What are the types and management strategies for supraventricular tachycardia (SVT)?

Types and Management of Supraventricular Tachycardia (SVT)

Supraventricular tachycardia encompasses eight distinct types that originate above the ventricles, with catheter ablation being the most effective long-term management strategy for most symptomatic recurrent forms. 1, 2

The Eight Types of SVT

1. Atrioventricular Nodal Reentrant Tachycardia (AVNRT)

   • Most common form of SVT (50-60% of cases)
   • Involves dual pathways within the AV node
   • Typically presents with sudden onset/offset of symptoms

2. Atrioventricular Reentrant Tachycardia (AVRT)

   • Involves an accessory pathway between atria and ventricles
   • Includes Wolff-Parkinson-White syndrome (pre-excitation)
   • Orthodromic (narrow QRS) or antidromic (wide QRS) variants

3. Atrial Tachycardia (AT)

   • Focal or microreentrant mechanism in atrial tissue
   • Can be automatic, triggered, or reentrant
   • Often seen after atrial fibrillation ablation

4. Sinus Tachycardia

   • Appropriate (physiologic) response to exercise/stress
   • Inappropriate sinus tachycardia (IST) - abnormal elevation at rest

5. Sinus Nodal Reentry Tachycardia

   • Reentry circuit within or near the sinus node
   • Relatively uncommon form of SVT

6. Junctional Ectopic Tachycardia

   • Originates from the AV junction
   • More common in pediatric population or after cardiac surgery

7. Atrial Flutter

   • Macro-reentrant circuit in atrium (typically right)
   • Typical (counterclockwise) or atypical variants
   • Regular "sawtooth" pattern on ECG

8. Multifocal Atrial Tachycardia

   • Multiple atrial foci firing
   • Irregular rhythm with ≥3 different P wave morphologies
   • Often associated with pulmonary disease

Acute Management Algorithm

Step 1: Assess Hemodynamic Stability

• If unstable (hypotension, altered mental status, chest pain, heart failure):
  • Immediate synchronized cardioversion 1, 2

Step 2: For Stable Patients

1. Vagal Maneuvers (first-line)

   • Modified Valsalva maneuver (43% effective) 2
   • Carotid sinus massage (in appropriate patients)

2. If vagal maneuvers fail, administer Adenosine IV

   • Initial dose: 6mg rapid IV push
   • If ineffective: 12mg IV push (may repeat once)
   • Success rate ~91% 2
   • Contraindicated in asthma, 2nd/3rd degree AV block 3

3. If adenosine fails:

   • IV calcium channel blockers (diltiazem, verapamil) OR
   • IV beta-blockers (metoprolol, esmolol)
   • If still unsuccessful: synchronized cardioversion 1

Long-Term Management

First-Line Therapy

• Catheter ablation (94-98% success rate) 2
  • Recommended for recurrent, symptomatic SVT
  • Especially for AVNRT, AVRT, and focal AT
  • Curative in most cases with low complication rate

Pharmacologic Options (if ablation declined/contraindicated)

1. AV nodal blocking agents:

   • Beta-blockers (metoprolol, propranolol)
   • Calcium channel blockers (diltiazem, verapamil)

2. Antiarrhythmic medications:

   • Class IC: Flecainide, propafenone (in structurally normal hearts)
   • Class III: Sotalol, amiodarone (reserved for refractory cases)

3. "Pill-in-pocket" approach 1, 4

   • Single-dose oral medication taken at arrhythmia onset
   • Option for infrequent, well-tolerated episodes
   • Diltiazem/propranolol combination or flecainide

Special Considerations

Pregnancy

• Acute management:

  • Vagal maneuvers first
  • Adenosine if needed (safe in pregnancy)

• Chronic management: 1

  • Beta-blockers (metoprolol, propranolol)
  • Calcium channel blockers (verapamil)
  • Ablation with minimal radiation if drug-refractory

Wolff-Parkinson-White Syndrome

• Higher risk of sudden cardiac death
• Catheter ablation strongly recommended
• Avoid AV nodal blockers alone (may accelerate conduction through accessory pathway)

Wide-Complex SVT

• May represent SVT with aberrancy or pre-excitation
• If uncertain, treat as ventricular tachycardia 1
• Diagnostic features of SVT with aberrancy:
  • RS interval <100ms in precordial leads
  • AV dissociation absent
  • Typical BBB morphology

Pitfalls to Avoid

1. Misdiagnosing SVT as sinus tachycardia

   • Look for abrupt onset/offset and P wave morphology

2. Using verapamil/diltiazem in wide-complex tachycardias of uncertain origin

   • May cause hemodynamic collapse in VT 1

3. Failing to recognize pre-excitation

   • Delta waves may be subtle
   • Avoid AV nodal blockers alone in WPW

4. Overlooking underlying causes

   • Thyroid disease, anemia, infection, heart failure
   • Electrolyte abnormalities

5. Delaying referral for definitive treatment

   • Catheter ablation has high success and low complication rates
   • Should be considered early for symptomatic patients 5, 2

Shared decision-making is essential when determining the optimal management strategy, considering the patient's preferences, frequency of episodes, symptom severity, and quality of life impact 1.