OFFICIAL ABP TOPIC:

Evaluate and manage a patient with supraventricular tachycardia

BACKGROUND

Supraventricular tachycardia (SVT), a rapid heart rhythm originating above the ventricles, is the most common pediatric tachyarrhythmia. The majority of patients have structurally normal hearts, although children with congenital heart disease are at higher risk.

EVALUATION

The two most common mechanisms of SVT are:

• Atrioventricular reentrant tachycardia (AVRT) associated with accessory pathways, such as Wolff-Parkinson-White (WPW) syndrome. This is the primary cause of SVT in infants, with a higher risk of sudden cardiac death.
• Atrioventricular nodal reentrant tachycardia (AVNRT), more common in older children and adolescents.

CLINICAL FEATURES

• Infants: May present with pallor, fussiness, poor feeding, tachypnea, and signs of heart failure.
• Children and Adolescents: Palpitations, chest discomfort, lightheadedness. Syncope warrants urgent evaluation.
• Heart Rates: Typically 220-280 bpm in infants; 180-240 bpm in older children.
• Physical Exam: Tachycardia, possible hypotension, diaphoresis. Infants may have hepatomegaly or signs of heart failure.

ELECTROCARDIOGRAM (ECG)

• During SVT: Regular, narrow-complex tachycardia. Absence of respiratory variation. P waves abnormal or absent.
• Image: www.pbrlinks.com/MOCA2025-SVT
• During sinus rhythm: Look for a preexcitation pattern suggestive of WPW, including a short PR interval, a delta wave (slurring of the QRS complex upstroke), and wide QRS complex if the pathway conducts antegrade.
• Image: www.pbrlinks.com/MOCA2025-WPW

ADDITIONAL STUDIES

• Echocardiogram: To evaluate for structural heart disease.
• Ambulatory monitoring: May capture an episode of SVT if not seen on ECG and establish frequency and duration of episodes.
• Electrophysiologic study: Used to evaluate clinically significant SVT.
  • Indications:
    • Planning catheter ablation
    • Mapping the location of an accessory pathway
    • Determining the mechanism of an unknown type of SVT
• Exercise testing: May assess risk of fatal arrhythmias in WPW.

ACUTE MANAGEMENT

HEMODYNAMICALLY STABLE SVT

1. Assess and support ABCs as needed.
2. Obtain a 12-lead ECG and continuous monitoring.
3. Perform vagal maneuvers:
   • Infants: Apply ice to the face.
   • Older children: Encourage bearing down (Valsalva), blowing into an occluded straw, or placing the head down for 15-20 seconds.
   • Avoid carotid massage: It can cause bradycardia, hypotension, or stroke in children.
   • If successful, observe the patient.
   • If unsuccessful, administer adenosine 0.1 mg/kg IV (max 6 mg).
     • Caution in asthmatics: Adenosine may cause bronchospasm.
     • Caution in heart transplant patients: Denervated hearts are extremely sensitive to adenosine, leading to prolonged asystole.
4. If adenosine is unsuccessful, repeat with 0.2 mg/kg IV (max 12 mg).
5. If adenosine is still unsuccessful, consult with pediatric cardiology to consider alternative medications such as IV procainamide, amiodarone, or beta-blockers.
   • Avoid verapamil in infants due to the risk of cardiovascular collapse.

HEMODYNAMICALLY UNSTABLE SVT

Synchronized cardioversion is the first-line treatment for unstable patients with SVT.

1. Assess and support ABCs as needed.
2. Obtain a 12-lead ECG if possible, but do not delay therapy.
3. Perform synchronized cardioversion at 0.5-1 J/kg.
   • If unsuccessful, increase to 2 J/kg.
   • Repeat as needed.
4. If IV access is available, administer rapid adenosine while preparing for repeat cardioversion.

REFERRAL

Infants and children with preexcitation on ECG or documented SVT should be referred to a pediatric cardiologist to guide diagnostic evaluation, risk assessment, and management, including possible ablation.

Urgent referral is warranted for children with SVT associated with syncope, heart failure, incessant tachycardia, or depressed ventricular function.

CHRONIC MANAGEMENT

Infants

• Prophylaxis: Typically with propranolol for recurrent, symptomatic episodes.
• Expectant management: Reasonable for asymptomatic infants with normal function, even with recurrent episodes.

Children ≥1 year

• First episode, minimal symptoms: Consider expectant management.
• Recurrent/Symptomatic SVT: Intervention indicated.
  • Under 15 kg: Typically treated with a beta-blocker (e.g., propranolol, atenolol, nadolol).
  • Over 15 kg: Consider referral for radiofrequency ablation.

REFERENCES

https://www.uptodate.com/contents/clinical-features-and-diagnosis-of-supraventricular-tachycardia-svt-in-children

https://www.uptodate.com/contents/management-of-supraventricular-tachycardia-svt-in-children