A Case of Supraventricular Tachycardia in a Neonate

Background Supraventricular tachycardia (SVT) is the most common neonatal arrhythmia. Rapid recognition and targeted therapy are essential to avert hemodynamic compromise and prevent tachycardia–induced cardiomyopathy. Case A term female neonate (3.4 kg; Apgar 9/10) developed sustained narrow–complex tachycardia at 240 bpm within minutes of birth (Figure 1). Vagal maneuvers failed. Intravenous adenosine (0.2 mg/kg) abruptly restored sinus rhythm and unmasked a short PR interval (80 ms). Echocardiography and laboratory testing were unremarkable. During tertiary–center monitoring no recurrences occurred; prophylactic oral flecainide (2 mg/kg/day) was initiated. At two months, the infant remained asymptomatic with sinus rhythm (PR 98 ms). Interpretation. Immediate adenosine termination, coupled with a persistently short PR, strongly supports orthodromic atrioventricular re–entrant tachycardia via an accessory pathway (probable WPW physiology). In this age group, AVNRT is uncommon and does not explain marked PR shortening; atrial flutter typically shows saw–tooth activity and is seldom terminated by adenosine; focal atrial tachycardia usually displays warm–up/cool–down and rarely stops abruptly. Management and implications. Adenosine is both diagnostic and therapeutic in neonatal SVT, helping reveal concealed pre–excitation that informs risk stratification. Current pediatric practice favors inpatient observation after a first episode and selective prophylaxis; flecainide is effective for early–life recurrence prevention. Electrophysiological study/ablation is generally deferred unless drug–refractory recurrences, drug intolerance, or high–risk pre–excitation persists. Conclusion This case underscores that prompt ECG–based diagnosis and adenosine–guided management enable safe early stabilization of neonatal accessory–pathway–mediated SVT, with excellent short–term outcomes.Figure 1