What is the treatment approach for supraventricular tachycardia (SVT)?

Treatment Approach for Supraventricular Tachycardia (SVT)

The first-line treatment for SVT should begin with vagal maneuvers, followed by adenosine in hemodynamically stable patients, and synchronized cardioversion for unstable patients or when other methods fail. 1

Initial Assessment and Management Algorithm

Step 1: Determine Hemodynamic Stability

• Assess for signs of instability: hypotension, altered mental status, signs of shock, chest pain, or acute heart failure 1
• If the patient is hemodynamically unstable, proceed immediately to synchronized cardioversion 2, 1

Step 2: For Hemodynamically Stable Patients

1. Vagal Maneuvers (First-Line):

   • Perform in supine position 2
   • Valsalva maneuver: Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) 2
   • Modified Valsalva maneuver is most effective (43% success rate) 1, 3
   • Carotid sinus massage: After confirming absence of carotid bruit, apply steady pressure over carotid sinus for 5-10 seconds 2
   • Cold stimulus: Apply ice-cold wet towel to face 2
   • Overall success rate of vagal maneuvers is approximately 27.7% 2, 1

2. Adenosine (If Vagal Maneuvers Fail):

   • Highly effective with 90-95% success rate for AVNRT and AVRT 1, 3
   • Administer via proximal IV as rapid bolus followed by saline flush 2
   • Continuous ECG recording during administration helps diagnostically 2
   • May cause brief side effects (chest discomfort, shortness of breath, flushing) in about 30% of patients 2, 1

3. IV Calcium Channel Blockers or Beta Blockers (If Adenosine Fails):

   • Success rates of 80-98% for conversion to sinus rhythm 2, 1
   • Options include verapamil, diltiazem, or beta blockers 2
   • Caution: Avoid in patients with suspected VT, pre-excited AF, or systolic heart failure 1

4. Synchronized Cardioversion (If Medications Fail):

   • Indicated when pharmacological therapy does not terminate the tachycardia or is contraindicated 2
   • Highly effective for terminating SVT 2

Special Considerations

• Pre-excited AF: Use ibutilide or IV procainamide; avoid AV nodal blocking agents that may enhance conduction over accessory pathway 1
• Wolff-Parkinson-White Syndrome: Patients with antegrade accessory pathway conduction and history of atrial fibrillation should receive IV procainamide if stable, or synchronized cardioversion if unstable 4
• Tachycardia-Mediated Cardiomyopathy: Rare complication (1%) that may develop in untreated PSVT 3

Long-term Management

• Catheter Ablation:

  • Most effective therapy to prevent recurrent SVT 1, 3
  • Success rates of 94.3-98.5% 1, 3
  • Recommended as first-line therapy for prevention of recurrence 3
  • All patients treated for SVT should be referred for heart rhythm specialist opinion 5

• Pharmacological Options (for patients who decline ablation or are not candidates):

  • Oral beta blockers, diltiazem, or verapamil 1
  • Flecainide or propafenone for patients without structural heart disease 1

Common Pitfalls and Caveats

• Ensure a 12-lead ECG is obtained to confirm narrow complex tachycardia, as ventricular tachycardia may masquerade as SVT if only a single lead is examined 6
• The practice of applying pressure to the eyeball is potentially dangerous and has been abandoned 2
• Adenosine may unmask atrial flutter or atrial tachycardia but is uncommon to terminate these atrial arrhythmias 2
• Modified Valsalva maneuver has higher success rates than traditional techniques and may help avoid the need for more invasive treatments 7