Atrial selective effect of amiodarone to increase threshold of excitation.

Increases of pacing threshold stimulation are well documented with different antiarrhythmic drugs, but not with amiodarone. We report a case of a patient with dual-chamber pacing, with stable thresholds on repeated measurements on the last year, who presented severe increase of atrial pacing threshold resulting in loss of atrial capture after a year of treatment with amiodarone. Thresholds were normalized once amiodarone was removed. Ventricular thresholds were not affected.

Clinical effectiveness of antiarrhythmic treatment after electrical cardioversion in patients without structural heart disease.

INTRODUCTION AND OBJECTIVES: The aim was to investigate the clinical effectiveness of using antiarrhythmic drugs after electrical cardioversion in patients without structural heart disease, including their effect on the maintenance of sinus rhythm. METHODS: In total, 528 patients with persistent atrial fibrillation but without significant structural heart disease who underwent successful electrical cardioversion at 96 Spanish hospitals were followed up for 1 year. Patients were assessed at 1, 3, 6 and 12 months. The use and effectiveness of antiarrhythmic drugs for preventing the recurrence of persistent atrial fibrillation was evaluated. RESULTS: Some 80% of patients were receiving antiarrhythmic drugs at discharge, most frequently amiodarone. No specific clinical factor was associated with greater use of antiarrhythmics. Overall, 37% of patients were in sinus rhythm at all follow-up assessments. At the 1-year assessment, 59% of patients who remained in sinus rhythm were still taking antiarrhythmic drugs. Multivariate Cox regression analysis identified weight (hazard ratio [HR]=1.01 per kg; P=.04) and no antiarrhythmic treatment (HR=1.59; P=.001) as being independently associated with the recurrence of persistent atrial fibrillation. Amiodarone tended to be better than other antiarrhythmic drugs. CONCLUSIONS: In routine clinical practice, the large majority of patients without structural heart disease received antiarrhythmic drugs, most frequently amiodarone, after successful electrical cardioversion. Drug use was the principal factor associated with the maintenance of sinus rhythm at 1 year.