Physiology - Effects of Denervation
The incisions in heart and combined heart and lung transplantation sever the sympathetic and parasympathetic nerves which ordinarily regulate your heart rate. This lack of neural connections is known as denervation.
Before your transplant, stimulation of the sympathetic nervous system would speed up your heart rate and the parasympathetic nervous system would slow your heart rate. Your new heart, without the direct control of your central nervous system, will beat faster in the resting state than did your own heart. These nerves rarely grow back.
The "resting rate" of a denervated heart usually ranges between 90 and 110 beats per minute. While this rate is faster than "normal," it is associated with perfectly normal function and the capability to sustain vigorous physical activity.
Any change in the rate of your transplanted heart is dependent upon circulating adrenaline and related hormones produced by the adrenal gland. These will affect your heart rate through the circulatory system rather than by direct nerve action on the heart. The response is slower.
A response to stimulation causing increased adrenaline, such as exercise, may take up to 10 minutes " until the heart's pacemaker (the sinus node) picks up the message through the circulating blood rather than by direct electrical brain impulse. Conversely, the circulating hormones may take up to an hour to decline and allow the heart rate to return to its normal rate after exercise.
Another effect of denervation is that you may not perceive chest pain or angina pectoris should you develop coronary artery disease in your new heart. Chest pain that you may feel can be associated with lung and chest wall healing or strain due to exercise, rather than lack of blood supply to the heart.
When your lung(s) are transplanted they are denervated also. You cannot feel irritation below the tracheal suture line, and you will not be stimulated to cough spontaneously by the presence of infection or secretions in the lungs. It is important that if you feel mucous or fluid in the back of your throat, you make a conscious effort to cough and attempt to clear it.
Pulmonary transplant patients especially must notify their physician at the earliest signs of:
- Any unusual or persistent cough
- Shortness of breath
- Any difficulty exchanging air, such as getting air in and out
- Any change in color or amount of sputum.
Your respiratory therapist will assist you with a routine airway-care program in the hospital and outline a regimen for you to follow after discharge.
At specified intervals and during your annual visit, detailed pulmonary function tests will be performed to evaluate your transplanted lung's function.