Down Syndrome and Pulmonary Hypertension
Usha S. Krishnan, MD, DM, FAHA
Professor, Pediatrics (Cardiology) at CUMC
Associate Director, Pulmonary Hypertension Center
Columbia University Irving Medical Center
New York, NY 10032
“My baby has already been seen by her cardiologist, so why are we seeing another cardiologist?” This is a very common question I am asked, when I consult on a child with Down syndrome and pulmonary hypertension. Most infants with Down syndrome (DS) in the current era have been diagnosed prenatally and families do know what to expect with regards to congenital heart disease, hypothyroidism, gut abnormalities etc. But pulmonary hypertension is something that really cannot be predicted with prenatal echocardiography or ultrasound scans or by any other form of routine testing.
What is pulmonary hypertension? Simply speaking, it means high blood pressures in the pulmonary arteries. When we speak of high blood pressures in an adult, we are referring to pressures in the aorta and its branches, something we can measure using a BP cuff around the arm or leg. But pulmonary hypertension (PH) refers to high pressures in the pulmonary arteries which take blood from the right ventricle to the lungs. The only way to suspect PH is by doing an echocardiogram where the cardiologist gets indirect evidence of increased pressures in the right side of the heart and pulmonary arteries. PH can be confirmed by cardiac catheterization where the pressures are directly measured in the “Cath lab” and the child is usually under anesthesia for the procedure.
There are multiple reasons why children with Down syndrome develop PH. Firstly, they may have persistent PH of the newborn. All babies are born with high pressures in the right side of the heart. But in most babies, this comes down rapidly to normal levels (of 20% of the left sided pressures) in a few days to a few weeks. If the normal decrease in right sided pressures does not happen (due to various newborn causes including DS), we call this condition as persistent PH of the newborn or PPHN. Often this may just represent a delay in the normal process and the baby recovers after initial intensive care and don’t need long-term PH medications. In some infants, the pressures do not come down and they may need specific testing and directed therapies for their PH.
Nearly half of all infants with DS have heart defects, commonly, patent ductus arteriosus, ventricular septal defect or atrioventricular septal defects. Babies with large PDA or VSD with DS can develop PH early because of large shunts and may need earlier surgery than non -DS infants. Atrioventricular septal defects are caused by failure of complete formation of the walls between the two sides of the heart and separation into right and left atrioventricular valves. The baby often develops symptoms very early and may need a lot of help with feeding, breathing and growth. They usually need surgery in the first 2-6 months of life. These infants develop PH because of excessive blood flow to the lungs from the shunts within the heart. After surgery, they may have residual defects and the pulmonary hypertension may persist. When an infant has congenital heart disease involving elevated pressures in the left side of the heart they can develop PH because of backpressure into the pulmonary capillaries within the lungs. At baseline or after surgery, if there is significant mitral valve regurgitation (leaking) or valve narrowing, or if there is narrowing of the pulmonary veins coming to the left atrium, there is back pressure into the lungs, causing PH. These children may need reoperation to fix the mitral valve or pulmonary veins as the case may be.
Even without congenital heart disease, babies with DS can have PH. They are often born with immature lungs, lungs which have not developed normally (hypoplastic lungs or simplified alveoli), or lungs with subpleural cysts in them. Because of abnormal lungs, they are prone to infections leading to further lung damage, leading to inflammation and secondary PH. Infants with DS may have bronchomalacia, where the larger airways may collapse (because they are softer), and this can lead to collapse of the lungs beyond, leading to inflammation and PH. Older children with DS often develop enlarged tonsils and adenoids or their large tongue may obstruct the airways during sleep and they can develop obstructive sleep apnea, which results in PH. These children may need their tonsils and adenoids removed and older patients may need CPAP to keep their airways open and prevent obstructive sleep apnea.
Infants and children with DS often also have gastroesophageal reflux (GER), which causes stomach acid/ and foods to come up the food-pipe, and sometimes enter the airways. This leads to aspiration pneumonias and lung infections and damage with associated PH.
So, in answer to the question, why are you seeing my child, I do give a detailed explanation to my families, and also evaluate for these issues which may impact the care of a child with DS and PH.