After the Lateral Tunnel Fontan, the Intra-Atrial Channel Grows and Remains Phasic, Expanding in Systole

Although the extracardiac conduit (ECC) Fontan is now widely preferred, recent reports of improved early outcomes with the lateral tunnel (LT) have renewed interest in LT physiology. We evaluated long-term growth and phasic diameter changes of the intra-atrial channel after LT Fontan. We reviewed 67 patients who underwent LT Fontan at our center (1989-2009). Patients with transplantation, Fontan takedown, or no follow-up within the past 5 years were excluded. Forty-seven patients with follow-up within 5 years were included; 37 had transthoracic echocardiograms (TTE) of sufficient quality for analysis. Because the channel is non-circumferential and often elliptical, minimal and maximal cross-sectional diameters were measured during systole and diastole. Median follow-up among the 47 included patients was 18 years (IQR 16.5-19.5). Diagnoses included tricuspid atresia (23%), double outlet right ventricle (23%), hypoplastic left heart syndrome (21%), double inlet left ventricle (11%), unbalanced atrioventricular septal defect (11%), and other (11%). All but one patient had a fenestrated LT. No mortality occurred among patients included. One patient (2%) underwent Fontan takedown. Three patients (6%) underwent heart transplantation; Fontan-associated liver disease was present in 4 (8%). Protein-losing enteropathy, chylothorax, and pleural effusion occurred in 1 patient (2%) each. On TTE (n = 37), the median diameter in systole exceeded diastole (23.8 mm [IQR 20.1-26.2] vs. 21.9 mm [IQR 19.0-25.4]). The intra-atrial channel demonstrates long-term growth to adult size dimensions and remains pulsatile, with larger systolic than diastolic diameter. These features may help accommodate flow variation in Fontan circulation.