Pressure Gradients within the Fontan Anastomosis in Patients with Total Cavopulmonary Connection by 4D-MR Pressure Mapping

Background: Pressure measurement in TCPC patients is a domain of cardiac catheterization. 4D-MR flow pressure mapping offers an alternative for assessment of even minor pressure differences using Navier–Stokes and Poisson's equations for pressure. The scope of this study was to define flow characteristics over the Fontan anastomosis and measure even minor pressure differences between caval veins and pulmonary arteries.

Method: Twenty-four patients (median = 15 years [8; 34]) with clinically uncompromised TCPC and 18-mm extracardiac conduit were studied by 4D-MR flow pressure mapping. Pressure differences between superior vena cava (SVC) and extracardiac conduit (C) to both pulmonary arteries (RPA and LPA) were assessed. For this purpose, anatomically correct centerlines were created on predefined vessel masks and maximal pressure drop was taken from time resolved pressure curves along these centerlines. Vortices and direction of flow within the anastomosis were registered by flow pathlines from 4D-MR flow maps

Results: Median values of pressure drops in the anastomosis between SVC and RPA were 0.63 [0.21–2.1] mm Hg, between C and RPA 0.67 [0.3–2.4] mm Hg, between SVC and LPA are 0.8 [0.3–2.4 mm Hg and between C and LPA 0.7 [0.2–1.9] mm Hg. There was no significant difference between the gradients along the four defined centerlines. Patients with potential flow obstruction (stents, occluder, and vortices) had significantly higher gradients along tunnel-LPA, SVC-RPA, and tunnel-RPA (p < 0.05) than patients without potential obstructions, although the absolute values were small.

Conclusion: Even minor pressure drops over the Fontan anastomosis in venous low-pressure circulation can be assessed by 4D-MR flow pressure mapping. These values are below the magnitude of conventional cardiac catheterization. Pressure drops can be detected in even clinically uncompromised TCPC patients, in particular, in patients with potential flow obstruction.

Publication History

Article published online:
12 February 2022