An alternative method for phrenic nerve monitoring during cryoballoon procedures

Background Cryoballoon ablation is associated with a consistent risk of phrenic nerve (PN) damage. Abdominal palpation associated with other strategies such as the diaphragmatic compound motor action potential (CMAP) has been shown to be an effective and reliable method for preventing this complication. Objective The purpose of this study was to evaluate the diagnostic performance of a new surface CMAP electrodes positioning. Methods A total of 150 patients underwent cryoballoon ablation. During the procedure, we placed the CMAP leads per the manufacturer's instructions and our alternative method, named NeedMAP, by placing electrocardiographic electrodes on the anterior axillary line. We simultaneously recorded the CMAP and the NeedMAP. CMAP monitoring with a 35% decrease cutoff for the diagnosis of nerve threatening was considered the gold standard. The NeedMAP decrease threshold also was set at 35%. Results A total of 438 cryoballoon applications were performed on the right pulmonary veins. Mean CMAP amplitude was 0.60 +/- 0.33 mV compared to NeedMAP amplitude 0.85 +/- 0.46 mV (P <.001). Among the 150 patients, 15 (10%) showed a nerve threat. In our population, the CMAP with regard to nerve damage had sensitivity of 38%, specificity 76%, negative predictive value (NPV) 89%, and positive predictive value (PPV) 19%. The NeedMAP showed sensitivity of 61%, specificity 86%, NPV 93%, and PPV 40%. Conclusion The NeedMAP signal for PN monitoring during cryoballoon ablation seems to be a reliable method, shows good sensitivity and specificity, and can help clinicians in preventing PN damage.