Differentiating between SVT with aberrancy versus VT can be very difficult. It is crucial to be able to make this distinction as therapeutic decisions are anchored to this differentiation. In our case according to Brugada’s algorithm, we note an Rs complex, there is no AV dissociation, in V1 lead there is no monophasic R wave or qR wave and in V6 lead R/S > 1 (fig1).
All these criteria argue in favor of SVT with aberrancy. The narrow QRS in tachycardia is unlikely a ventricular capture beat in the absence of AV dissociation (fig1). The tachycardia terminates in AV node producing a retrograde P wave at the end of the arrhythmia run which is against the diagnosis of atrial tachycardia (fig2).
Finely the long RP interval > 80ms more often pleads in favor of an AVRT utilizing a concealed accessory pathway without formally eliminating an atypical AVNRT. The electrophysiologic investigation confirm the diagnosis of AVRT utilizing a concealed accessory pathway with aberrancy by delivering a ventricular premature extra stimulus at a time when His is refractory during the tachycardia which advances A and terminates tachycardia (fig3)