Phrenic nerve stimulation in an ovine model with temporary removable pacing leads.

Background: The objective of this study was to assess the feasibility and safety of a novel, removable, surgically implanted, temporary neurostimulation approach involving the distal portion of the phrenic nerve.

Methods: Temporary phrenic nerve pacing electrodes were implanted surgically using an ovine model (4 animals). The primary endpoint was the ability to successfully match the animal's minute-ventilation upon implantation of both phrenic nerve pacers on day 1. Secondary endpoints were successful phrenic neurostimulation by both electrodes 15 and 30 days after initial implantation. We also assessed safe removal of the electrodes at 15 and 30 days after implementation.

Results: In 3 of 4 animals, electrodes were successfully implanted in both right and left phrenic nerves. On day 1, median ventilation-minute induced by neurostimulation was not significantly different from baseline ventilation-minute [4.9 L·min-1 (4.4-5.5) vs. 4.4 L·min-1 (4.3-5.2); P=0.4] after 15 minutes. Neurostimulation was still possible 15 and 30 days after implementation in all left side phrenic nerves. On the right side, stimulation was possible at all times in 1 animal but not in the remaining 3 animals for at least one time point, possibly due to lead displacement. Analysis of pathology after percutaneous electrode removal showed integrity of the distal portion of all phrenic nerves.

Conclusions: Efficient temporary neurostimulation through the distal portion of the phrenic nerve was possible at baseline. The main complication was the displacement of electrodes on the right phrenic nerve on two occasions, which was due to the anatomy of the ovine model. It compromised diaphragm pacing on day 15 and day 30. The electrodes could be safely removed percutaneously without damage to the phrenic nerves.