Clinical Experience with a Novel Electromyographic Approach to Preventing Phrenic Nerve Injury during Cryoballoon Ablation in Atrial Fibrillation
Background—Phrenic nerve palsy (PNP) remains the most frequent complication associated with cryoballoon-based pulmonary vein (PV) isolation. We sought to characterize our experience using a novel monitoring technique for the prevention of PNP.
Methods and Results—Two hundred consecutive cryoballoon-based PVI procedures between October 2010 and October 2013 were studied. In addition to standard abdominal palpation during right phrenic nerve pacing from the superior vena cava, all patients underwent diaphragmatic electromyographic monitoring using surface electrodes. Cryoablation was terminated upon any perceived reduction in diaphragmatic motion or a 30% decrease in the compound motor action potential (CMAP). During right-sided ablation, a ≥30% reduction in CMAP amplitude occurred in 49 patients (24.5%). Diaphragmatic motion decreased in 30/49 patients and was preceded by a 30% reduction in CMAP amplitude in all. In 80.4% of cases, this reduction in CMAP amplitude occurred during right superior PVI. The baseline CMAP amplitude was 876.2±583.3mV and decreased by 17.3±15.7% at the end of application. This decrease was more marked in the 33 PVs with a reduction in diaphragmatic motion than in those without (32.8±27.5% vs. 14.4±10.2%; P<0.001). In 3 cases PNP persisted beyond the end of the procedure, with all cases recovering within 6 months. Despite the shortened application all veins were isolated. At repeat procedure the right-sided PVs reconnected less frequently than the left-sided PVs in those with PNP.
Conclusions—Electromyographic phrenic nerve monitoring using the surface CMAP is reliable, easy to perform, and offers an "early warning" to impending phrenic nerve injury.
- Received November 3, 2013.
- Revision received May 12, 2014.
- Accepted June 16, 2014.