ATRIAL TACHYARRHYTHMIAS AFTER CARDIAC SURGERY: RESULTS OF DISOPYRAMIDE THERAPY T. P. GAVAGHAN T. J. CAMPBELL zyxw Card!ology Research Fellow. St Vincent's HospJtal, Sydney, NSW Cardology Research fellow, zyxwvuts St Vincent s Hospitai, Sydney, NSW M. P. FENELEY J. J. MORGAN Cardiology Research fellow. St. Vincent's Hospital, Sydney, NSW Senior Staff Carddogist, St Vincent's Hosptal, Sydney. NSW Abstract: zyxwvutsr Of 1,247 consecutive patients who underwent cardiac surgery, 297 (24%) developed a post-operative atrial tachyarrhythmia. Of these patients, 201 were suitable for treatment according to the study protocol. All patients were initially given digoxin 0.75 mg intravenously (i.v.). After two hours, those 156 patients whose atrial arrhythmias persisted were given a 2 mg/kg loading dose of disopyramide (i.v.), followed by a constant i.v. infusion (0.4 mg kg-' h-l) or oral therapy (600 mg daily). Within a further 12 hours, 75 patients (48%) reverted to sinus rhythm, 24 within one hour. Thus 120/201 patients zyx (60%) reverted to sinus rhythm within 14 hours of commencing therapy. Reversion rates of those patients with both atrial fibrillation and flutter (AF/AFL) were significantly lower ' than those with AF zyxwvuts (p<O.OOl) or AFL (p<0.02) alone. A further 70 patients reverted to sinus rhythm in one to 13 (mean four) days on continued drug therapy. Elective cardioversion restored sinus rhythm in six subjects. Atrial arrhythmias persisted in five patients (2.5%) at hospital discharge. Side-effects of disopyramide were noted in 19% of patients. Urinary retention was common (1 1.5%). Four patients with atrial flutter developed 1 :1 atrioventricular conduction with the disopyramide loading dose. One patient with atrial fibrillation developed ventricular tachycardia during injection of the loading dose of disopyramide, but was successfully cardioverted to sinus rhythm. Two further patients developed significant hypotension ( < 90 mmHg systolic). Disopyramide is effective in the treatment of post-operative atrial tachyarrhythmias, but its routine use in this situation may be associated with an unacceptably high incidence of side-effects. (Aust NZ J Med 1985; 15: 27-32.) zyxwvu Key words: Atrial tachyarrhythmias, atrial fibrillation, atrial flutter, cardiac surgery, disopyrarnide. zyx INTRODUCTION Atrial tachyarrhythmias occur frequently in the first few days following cardiac surgery. '.* These arrhythmias may be transient but can persist despite adequate digitalisation. While direct current (DC) cardioversion will almost always restore sinus rhythm in those with persistent tachyarrhythmias, recurrence is common unless antiarrhythmic drugs are administered concomitantly. Further, cardio- version usually entails a general anesthetic and the potential hazard of inducing ventricular arrhythmias in digitalised patients. Rapid atrial pacing, zyxwv via epicardial pacing wires attached at operation, may terminate atrial f l ~ t t e r , ~ . ~ but not atrial fibrillation. Verapamil, a calcium channel blocker which significantly slows atrio-ventricular (AV) conduction, has proven effective in rapidly controlling the ventricular rate in both atrial fibril- lation and atrial flutter when administered as an intravenous bolus.s The duration of this effect, however, is highly variable. Disopyramide, a butyramide derivative with Class I antiarrhythmic activity6similar to quinidine, has been administered intravenously for recent- ~~ Reprint requests to: Dr T. P. Gavaghan, Cardiovascular Unit, St. Vincent's Hospital, Darlinghurst, N.S.W. 2010. DISOPYRAMIDE FOR ATRIAL TACHYARRHYTHMIAS Aust NZ J Med 1985; 15 27