Safety of Electrical Cardioversion in Patients Without Digitalis Toxicity

To ascertain whether electrical cardioversion increases ventricular ectopy in patients receiving nontoxic doses of digitalis, we recorded continuous electrocardiograms in 21 patients for at least 1 hour before and immediately after direct-current countershock. Seventeen patients also received specific antiarrhythmic therapy. There were no consistent differences in the frequency of severity of ventricular ectopy before and after cardioversion despite a wide range of serum digoxin levels (0.1 to 3.0 ng/mL; mean, 1.6 ng/mL). No patient had ventricular tachycardia after cardioversion, and all eight patients with serum digoxin levels greater than 2.0 ng/mL had the same or fewer ventricular ectopic beats per hour and the same or lower ectopy grades after cardioversion when pre- and postshock recordings were compared. These findings suggest that patients receiving digoxin without clinical evidence of digitalis toxicity are at low risk for serious postcardioversion ventricular arrhythmias, even when serum digoxin levels are modestly elevated. The extent to which this low risk is due to concomitant antiarrhythmic therapy is unknown