This case is about atrial tachycardia with cycle length variability originating from the vicinity of the sinus node and diagnostic pacing maneuvers to assess the tachycardia circuit were not achieved. Activation mapping revealed that the origin of atrial tachycardia was 15â¯mm away from the sinus node and the phrenic nerve was captured by pacing at the posterior portion of atrial tachycardia. A multipolar catheter was placed in the right brachiocephalic vein to capture the right phrenic nerve by pacing. The absence of phrenic nerve palsy was confirmed by palpation of constant diaphragmatic movement. The cryoablation could be safely and efficiently performed without ablation-induced injury of sinus node and phrenic nerve palsy by confirming constant diaphragmatic movement. The efficacy of cryoablation in the vicinity of the conduction system and phrenic nerve will be increasingly confirmed in the future. Learning Objective: Cryoablation for atrial tachycardia might be more safe and effective in terms of ablation-induced injury of conduction system and phrenic nerve palsy compared with conventional radiofrequency ablation when diagnostic pacing maneuvers are not able to estimate the circuit due to variability of tachycardia cycle length.
