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Tachycardia-Induced TachycardiaRUSSELL HEATH, M.D., WILLIAM H. SAUER, M.D., RYAN ALEONG, M.D.,

and DUY THAI NGUYEN, M.D.

From the Cardiac Electrophysiology, Cardiology Division, University of Colorado, Aurora, Colorado, USA

Clinical History

A 39-year-old woman with a nonischemic dilated car-diomyopathy was admitted for an exacerbation of congestiveheart failure. During her hospitalization, she had a witnessedcardiac arrest. Telemetry findings (Fig. 1) demonstrated abaseline normal sinus rhythm transitioning to atrial fibril-lation (AF) with rapid ventricular rates that subsequentlyinitiated polymorphous ventricular tachycardia (PMVT) anddegenerated into ventricular fibrillation. The same finding isnoted on the intracardiac electrogram from her single cham-ber defibrillator (Fig. 2). Normal sinus rhythm was restoredwith a shock by the patient’s internal defibrillator. Her AF

J Cardiovasc Electrophysiol, Vol. pp.3

No disclosures.

Address for correspondence: Duy Nguyen, M.D., Cardiac Electrophysiol-ogy, Cardiology Division, University of Colorado, 12401 E. 17th Ave., Lep-rino Building, 5th Floor, Mailstop B-132, Aurora, CO 80045-2548, USA.Fax: 720-848-0475; E-mail duy.t.nguyen@ucdenver.edu

doi: 10.1111/j.1540-8167.2012.02326.x

was more aggressively rate controlled to minimize the risksof further defibrillator shocks. It is a well-known electro-physiological phenomenon that arrhythmias can beget otherarrhythmias, such as supraventricular tachycardias initiatingAF. In this situation, an atrial arrhythmia induced a ventricu-lar arrhythmia. Ischemia caused by rapid AF is one possiblemechanism for the resulting PMVT. Another explanation isthat the irregularity of AF led to closely coupled ventriculardepolarizations falling into a vulnerable period (R on T), thusinitiating PMVT. Although AF is not typically considered alethal arrhythmia, clinicians should be aware of this abilityto initiate fatal arrhythmias.

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Figure 1. Telemetry tracing showed a baseline normal sinus rhythm with onset of atrial fibrillation with rapid ventricular rates (asterisk). Subsequently,polymorphous ventricular tachycardia (arrows) was initiated and then degenerated into ventricular fibrillation.

Heath et al. EP Image 3

Figure 2. Intracardiac electrogram tracing from the patient’s single chamber defibrillator showing normal sinus rhythm, then atrial fibrillation initiatingventricular tachycardia. Ventricular tachycardia degenerates to ventricular fibrillation, and sinus rhythm is restored with the second shock from thedefibrillator (noted as HV). Of note, 2 shocks are required to convert the patient to sinus rhythm.