Chaotic atrial rhythm (CAR) is characterized by the presence of three or more P-wave morphologic features on the surface electrogram, absence of a dominant atrial pacemaker, and variable P-P, R-R, and P-R intervals with an atrial rate of over 100 beats/min. CAR is infrequently seen in pediatric ages and its clinical course, management and underlying mechanism are uncertain. We report our recent experience with 11 infants with CAR and describe their clinical characteristics and reponse to treatment.

We retrospectively reveiwed the medical records, electrocardiograms, Holter recordings, echocrdiographic reports of 11 cases of CAR managed at Sejong general hospital and Asan medical center from January 1991 to June 1995.

1) All patients were ≤6 months old and 5 of 11 patients had symptoms at neonatal period. The duration of follow-up was 3-42 months(mean : 18 months). 2 patients had structural heart disease and 3 patients showed signs of ventricular dysfunction. In 10 of 11 patients tachycardia was sustained or recurrent. 1 patient died of severe congestive heart failure due to incessant rapid tachycardia.

2) 3 of 10 patients took digoxin only and others took more than 2 medications. Full control within 1 month after medication was in 2 patients, with digoxin only in one and digoxin and amiodarone in another patient. At discharge, state of arrhythmia control in 8 patients with medications were full control in 2, good control in 3, and partial control in 3. At last follow-up, full control in 5, good control in 1 were confirmed through Holter recordings and the other 4 patients showed sinus rhythm in surface electrocardiograms. The total duration of medications were ≤1 year except 1 patient.

3) In 3 patients with ventricular dysfunction, ventricular function was normalized after restoration of sinus rhythm.

CAR in children usually occurs in the first month of life and genenally takes benign course, but sometimes it causes severe congestive heart failure or ventricular dysfunction. Frequently, the patients remain asymptomatic despite persistence of the tachycardia for weeks or months. CAR is difficult to convert to sinus rhythm with medications but tends to resolve spontaneously within 1 year. We think treatment is necessary only in the symptomatic patients with rapid ventricular response and it is enough to control the ventricular rate with antiarrhythmic agents.