Atrial fibrillation threshold predicted long-term efficacy of pharmacological treatment of patients without structural heart disease.

Aims To ascertain if an electrophysiological study could predict long-term efficacy of anti-arrhythmic drugs in the treatment of lone atrial fibrillation. Methods and results Forty-four patients (36 males, 8 females, age 55·5±10·6) with paroxysmal atrial fibrillation were enroled to undergo serial electrophysiological studies at the bedside. Two quadripolar catheters were inserted via the subclavian vein. Disopyramide (D: 2 mg/kg iv), cibenzoline (C: 1·4 mg/kg iv), aprindine (A: 2 mg/kg iv), pilsicainide (P: 2 mg/kg po) and flecainide (F: 3 mg/kg po) were tested. Atrial fibrillation threshold (AFT) was measured as the lowest current amplitude of rapid pacing (50 Hz for 1 s) to induce atrial fibrillation lasting more than 30 s. Before drug treatment, AFT was 3·9±0·3 mA. Pharmacological treatment raised AFT as follows: D 5·9±0·9 mA, C 7·6±1·2 mA, A 8·1±1·1 mA, P 6·0±0·8 mA, F 7·3±1·1 mA. Recurrence of atrial fibrillation was observed during 1-year follow-up in 12% of cases when they were treated with a drug that raised AFT by 5 mA or more. On the other hand, the recurrence rate was 87% when patients were treated with a drug that raised AFT by less than 5 mA ( P =0·001). Conclusion AFT was a good predictor of long-term efficacy of pharmacological treatment against atrial fibrillation.