Factors Associated With Normal Exercise Capacity in Patients With Single Ventricle

The congenital heart disease (CHD) is the firts cause of congenital birth defects. Medical and surgical advances completely changed the epidemiology of CHD. Among these CHD, the univentricular heart, or single ventricle (SV), is a disease whose medical-surgical progress has completely changed the epidemiology.

The SV at birth receives systemic and pulmonary venous returns in the single functional cavity and provides systemic and pulmonary flow. The SV undergoes a severe volumetric overload and considerably increases its work, which is not viable for the long time.

In 1968, Professor Francis Fontan created the palliative surgery of the univentricular heart. It consists in establishing a derivation of the systemic venous blood from the two vena cava veins directly to the pulmonary arteries, without a sub-pulmonary ventricle. So, the VU no longer undergoes volumetric overload, and eliminates cyanosis.

In this "Fontan circulation", there is no pump to push the blood in the pulmonary arteries, only the remaining systemic post-capillary energy (reflection of the central venous pressure) allows to drive the blood through the lungs with a risk of stasis upstream (right overload) and a limited pre-charge downstream, which can lead to severe consequences: limited exercise capacity, systolic and diastolic dysfunction of the SV, arrhythmia, cyanosis, cirrhosis and hepatic carcinoma, exudative enteropathy , plastic bronchitis, venous thromboses, deaths.

There is a great heterogeneity within this family of SV with extremely varied evolutionary profiles. The cardiorespiratory exercise test, which has become a "gold standard", makes it possible to assess the severity of CHD. In our study on the aerobic fitness of children with CHD, the investigators found that 44% of children with SV had normal aerobic fitness (> 80% of the theoretical VO2max)1. Some good prognostic criteria are already described: left SV, good VU function, total cavopulmonary shunt in young age, etc. But the investigators know that these elements are not enough to explain why some SV, which the investigators will call the "great-SV", have a better aerobic fitness.

The main objective of our study is to describe the population of "great SV" (VO2max ≥ 80%) within the general population of SV. The investigators thus wish to determine the prognostic criteria favorable to a good aerobic fitness in univenticular heart disease.