Characteristics, management, and midterm outcome in infants with atrioventricular nodal reentry tachycardia.

Atrioventricular nodal reentry is a commonly recognized mechanism of supraventricular tachycardia (SVT) in adults, but is only rarely documented in the first year of life. The aim of this study was to elucidate characteristics, management, and outcome in infants with atrioventricular nodal reentrant tachycardia (AVNRT). Electrophysiologic studies performed between January 1988 and June 1996 were reviewed. Fifteen infants with AVNRT at 58 +/- 27 days (mean +/- SEM) were identified. Five had AVNRT detected following palliation of structural cardiac anomalies, including 4 with critical obstructions to left ventricular outflow. Typical AVNRT (ventriculoatrial interval 49 +/- 5 ms) was observed in 14 of 15 patients and atypical AVNRT (ventriculoatrial interval 191 +/- 22 ms) in 4 of 15. All patients received long-term therapy, beginning with digoxin in 13. Eight had symptomatic recurrences on digoxin and 6 of these were given beta blockers, with satisfactory control in 4. Three patients were controlled with class III agents, and 2 underwent slow pathway radiofrequency modification at ages 4.1 and 6.7 years, respectively. AVNRT was still inducible in 6 of 6 asymptomatic patients who underwent follow-up atrial stimulation studies after discontinuation of medical therapy. All 15 patients were alive with either absent or well-controlled AVNRT at age 45 +/- 7 months. We conclude that the course and outcome of AVNRT diagnosed in the first year of life are generally benign, but that a minority of patients have symptoms persisting beyond infancy. Digoxin is of questionable benefit in long-term control. AVNRT often remains inducible in asymptomatic patients, although the significance of this finding remains to be determined by long-term follow-up.