What are the management options for Supraventricular Tachycardia (SVT)?

Management of Supraventricular Tachycardia

For acute SVT management, perform vagal maneuvers first (modified Valsalva maneuver is most effective), followed by adenosine 6 mg IV bolus if vagal maneuvers fail, and proceed to synchronized cardioversion for hemodynamically unstable patients or when pharmacological therapy is ineffective. 1, 2

Acute Management Algorithm

Step 1: Initial Assessment and First-Line Intervention

• Perform vagal maneuvers immediately in the supine position as the first-line intervention for all hemodynamically stable patients 1, 2
• The modified Valsalva maneuver is superior to standard Valsalva and carotid sinus massage, with the highest effectiveness ranking (SUCRA: 0.9992) 3
• Modified Valsalva technique: patient bears down against a closed glottis for 10-30 seconds (equivalent to 30-40 mm Hg intrathoracic pressure), then immediately lies supine with legs elevated 1, 2
• Alternative vagal maneuvers include carotid sinus massage (only after confirming absence of carotid bruits by auscultation) for 5-10 seconds, or applying ice-cold wet towel to the face 1, 2
• Never apply pressure to the eyeball—this practice is dangerous and abandoned 1, 2
• Switching between vagal maneuver techniques achieves a 27.7% overall success rate 1, 2

Step 2: Pharmacological Therapy for Stable Patients

• Administer adenosine 6 mg rapid IV bolus if vagal maneuvers fail 1, 2
• Adenosine is 91-95% effective for converting orthodromic AVRT to sinus rhythm 1, 2, 4
• If initial 6 mg dose fails, give up to two subsequent 12 mg doses 1
• Have electrical cardioversion immediately available because adenosine may precipitate atrial fibrillation that conducts rapidly down an accessory pathway, potentially causing ventricular fibrillation 1
• Minor side effects (chest discomfort, flushing) occur in approximately 30% of patients but last less than 1 minute 1

Step 3: Alternative Pharmacological Options

• Intravenous diltiazem or verapamil (calcium channel blockers) are highly effective for converting AVNRT to sinus rhythm in hemodynamically stable patients 2, 5
• Beta-blockers are less effective than calcium channel blockers but remain reasonable alternatives 2
• Critical caveat: Avoid AV nodal blocking agents (verapamil, diltiazem, beta-blockers) in patients with suspected pre-excitation or Wolff-Parkinson-White syndrome, as they may accelerate ventricular rate and precipitate ventricular fibrillation 2, 5

Step 4: Electrical Cardioversion

• Perform synchronized cardioversion immediately for hemodynamically unstable patients regardless of pharmacological therapy attempts 1, 2
• Synchronized cardioversion is also indicated for hemodynamically stable patients when pharmacological therapy is ineffective or contraindicated 1

Special Situation: Pre-Excited Atrial Fibrillation

Hemodynamically Unstable Patients

• Perform synchronized cardioversion immediately 1, 2

Hemodynamically Stable Patients

• Administer ibutilide or intravenous procainamide 1, 2, 5
• Absolutely avoid AV nodal blocking agents (adenosine, calcium channel blockers, beta-blockers, digoxin) as they can cause life-threatening ventricular rates 2, 5

Long-Term Management

First-Line Definitive Therapy

• Catheter ablation is the most effective long-term treatment with single-procedure success rates of 94.3-98.5% and low complication rates 2, 4
• Catheter ablation provides potential cure without need for chronic pharmacological therapy 2, 4
• Consider ablation based on frequency and duration of episodes, severity of symptoms, patient preference, and occupational requirements 2

Pharmacological Prevention

• Oral beta-blockers, diltiazem, or verapamil are first-line pharmacological options for patients with symptomatic SVT without ventricular pre-excitation 2
• These agents reduce frequency and duration of SVT episodes 2
• For patients without structural heart disease who decline ablation, flecainide or propafenone are reasonable alternatives 2, 6, 7
• Flecainide is contraindicated in patients with structural heart disease, recent myocardial infarction, or ventricular dysfunction due to proarrhythmic effects 1, 6
• Propafenone reduced attack rates in clinical trials, with 47-67% of patients remaining attack-free compared to 7-22% on placebo 7

Patient Education

• Teach all patients proper vagal maneuver techniques for self-management of future episodes 2
• Specifically instruct on modified Valsalva maneuver: forcefully exhale against closed airway for 10-30 seconds while supine, then lie back with legs elevated 2

Critical Pitfalls to Avoid

• Never use AV nodal blockers in pre-excited atrial fibrillation or suspected WPW syndrome—this can cause ventricular fibrillation 2, 5
• Always confirm absence of carotid bruits before carotid sinus massage 1, 2
• Ensure proper ECG diagnosis before treatment to distinguish SVT from ventricular tachycardia 2
• Avoid calcium channel blockers and beta-blockers in systolic heart failure 2
• Do not use flecainide in patients with structural heart disease or ventricular dysfunction—risk of cardiac arrest is significantly elevated 1, 6