## Why Vagal maneuvers (Valsalva with supine positioning and leg elevation) is right Vagal maneuvers are the FIRST-LINE acute management for hemodynamically stable AVNRT. The modified Valsalva maneuver (supine position with leg elevation post-strain, per the REVERT trial) has the highest success rate and should be attempted before pharmacological intervention. This directly reflects the clinical anchor: AVNRT terminates abruptly with vagal maneuvers or adenosine, and vagal maneuvers are the initial step in stable patients. (Harrison 21e, Ch 247) ## Why each distractor is wrong - **Intravenous adenosine 6 mg bolus via large-bore IV with flush**: While adenosine is highly effective for AVNRT termination and is the second-line agent when vagal maneuvers fail, it is NOT first-line. Adenosine carries risks (transient flushing, chest discomfort, brief asystole, bronchospasm) and should be reserved for when vagal maneuvers have been attempted and failed. - **Synchronized electrical cardioversion at 50–100 J**: Cardioversion is reserved for hemodynamically UNSTABLE patients or those in whom pharmacological/vagal approaches have failed. This patient is stable and conscious, making cardioversion inappropriate as first-line therapy. - **Intravenous verapamil 5 mg over 2 minutes**: IV verapamil is a third-line agent, used only when adenosine has failed or is contraindicated. It is not first-line management in stable AVNRT. **High-Yield:** AVNRT = sudden onset + sudden termination; stable patient = vagal maneuvers first → adenosine → IV CCB/beta-blocker; unstable = cardioversion. [cite: Harrison 21e, Ch 247 — Supraventricular Tachycardia]
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