Use of isoprenaline as an antiarrhythmic agent after valve replacement surgery.

Abstract

The sympathomimetic drugs are generally considered to increase cardiac automaticity, thus predisposing to ventricular ectopic beats, ventricular tachycardia, and ventricular fibrillation (Foster, 1966;Hellerstein, Brofman, and Caskey, 1952). This paper describes the use of isoprenaline, a sympathomimetic drug, as an antiarrhythmic agent in three patients. These patients were having recurrent ventricular tachycardia and ventricular fibrillation in the early post-operative period after cardiac valve replacement. CASE REPORTS Case 1. A married woman, aged 53 years, had become increasingly breathless over 10 years. This was accompanied by lethargy and recurrent bronchitis and orthopnoea. The clinical signs of mitral stenosis, aortic stenosis and incompetence, and tricuspid incompetence were present. Chest x-ray showed biventricular and left atrial enlargement, increased pulmonary vascular markings, and septal lymphatic lines. Electrocardiogram showed atrial fibrillation and left ventricular hypertrophy. Cardiac catheterization and cine-angiography confirmed the clinical diagnosis. Both the mitral and aortic valves were calcified.Aortic replacement with a No. 8 Starr-Edwards prosthesis, mitral commissurotomy, and tricuspid valve annuloplasty were performed. Two hours after operation carried out on January 26, 1967, the electrocardiogram showed atrial fibrillation with ventricular bigeminy (Fig. A). Serum potassium was 2-0 mEq/litre, and 50 mEq potassium were given by infusion in the following 3 hours. After this ventricular bigeminy ceased. Serum potassium 5 hours after operation was 3-3 mEq/ litre. Four hours later ventricular bigeminy again developed and was followed by short episodes of ventricular tachycardia and fibrillation which reverted spontaneously (Fig. B). Procainamide 500 mg. intravenously, and 40 mEq/litre potassium by intravenous infusion were given. An hour later ventricular fibrilla-83 tion occurred and in the subsequent 90 minutes, 50 defibrillations were performed. Procainamide 500 mg. was repeated and lignocaine 40 mg. was given at 10-minute intervals for 5 doses without effect. Between episodes of ventricular fibrillation, the cerebral state was lucid and the systemic blood pressure was 115/70 mm. Hg. An hour later an isoprenaline infusion, 1 mg. in 500 ml. 5% dextrose in water, was begun. Almost immediately the episodes of ventricular arrhythmia ceased. Blood pressure remained at 120/80 mm. Hg. Two hours later episodes of ventricular tachycardia recurred followed by ventricular fibrillation requiring electric countershock When the rate of the isoprenaline infusion was increased, the arrhythmias ceased (Fig. C). Between 17 hours and 21 hours after the operation 100 defibrillations were necessary. During this period, isoprenaline infusion, 2 mg. in 500 ml., was continued. Other treatment included an infusion of lignocaine 300 mg., digoxin 0 5 mg. intravenously, procainamide 500 mg. intramuscularly six-hourly, and potassium 10 mEq/litre/hour intravenously. Subsequent serum potassium estimations were...