The Influence of Atrial Strain on Functional Capacity in Patients with the Fontan Circulation.

Speckle-tracking echocardiography has been used to assess atrial function. This analysis is feasible in univentricular hearts. The aim of this study was to characterize the relationship between atrial strain and functional capacity in the Fontan circulation. Apical four-chamber echocardiographic loops of 39 Fontan patients were reviewed. The dominant atrium was assessed for active (ε), conduit (ε), and reservoir (ε) strain and ε/ε ratio. Cardiopulmonary exercise test was performed on the same day and oxygen uptake (VO) at ventilatory threshold (VT) and peak VO were chosen as the dependent variables. Statistical analysis was performed using SPSS version 23. Unpaired t test was used for binomial and continuous variable correlation; single and multivariable linear regression were used for continuous variable correlation. Statistical significance was defined as p value < 0.05. VO at VT as a percentage of predicted VO was 36.8% (SD 10.7). Peak VO was 64.7% (SD 18.9) of the predicted value. In univariate analysis, both were associated with age, atrioventricular regurgitation, ejection fraction, ε, ε, and ε/ε. In multivariate regression, higher VO at VT and peak VO were associated with younger age (p = 0.003 and p = 0.001, respectively) and higher ε (p = 0.026 and p = 0.020). Evaluation of heart function is difficult in the Fontan circulation, hindered by complex ventricular morphology and lack of normative data. VO provides a good surrogate. Atrial strain parameters are compromised in these patients and associated with VO. Therefore, whenever possible, atrial strain should be measured as it may provide a new method of risk stratification.