Supraventricular Tachycardia (SVT) is a common rapid heart rate in newborns. Many infants experience spontaneous resolution of this arrhythmia as they grow. This article explores SVT in newborns, its management, and prognosis.
Understanding Supraventricular Tachycardia in Newborns
SVT is the most common abnormal heart rhythm in children, with an estimated incidence of 1 in 250 to 1,000 pediatric patients. In newborns, the heart beats very fast, often ranging from 220 to 320 beats per minute. This rapid rhythm originates from the heart’s upper chambers. The most common cause of neonatal SVT is an additional electrical pathway within the heart, which can create a “short circuit.”
Newborns with SVT may present with subtle symptoms, making identification challenging. Common signs include poor feeding, unusual sleepiness, vomiting, irritability, or decreased activity. If the rapid heart rate persists for many hours, the heart muscle can become fatigued, potentially leading to heart failure symptoms like rapid breathing or pale skin.
A diagnosis of SVT is suspected when a healthcare provider measures a rapid heart rate. An electrocardiogram (ECG) confirms the diagnosis by recording the heart’s electrical activity. An echocardiogram, an ultrasound of the heart, may also be suggested to assess heart structure.
Managing Acute SVT Episodes
When a newborn experiences an acute SVT episode, immediate medical interventions aim to restore a normal heart rhythm. For stable infants, vagal maneuvers are often the first approach. These techniques stimulate the vagus nerve, which helps slow the heart rate. A common vagal maneuver involves applying ice water to the face for 5 to 15 seconds, eliciting the “diving reflex.” This maneuver should not be used for infants in circulatory shock.
If vagal maneuvers are unsuccessful, medications are used. Adenosine is the primary medication for acutely terminating SVT episodes. It is given intravenously as a rapid bolus due to its very short half-life. Adenosine works by briefly blocking electrical conduction through the atrioventricular (AV) node, interrupting the abnormal electrical circuit. If adenosine is ineffective or the infant is unstable, other medications like amiodarone or esmolol, or electrical cardioversion, may be considered.
The Prognosis of Newborn SVT
Many babies with SVT “grow out” of the arrhythmia, with spontaneous resolution often occurring by their first birthday. Approximately 30% may experience a recurrence. The likelihood of recurrence varies widely, even with medical treatment.
Several factors influence the prognosis and chance of recurrence. Infants diagnosed with SVT at 60 days of age or younger, particularly those without Wolff-Parkinson-White (WPW) syndrome, tend to have the lowest risk of recurrence. WPW syndrome, which involves an extra electrical pathway, is a significant risk factor for SVT recurrence. Infants requiring multiple antiarrhythmic medications or second-line therapies also face a higher risk of recurrence. If SVT begins after the first year of life, it is more likely to persist.
Ongoing Care and Monitoring
Following an SVT diagnosis, ongoing care and monitoring are important. Regular follow-up appointments with a pediatric cardiologist are typically recommended. These visits allow for continuous assessment of the heart’s rhythm and overall function.
For infants who experience frequent or symptomatic SVT episodes, long-term daily medication may be prescribed to prevent recurrences or lessen their impact. Commonly used medications include beta-blockers like propranolol, as well as flecainide, digoxin, or amiodarone. Monitoring at home might also be recommended, such as using a Holter monitor to continuously record heart rhythm over a period, or a home heart rate monitor. Parents are often taught how to check their child’s pulse and recognize signs that warrant further medical attention.