Diaphragm pacing via the phrenic nerve allows patients with Congenital Central Hypoventilation Syndrome (CCHS), as well as some patients with high cervical spinal cord injury, to be free from the need of a ventilator.
Pediatric Surgeons of Phoenix has been placing the Avery phrenic nerve pacing system at Phoenix Children’s Hospital. Unlike cardiac pacemakers, the battery is not implanted. The Avery system is the only FDA-approved phrenic pacing system available for children. The phrenic electrode is placed under the nerve and a receiver is placed under the skin on the chest wall. The receiver converts radio frequency (RF) energy to an electrical signal for the phrenic nerve. The radio frequency is generated by an external transmitter (Mark IV) attached to 2 antennae (one per implanted receiver). The Mark IV has been FDA approved since 1998 and is the current version available in the United States.
The external transmitter is powered by 2 9-Volt batteries. The transmitter weighs about 1 lb, 3 oz (540 grams; with batteries). The antennae are placed on the skin overlying the receivers and held in place with tegaderm or tape.
Approximately 50 devices are implanted per year in the world. While most centers in the U.S. place the leads in the chest, the program at Phoenix Children’s Hospital places the leads in the neck. This allows for quicker recovery, less pain, and avoids the risks associated with chest surgery. This is the primary approach already used by Dr. Pelle Nilsson in Sweden with excellent results. It was Dr. Nilsson who provided insights into avoiding the risks of the chest procedure by the cervical approach in children. Initial concerns for stimulating the nearby neck muscles have not been an issue in his large series of patients.
Once the pacer system is implanted, the nerves are not stimulated for 28 days, per the manufacturer’s recommendation. Once pacing begins, a sleep study is arranged by the primary pulmonologist to determine the optimal settings for the individual patient based on CO2 and other factors.
All surgeries carry risk, so be sure to speak with your surgeon about the risks and benefits for surgery for your child.
CCHS is typically diagnosed with a genetic test for the PHOX2B gene defect. This gene defect is autosomal dominant, but affected individuals typically have a new (non-inherited) gene defect. Surveillance for patients with known CCHS is recommended. See link below for frequency of inpatient and 72-hour Holter monitoring. Neurocognitive testing is also recommended.