Exercise Evaluation of Systolic Cardiac Function in Single Ventricle Fontan Patients using Tissue Doppler Echocardiography

Abstract

PURPOSE: Single ventricle patients who have undergone the Fontan operation have been shown to have impaired aerobic capacity. We sought to confirm this and determine whether systolic dysfunction may be responsible for this impairment by utilizing echocardiographic methods during peak exercise testing. METHODS: We evaluated 44 pediatric subjects with normal systolic function at rest, as assessed by standard echocardiography; 20 normal controls (N, 14 females, mean age 14.8 yrs) and 24 patients status post Fontan (FON, 8 females, mean age 14.6 yrs) using cycle Ergometry and echocardiography with tissue Doppler. The myocardial performance index (MPI) is an echocardiographic derived composite measure of isovolumic contraction and relaxation. RESULTS: There were significant differences in N and FON height (1.61 vs 1.53 meters, P<0.05) and weight (59.8 vs 46.5 kilograms, P<0.01)). Aerobic capacity (VO2), heart rate (HR), cardiac output index (CI), and systolic tissue velocity (SaLAT) were significantly decreased in FON compared to N. MPI was significantly impaired in the FON group at rest and maximal exercise.Table: Caption not availableCONCLUSION: This group of single ventricle pediatric patients, status post Fontan, showed impaired aerobic capacity and cardiac output at peak exercise. Despite having normal systolic function at rest as judged by standard echocardiography, they exhibited impaired myocardial performance and systolic tissue velocity during exercise. This suggests that occult systolic dysfunction may play a key role in limiting exercise capacity in Fontan patients.