Proarrhythmia in Patients with the Wolff-Parkinson-White Syndrome after Standard Doses of Intravenous Adenosine

Adenosine, an endogenous nucleoside, has various effects on the heart and cardiovascular system [1]. Its actions on the heart's conduction system and its ability to terminate re-entrant supraventricular arrhythmias involving the atrioventricular node have been well described [1, 2]. The use of adenosine in the diagnosis and treatment of tachycardias that are not clearly of ventricular origin is now commonplace in many North American emergency departments. Adenosine is considered a safe diagnostic tool for distinguishing between regular wide-complex tachycardias (ventricular compared with aberrant supraventricular), including those seen in the setting of ventricular pre-excitation (the Wolff-Parkinson-White syndrome) [3].

Electrophysiologic studies [3, 4] in patients with the Wolff-Parkinson-White syndrome have suggested that the risk that adenosine will cause hemodynamic compromise or that atrial flutter or atrial fibrillation will convert to ventricular fibrillation is small. We describe two patients with the Wolff-Parkinson-White syndrome who had hemodynamically unstable proarrhythmia after the administration of standard doses of adenosine.