From the Guidelines
Denervation of the phrenic nerve during open heart transplant occurs due to the surgical disruption of neural connections and potential direct damage to the nerve, leading to temporary diaphragmatic dysfunction and impacting respiratory mechanics post-surgery. During open heart transplantation, the surgical procedure involves completely removing the recipient's diseased heart and replacing it with the donor heart, which severs all neural connections to the heart, including the phrenic nerve innervation. The phrenic nerve normally provides motor innervation to the diaphragm, controlling its contraction for breathing. When the heart is removed and replaced, the surgical field extends to areas where the phrenic nerve runs along the pericardium, and the nerve may be directly damaged or its pathway disrupted. Additionally, the transplanted donor heart arrives completely denervated, lacking all original neural connections. Over time, some reinnervation may occur, but it is typically incomplete. This denervation affects diaphragmatic function temporarily, which can impact respiratory mechanics post-surgery. Patients may experience diaphragmatic dysfunction, potentially requiring longer ventilatory support. Respiratory therapy and diaphragmatic strengthening exercises are often prescribed during recovery to help restore optimal breathing function while the body adapts to these neurological changes. It is worth noting that bilateral phrenic nerve resection is contraindicated due to severe respiratory morbidity, as highlighted in a clinical practice guideline published in the Journal of Thoracic Oncology 1. Key considerations for managing patients post-open heart transplant include:
- Monitoring for signs of diaphragmatic dysfunction
- Providing respiratory therapy to support breathing
- Prescribing diaphragmatic strengthening exercises to aid in recovery
- Being aware of the potential for severe respiratory morbidity if bilateral phrenic nerve damage occurs, as this would significantly impact the patient's quality of life and mortality risk.
From the Research
Phrenic Nerve Deinnervation in Open Heart Transplant
- The phrenic nerve plays a crucial role in controlling the diaphragm, and its deinnervation can lead to significant respiratory complications 2.
- Studies have shown that phrenic nerve dysfunction (PND) is a common complication after cardiac surgery, including heart-lung and lung transplantation, resulting in prolonged ventilator days and intensive-care unit length of stay 2.
- The exact mechanisms of phrenic nerve injury during cardiac surgery are not fully understood but may include hypothermia, mechanical trauma, and ischemia 3.
- Deinnervation of the phrenic nerve can lead to diaphragmatic dysfunction, which can be disabling, especially in patients with a history of chronic obstructive airway disease 3.
- Research has focused on preventing and managing phrenic nerve injury, including the use of non-invasive phrenic nerve stimulation to maintain diaphragm function during mechanical ventilation 4, 5.
Clinical Implications
- Phrenic nerve deinnervation can have significant clinical consequences, including prolonged ventilator days, increased intensive-care unit length of stay, and tracheostomies 2.
- Restoring cardiac innervation, including the phrenic nerve, can improve exercise capacity, blood flow regulation, and quality of life in patients after heart transplantation 6.
- Diaphragm neurostimulation assisted ventilation has shown promise in maintaining diaphragm function, preventing atelectasis, and reducing lung stress and strain in critically ill patients 5.