Antiarrhythmic
therapy for the suppression of
atrial flutter has conventionally entailed the use of a class Ia agent such as
quinidine or
procainamide. However,
atrial flutter often recurs despite the use of these conventional antiarrhythmic regimens. Experimental and clinical evidence suggests that the pharmacologic suppression of
atrial flutter may depend on the prolongation of the atrial action potential duration and consequently the voltage-dependent refractoriness. Therefore, the efficacy and tolerance of the class III antiarrhythmic agent
N-acetylprocainamide was compared to that of the conventional regimen of the class Ia agent
quinidine combined with
digoxin (to control ventricular response) in patients with a history of symptomatic sustained
atrial flutter. The study was randomized but nonblinded, with a crossover to the alternate regimen if the first failed. Eighteen patients entered the study and were followed for up to 18 months. Of the 12 receiving
N-acetylprocainamide (eight randomized and four crossovers), one (8%) failed
therapy due to side effects, but none had
atrial flutter. Of the 11 receiving
quinidine and
digoxin (10 randomized and one crossover), three (28%) had a recurrence of
atrial flutter, two of whom also had intolerable side effects, and two more (18%) had side effects alone requiring withdrawal of
therapy (total 46% failed). The probability of therapeutic success over time was greater (p less than 0.04) for
N-acetylprocainamide than for
quinidine and
digoxin. The data suggest that
N-acetylprocainamide may be more effective and better tolerated than the conventional regimen of
quinidine plus
digoxin. Therefore, large-scale blinded studies of the efficacy of
N-acetylprocainamide in the suppression of
atrial flutter may be warranted.