Grant: Travel Awards - Institute Community Support

The normal healthy heart has four chambers: two atria and two ventricles. However, some people are born with only one ventricle in their heart. This means blood does not flow correctly through the heart, and oxygen-rich blood mixes with oxygen-poor blood. A surgery called the Fontan Procedure can help correct the flow of blood by directing oxygen-poor blood directly to the lungs so that only oxygen-rich blood is pumped to the rest of the body. After the Fontan procedure, adults are less capable of performing exercise than adults who have not have the procedure. This reduced ability to exercise is partly a result of poor heart function, but we were interested to see if it may also occur because of difficulty breathing during exercise. We therefore studied how 17 adult men and women who have had Fontan surgeries breathe during exercise and compared them to 17 healthy controls. The two groups were similar in age, sex, and weekly levels of physical activity. All participants began the study by performing tests to measure their lung function and filling out questionnaires asking how breathless they feel at rest. Afterward, they exercised on a stationary bicycle. The exercise test increased in workload every two minutes until the participant could no longer exercise. Based on lung function tests, Fontan patients had much smaller lungs than expected. Smaller lungs may explain why Fontan patients take more breaths during exercise and breathe less efficiently than healthy controls. Fontan patients also had a greater feeling of breathing discomfort than controls while exercising below their maximal level. Our study shows that the limiting factors to exercise in Fontan patients are due to both their poor heart function and breathing pattern. Their smaller than expected lungs may be the cause of these breathing limitations during exercise. Future studies that wish to improve the exercise capacity of Fontan patients should take breathing pattern during exercise into account.