Ventricular Dyssynchrony Late after the Fontan Operation is Associated with Decreased Survival and the Presence of Arrhythmias

Background Ventricular dyssynchrony and its relationship to clinical outcomes is not well characterized in patients following Fontan palliation. Methods Single-center retrospective analysis of cardiac magnetic resonance (CMR) imaging of patients with a Fontan circulation and age-matched healthy comparison cohort as controls. Feature tracking was performed on all slices of a ventricular short-axis cine stack. Circumferential and radial strain, strain rate, and displacement were measured; and multiple dyssynchrony metrics were calculated based on timing of these measurements (including standard deviation of time-to-peak, maximum opposing wall delay, and maximum base-to-apex delay). Primary endpoint was a composite measure including time to death or heart transplant listing (D/HTx); secondary outcomes were the presence of atrial or ventricular arrhythmias. Results A total of 503 cases (15y; IQR 10, 21) and 42 controls (16y; IQR 11, 20) were analyzed. Compared to controls, Fontan patients had increased dyssynchrony metrics, longer QRS duration, larger ventricular volumes, and worse systolic function. Dyssynchrony metrics were higher in patients with right ventricular (RV) or mixed morphology compared to those with LV morphology. At median follow-up of 4.3 years, 11% had D/HTx, 7% ventricular arrhythmia, and 38% atrial arrhythmia. Multiple risk factors for D/HTx were identified, including RV morphology, ventricular dilation, dysfunction, QRS prolongation, and dyssynchrony. Ventricular dilation and RV morphology were independently associated with D/HTx; ventricular dilation and global circumferential strain were independently associated with ventricular and atrial arrhythmias. Conclusions Mechanical dyssynchrony is highly prevalent in functional single ventricles palliated to the Fontan circulation and is more pronounced in hearts with RV or mixed ventricular morphology compared to those with LV morphology. Dyssynchrony is associated with death or need for heart transplantation and cardiac arrhythmias. These data add to the growing understanding regarding factors that can be used to risk-stratify patients with the Fontan circulation.