Pulsed field ablation of a focal atrial tachycardia from the superior vena cava in proximity to the phrenic nerve: a case report.

Background: Right phrenic nerve (PN) injury is a major complication of thermal ablation of atrial tachycardias (ATs) originated from the superior vena cava (SVC). Case summary: We report the case of a 41-year-old female patient admitted for catheter ablation of a frequent paroxysmal AT resistant to antiarrhythmic drugs. Electroanatomical activation map demonstrated a focal origin located at the lateral aspect of the SVC, ∼17 mm above the breakthrough of the sinus node wavefront. Importantly, high-output pacing from this site resulted in PN capture. To avoid PN injury, low-output radiofrequency (RF) ablation, with a power output limited to 20 W, was performed. However, this approach was insufficient to terminate AT. High-power RF applications in proximity to the PN were avoided and pulsed-field ablation (PFA) with a pentaspline catheter was chosen. The catheter was advanced into the SVC to the level of the earliest activation under fluoroscopic guidance and visualization within the mapping system. Two pairs of applications, in basket configuration, were delivered inside the SVC, rendering AT non-inducible while sinus node function was not compromised. Discussion: Phrenic nerve is vulnerable to injury during ablation within the SVC using thermal ablation modalities. Low-output RF ablation may be safe but less efficient. In contrast, non-thermal approaches such as PFA may be preferable to avoid damage to the collateral tissues as PN. Electroanatomical mapping may be important to avoid lesions in proximity to the sinus node.