Abstract 15009: Detection of a Low Ventricular Stiffness With Preserved Ejection Fraction Phenotype in Single Ventricle Physiology

Introduction: Patients with single ventricle physiology frequently demonstrate decreased exercise tolerance after the Fontan operation. The objective of this study was to investigate the contribution of ventricular stiffness to exercise function in these patients. Hypothesis: We hypothesized that ventricular stiffness, both extremes of high and low stiffness, would be associated with exercise tolerance in Fontan patients. Methods: We previously validated an echocardiographic measure of ventricular stiffness, lateral Doppler E: tissue Doppler e’/end-diastolic volume (lateral E:e’/EDV) in children. Core-lab echocardiograms and exercise test results were obtained from the publicly-available Pediatric Heart Network Fontan Cross-sectional Study database. Exercise function was quantified as % predicted VO 2 . Ejection fraction (EF) was considered abnormal if < 50%. Diastolic function was defined as high stiffness if the lateral E:e’/EDV was > 90th percentile or low stiffness if < 10th percentile. Patients were divided into four groups: 1 = normal EF and normal diastolic function, 2 = decreased EF with normal diastolic function, 3 = normal EF with high ventricular stiffness, and 4 = normal EF with low ventricular stiffness. Results: 239 patients (61% left, 29% right, 10% mixed ventricular dominance) had EF, lateral E:e’/EDV, and VO 2 measured. Differences between groups are reported in the Table. Conclusion: Single ventricle patients with both high and low stiffness and preserved EF had worse exercise capacity than patients with both normal and abnormal EF. To our knowledge, this is the first study detecting a low stiffness heart failure phenotype in single ventricle physiology. Future studies should further investigate the pathophysiologic mechanisms that lead to these extremes of stiffness in Fontan patients.