Is there a place for the late cardioversion of atrial fibrillation? A long-term follow-up study of patients with post-thyrotoxic atrial fibrillation

Aims As atrial fibrillation is associated with significant mortality and mo rbidity, restoration of sinus rhythm is desirable. However, previous data s uggest that cardioversion should be restricted to patients in whom the fibr illation is of limited duration (<1-2 years) because of high relapse rates. It may be the frequent association with cardiac disease, rather than the d uration of fibrillation itself, which determined the high relapse of earlie r studies. The aim of this study was to investigate rates of cardioversion. maintenance of sinus rhythm and predictors of subsequent relapse in a homo geneous group of patients without evidence of any co-existent cardiac disea se. Methods and Results We report on a retrospective series of 106 patients wit h thyrotoxicosis-induced fibrillation but no other heart disease: 87% had b een in atrial fibrillation for >12 months (median duration 28.5, interquart ile range 15-47 months). Cardioversion was attempted using disopyramide and then electric shock. Ninety-eight patients were successfully cardioverted: at late follow-up, 80.6 +/- 37 months (mean +/- SD), 67% were in sinus rhy thm. Conclusion Although a relationship between the duration of fibrillation and maintenance of sinus rhythm was found, the high proportion remaining in si nus rhythm, compared with other series, suggests this influence may be less important than the presence or absence of structural heart disease. (C) 20 00 The European Society of Cardiology.