A 58-year-old man with acute inferior STEMI undergoes successful primary PCI to the right coronary artery. Within 30 minutes of reperfusion, the monitor shows a regular wide-complex rhythm at 75 bpm with AV dissociation and fusion beats at the onset. The structure marked **B** in the diagram is identified. The patient is hemodynamically stable with normal blood pressure and adequate perfusion. Which of the following is the most appropriate management?
A. IV atropine 0.5–1 mg to increase the sinus rate and restore sinus capture
B. Observation without antiarrhythmic therapy, as the rhythm is self-limiting and hemodynamically tolerated
C. Immediate IV amiodarone 150 mg bolus to suppress the ventricular focus
D. IV lidocaine 1.5 mg/kg to prevent degeneration to ventricular fibrillation
Explanation
Why "Observation without antiarrhythmic therapy, as the rhythm is self-limiting and hemodynamically tolerated" is right
The structure marked B is accelerated idioventricular rhythm (AIVR), the quintessential reperfusion arrhythmia occurring in up to 50% of patients after successful coronary reperfusion. AIVR is characterized by a regular wide-complex rhythm at 50–110 bpm with AV dissociation and fusion/capture beats, arising from enhanced automaticity of a subsidiary ventricular pacemaker. Critically, AIVR is hemodynamically stable, self-limiting, and does NOT independently predict malignant arrhythmia or mortality. It is a useful bedside clue to successful reperfusion. Management is observation without antiarrhythmic therapy because: (1) the rhythm is transient and resolves as the sinus rate accelerates, (2) it is well tolerated, and (3) suppressing AIVR with antiarrhythmics risks removing the only effective ventricular pacemaker if concurrent AV block or sinus arrest develops, potentially leading to asystole. (Harrison 21e Ch 269; Braunwald 12e)
Why each distractor is wrong
Immediate IV amiodarone 150 mg bolus to suppress the ventricular focus: Antiarrhythmic suppression of AIVR is contraindicated in the stable, hemodynamically tolerated setting because AIVR may be the only effective pacemaker if AV block or sinus arrest occurs. Amiodarone risks asystole without improving outcomes.
IV lidocaine 1.5 mg/kg to prevent degeneration to ventricular fibrillation: AIVR is NOT a marker of impending VF and does not independently predict malignant arrhythmia. Prophylactic lidocaine is unnecessary and carries the same risk of removing a vital escape rhythm.
IV atropine 0.5–1 mg to increase the sinus rate and restore sinus capture: Atropine is reserved only for hemodynamically poorly tolerated AIVR (e.g., in restrictive cardiomyopathy or severe LV dysfunction with loss of AV synchrony). In this stable patient, observation is preferred; atropine is not first-line.
High-YieldNEET PG
AIVR post-reperfusion = observe, do not suppress; it is a reassuring sign of successful reperfusion, not a harbinger of VF.
Harrison 21e Ch 269; Braunwald 12e
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