The use of atropine for facilitation of direct current cardioversion from atrial fibrillation--results of a pilot study.

BACKGROUND: The importance of the role of the autonomic nervous system (ANS) in the initiation and propagation of atrial fibrillation has been demonstrated in the condition of paroxysmal atrial fibrillation. However, the role of the ANS in patients with chronic atrial fibrillation is less clear. Some patients with chronic atrial fibrillation are resistant to the standard techniques of direct current (DC) cardioversion. HYPOTHESIS: We sought to investigate whether excessive vagal tone might prevent the restoration of sinus rhythm and to establish that the abolition of vagal tone using intravenous atropine will facilitate DC cardioversion in patients with atrial fibrillation who are resistant to the standard cardioversion techniques. METHODS: Beginning in August 1994, a change in the protocol for elective DC cardioversion of atrial fibrillation was made to include the use of intravenous atropine for patients resistant to the standard techniques of DC cardioversion. RESULTS: Over a 2-year period, 140 elective cardioversions were performed for atrial fibrillation. Sinus rhythm could not be restored on 31 occasions. Intravenous atropine prior to a further 360 J shock with paddles in the anteroposterior position allowed sinus rhythm to be restored on nine occasions. Patients with successful cardioversion after atropine had significantly better left ventricular function than those who remained in atrial fibrillation (p = 0.001) as well as a tendency toward a smaller left atrium. CONCLUSION: This study suggests that high vagal tone, which is dominant in patients with structurally normal hearts, may prevent the termination of atrial fibrillation by standard techniques of DC cardioversion, and that the abolition of high vagal tone by atropine facilitates the restoration of sinus rhythm.