Synchronized Cardioversion

Q: Synchronized electrical cardioversion is targeted to which part of the electrocardiogram (EKG) cycle? 

A) P wave
B) PR interval
C) QT interval
D) QRS complex
E) T wave


Answer: D


Cardiac cycle has a vulnerable and a refractory period. The refractory period is during the QRS complex, and the vulnerable period is during the T wave. Application of electrical cardioversion during vulnerable period may induce ventricular fibrillation.

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Reference:

Link, M. Arkins D. 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010, Volume 122, Issue 18 suppl 3 :: http://circ.ahajournals.org/content/122/18_suppl_3/S706.full#sec-24