- History of symptomatic, continuous atrial fibrillation defined as: Continuous atrial fibrillation lasting greater than 1 year but less than 4 years or nonself-terminating atrial fibrillation, lasting greater than 7 days but no more than 1 year, with at least one failed direct current cardioversion. A failed cardioversion was defined as an unsuccessful cardioversion or one in which normal sinus rhythm was established but not maintained beyond 7 days.