New implications for the recurrence mechanism of an upper septal ventricular tachycardia: a case report

Background Verapamil-sensitive fascicular ventricular tachycardia (VT) is the most common type of idiopathic left ventricular tachycardia, and it is divided into three types. Upper septal ventricular tachycardia (US-VT) is likely in patients with prior episodes of left posterior fascicular (LPF)-VT ablation, however, little is known about the recurrence mechanism of US-VT. Case summary A 53-year-old man had an US-VT after two catheter ablation sessions for a common idiopathic LPF-VT. The US-VT was successfully treated by ablating the proximal site of the LPF without making any further branch or fascicular block. This successful ablation point corresponded completely with the earliest pre-systolic potential (P2) site of the LPF-VT during the 1st session of catheter ablation. Discussion An US-VT recurrence could occur if a critical slow conduction is not affected by the catheter ablation. This recurrence might be the result of changing the re-entrant circuit after damage to the LPF. In order to eliminate the LPF-VT and prevent an US-VT recurrence, the earliest P2 site should be investigated carefully and ablated sufficiently.