What is the workup for supraventricular tachycardia (SVT)?

Workup for Supraventricular Tachycardia (SVT)

The workup for supraventricular tachycardia should begin with a 12-lead ECG during tachycardia and during sinus rhythm to identify the arrhythmia mechanism, followed by appropriate diagnostic testing based on the suspected type of SVT. 1

Initial Assessment

• Obtain a 12-lead ECG during tachycardia and during sinus rhythm to potentially identify the etiology of tachycardia 1
• For patients with prior symptoms but not currently in tachycardia, a resting ECG can identify pre-excitation that should prompt referral to a cardiac electrophysiologist 1
• Assess hemodynamic stability, as this will guide immediate management decisions 1

ECG Analysis During Tachycardia

Step 1: Determine QRS Duration

• QRS duration <120 ms suggests SVT 1
• QRS duration >120 ms may represent either ventricular tachycardia (VT) or SVT with abnormal conduction 1

Step 2: For Wide-Complex Tachycardia, Rule Out VT

• Look for AV dissociation (ventricular rate faster than atrial rate) or fusion complexes, which indicate VT 1
• Assess QRS morphology using criteria such as Brugada criteria or Vereckei algorithm 1
• Concordance of precordial QRS complexes (all positive or all negative) suggests VT or pre-excitation 1

Step 3: For Narrow-Complex Tachycardia, Assess Regularity

• Regular ventricular rate suggests AVNRT, AVRT, or atrial tachycardia with 1:1 conduction 1
• Irregular ventricular rate suggests atrial fibrillation, multifocal atrial tachycardia, or atrial flutter with variable AV conduction 1

Step 4: Identify P Waves and Their Relationship to QRS

• If atrial rate exceeds ventricular rate, consider atrial flutter or atrial tachycardia 1
• For regular SVT with 1:1 AV relationship, analyze the RP interval 1:
  • Short RP interval (RP < PR): Typical AVNRT or AVRT 1
  • RP < 90 ms: Typical AVNRT 1
  • RP > PR: Atypical AVNRT, atrial tachycardia, or PJRT (permanent form of junctional reciprocating tachycardia) 1

Additional Diagnostic Testing

• For patients with intermittent symptoms and normal resting ECG, extended cardiac monitoring may be necessary 2:
  • 24-hour Holter monitoring for frequent episodes 1
  • Event recorder for less frequent episodes 2
• Echocardiogram to assess for structural heart disease, ventricular function, and congenital abnormalities 1
• Laboratory tests to rule out secondary causes of tachycardia (thyroid function, electrolytes, etc.) 2

Special Considerations

• In patients with pre-excitation on resting ECG, referral to electrophysiology is indicated even without documented tachycardia 1
• For complex ventricular arrhythmias that may mimic SVT, 24-hour Holter monitoring is recommended 1
• In infants and children, SVT typically presents with heart rates of 260-300 bpm, and P waves are visible in 60% of cases 1

Pitfalls to Avoid

• Misdiagnosing VT as SVT with aberrancy can lead to inappropriate treatment and potentially life-threatening outcomes 1
• Atrial fibrillation with rapid ventricular response may appear regular and be misdiagnosed as a regular SVT 1
• Administering verapamil or diltiazem for treatment of VT or pre-excited atrial fibrillation can lead to hemodynamic compromise or accelerate the ventricular rate 1
• Failure to identify pre-excitation patterns on resting ECG in patients with palpitations but no active tachycardia 1

Diagnostic Algorithm

1. Obtain 12-lead ECG during tachycardia if possible 1
2. Determine if QRS is narrow (<120 ms) or wide (>120 ms) 1
3. For narrow QRS:
   • Regular rhythm: Analyze P wave relationship to QRS 1
   • Irregular rhythm: Consider atrial fibrillation, atrial flutter with variable conduction, or MAT 1
4. For wide QRS:
   • Apply criteria to differentiate VT from SVT with aberrancy 1
   • Look for AV dissociation, fusion beats, or concordance in precordial leads 1
5. If diagnosis remains unclear, consider vagal maneuvers or adenosine during continuous ECG recording to help reveal the underlying mechanism 1, 2
6. For recurrent but undocumented symptoms, use appropriate monitoring strategy 2
7. Consider echocardiogram to evaluate for structural heart disease 1

Following this systematic approach will help identify the specific type of SVT and guide appropriate management decisions.