What is the treatment for supraventricular tachycardia (SVT) in a young adult with no known history of heart disease?

Supraventricular Tachycardia (SVT) Treatment in Young Adults

For a young adult with SVT and no structural heart disease, immediately perform vagal maneuvers as first-line treatment, followed by IV adenosine if unsuccessful, with catheter ablation being the definitive curative therapy for recurrent episodes. 1

Understanding SVT in Young Adults

SVT most commonly presents as atrioventricular nodal reentrant tachycardia (AVNRT) in young adults without structural heart disease, with over 60% occurring in women. 1 The heart rate typically ranges from 180-200 bpm but can vary from 110 to >250 bpm. 2 Patients experience sudden-onset palpitations, shortness of breath, dizziness, and characteristic neck pulsations. 1 The arrhythmia is usually well tolerated and rarely life-threatening. 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

Determine if the patient shows signs of instability including hypotension, altered mental status, signs of shock, chest pain, or acute heart failure. 3 If unstable, proceed immediately to synchronized cardioversion. 1

Step 2: Vagal Maneuvers (First-Line for Stable Patients)

Perform vagal maneuvers immediately with the patient in the supine position. 1

• Modified Valsalva maneuver: Patient bears down against a closed glottis for 10-30 seconds, generating at least 30-40 mm Hg intrathoracic pressure 1
• Carotid sinus massage: After confirming absence of bruit by auscultation, apply steady pressure over the carotid sinus for 5-10 seconds 1
• Ice-cold towel to face: Apply ice-cold, wet towel to activate the diving reflex 1
• Success rate: Approximately 27.7% overall, with Valsalva being more effective than carotid massage 1, 2

Step 3: IV Adenosine (Second-Line)

If vagal maneuvers fail, administer IV adenosine immediately. 1

• Efficacy: 90-95% success rate for terminating AVNRT and orthodromic AVRT 2, 3
• Dosing: Rapid IV push followed by saline flush 1
• Side effects: Brief adverse effects occur in approximately 30% of patients but are transient 3
• Contraindications: High-grade AV block, sinus node dysfunction (without pacemaker), bronchospastic lung disease, and known hypersensitivity 4

Critical Pitfall: Adenosine can cause AV block (6% of patients), bronchoconstriction, hypotension, and rarely seizures or cerebrovascular accidents. 4 Have resuscitative equipment immediately available. 4

Step 4: IV Calcium Channel Blockers or Beta Blockers (Third-Line)

If adenosine fails or is contraindicated, administer IV diltiazem, verapamil, or beta blockers. 1

• Success rate: 80-98% for conversion to sinus rhythm 2
• Class IIa recommendation for hemodynamically stable patients 1

Critical Pitfall: Never administer verapamil or diltiazem for wide-complex tachycardia unless SVT with aberrancy is definitively proven, as these agents may cause hemodynamic collapse in ventricular tachycardia. 2 Never use AV nodal blocking agents in patients with pre-excited atrial fibrillation. 2

Step 5: Synchronized Cardioversion

Perform synchronized cardioversion if pharmacological therapy fails or is contraindicated. 1 This is highly effective for terminating SVT and is the immediate first-line treatment for hemodynamically unstable patients. 3

Long-Term Management

Definitive Treatment: Catheter Ablation

Catheter ablation is the most effective first-line therapy for preventing recurrent symptomatic SVT. 2, 3

• Success rate: 94.3-98.5% 2, 3
• Recurrence rate: <5% 2
• Class I recommendation for diagnosis and potential treatment 1

This is particularly appropriate for young adults who desire curative treatment and wish to avoid lifelong medication. 1

Pharmacological Prevention (Alternative to Ablation)

For patients who decline ablation or are unsuitable candidates:

• First-line: Oral beta blockers, diltiazem, or verapamil (Class I recommendation) 1
• Second-line: Flecainide or propafenone for patients without structural heart disease (Class IIa recommendation) 1
• Third-line options: Sotalol, dofetilide, or amiodarone if first-line agents are ineffective or contraindicated 1

Patient Education

Educate patients on performing vagal maneuvers for self-termination of future episodes (Class I recommendation). 1 This empowers patients to manage episodes independently and may reduce emergency department visits.

Common Triggers to Avoid

Patients should be counseled that SVT may be triggered by exertion, coffee, tea, or alcohol. 1 Avoiding these triggers may reduce episode frequency.