (P less than 0.001). Tolamolol had no effect on His-Purkinje system (HPS) conduction time in any patient, including 3 patients with abnormal H-V intervals. Because of the marked increase in A-V nodal conduction time encountered by premature atrial depolarizations, the relative and effective refractory periods of the HPS could not be determined in any patient after tolamolol. Atropine (0.5 or 1.0 mg. intravenously) significantly reversed the effects of tolamolol on: sinus cycle length (4 of 5 patients); sinus escape time (3 of 3 patients); A-V nodal conduction time (4 of 5 patients); and A-V nodal refractioriness (5 of 5 patients).