What is the treatment for Supraventricular Tachycardia (SVT)?

Treatment of Supraventricular Tachycardia (SVT)

Begin with vagal maneuvers immediately in all hemodynamically stable patients, followed by adenosine 6 mg rapid IV push if vagal maneuvers fail, and proceed to synchronized cardioversion for any hemodynamically unstable patient. 1, 2

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

• Hemodynamically unstable patients (hypotension, altered mental status, chest pain, acute heart failure) require immediate synchronized cardioversion without attempting vagal maneuvers or medications 1
• Stable patients proceed through the stepwise approach below 1

Step 2: First-Line Therapy - Vagal Maneuvers

Perform vagal maneuvers with the patient in the supine position as the initial intervention: 1, 2

• 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: After confirming absence of carotid bruit by auscultation, apply steady pressure over the right or left carotid sinus for 5-10 seconds 1
• Ice-cold towel to face: Apply an ice-cold, wet towel to activate the diving reflex 1
• Success rate is approximately 27.7% when switching between techniques, with Valsalva being more effective than carotid massage 1
• Modified Valsalva has 43% effectiveness when performed correctly 3

Critical pitfall: Never apply pressure to the eyeball—this practice is dangerous and abandoned 1

Step 3: Pharmacologic Therapy - Adenosine

If vagal maneuvers fail, adenosine is the first-line medication: 1, 2

• Dose: 6 mg rapid IV bolus followed immediately by saline flush 2
• Effectiveness: 90-95% success rate in terminating AVNRT 1, 2, 3
• Adenosine serves dual purpose as both therapeutic and diagnostic agent, unmasking atrial activity in other arrhythmias like atrial flutter 1

Step 4: Alternative Pharmacologic Agents

For hemodynamically stable patients who don't respond to adenosine: 1, 2

• 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, 2

Critical caveats for calcium channel blockers and beta blockers: 1

• Must ensure absence of ventricular tachycardia or pre-excited atrial fibrillation before administration
• Patients with these rhythms may become hemodynamically unstable and develop ventricular fibrillation if given diltiazem or verapamil
• Avoid in patients with suspected systolic heart failure
• For patients with pre-excitation, AV nodal blocking agents should be avoided entirely 2

Step 5: Synchronized Cardioversion

Indicated when: 1

• Pharmacologic therapy fails to terminate the tachycardia in stable patients
• Medications are contraindicated
• Patient remains hemodynamically unstable despite initial interventions

Long-Term Management

First-Line Preventive Therapy

Beta blockers are the first-line option for long-term prevention of recurrent SVT 1, 2

• Calcium channel blockers (diltiazem or verapamil) serve as alternatives to beta blockers 1, 2
• Both are useful for ongoing management in patients without ventricular pre-excitation during sinus rhythm 1

Second-Line Pharmacologic Options

For patients without structural heart disease or ischemic heart disease: 1, 4

• Flecainide or propafenone: Reasonable for symptomatic patients who are not candidates for or prefer not to undergo catheter ablation 1
• FDA indication: Flecainide is specifically indicated for prevention of paroxysmal supraventricular tachycardias including AVNRT and AVRT in patients without structural heart disease 4
• Critical warning: Flecainide should not be used in patients with recent myocardial infarction and carries proarrhythmic risk (4% in SVT patients, with 7 of 9 events being exacerbations of supraventricular arrhythmias) 4

Additional options when first-line agents fail or are contraindicated: 1

• Sotalol may be reasonable 1
• Dofetilide may be reasonable 1
• Oral amiodarone may be considered 1
• Oral digoxin may be reasonable in patients without pre-excitation 1

Definitive Therapy - Catheter Ablation

Catheter ablation is the most effective curative option and should be considered first-line for definitive management: 1, 2, 3

• Success rates: 94.3% to 98.5% with single procedure 3
• Indications: Frequent symptomatic episodes, poor tolerance or ineffectiveness of medications, or patient preference for non-pharmacological approach 2
• Electrophysiological study with option of ablation is useful for both diagnosis and potential treatment 1
• All patients treated for SVT should be referred for heart rhythm specialist opinion 5

Patient Education

Patients should be educated on performing vagal maneuvers for self-management of recurrent episodes 1

Special Populations

Pregnancy

SVT is the most common tachyarrhythmia of pregnancy: 6

• Vagal maneuvers remain safe and first-line 2, 6
• Adenosine is considered safe due to its short half-life 2, 6
• Synchronized cardioversion can be performed safely at all stages of pregnancy if necessary 2, 6
• Avoid atenolol and verapamil due to teratogenic effects 6

Pre-excitation Syndromes

Critical distinction for patients with Wolff-Parkinson-White or other pre-excitation patterns: 2

• AV nodal blocking agents (adenosine, beta blockers, calcium channel blockers, digoxin) should be avoided 2
• For hemodynamically stable pre-excited atrial fibrillation, use ibutilide or IV procainamide 2

Diagnostic Considerations

Always record a 12-lead ECG to differentiate tachycardia mechanisms before initiating treatment 1, 2

• Essential to distinguish SVT with aberrancy from ventricular tachycardia 2
• Compare ECG during tachycardia with sinus rhythm 5
• Assess onset and offset of tachycardia to deduce underlying mechanism 5