Study on congenital complete heart block in children by 24-hour ambulatory electrocardiographic monitoring.

Ambulatory electrocardiographic monitoring was performed in 18 children with a congenital complete heart block (CCHB). They had no cardiac structural anomalies. These patients could be divided into 3 groups according to the pattern of fluctuations in beat-to-beat ventricular rates. Type 1 patients showed rapid and transient fluctuations and demonstrated a high correlation between atrial and ventricular rates. Type 3 patients showed a constant ventricular rate and little variation through the 24 hour period and there was no appreciable correlation between atrial and ventricular rates. Twelve of 18 patients had additional arrhythmias. A few sporadic ventricular premature contractions (VPCs) were found in 9 patients, and bigeminy of VPCs or ventricular tachycardias were seen in 2 patients during exercise. Frequent and sudden prolongation of RR intervals was found during sleep in 3 patients. The longest intervals of ventricular asystoles were 7.2, 3.2 and 3.2 sec, respectively. The mechanism of this phenomenon appeared to be not only an exit block, but also arrest or a lack of automaticity of a subsidiary pacemaker. One of these patients developed frequent Stokes-Adams attacks. Type 3 patients with sudden prolongation of RR intervals and/or frequent ventricular arrhythmias should be under careful observation. Ambulatory electrocardiographic monitoring is recommended for children with CCHB for evaluation of potential risk factors for Stokes-Adams attacks.