When should supraventricular tachycardia (SVT) be treated?

When to Treat Supraventricular Tachycardia

Treat SVT immediately when the patient is hemodynamically unstable (hypotension, altered mental status, signs of shock, chest pain, or acute heart failure), and treat hemodynamically stable patients when symptoms are present or when there is risk of tachycardia-mediated cardiomyopathy. 1, 2

Immediate Treatment Indications (Hemodynamically Unstable)

Proceed directly to synchronized cardioversion in any patient with SVT presenting with:

• Hypotension 1
• Acutely altered mental status 1
• Signs of shock 1
• Chest pain 1
• Acute heart failure symptoms 1

Exception: If the tachycardia is regular with narrow QRS complex, adenosine may be considered first even in unstable patients, though cardioversion should not be delayed if adenosine fails or is not immediately available. 1, 3 Recent 2025 data suggests adenosine may be a safe first-line attempt in unstable cases before cardioversion, potentially reducing sedation-related risks, with a propensity-weighted analysis showing ECV had an odds ratio of 2.41 for successful conversion but adenosine still achieved 80% success. 3

Treatment Indications for Hemodynamically Stable Patients

Treat stable SVT when:

• Patient is symptomatic with palpitations (86% of cases), chest discomfort (47%), or dyspnea (38%) 4
• SVT is persistent and not self-terminating 1
• There is concern for tachycardia-mediated cardiomyopathy (occurs in approximately 1% of untreated cases) 4

Treatment Algorithm for Stable SVT:

First-line: Vagal maneuvers 1, 2

• Modified Valsalva maneuver (patient supine, bearing down against closed glottis for 10-30 seconds, equivalent to 30-40 mm Hg pressure) - 43% effective 1, 2
• Carotid sinus massage (after confirming no bruit, apply steady pressure for 5-10 seconds) 1, 2
• Never use eyeball pressure - this is dangerous and abandoned 1, 2

Second-line: Adenosine if vagal maneuvers fail 1, 2

• 90-95% effective for terminating AVRT and AVNRT 1, 2
• Have cardioversion equipment available as adenosine may precipitate atrial fibrillation 1

Third-line: If adenosine fails or is contraindicated 1, 2

• Intravenous diltiazem or verapamil (64-98% success rate) 1, 2
• Intravenous beta blockers (reasonable alternative, though slightly less effective) 1, 2

Fourth-line: Synchronized cardioversion when pharmacological therapy is ineffective or contraindicated 1

Critical Caveats

Before administering calcium channel blockers or beta blockers, ensure:

• The rhythm is not ventricular tachycardia (VT) - these agents can cause hemodynamic collapse in VT 1, 2
• The rhythm is not pre-excited atrial fibrillation - these agents can accelerate ventricular rate and precipitate ventricular fibrillation 1, 2
• Always obtain a 12-lead ECG to characterize the tachycardia mechanism 2

For patients with pre-excitation (Wolff-Parkinson-White) on resting ECG:

• Avoid calcium channel blockers and beta blockers as first-line agents 1
• Use procainamide or ibutilide if hemodynamically stable with pre-excited AF 1
• Proceed directly to cardioversion if hemodynamically unstable 1

Post-Conversion Management

After successful conversion:

• Observe for approximately 4 hours with continuous cardiac monitoring 2
• Consider electrophysiology consultation for recurrent symptomatic SVT 2
• Catheter ablation is first-line for preventing recurrence with 94.3-98.5% single-procedure success rates 4
• Oral beta blockers, diltiazem, or verapamil are first-line pharmacotherapy for ongoing management in patients without ventricular pre-excitation 2