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

Initial Treatment for Supraventricular Tachycardia (SVT)

The initial treatment for supraventricular tachycardia should be vagal maneuvers, particularly the Valsalva maneuver, performed with the patient in the supine position. 1

Treatment Algorithm for SVT

Step 1: Assess Hemodynamic Stability

• If patient is hemodynamically unstable (hypotension, altered mental status, shock, acute heart failure):
  • Proceed directly to synchronized cardioversion 1
• If patient is hemodynamically stable:
  • Proceed to Step 2

Step 2: Vagal Maneuvers (First-Line Treatment)

• Valsalva maneuver: Patient bears down against closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) while supine 1
• Carotid sinus massage: After confirming absence of carotid bruit, apply steady pressure over right or left carotid sinus for 5-10 seconds 1
• Modified Valsalva maneuver has shown superior efficacy compared to standard techniques 2
• Cold stimulus: Applying ice-cold wet towel to face (based on diving reflex) 1

Step 3: Pharmacological Treatment (If Vagal Maneuvers Fail)

• Adenosine (Class I, Level B-R recommendation):

  • First-line medication
  • Administered as rapid IV bolus
  • Terminates approximately 95% of AVNRT cases
  • Short half-life with transient side effects 1, 3

• IV calcium channel blockers (Class IIa, Level B-R):

  • Verapamil is highly effective for converting SVT to sinus rhythm
  • About 60% of SVT patients convert to normal sinus rhythm within 10 minutes 4
  • Only for hemodynamically stable patients
  • Contraindicated in patients with VT, pre-excited AF, severe heart failure 1

• IV beta blockers (Class IIa, Level B-R):

  • Alternative for hemodynamically stable patients
  • Particularly useful when calcium channel blockers are contraindicated 1

Step 4: Synchronized Cardioversion

• Indicated when:
  • Patient is hemodynamically unstable despite vagal maneuvers and adenosine
  • Pharmacological therapy fails or is contraindicated in stable patients 1

Important Considerations and Pitfalls

• Diagnostic value: Adenosine can help diagnose the mechanism of tachycardia by unmasking atrial activity in arrhythmias like atrial flutter 1

• Critical contraindications:

  • Avoid verapamil/diltiazem in patients with suspected ventricular tachycardia or pre-excited atrial fibrillation as they may cause hemodynamic compromise or accelerate ventricular rate 1
  • Avoid beta blockers in patients with severe conduction abnormalities or sinus node dysfunction 1

• Documentation: Record a 12-lead ECG before treatment to differentiate tachycardia mechanisms and determine if the AV node is an obligate component 1

• Recurrence risk: SVT may recur within minutes after successful conversion in some patients, particularly after adenosine due to its short half-life 3

• Eyeball pressure: The practice of applying pressure to the eyeball has been abandoned due to potential dangers 1

The evidence strongly supports vagal maneuvers as the initial approach for SVT treatment, with adenosine as the first pharmacological agent if vagal maneuvers fail. This approach maximizes the chance of successful conversion while minimizing risks associated with more invasive interventions.