What is the initial treatment for a 20-year-old patient with Supraventricular Tachycardia (SVT)?

Initial Treatment for Supraventricular Tachycardia (SVT) in a 20-Year-Old Patient

Vagal maneuvers should be the first-line treatment for a 20-year-old patient with SVT, followed by adenosine if vagal maneuvers fail, and synchronized cardioversion for hemodynamically unstable patients. 1, 2

First-Line Treatment: Vagal Maneuvers

• Perform vagal maneuvers with the patient in the supine position as the initial intervention to terminate SVT 1
• Recommended vagal maneuvers include:
  • Valsalva maneuver: Have the patient bear down against a closed glottis for 10-30 seconds (equivalent to 30-40 mmHg pressure) 1, 2
  • Carotid sinus massage: After confirming absence of carotid bruits, apply steady pressure over the right or left carotid sinus for 5-10 seconds 1
  • Cold stimulus: Apply an ice-cold, wet towel to the face 1, 2
• Success rates of vagal maneuvers range from 19.4% to 54.3%, with modified Valsalva maneuver showing higher success rates (43.7%) compared to standard Valsalva (24.2%) 3, 4
• Avoid applying pressure to the eyeball as this practice is dangerous and has been abandoned 1, 2

Second-Line Treatment: Adenosine

• If vagal maneuvers fail, adenosine is the recommended pharmacological treatment 1
• Administer adenosine as a rapid IV push through a large vein (e.g., antecubital) followed by a saline flush 1
• Initial dose: 6 mg IV push; if ineffective after 1-2 minutes, give 12 mg IV push 1
• Adenosine has a 78-96% success rate in terminating SVT due to AVNRT or AVRT 1, 2
• Side effects include chest discomfort, shortness of breath, and flushing, but are transient due to the drug's short half-life 1
• A defibrillator should be available when administering adenosine due to the possibility of initiating atrial fibrillation with rapid ventricular rates in patients with Wolff-Parkinson-White syndrome 1, 2

Third-Line Treatment: Other Pharmacological Options

• If adenosine is ineffective or contraindicated, consider:
  • Intravenous beta-blockers (metoprolol, propranolol) 1, 2
  • Calcium channel blockers (diltiazem, verapamil) 1, 2
• Avoid AV nodal blocking agents (verapamil, diltiazem, beta-blockers) in patients with suspected pre-excitation, as they may accelerate ventricular rate and lead to ventricular fibrillation 2

For Hemodynamically Unstable Patients

• Perform synchronized cardioversion immediately for hemodynamically unstable patients 1
• Initial energy for cardioversion of SVT: 50-100 J (biphasic) 1
• If initial shock fails, increase energy in a stepwise fashion 1

Special Considerations

• For pre-excited AF (in WPW syndrome):
  • Hemodynamically unstable: Immediate synchronized cardioversion 1, 2
  • Hemodynamically stable: Ibutilide or intravenous procainamide 1, 2
• Continuous ECG monitoring during treatment helps distinguish drug failure from successful termination with immediate arrhythmia reinitiation 1
• After successful conversion, monitor the patient for recurrence 1

Pitfalls to Avoid

• Never apply pressure to the eyeball as a vagal maneuver 1, 2
• Don't administer adenosine to patients with asthma 1
• Avoid calcium channel blockers and beta-blockers in patients with suspected pre-excited AF or ventricular tachycardia 2
• Ensure proper ECG diagnosis before treatment to distinguish SVT from ventricular tachycardia 2