Direct current cardioversion is not useful in unstable patients with which of the following arrhythmias?

Direct current cardioversion is not useful in unstable patients with which of the following arrhythmias?

• A. Supraventricular tachycardia in a patient with Wolff-Parkinson-White syndrome
• B. Atrial flutter
• C. Multifocal atrial tachycardia
• D. New-onset atrial fibrillation

Answer: (C)

Direct current cardioversion works best when a tachyarrhythmia is driven by a single, resettable circuit, so a synchronized shock can abruptly restore normal rhythm and improve perfusion. Atrial fibrillation, atrial flutter, and many SVTs in an unstable patient fit that scenario because one strong reentrant mechanism or a dominant focus can be terminated with a shock. Mult focal atrial tachycardia is different: it comes from multiple atrial foci, producing several distinct P-wave morphologies and an irregular rhythm. There isn’t a single circuit to “reset,” so a shock rarely converts MAT to sinus rhythm. In unstable MAT, the priority is to stabilize the patient and address underlying causes (such as hypoxemia, electrolyte disturbances, or COPD), and to manage rate, rather than attempting cardioversion. Hence, MAT in the unstable patient is not a useful target for direct current cardioversion.

Direct current cardioversion works best when a tachyarrhythmia is driven by a single, resettable circuit, so a synchronized shock can abruptly restore normal rhythm and improve perfusion. Atrial fibrillation, atrial flutter, and many SVTs in an unstable patient fit that scenario because one strong reentrant mechanism or a dominant focus can be terminated with a shock.

Mult focal atrial tachycardia is different: it comes from multiple atrial foci, producing several distinct P-wave morphologies and an irregular rhythm. There isn’t a single circuit to “reset,” so a shock rarely converts MAT to sinus rhythm. In unstable MAT, the priority is to stabilize the patient and address underlying causes (such as hypoxemia, electrolyte disturbances, or COPD), and to manage rate, rather than attempting cardioversion. Hence, MAT in the unstable patient is not a useful target for direct current cardioversion.