Wide Complex Tachycardia on Telemetry

A 76-year-old woman with a history of hypertension, diabetes mellitus, dilated nonischemic cardiomyopathy (ejection fraction of 35%), and normal pressure hydrocephalus for which she had received a ventriculoperitoneal shunt 5 years ago was found unresponsive at home. She was intubated for airway protection in the field and was admitted to an outside hospital where an extensive neurological workup did not reveal the cause of her unconsciousness. She was transferred to our hospital to evaluate a potential cardiac etiology for her symptoms. On admission, she was noted to have an incessant wide complex tachycardia at a rate of ≈230 beats per minute on telemetry (Figure 1A and 1B). What is the most likely diagnosis, and what is the cause for the intermittent pauses during tachycardia?Please turn the page to read the diagnosis.Figure 1. Telemetry strip showing a wide complex tachycardia. A and B show a wide complex tachycardia at a rate of ≈230 beats per minute with intermittent pauses.Differential diagnosis of this wide complex tachycardia included supraventricular tachycardia with aberrancy (functional or preexisting bundle-branch block), preexcited tachycardia (antidromic tachycardia …