What is the treatment approach for a patient with Supraventricular Tachycardia (SVT)?

Treatment of Supraventricular Tachycardia

Immediate Assessment: Hemodynamic Stability

The first critical decision is determining hemodynamic stability—if the patient is unstable (hypotensive, altered mental status, chest pain, acute heart failure), proceed directly to synchronized cardioversion without attempting vagal maneuvers or medications. 1, 2, 3

Hemodynamically Unstable Patients

• Perform immediate synchronized cardioversion starting at 50-100 J biphasic energy, increasing stepwise if initial shock fails 2
• Do not delay for vagal maneuvers or adenosine—unstable patients require immediate rhythm conversion 1, 2
• Ensure adequate sedation/anesthesia if time permits in stable-appearing patients 2

Hemodynamically Stable Patients: Stepwise Approach

Step 1: Vagal Maneuvers (First-Line)

Vagal maneuvers are the immediate first-line intervention for all stable SVT patients (Class I, Level B evidence). 1, 2, 3

• Modified Valsalva maneuver is most effective: patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mm Hg intrathoracic pressure) while supine, then immediately lie flat with legs elevated 1, 2
• Carotid sinus massage: Apply steady pressure over right or left carotid sinus for 5-10 seconds—only after confirming absence of carotid bruit by auscultation 1, 3
• Diving reflex: Apply ice-cold wet towel to face 1, 3
• Success rate approximately 27.7% when switching between techniques 1, 3
• Never apply pressure to the eyeball—this practice is dangerous and abandoned 1, 3

Step 2: Adenosine (If Vagal Maneuvers Fail)

Adenosine is the next intervention with 90-95% effectiveness for terminating SVT (Class I, Level B recommendation). 1, 2, 3

• Dosing: 6 mg rapid IV push through large peripheral vein, followed immediately by 20 mL saline flush 2
• If no response, give 12 mg, then another 12 mg if needed 1
• Critical dosing adjustments: 2
  • Reduce to 3 mg for patients on dipyridamole, carbamazepine, or with transplanted heart
  • Larger doses needed with theophylline, caffeine, or theobromine
• Contraindicated in asthma patients—can cause severe bronchoconstriction 2
• Always have resuscitation equipment and cardioversion capability immediately available 1, 2

Step 3: Alternative Pharmacologic Agents

If adenosine fails or is contraindicated in stable patients:

• Intravenous calcium channel blockers (diltiazem or verapamil) are highly effective for AVNRT conversion (Class IIa recommendation) 1, 3, 4
  • Verapamil: 60% conversion rate within 10 minutes in controlled studies 4
  • Peak therapeutic effects occur within 3-5 minutes 4
• Intravenous beta-blockers are reasonable but less effective than calcium channel blockers (Class IIa recommendation) 1, 3

Step 4: Synchronized Cardioversion

If pharmacologic therapy fails in stable patients, proceed to synchronized cardioversion (Class I, Level B-NR recommendation). 1, 2

Critical Safety Warnings and Pitfalls

Avoid AV Nodal Blocking Agents in These Situations:

Never use verapamil, diltiazem, or beta-blockers in patients with: 2, 3

• Wide-complex tachycardia of uncertain etiology
• Known accessory pathways with pre-excited atrial fibrillation (Wolff-Parkinson-White syndrome)
• Suspected systolic heart failure
• These agents can precipitate ventricular fibrillation or hemodynamic collapse 2, 3

Pre-Excited Atrial Fibrillation (Special Case):

• If hemodynamically unstable: immediate synchronized cardioversion 3
• If hemodynamically stable: use ibutilide or IV procainamide (Class I recommendation)—not AV nodal blockers 3

Automatic Tachycardias:

• Ectopic atrial tachycardia, multifocal atrial tachycardia, and junctional tachycardia do not respond to cardioversion 2
• These require rate control with AV nodal blocking agents instead 2

Long-Term Management Considerations

For Recurrent Symptomatic SVT:

• Catheter ablation is first-line definitive treatment with high success rates and low complication rates 3, 5, 6
• Oral beta-blockers, diltiazem, or verapamil for ongoing suppression in patients without ventricular pre-excitation 3
• Flecainide or propafenone for patients without structural heart disease who are not ablation candidates 3
• All patients treated for SVT should be referred to a heart rhythm specialist 6

Patient Education:

• Teach proper vagal maneuver techniques for self-termination of future episodes 3
• Valsalva maneuver: forcefully exhale against closed airway for 10-30 seconds while supine 3