Duodromic atrioventricular reentry tachycardia: a case report of a rare adenosine insensitive supraventricular tachycardia.

Background: Accessory pathways (AP) are associated with an increased risk of atrioventricular reentry tachycardia (AVRT), presenting as a wide QRS tachycardia if the mechanism is antidromic. Rarely, AVRT may not respond to adenosine, suggesting a duodromic mechanism if the patient has multiple APs. Herein, we present a case of a male patient with multiple APs, wide QRS complex tachycardia, and resistance to adenosine.

Case Presentation: A 45-year-old man with Wolff-Parkinson-White (WPW) syndrome was referred for AP ablation. He had previously been admitted with persistent palpitations and wide QRS tachycardia, which was resistant to adenosine. Electrophysiologic study revealed both right lateral and left lateral APs. Ablation successfully eliminated conduction through both pathways. Six months later, the patient remained asymptomatic but exhibited recurrence of pre-excitation on electrocardiogram, suggesting the presence of a third AP. A repeat electrophysiology study confirmed a posteroseptal AP, which was successfully ablated. The patient remained free of pre-excitation at follow-up.

Discussion: This case highlights the complexity of the diagnosis and treatment of wide QRS tachycardias in a patient with WPW. In this case, the failure to respond to adenosine was attributed to the use of a second AP as the retrograde limb of the AVRT circuit, a rare phenomenon known as duodromic AVRT. Successful identification and ablation of all APs was crucial in preventing recurrent arrhythmias, and rare mechanisms such as duodromic tachycardia should be considered when standard treatments fail.