Fascicular Tachycardia: The Great Masquerader

Abstract

SESSION TITLE: Cardiovascular Disease SESSION TYPE: Affiliate Case Report Poster PRESENTED ON: Tuesday, October 31, 2017 at 01:30 PM - 02:30 PM INTRODUCTION: Hemodynamically stable tachycardia in a young seemingly healthy individual is generally assumed to be supraventricular in origin. However there is a type of ventricular tachycardia (VT) that has a relatively narrow complex that presents in young healthy individuals and is frequently misdiagnosed as supraventricular ventricular tachycardia (SVT). We present such a case and demonstrate the consequence of delayed diagnosis. CASE PRESENTATION: Our case is a 39 year old male with no past medical history who presented to our emergency department with one day of palpitations and diaphoresis. He first noted these symptoms in adolescence, which were of shorter duration and therefore medical attention was never sought. On arrival to our institution the patient was hemodynamically stable on presentation with an unremarkable physical exam other than a pulse rate of 200 bpm with an EKG showing wide complex tachycardia (figure 1). In addition his blood chemistries were all within normal limits. Despite receiving multiple rounds of adenosine (6mg, 12mg, 12mg) followed by electrical cardioversion, patient remained in wide complex tachycardia. Patient was then given Diltiazem 20mg IVP, which resulted in conversion to normal sinus rhythm (figure 2). Closer investigation of the presenting ECG revealed a leftward (northwest) axis and an incomplete RBBB pattern with RSR’ complexes, a finding highly specific for ventricular tachycardia (VT). An Echocardiogram at our institution revealed no structural heart disease with normal ventricular systolic function. Patient was taken for further electrophysiological testing which confirmed Left Fascicular VT. Patient underwent radiofrequency catheter ablation without any complications. DISCUSSION: Fascicular tachycardia typically originates in the region of the left posterior fascicle and has a RBBB, left superior axis morphology and AV disassociation. In most, a resting EKG is normal and there is no evidence of structural heart disease evidenced by echocardiography and coronary angiography. The narrow QRS complex (typically 0.12 to 0.14 sec) morphology distinguishes fascicular VT from most VTs, but it also resembles SVT frequently leading to misdiagnosis. CONCLUSIONS: Our goal is to help clinicians, especially those who first encounter patients’ with this presentation, be cognizant about the subtle important features of fascicular tachycardia. When it comes to wide complex tachyarrhythmias’ clinicians often have a sense of uneasiness, further clouding their clinical judgment. It is therefore imperative to recognize cases of Idiopathic VT, precisely fascicular tachycardia so they can be differentiated from svt and treated appropriately. Reference #1: Brooks R, Burgess JH. Idiopathic ventricular tachycardia. A review. Medicine (Baltimore) 1988; 67:271. Reference #2: Belhassen B, Viskin S. Idiopathic ventricular tachycardia and fibrillation. J Cardiovasc Electrophysiol 1993; 4:356. DISCLOSURE: The following authors have nothing to disclose: Shahab Khan, Ravi Mann, Fawzi Ameer, David Slotwiner No Product/Research Disclosure Information