Fascicular Ventricular Tachycardia: An Electrophysiological Paradox.

We present a case of fascicular ventricular tachycardia (VT) in a 27-year-old man. Fascicular VT arises within the fascicles of the left bundle of His and is associated with right bundle branch block and axis deviation on ECG. Fascicular VT can often be mislabelled as a narrow-complex tachycardia due to the proximity of the arrhythmic origin to the normal conduction system, creating a widened, but not classically "broad," QRS complex, as occurred in our case. Our patient was resistant to adenosine but sensitive to verapamil, as is characteristic of fascicular VT owing to its origin in a macroscopic reentry circuit within the left bundle of His. Indeed, the patient developed recurrences of fascicular VT whenever verapamil doses were missed. Due to the potential for future hemodynamic instability and myocardial ischemia associated with VT, ablation was considered as a long-term management option for this patient. However, because of his high BMI and the associated theoretical reduction in efficacy, ablation was delayed until the patient achieved weight loss. Further research is needed to determine whether obesity affects ablation outcomes in fascicular VT.