Cyanotic congenital heart disease: dynamics of oxygen uptake and ventilation during exercise

The presence of intracardiac shunts dissociates the right and left circulations, making dynamic coupling of cellular and pulmonary gas exchange inefficient or impossible. As a result, patients may have profound changes in arterial blood gases and prolongation of adaptation and recovery even with low levels of physical activity. Because the exercise-induced symptoms in patients with cyanotic congenital heart disease have bases apart from heart failure, assignment of a New York Heart Association functional class may be misleading if not erroneous. Dr. Jane Somerville recommends the "Ability Index" shown in Table 1.