Magnetic Resonance Imaging Assessment of Blood Flow Distribution in Fenestrated and Completed Fontan Circulation with Special Emphasis on Abdominal Blood Flow

Abstract

Objective: To investigate the regional flow distribution in patients with Fontan circulation by using magnetic resonance imaging (MRI).

Materials and methods: We identified 39 children (18 females and 21 males; mean age, 9.3 years; age range, 3.3-17.0 years) with Fontan circulation in whom flow volumes across the thoracic and abdominal arteries and veins were measured by using MRI. The patients were divided into three groups: fenestrated Fontan circulation group with MRI performed under general anesthesia (GA) (Group 1, 15 patients; average age, 5.9 years), completed Fontan circulation group with MRI performed under GA (Group 2, 6 patients; average age, 8.7 years), and completed Fontan circulation group with MRI performed without GA (Group 3, 18 patients; average age, 12.5 years). The patient data were compared with the reference ranges in healthy controls.

Results: In comparison with the controls, Group 1 showed normal cardiac output (3.92 ± 0.40 vs. 3.72 ± 0.69 L/min/m², p = 0.30), while Group 3 showed decreased cardiac output (3.24 ± 0.71 vs. 3.96 ± 0.64 L/min/m², p = 0.003). Groups 1 and 3 showed reduced abdominal flow (1.21 ± 0.28 vs. 2.37 ± 0.45 L/min/m², p < 0.001 and 1.89 ± 0.39 vs. 2.64 ± 0.38 L/min/m², p < 0.001, respectively), which was mainly due to the diversion of the cardiac output to the aortopulmonary collaterals in Group 1 and the reduced cardiac output in Group 3. Superior mesenteric and portal venous flows were more severely reduced in Group 3 than in Group 1 (ratios between the flow volumes of the patients and healthy controls was 0.26 and 0.37 in Group 3 and 0.63 and 0.53 in Group 1, respectively). Hepatic arterial flow was decreased in Group 1 (0.11 ± 0.22 vs. 0.34 ± 0.38 L/min/m², p = 0.04) and markedly increased in Group 3 (0.38 ± 0.22 vs. -0.08 ± 0.29 L/min/m², p < 0.0001). Group 2 showed a mixture of the patterns seen in Groups 1 and 3.

Conclusion: Fontan circulation is associated with reduced abdominal flow, which can be attributed to reduced cardiac output and portal venous return in completed Fontan circulation, and diversion of the cardiac output to the aortopulmonary collaterals in fenestrated Fontan circulation.

Keywords: Abdominal flow; Fenestrated Fontan; Fontan associated liver disease; Fontan operation; Protein-losing enteropathy.

Fig. 1. Drawing showing locations of blood flow sampling for phase-contrast magnetic resonance imaging.

Ao = aorta, AsAo = ascending aorta, DsAo = descending aorta at diaphragm, F-a = Fontan above fenestration, F-b = Fontan below fenestration, Fen. = fenestration, HV-RV = between hepatic venous and renal venous connections, IVC = inferior vena cava, LPA = left pulmonary artery, LPVs = left pulmonary veins, RPA = right pulmonary artery, RPVs = right pulmonary veins, SMA = superior mesenteric artery, SMV = superior mesenteric vein, SVC = superior vena cava

Fig. 2. Magnitude and phase-contrast magnetic resonance images (A) and flow curve of portal vein (B) from patient with completed Fontan circulation showing normal flow pattern and volume.

Fig. 3. Interobserver correlation (A) and agreement (B) for analysis of 187 measurements from 11 randomly selected cases.

Interobserver agreement between two readers was excellent. SD = standard deviation

Fig. 4. Graphs showing blood flow distribution in patient groups in comparison with healthy controls.

Y axis represents ratios between mean values of blood flow volumes in patient groups and healthy controls, except for ratio between hepatic arterial and venous flows (hepatic artery/vein) and AP collateral flow. Y axis for AP collateral flow indicates contribution of AP collateral flow to total pulmonary venous return. AP= aortopulmonary