Pulmonary blood flow patterns in patients with Fontan circulation

After Fontan surgery there is no subpulmonary ventricle to modify pulmonary blood flow. The influence of the cardiac cycle on pulmonary blood flow patterns in various types of Fontan patients is unknown.

Blood flow patterns were investigated using phase-velocity cine magnetic resonance imaging in the pulmonary artery of 17 patients (21.1 +/- 7.3 years old, 6 females) with Fontan circulation. These patterns were compared with those of 12 healthy volunteers (26.3 +/- 6.0 years old, 10 females) obtained in the superior vena cava and the main pulmonary artery. Measurements were sampled for a period of about 3 minutes to rule out respiratory effects. Blood flow patterns were depicted by interpolating the variable number of measured phases in every patient to 100 phases and normalizing flow to mean blood flow in that vessel. Then, average flow patterns were calculated throughout the patient groups to depict a typical pattern.

In Fontan patients, peaks and troughs are highly variable. In averaged flow patterns for the whole Fontan group, only a slight late diastolic flow acceleration could be detected. This is in contrast to the pattern of the control subjects in whom typical systolic peaks and late diastolic troughs could be found in both the superior vena cava and in the pulmonary artery.

There are no typical pulmonary blood flow patterns of cardiac origin in patients with Fontan circulation, except for slight late diastolic flow acceleration representing diastolic inflow restriction.