An Endless Riddle of Wide Complex Tachycardia: Ventricular Tachycardia (VT) or Supraventricular Tachycardia (SVT)?

Wide complex tachycardia (WCT) presents a diagnostic challenge, particularly in distinguishing ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberrancy. We report an 81-year-old man with recurrent WCT initially suspected to be VT based on clinical and electrocardiographic features. However, inconsistencies across serial electrocardiographic tracings limited diagnostic certainty. Specifically, variations in polarity across all limb leads, except aVR and the precordial leads, raised suspicion for limb lead misplacement, particularly left arm-left leg reversal. This electrocardiographic perplexity further complicated the clinical interpretation. To clarify the underlying arrhythmia mechanism, an electrophysiology (EP) study was performed, which demonstrated inducible tachycardia with simultaneous atrioventricular activation (VA = 0), consistent with typical atrioventricular nodal reentrant tachycardia (AVNRT) with aberrancy. Successful slow pathway ablation rendered the arrhythmia noninducible, and the patient has remained free of recurrent arrhythmia during five months of follow-up. This case highlights the limitations of ECG-based algorithms and the importance of careful ECG interpretation and invasive evaluation.