Abstract 16091: Cardiac Mechanical Determinants of Exercise Function in Differing Fontan Heart Failure Phenotypes

Abstract

Introduction: The objective of this study was to investigate the association of contractility, afterload, and diastolic dysfunction to exercise function between patients with heart failure and preserved ejection fraction (HFpEF) versus heart failure with reduced ejection fraction (HFrEF). Hypothesis: Cardiac mechanical determinants of exercise would be different in HFrEF versus HFpEF Methods: Core-lab echocardiograms were obtained from the publically-available Pediatric Heart Network Fontan Cross-sectional Study database. Ejection fraction was considered abnormal if < 50%. Diastolic function was defined as abnormal if the diastolic pressure:volume quotient (lateral E:e’/end-diastolic volume) was > 10 th percentile. Patients were divided into three groups: 1 = normal EF and normal diastolic function, 2 = decreased EF with normal diastolic function (HFrEF), 3 = normal EF with abnormal diastolic function (HFpEF). End-systolic elastance (Ees), a measure of contractility, and arterial elastance (Ea), a measure of afterload, were calculated. Results: 238 patients were included. Differences between groups are reported in the Table. In group 1, there were no significant correlations between exercise and echocardiographic measures. In patients with HFrEF, Ea was correlated with percent predicted max O 2 pulse (ppO 2 P-max) (r = -0.40, p = 0.03). In patients with HFpEF, lateral E:e’/EDV was correlated with ppO 2 P-max (r = -0.57, p = 0.02). No measures correlated with percent predicted peak VO 2 in either group. Conclusions: As Fontan patients progress to heart failure, stroke volume during exercise is limited by afterload in patients with HFrEF. Alternatively, stroke volume is limited by diastolic dysfunction in HFpEF patients. These measures of cardiac mechanics may be useful in identifying the mechanisms that drive exercise dysfunction in Fontan patients of varying heart failure phenotypes.