A new method of superior vena cava isolation without phrenic nerve injury by longitudinal ablation parallel to the phrenic nerve: a case report

BACKGROUND: Superior vena cava (SVC) isolation has improved the outcomes of paroxysmal atrial fibrillation (AF) originating from the SVC. However, right phrenic nerve (PN) injury is a major complication of this procedure. Therefore, in cases where the right atrium (RA)-SVC conduction site is near the PN, tremendous care is required to prevent PN injury. CASE SUMMARY: Repeated SVC isolation was performed due to the recurrence of SVC-triggered AF. The RA-SVC activation map revealed that the partial conduction block line was detected, and the propagation broke through the gap at the course of the PN site from the RA to the SVC. Since the course of the PN identified at high-output pacing was wide, the SVC was isolated by making longitudinal lines on both sides of the PN in a cranial direction, except for where low-output pacing captured, confirming compound muscle action potential to detect PN injury. Eventually, the SVC was successfully isolated without PN injury, and the sinus rhythm was maintained without antiarrhythmic drugs during a 14-month follow-up period. CONCLUSION: Superior vena cava isolation was difficult depending on the course of the PN, and some methods to avoid PN injury were reported. However, this method can facilitate safe and effective SVC isolation with the conventional system, including the cases with AF foci located on the course of the PN.