Positioning an ECG electrode to the dorsal side can record higher amplitude of CMAPs during cryoballoon ablation

Abstract

Purpose: Phrenic nerve injury (PNI) is one of the important complications during cryoballoon (CB) ablation. Recording diaphragmatic compound motor action potentials (CMAPs) during CB ablation can predict PNI. CMAP monitoring may be inaccurate when CMAP amplitudes are low. We examined the effect of positioning an electrocardiography (ECG) electrode at the dorsal side. Methods: We retrospectively analyzed the cases of 197 consecutive patients who underwent CB ablation for pulmonary vein isolation (PVI) (April 2016 to December 2018) at our institution. CMAP amplitudes were monitored using two recording methods just before cryoapplication. (a) Conventional method: right-arm ECG electrode positioned 5 cm above the xiphoid on the ventral side; left-arm ECG electrode positioned along the costal margin. (b) Our original method: right-arm electrode positioned 5 cm above the xiphoid on the dorsal side; left-arm electrode positioned along the costal margin. Results: The CMAP amplitude during right phrenic nerve pacing was significantly higher at the dorsal side than the ventral side (0.80 ± 0.31 mV vs 0.66 ± 0.29 mV, P