Background: The effectiveness of oral propafenone in converting recent-onset atrial fibrillation to sinus rhythm has been established by controlled trials. However, it is not clear whether the effectiveness of propafenone is affected by the presence or absence of underlying heart disease.
Objectives: To investigate the safety and effectiveness of oral propafenone and the role of underlying heart disease.
Design: Randomized, single-blind, controlled study.
Setting: 3 teaching hospitals.
Patients: 240 hospitalized patients with recent-onset atrial fibrillation.
Intervention: Propafenone (one 500-mg oral dose) or placebo.
Measurements: Conversion rates at 3 and 8 hours.
Results: Propafenone was more effective than placebo for converting atrial fibrillation to sinus rhythm at 3 hours: Fifty-four of 119 patients (45%) receiving propafenone and 22 of 121 patients (18%) receiving placebo had conversion (P < 0.001). It was also more effective at 8 hours: Ninety-one of 119 patients (76%) receiving propafenone and 45 of 121 patients (37%) receiving placebo had conversion (P < 0.001). Subgroup analysis showed that among patients without heart disease, 78% of those receiving propafenone and 56% of those receiving placebo converted to sinus rhythm within 8 hours (P = 0.02). In those with hypertension, the rate was 70% for those receiving propafenone and 27% for those receiving placebo (P < 0.001); in patients with structural heart disease, the rate was 81% for those receiving propafenone and 17% for those receiving placebo (P < 0.001).
Conclusions: Oral loading of propafenone was more effective than placebo for conversion to sinus rhythm within 8 hours and had a favorable safety profile. The rate of spontaneous conversion to sinus rhythm was higher in patients without structural heart disease; this finding has important implications for the assessment of drug effectiveness in recent-onset atrial fibrillation.