Adenosine-Sensitive Wide-Complex Tachycardia: An Uncommon Variant of Idiopathic Fascicular Ventricular Tachycardia

Abstract

Most wide-complex tachycardias encountered in the emergency department (ED) are ventric ular in origin, most commonly associated with structural heart disease. Ventricular tach yarrhythmias range in severity from life-threatening rhythms (eg, ventricular fibrillation and hemodynamically compromising ventricular tachycardia [VT]) to idiopathic forms of VT, which have a benign clinical course and a more favorable prognosis. The authors present the case of a 34-year-old woman who presented to the ED, with a wide-complex tachycardia with a right- bundle-branch block (RBBB) morphology and a right inferior axis, which was terminated with adenosine. The patient was previously misdiagnosed as suffering from a paroxysmal supraven tricular tachycardia (SVT), which was unresponsive to beta-blocker therapy. Although the tachycardia responded to adenosine, suggestive of an SVT, the patient was referred to the arrhythmia service, where further work-up revealed an uncommon form of an idiopathic VT, originating from the left anterior fascicle. The authors discuss the unique electrocardiographic and electrophysiologic properties and useful diagnostic maneuvers required to properly identify this form of VT.