Transesophageal atrial pacing was used to initiate and terminate
tachycardia in 24 infants (seven female and 17 male, aged 1 to 34 days) with ECG documentation of
supraventricular tachycardia. Six infants received no chronic treatment, and chronic oral
digoxin prophylaxis was administered to 18 infants in an effort to prevent recurrences of
tachycardia. In these 18 infants, the effectiveness of
digoxin therapy in preventing the initiation of
tachycardia by transesophageal pacing was compared with its ability to prevent spontaneous recurrences of
supraventricular tachycardia. While receiving chronic oral
digoxin therapy,
tachycardia could be reinitiated in 15/18 (83%) infants. In these infants, the cycle length of
tachycardia and the atrioventricular interval were the same before and during chronic
digoxin treatment. Three infants in whom
tachycardia could not be initiated during chronic
digoxin therapy had no spontaneous recurrences during 6 months of follow-up, whereas 10/15 (67%) infants in whom
tachycardia could be reinitiated had clinically significant recurrences in spite of chronic
digoxin therapy. Six infants who received no chronic
drug treatment had no documented recurrences during 6 months of follow-up. This study demonstrates that
digoxin was effective in preventing significant spontaneous recurrences of
supraventricular tachycardia in only 8/18 (44%) infants treated with
digoxin. The ability to initiate
supraventricular tachycardia with transesophageal pacing may be useful in determining which
digoxin-treated infants are at risk for recurrence. Finally, not all infants with
supraventricular tachycardia require chronic prophylaxis; six of the untreated infants had no documented recurrences.