The Practice of Catheter Cryoablation for Cardiac Arrhythmias

Case 6.2. Prevention of phrenic nerve palsy during cryoballoon ablation for atrial fibrillation

A 54-year-old woman underwent pulmonary vein isolation using cryoballoon ablation for symptomatic paroxysmal atrial fibrillation. During the ablation of the right-sided pulmonary veins, the phrenic nerve function was monitored by pacing the nerve from the superior vena cava at 10 mV at 1 ms and palpating the diaphragmatic exertion. Twenty seconds into the ablation of the right inferior pulmonary vein, the exertion of the diaphragm became weaker. (See also Video Clip 6.1.)

• 1. What is the next best step – continue ablation until the diaphragmatic excretions stop, reposition the pacing catheter as it most likely dislodged, increase the pacing current to 20 mV at 1 ms, or immediately terminate ablation and assess antral position of the balloon?

  Show Answer

  Correct answer: Immediately terminate ablation and assess antral position of the balloon.
  Ablation should be terminated immediately at any signs of phrenic nerve injury. Early diagnosis of phrenic nerve palsy and immediate termination of ablation are essential to prevent prolonged or permanent phrenic nerve palsy. Assuming that the catheter has moved can delay the diagnosis. It is safer to stop the ablation and reassess the position of the balloon and the pacing catheter. A more antral position of the balloon can reduce the chance of phrenic nerve injury.