Background
Differentiating ventricular tachycardia (VT) from antidromic atrioventricular reentrant tachycardia (AVRT) in patients with documented wide-complex tachycardia remains a diagnostic challenge. Antidromic AVRT conducted through a left-sided accessory pathway is particularly prone to being misidentified as VT when conventional ECG algorithms such as the Basel or Brugada criteria are applied. Such misclassification may lead to significant therapeutic consequences. In these situations, an electrophysiological study (EPS) may be a valuable tool for accurate diagnosis and therapy.
Case Presentation
A 24-year-old man without any history of heart disease presented with a wide-complex tachycardia (heart rate 210 bpm, QRS duration 200 ms) accompanied by hypotension and dizziness. Based on the Basel and Brugada algorithms, the 12-lead ECG met criteria consistent with ventricular tachycardia (VT). Intravenous amiodarone was therefore administered, leading to termination of the tachycardia. Subsequent diagnostic evaluation, including echocardiography and cardiac magnetic resonance imaging, revealed no structural abnormalities; however, a preexcitation pattern was suspected on the resting ECG. During the electrophysiological study, a left lateral accessory pathway with both antegrade and retrograde conduction was identified. Programmed atrial stimulation induced the clinical tachycardia, which was confirmed to represent an antidromic atrioventricular reentrant tachycardia (AVRT). Targeted radiofrequency ablation resulted in permanent conduction block across the accessory pathway. The previously initiated wearable cardioverter-defibrillator therapy was discontinued, and the patient was discharged the following day in good condition.
Conclusion
This case highlights the limitations of conventional ECG algorithms in distinguishing wide-complex tachycardias and emphasizes the pivotal role of electrophysiological studies in establishing the correct diagnosis. Particularly in young patients without structural heart disease who present with a wide-complex tachycardia, antidromic AVRT should be considered even when the ECG appears consistent with VT. In such cases, invasive electrophysiological evaluation not only enables definitive diagnosis but also offers the possibility of curative treatment through catheter ablation of the accessory pathway.
