The clinical course of multifocal atrial tachycardia in infants and children.

OBJECTIVES: This study outlines the clinical course, treatment and the late outcome of infants and children with multifocal atrial tachycardia (MAT).
BACKGROUND: Multifocal atrial tachycardia is defined by three distinct P-waveforms, irregular P-P intervals, isoelectric baseline between P-waves and rapid rate on an electrocardiogram. Several smaller prior reports have described pediatric patients with MAT, but their long-term outcome has not been fully assessed.
METHODS: The clinical records, echocardiograms and long-term follow-up of patients with MAT were reviewed and compared to previous reports of MAT.
RESULTS: Fourteen boys and seven girls (median age 1.8 months) presented with MAT. At diagnosis, six patients had respiratory illness, of whom two were critical. Ten were asymptomatic. Seven patients had structural heart disease (SHD), one of whom died. Four of 15 patients (27%) with echocardiograms had diminished ventricular function. Ventricular rates were 111 to 253 beats/min (mean 181 beats/min). Median duration of the arrhythmia was 4.9 months (mean 6.7 months). Electrical cardioversion was attempted in 4 patients without success and 15 patients received antiarrhythmic medication. Seventeen patients were followed for a mean of 60 months. Four patients were lost to follow-up. There were no late arrhythmias.
CONCLUSIONS: The majority of children with MAT are healthy infants under one year of age; a few may exhibit mild to life-threatening cardiorespiratory disease. Less often, MAT accompanies SHD. Mild ventricular dysfunction may be observed in the presence of MAT, but symptoms are few and resolution is generally complete. Response to antiarrhythmic agents is mixed, and cardioversion is of no avail. Finally, long-term cardiovascular and developmental outcome depends principally on underlying condition; for otherwise healthy children, it is excellent.