Which is a first-line non-pharmacologic treatment for stable supraventricular tachycardia?

• A. IV adenosine (6-12 mg)
• B. Valsalva maneuver
• C. Cardioversion if unstable w/ pulse
• D. Bystander defibrillation

Answer: (B)

For stable supraventricular tachycardia, the first-line nonpharmacologic approach is a vagal maneuver, with the Valsalva maneuver being the classic example. This technique boosts parasympathetic tone to the AV node, slowing conduction and sometimes interrupting the reentrant circuit that drives the tachycardia. Mechanically, bearing down or straining for about 10–15 seconds transiently changes intrathoracic pressure and cardiac venous return, and when the maneuver ends, a reflex surge in vagal activity can reset the rhythm. If it succeeds, the heart returns to normal sinus rhythm without medications. If it fails, the next step is pharmacologic therapy with adenosine, which rapidly slows AV nodal conduction to terminate many SVTs. If the patient is unstable—showing poor perfusion, chest pain, or altered mental status—synchronized cardioversion is indicated rather than attempting vagal maneuvers. Bystander defibrillation is reserved for pulseless cardiac arrest scenarios and not for stable SVT.