Pulmonary hypertension is one of the results that may occur because of extra blood being pumped through the lungs and at an excessive pressure. This may occur when the normal separation between the right sided (lung) and left sided (body) circulation is incomplete, as when there is a hole or holes in the central wall of the heart (VSD or AVSD), or when there is a connection between the aorta and the pulmonary artery (PDA). Pulmonary hypertension may also occur in many other conditions, for example if there is obstruction to the blood flow coming back to the heart from the lungs, or if there is upper airway obstruction.
In the normal heart the right side pumps blood to the lungs, which is a relatively easy task, whilst the left side has the more difficult job of pumping blood all around the body. As a result the pressure in the left ventricle (pumping chamber) is generally about four times that in the right ventricle, and the wall of the left ventricle is thicker than that of the right.
Many defects that involve holes in the septum (central heart wall) allow blood to flow (shunt) from the high pressure left side of the heart to the lower pressure right side. This results in an increase in the pressure on the right, and causes too much blood to be pumped to the lungs. The body’s natural reaction to this, is to constrict (narrow) the blood vessels in the lungs in an effort to limit this excess blood flow.
Over a period of time, this narrowing of the pulmonary (lung) arteries increases due to thickening in the surrounding muscle due to the increased workload, and also the closure of smaller lung arteries. These changes reduce the blood flow into the lungs, and increase the pressure needed by the right ventricle to pump blood into the lungs to be oxygenated.
As the resistance to flow increases, there is less left to right shunting (blood flow) within the heart, and eventually the pressure is such that the shunt is reversed, i.e.. right to left shunting occurs. This process is called Pulmonary Vascular Disease or Eisenmenger Syndrome (see Eisenmenger Complex Topic Note), and ultimately results in low oxygen levels and therefore cyanosis (blueness) and increased haemoglobin levels in the blood of the patient.
It is the damage caused by prolonged pulmonary hypertension that generally prohibits late repair of cardiac defects. As patients with Down's Syndrome have a propensity to develop Pulmonary Vascular Disease due to the fact that they tend to have larger holes in the heart and smaller airways, surgical repair is generally carried out fairly early in life, although timing will vary depending on the exact heart defect.
Special attention should be paid to treating obstructed breathing (e.g. inhalations, nose drops, antibiotics, referral to ENT surgeon), as long term obstruction may aggravate the condition.
The rate of development of pulmonary vascular disease depends on the nature and size of the defect, but varies greatly from patient to patient, even between those with the same cardiac problem. Routine checks that the patient has at clinic appointments, such as echocardiograms, help the cardiologist to monitor the patient's pulmonary artery pressure.
Successful surgery will usually prevent the continuance of pulmonary hypertension, and the development of Pulmonary Vascular Disease. This is usually performed before 6 months of age.
In a young child with abnormally elevated pressure in the pulmonary artery due to a left to right shunt, it is sometimes needed to perform pulmonary artery banding (pa banding / banding). This procedure requires the surgeon to place a restrictive band around the artery, thus reducing the blood flow into the lungs, and preventing or reversing some of the damage to the lung arteries. If successful, the development of pulmonary vascular disease may be slowed or stopped, and surgical repair of the hole(s) may be possible at a later date.
In cases where banding is not successful or inappropriate, treatment includes the use of oxygen and certain medications which relax the pulmonary vessels and increase the blood flow into the lungs. There are now several medications available to lessen the effect of pulmonary hypertension. At the time of writing, these are only used when there has already been damage to the lung arteries (pulmonary vascular disease) and there is no evidence that they can prevent such damage in young children.
Sildenafil and Tadalafil are phosphodiesterase inhibitors that can be taken as oral medication and are now in common use. These medications are easy to give and are the first line in many children with pulmonary hypertension. Bosentan and Ambrisentan are Endothelin receptors antagonists and are more expensive. These are only given when there is significant pulmonary vascular disease.
Follow Up Advice
Antibiotic cover during any dental treatment has now been discontinued for most patients with a cardiac defect, whether repaired or not. But good dental care is important, so it is best to encourage regular brushing and to avoid too many sweet drinks etc. while the child is young.
"The doctor explained that my baby had pulmonary hypertension due to a very large hole in the heart and that if the pressure stayed very high, like my daughter’s, it would be too dangerous to operate Then the doctor told me about an operation to put a band around the lung artery, which would protect her lungs from further damage and hopefully give her the chance for surgery later on. She had the banding done at four weeks and when she was ten months, her pulmonary pressure had reduced and she had a complete repair."