Rhythm conversion in patients with post-thyrotoxic
atrial fibrillation (AF) has been performed with
disopyramide in order to evaluate the conversion rate and to test its effect on the maintenance of sinus rhythm after
cardioversion. The duration of AF ranged from 9 to 122 months (mean 31.8 months). Of 81 patients, 12 (15%) with relatively short duration AF were converted to sinus rhythm with
disopyramide. The remaining 69 patients required DC
cardioversion, which restored sinus rhythm in 58 patients. The 58 DC-converted patients were divided into two groups: a
disopyramide group (D group) and a non-
disopyramide group (non-D group). The D group received
disopyramide 300 mg per day for 3 months after DC
cardioversion and the non-D group did not receive
anti-arrhythmic drugs. During the early observation period, only one patient relapsed in the D group into AF, but 5 successive patients in the non-D group reverted to AF, forcing discontinuation of the non-D protocol. A second DC
cardioversion performed on 3 of those 5 patients was followed by maintenance
therapy with
disopyramide 300 mg per day, and they remained in sinus rhythm. With the inclusion of those three subjects, sinus rhythm was still present in 44 of the total of 58 patients converted by DC (76%) at the time of follow-up (64 months). Thus,
disopyramide was effective in rhythm conversion and it was essential for the maintenance of sinus rhythm after
cardioversion in patients with post-thyrotoxic AF.