What is the treatment for Supraventricular Tachycardia (SVT)?

Treatment of Supraventricular Tachycardia (SVT)

Begin with vagal maneuvers as first-line therapy, followed immediately by adenosine if unsuccessful, and proceed to synchronized cardioversion for hemodynamically unstable patients or those who fail pharmacological therapy. 1

Acute Management Algorithm

Step 1: Hemodynamic Assessment and Initial Intervention

For all hemodynamically stable patients, initiate vagal maneuvers immediately 1:

• Modified Valsalva maneuver: Patient bears down against a closed glottis for 10-30 seconds (equivalent to 30-40 mm Hg intrathoracic pressure), then immediately lies flat with legs raised 1, 2
• Carotid sinus massage: Apply steady pressure over the right or left carotid sinus for 5-10 seconds after confirming absence of bruit by auscultation 1
• Diving reflex: Apply ice-cold, wet towel to the face 1
• Success rate is approximately 27.7% when switching between techniques, with Valsalva being more successful than carotid massage 1
• Critical caveat: Never apply pressure to the eyeball—this practice is dangerous and abandoned 1

Step 2: Pharmacological Therapy (if vagal maneuvers fail)

Adenosine is the first-line medication 1:

• Dosing: 6 mg rapid IV bolus followed by saline flush; if unsuccessful, give 12 mg 2
• Effectiveness: Terminates AVNRT in approximately 90-95% of patients 1, 2
• Dual role: Functions as both therapeutic and diagnostic agent, unmasking atrial activity in flutter or atrial tachycardia 1

Alternative pharmacological agents for hemodynamically stable patients 1:

• IV diltiazem or verapamil: Particularly effective with 80-98% success rates 1
• IV beta blockers: Reasonable alternative with excellent safety profile, though less effective than calcium channel blockers 1
• Important warning: Avoid diltiazem, verapamil, and beta blockers in patients with suspected ventricular tachycardia, pre-excited atrial fibrillation, or systolic heart failure—these patients may become hemodynamically unstable or develop ventricular fibrillation 1

Step 3: Electrical Cardioversion

Synchronized cardioversion is mandatory for hemodynamically unstable patients 1:

• Perform immediately when adenosine and vagal maneuvers fail or are not feasible 1
• Highly effective in terminating SVT (including AVRT and AVNRT) 1

For hemodynamically stable patients, synchronized cardioversion is indicated when 1:

• Pharmacological therapy fails to terminate the tachycardia 1
• Pharmacological therapy is contraindicated 1
• A second drug bolus or higher dose may be attempted before proceeding to cardioversion 1

Long-Term Management

First-Line Ongoing Therapy

Oral beta blockers, diltiazem, or verapamil are the first-line options for ongoing management 1, 2:

• Recommended for symptomatic SVT patients without ventricular pre-excitation during sinus rhythm 1
• Beta blockers are specifically recommended as first-line by the American College of Cardiology 2
• Calcium channel blockers serve as alternatives to beta blockers 2

Catheter Ablation

Catheter ablation is the definitive curative option 1, 2, 3:

• Success rates: 94.3% to 98.5% for single procedure 3
• Indications: Frequent symptomatic episodes, poor tolerance or ineffectiveness of medications, or patient preference for non-pharmacological approach 2
• Recommended as first-line therapy to prevent recurrence 3
• All patients treated for SVT should be referred for heart rhythm specialist opinion 4

Alternative Pharmacological Agents

For patients who are not candidates for or prefer not to undergo catheter ablation 1:

• Flecainide or propafenone: Reasonable for patients without structural heart disease or ischemic heart disease 1, 5
  • Critical warning: Flecainide causes proarrhythmic effects in 4% of supraventricular arrhythmia patients, with 13-26% incidence in sustained VT patients 5
  • Reserved for patients where benefits outweigh risks 5
• Sotalol: May be reasonable when first-line agents fail 1
• Dofetilide: May be reasonable when beta blockers, diltiazem, flecainide, propafenone, or verapamil are ineffective or contraindicated 1
• Amiodarone: May be considered when all other agents are ineffective or contraindicated 1
• Digoxin: May be reasonable for patients without pre-excitation 1

Special Populations

Pregnancy

Vagal maneuvers remain first-line and are safe during pregnancy 2:

• Adenosine is considered safe due to its short half-life 2
• Synchronized cardioversion can be performed safely at all stages of pregnancy if necessary 2

Pre-excitation Syndromes

Avoid AV nodal blocking agents in patients with pre-excitation 2:

• Do not use adenosine, beta blockers, calcium channel blockers, or digoxin in pre-excited atrial fibrillation 2
• Consider ibutilide or IV procainamide for hemodynamically stable pre-excited AF 2
• Use synchronized cardioversion for hemodynamically unstable patients 6

Critical Diagnostic Considerations

Always record a 12-lead ECG before treatment 1, 2:

• Differentiate tachycardia mechanisms to guide therapy 1
• Distinguish SVT with aberrancy from ventricular tachycardia—this distinction is critical as treatment differs dramatically 2
• Compare ECG during tachycardia with sinus rhythm 4