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

Initial Treatment for Supraventricular Tachycardia (SVT) Using Vagal Maneuvers

Vagal maneuvers, particularly the modified Valsalva maneuver, should be the first-line intervention for acute treatment of hemodynamically stable patients with supraventricular tachycardia (SVT). 1, 2

Proper Technique for Vagal Maneuvers

• The modified Valsalva maneuver is 2.8-3.8 times more effective than standard Valsalva techniques and should be performed as follows: 2, 3

  • Patient should be in the supine position 1
  • Patient raises intrathoracic pressure by bearing down against a closed glottis for 10-30 seconds 1
  • Pressure should be equivalent to at least 30-40 mmHg 1, 2
  • For the modified technique, immediately after the strain, the patient is laid flat and their legs are raised to increase venous return 2, 4

• Alternative vagal maneuvers include: 1

  • Carotid sinus massage (less effective than Valsalva techniques) - performed after confirming absence of carotid bruits by auscultation, applying steady pressure over the right or left carotid sinus for 5-10 seconds 1, 3
  • Applying an ice-cold, wet towel to the face (based on the diving reflex) 1

Treatment Algorithm for SVT

1. First-line: Modified Valsalva maneuver - overall success rate around 27.7% for standard techniques, but significantly higher (up to 43%) with the modified technique 1, 2, 3

2. Second-line (if vagal maneuvers fail): Adenosine 1, 2

   • Terminates AVNRT in approximately 95% of patients 1
   • Should be administered via proximal IV as a rapid bolus followed by saline flush 1
   • Brief side effects (chest discomfort, shortness of breath, flushing) are common but serious adverse effects are rare due to very short half-life 1, 5

3. Third-line options for hemodynamically stable patients: 1

   • IV beta blockers, diltiazem, or verapamil 1
   • Success rates of 80-98% for agents such as verapamil, diltiazem, or adenosine 1

4. For hemodynamically unstable patients or when medications fail: 1

   • Synchronized cardioversion 1

Important Clinical Considerations

• Vagal maneuvers are most effective for SVTs that involve the AV node as a requisite component of a reentrant circuit (AVNRT, AVRT) 2

• Ensure the rhythm is not ventricular tachycardia or pre-excited atrial fibrillation before attempting vagal maneuvers or administering AV nodal blocking agents 2

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

• Continuous ECG recording during treatment attempts helps distinguish between drug failure and successful termination with immediate arrhythmia reinitiation 1

• Patients often have atrial or ventricular premature complexes immediately after conversion that may induce further episodes of SVT, sometimes requiring antiarrhythmic drugs to prevent acute reinitiation 1