Adenosine for Regular Wide-Complex Tachycardia

Interesting article I came across in "Journal Watch";

Adenosine is safe and effective for differentiating wide-complex supraventricular tachycardia from ventricular tachycardia.

Distinguishing ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy (preexisting bundle branch block or rate-related aberration in intraventricular conduction) is a dilemma in the management of regular wide-complex tachycardia. Historically, some clinicians have been reluctant to use adenosine in this setting, because of fear of degeneration of VT to fibrillation or promotion of rapid conduction through an accessory tract. To assess the safety and efficacy of adenosine in regular wide-complex tachycardia of unknown etiology, these authors reviewed patient records at nine U.S. medical centers from 1991 to 2006.

Case ascertainment criteria varied among centers. The main outcome was response to adenosine (slowing of rate sufficient to make a diagnosis or conversion to sinus rhythm). Nonresponders who did not receive a dose of at least 12 mg were excluded. The underlying rhythm was unknown at the time of adenosine administration and was determined retrospectively by the researchers, based on all available information. Of 116 patients with an ultimate diagnosis of SVT, 104 (90%) responded to adenosine; in contrast, 2 of 81 patients (2%) with an ultimate diagnosis of VT responded. No serious adverse effects from adenosine were documented. Two patients had histories of Wolff-Parkinson-White syndrome, but in no case was an atrioventricular nodal accessory tract determined to be the etiology of the tachycardia.

Comment: Regular wide-complex tachycardia is most often either VT or aberrantly conducted SVT, and this study confirms that adenosine is not harmful in either case. Rarely, antidromic conduction through an accessory pathway (e.g., Wolff-Parkinson-White syndrome) is involved, and traditional teaching is that adenosine is harmful in such cases. Because none of the patients in this study had arrhythmias caused by an accessory tract, the results cannot prove that adenosine is safe in such patients. When an accessory pathway is known or suspected in a patient with regular wide-complex tachycardia, we should exercise caution about using adenosine.

— Daniel J. Pallin, MD, MPH

Underwriting "Term Du Jour": WPW-Wolff Parkinson White Syndrome

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