An Adolescent with Complex Congenital Heart Disease at High Altitude
A 12-year-old active male presents for his routine annual cardiology follow-up with the following diagnoses: L-looped double inlet left ventricle (LV) with "corrected" transposition and coarctation, status/post (s/p) resection of the LV outflow tract and end-to-end repair of a coarctation, and s/p a fenestrated Fontan procedure done nine years ago. The result of this patient's anatomy and surgical palliation is that the LV pumps as the systemic ventricle, and, in the absence of a pumping right ventricle, a cavo-pulmonary anastamosis allows passive flow to the lungs. Often in these sorts of palliations, a fenestration is left as a pressure "pop off" from the passive Fontan connection into the systemic circulation, which can result in mild patient desaturation, particularly during times of exertion (Figure 1).
The patient and his family have just returned from a hiking trip, where they increased their elevation by ~500 feet (peak altitude >10,000 feet) and walked a total of 5 miles. His father states that his son walks this distance frequently without looking cyanotic or short of breath. He would like to continue as an Eagle Scout, which requires this type of activity.
On physical exam, he appears well, albeit slightly cyanotic. His oxygen saturations are 85%, and he is slightly clubbed. The blood pressure is normal, the resting heart rate is 60 bpm and junctional. The cardiac exam is remarkable for a normal S1 and a single S2. There are no murmurs. Of note, his hematocrit is 50% and stable.
The echocardiogram shows a well-functioning single ventricle with no regurgitation of the atrioventricular (AV) valves. The Fontan baffle is well-visualized, and there is a fenestration shunting from right to left with a peak gradient of 16 mm Hg. The branch pulmonary arteries are well-visualized with phasic flow.
Which of the following additional pieces of information would you like to have prior to "clearing" this patient for high altitude hiking and camping?