Interaction of bisoprolol and procainamide in human cardiac impulse generation and conduction

Combined treatment of beta-adrenoceptor-blocking agents and class I antiarrhythmic drugs can potentially have profound and deleterious effects on cardiac impulse formation and conduction. We studied the effect of 5 mg of oral bisoprolol daily and 10 mg/kg of procainamide intravenously with programmed electrical stimulation of the heart in 10 patients with postinfarction ventricular tachyarrhythmias. Oral bisoprolol slowed sinus rhythm and atrioventricular nodal conduction; ventricular effective refractory periods were increased significantly after several days of oral bisoprolol treatment. Combined treatment of oral bisoprolol and intravenous procainamide did not produce clinically relevant changes in parameters of cardiac impulse formation and conduction. This study shows that combined use of bisoprolol and a class I antiarrhythmic drug appears to be safe in patients with ventricular tachyarrhythrhythmias late after myocardial infarction.