Effects of altitude on children with congenital heart disease
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One question I frequently get from parents is whether it’s safe to travel with their children with congenital heart disease to high-altitude areas. Two considerations immediately come to mind: 1) what type of heart defect does the child have? and 2) specifically what altitude will you be traveling to?
The primary issue with high-altitude travel is the decreased concentration of oxygen. As you go up in altitude, the atmosphere gradually thins out and the concentration of oxygen (as well as the concentration of other molecules) decreases. With less oxygen in the air, the body gets tired more quickly. Anyone who has tried to go hiking in Colorado knows this very well! For the majority of children with congenital heart disease, the effects of altitude are no different than those on people with normal hearts. For example, a child with a minor valve issue or a small, hemodynamically insignificant hole should not be affected negatively in any way. Patients that can be affected are those in whom the lower concentration of oxygen alters the pulmonary vascular resistance in some way. Hypoxia (a decreased concentration of oxygen in the blood) naturally causes a constriction of blood vessels in the lungs. This can negatively (or sometimes positively) alter the hemodynamics in certain children with more significant forms of heart disease. In children with left to right shunts (eg excessive blood flow to the lungs), it may actually create a beneficial situation. For example, consider a 2-month-old child with a large ventricular septal defect and excessive blood flow to the lungs who lives at sea level and constantly breathes fast. When taken to high-altitude, he experiences vasoconstriction of his pulmonary artery bed. This actually results in a decreased amount of blood flow to the lungs and improvement in his symptoms! (I’m not advocating this as a potential treatment for a VSD however!).
The group of patients that can potentially be most negatively impacted by high-altitude travel are those with functional single ventricles. This includes patients with heart defects such as tricuspid atresia, pulmonary atresia with hypoplastic right ventricle, hypoplastic left heart syndrome, and certain variants of heterotaxy syndrome. These patients are especially at risk following either a bidirectional Glenn shunt or a Fontan procedure. These patients rely heavily on a normal pulmonary vascular resistance to assist in passive flow of blood to the lungs. Anything that can potentially raise the pulmonary vascular resistance, for example hypoxia associated with high-altitude, may negatively affect blood flow to the lungs. For this reason, I always caution patients who are status post either a Glenn shunt or a Fontan procedure about the potential negative effects of a trip to high-altitude. These effects may include a decrease in blood oxygen saturation, and the onset of symptoms of fatigue and exhaustion (even over and beyond what a person with a normal heart will feel). If the family still wants to attempt a trip, I will arrange for portable oxygen and a pulse oximeter. Supplemental oxygen can often counter the effects of altitude.
A similar issue arises in regard to plane trips. Most airplanes are pressurized to an altitude of 6000 feet. In other words, the partial pressure of oxygen in the airplane is similar to what one would experience at 6000 feet. In comparison, the city of Denver is slightly over 5000 feet. Most ski resorts in Colorado lie somewhere between 7000 and 8000 feet. This gives you an idea of comparative elevations. Fortunately, most of us aren’t exerting ourselves heavily when we ride an airplane. Usually I don't see a need for any special precautions if it's a relatively short plane ride. However if it's a longer ride (beyond 4-6 hours) then I usually arrange for supplemental oxygen and a pulse oximeter for single ventricle patients or the like.
Finally, in any patient with congenital heart disease who is having difficulty at high altitude, the immediate treatment is to return as quickly as possible to a more appropriate elevation. In the meantime, having access to supplemental oxygen can usually help alleviate symptoms.
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