Patel ND, Friedman C, Herrington C, Wood JC, Cheng AL.
J Thorac Cardiovasc Surg. 2021 Aug;162(2):372-380.e2. doi: 10.1016/j.jtcvs.2020.09.140. Epub 2020 Oct 29.PMID: 33220959
Take Home Points:
- Patients with Fontan circulation and an extra-cardiac conduit experience decrease in the cross-sectional area (CSA) as early as 6 months post Fontan.
- Longer term, almost all patients develop some decrease in Fontan CSA.
- Proactive surveillance can help identify patients with narrowing of the Fontan conduit and they can be referred for intervention to restore the Fontan conduit size.
Commentary from Dr. Konstantin Averin (Edmonton), catheterization section editor of Pediatric Cardiology Journal Watch:
Palliation for patients with single ventricle physiology culminates in a connection of the inferior vena cava (IVC) to the pulmonary arteries. The method of this connection has evolved over time but at many centers currently involves the use of Goretex conduit, typically 18 or 20mm diameter. The ideal diameter of this connection is unknown but it would be logical to think that it should approximate the size of the IVC. The authors sought to characterize changes to Fontan conduit size over time and determine if a decrease in cross sectional area (CSA) affects cardiac output, pulmonary artery growth or exercise capacity.
From January 2013 to October 2019; 165 patients with Fontan circulation underwent either cardiac catheterization (87) or cardiac MRI (93). After excluding those with a lateral tunnel Fontan and duplicate studies, 75 cardiac catheterizations and 83 cardiac MRI were included for analysis – with a mean time from Fontan to MRI/cath of 9.5 ± 3.9 years. The minimum Fontan CSA decreased by a median of 33% (24%, 40%) during a mean follow up of 9.6 years (Figure 1). Strikingly, even at less than 1-year post-Fontan the median decrease was already 33% (25%, 41%). The size of the conduit at implant did not impact the percentage decrease in CSA. Fontan CSA was not associated with median Nakata index (ρ = 0.09, P = 0.29) or cardiac index (ρ = -0.003, P = 0.013); but was moderately related with % predicted oxygen consumption (ρ = 0.31, p = 0.013).
Many additional analyses were performed and reported but the headline finding from this study is that Fontan CSA area decreases as early as 6 months post-Fontan. Luckily, children who are 3-5 years old have smaller IVC’s and can probably tolerate narrowing of the Fontan conduit. Looking at Figure 1, it also becomes clear that almost all patients who undergo an extra cardiac conduit Fontan will have some degree of conduit narrowing when the conduit is imaged. These findings should reinforce the importance of proactive Fontan imaging with some combination of cardiac MRI or cardiac catheterization. This would allow for the identification of patients who have a significant mismatch between their IVC and Fontan conduit and allow for intervention on the Fontan conduit to maximize the Fontan CSA and minimize resistance to venous return. It will be important to assess whether this approach will help to prolong Fontan longevity and minimize the incidence of Fontan failure.
Figure 1: A total of 158 patients underwent imaging of the Fontan conduit via MRI (n = 83) or cardiac catheterization (n = 75). There is a significant decrease in the minimum Fontan CSA that starts after the Fontan operation. MRI, Magnetic resonance imaging; CSA, cross-sectional area