Evolution and Predictors of Right Ventricular Failure in Fontan Patients: A Case-Control Study

Background: Patients with single right ventricular morphology (SRV) may exhibit impaired function with increased morbidity, mortality, and need for cardiac transplant due to progressive SRV failure after the Fontan procedure. The aim of the study was to longitudinally characterize the cardiac mechanics and trajectory of disease evolution of SRV failure in Fontan patients. Methods: We performed a case-controlled longitudinal study of 52 patients who underwent extracardiac Fontan palliation for SRV between 1994 and 2015 and compared echocardiographic measures of right ventricular (RV) function, RV-systemic vascular coupling and ventricular remodeling between patients who required heart transplants due to SRV failure (study group, n = 26) and those who did not (control group, n = 26). To define the trajectory, measurements were obtained at four matching time points equivalent in duration from Fontan. Results: RV circumferential shortening function declined in both groups over the time period, but was significantly lower (p < 0.01) in the study group farther from the Fontan. RV-systemic vascular coupling, assessed by systolic time interval measures and RV work, was preserved in the control group, but significantly altered (p < 0.001) in the study group. Relative wall thickness decreased, and the minor/major-axis ratio, as an index of ventricular geometry, increased in the study group, but both remained stable in the control group. Conclusions: This study suggests that positive ventricular remodeling with enhanced circumferential systolic function, and preserved RV-vascular coupling, appear to be adaptive and protective mechanisms against RV failure in Fontan with SRV. These indices of cardiac mechanics may serve as clinically relevant quantifiable markers of disease evolution, and early indicators for therapeutic intervention.