Paroxysmal reciprocating supraventricular tachycardia in infants: electrophysiologically guided medical treatment and long-term evolution of the re-entry circuit

The aim of this study is to evaluate the long-term prognosis in infants affected by paroxysmal reciprocating supraventricular tachycardia (SVT), to identify predictors of SVT disappearance, and to assess the efficacy of electrophysiologically guided drug therapy in preventing recurrences.A six step regimen of oral therapy was used in 55 infants with SVT: (i) propafenone (P); (ii) flecainide (F); (iii) flecainide plus propranolol (FP); (iv) amiodarone (A); (v) amiodarone plus propranolol (AP); (vi) amiodarone plus flecainide plus propranolol (AFP). If one step was not successful, the patient was passed on to the next treatment step and so on. Transesophageal atrial pacing (TAP) was used to evaluate treatment efficacy and the evolution of SVT at the end of the first, second, and third year. Propafenone was successful in 32.7% of the patients, F in 14.5%, FP in 23.6%, A alone in 5.4%, and AP in 18.1%; only 7.2% reached step 6. At month 12, after therapy wash out, SVT recurred spontaneously in 2 patients (3.6%) and remained inducible in 25 (45.5%). Inducibility was significantly higher in patients treated with A. At 24 months, SVT was inducible or spontaneous in 86% of the cases and at 36 months in 87%. There were no recurrences using the treatment confirmed by TAP. No further predictor of SVT inducibility was identified.Supraventricular tachycardia disappeared in approximately 50% of the patients during the first year of life and in another 20% thereafter. The necessity for A treatment is the only predictor of persistence of the re-entry circuit during the first year of life. Transesophageal atrial pacing is useful in guiding the medical treatment.