Original Article

The creation of circumferential lesions to electrically isolate pulmonary veins (PVs) by means of a cryoballoon catheter has emerged as an effective alternative approach to conventional point-by-point radiofrequency ablation in patients with atrial fibril-lation (AF).1–3 Phrenic nerve palsy (PNP) with hemidiaphragmatic paralysis is the most frequently observed complication with cryo-balloon ablation, occurring in ≈6 % of clinical procedures (range, 3%–11%).2,4,5 The most commonly used preventative measure is the use of continuous abdominal palpation during phrenic nerve pacing from a catheter placed in the superior vena cava cranial to the right-sided PVs. However, despite early interruption of ablation with the perceived onset of less vigorous diaphragmatic contractions, PNP continues to be observed. Although alterna-tive monitoring techniques, such as continuous diaphragmatic visualization and auditory monitoring of diaphragmatic contrac-tion have been proposed, the use of diaphragmatic electromyogra-phy represents a potentially more sensitive technique for detecting early changes to the phrenic nerve.4,6 During phrenic nerve pac-ing a reliable diaphragmatic signal (the diaphragmatic compound motor action potential [CMAP]) can be easily recorded using surface electrodes, providing valuable information about phrenic nerve function. In a recent preclinical studies, we demonstrated that a 30 % reduction in diaphragmatic CMAP amplitude pre-saged impending hemidiaphragmatic paralysis by ≈30 seconds.4,6 Herein, we characterize our clinical experience using diaphrag-matic electromyographic monitoring for the prevention of PNP