1302 Ablation Success, Breathing Distress: Hypoventilation Due to Phrenic Nerve Injury Post Cardiac Ablation

Abstract Introduction Catheter ablation is recommended for patients with persistent or paroxysmal atrial fibrillation (AF) who are refractory or intolerant to antiarrhythmic medication, with evidence supporting reduction in mortality, heart failure and stroke. Phrenic nerve injury (PNI) occurs in 0.2-4.2% of AF ablations and may lead to diaphragmatic paralysis. We report the case of a patient who after undergoing radiofrequency cardiac ablation developed PNI-related hypoventilation, which required support with noninvasive ventilation (NIV) until resolution, highlighting the importance of coordination between cardiology, pulmonary and sleep medicine. Report of case(s) A 62-year-old woman experienced abrupt onset of dyspnea following a pulmonary vein isolation radiofrequency cardiac ablation for persistent AF after failed cardioversion and intolerance to rate-control medication. Post-procedure chest x-ray demonstrated right hemi-diaphragm elevation and follow up with fluoroscopy/sniff test noted paradoxical movement of the right hemi-diaphragm confirming paralysis. Post discharge in respiratory failure clinic, pulmonary function tests noted vital capacity of 51% of predicted, with a significant 25% decrease in vital capacity with change from upright to supine position. Nocturnal oximetry was suggestive of sleep disordered breathing. Previous sleep study prior to injury was negative for sleep apnea. Due to concern for hypoventilation likely secondary to phrenic nerve injury, surgical intervention (with plication or diaphragmatic pacing) was discussed but not elected. Thus, noninvasive mechanical ventilation was initiated. Over six months, patient’s vital capacity significantly improved to 81% and repeat sniff test demonstrated resolution of diaphragmatic paralysis. Treatment with NIV was subsequently discontinued. Conclusion While phrenic nerve injury following AF ablation is often reversible with varying durations of recovery dependent on mode of ablation, it is important to evaluate patients for presence of hypoventilation as they may require support with NIV while awaiting recovery of diaphragm function. Sleep physicians and pulmonologists play a key role in recognizing this complication, initiating and managing NIV and understanding the natural course of recovery. Support (if any)