Phrenic nerve stimulator, and system and method for monitoring phrenic nerve stimulation

A phrenic nerve pacing monitor assembly for a cryogenic balloon catheter system used during a cryoablation procedure, which monitors movement of a diaphragm of a patient, includes a pacing detector and a safety system. The pacing detector directly monitors movement of the diaphragm of the patient to detect when phrenic nerve pacing is occurring. Additionally, the pacing detector generates monitor output based on the movement of the diaphragm of the patient. The safety system receives the monitor output and based at least in part on the monitor output selectively provides an alert when movement of the diaphragm of the patient is atypical. The safety system is configured to provide the alert only while at least one of (i) phrenic nerve pacing is occurring, and (ii) cryoablation is occurring.