Multicenter Study of Antiarrhythmic Medications for Treatment of Infants With Supraventricular Tachycardia

The purpose of the proposed research is to conduct a randomized double-blind, multi-centre study of two antiarrhythmic medications, digoxin and propranolol, to evaluate whether one of these medications is more effective in reducing risk of recurrent supraventricular tachycardia (SVT) in infants.

SVT is the most common sustained arrhythmia of infancy, occurring in 1 in 250-1000 children, and is a serious health burden in Canada and internationally [1, 5-8]. SVT is a common clinical problem facing many health care providers, including general pediatricians, emergency room physicians, nurses, cardiologists, and intensive care physicians. SVT carries significant morbidity and mortality, and patients typically receive long-term medical therapy. Untreated, an infant can tolerate SVT for only a short period before heart failure and shock (or even death) ensues. The management of SVT is currently under debate and often appears to depend on physician preference [9]. While spontaneous termination of the acute episode may occur [1, 2, 6, 9, 10], many infants require medical intervention to terminate the episode. Vagal maneuvres and adenosine have reasonable success in terminating an acute SVT episode, but other medications may also be required. Once the acute episode is treated, the physician(s) must make a decision whether or not to start maintenance (chronic) therapy.

At present, there is no clinical consensus for the management of SVT in infancy. The rationale for chronic therapy in SVT is to prevent recurrences and to limit symptoms during recurrences. Yet SVT recurrences are not readily predictable [11]. Many medications are available to treat SVT; however, these medications have associated risks and there are psychosocial implications for families. To date, most medications used to treat infant SVT have not been evaluated in controlled studies of infants. Thus, at present, physicians must make decisions about initiation and duration of chronic therapy and choice of medication in the absence of evidence from controlled clinical trials. A prospective, randomized clinical study is crucial to provide evidence to guide therapy of infant SVT.

As a preliminary study to inform the proposed trial, we carried out a survey of all pediatric cardiologists in North America [12]. In this survey, we presented hypothetical cases of infants with SVT and asked about acute and chronic management. Several points are clear:

• 11 different medications were chosen for the management of infant SVT;
• there was a discrepancy among respondents with respect to medication choices, based on whether the respondent had additional electrophysiology training or not; and
• several physicians selected digoxin in infants who have Wolff-Parkinson-White syndrome ; this medication choice may have deleterious effects in these infants.