Time-resolved three-dimensional magnetic resonance velocity mapping of cardiovascular flow paths in volunteers and patients with Fontan circulation

Objective: To apply flow-sensitive magnetic resonance imaging for the evaluation of whole-heart flow characteristics in healthy volunteers and patients with Fontan circulation. Methods: Time-resolved three-dimensional magnetic resonance velocity mapping (spatial resolution=2.5×2.8×2.8mm³, temporal resolution=38.4ms) was acquired in normal controls and in four Fontan patients with extracardiac total cavopulmonary connection. Data analysis included flow connectivity mapping and flow quantification of arterial and venous blood flow. Haemodynamics in four patients with Fontan circulation were individually evaluated in the aorta, caval veins and left and right pulmonary arteries. Results: In four controls, nine distinct flow features were consistently identified with good feature clarity (median=2 in 80.6% of readings) and image quality (median=2 in 75.0% of readings). In patients, a marked variability of flow from the caval veins towards the left and right pulmonary arteries (flow ratio=1.7±0.6, range 1.2-2.6 vs 1.1±0.1 in controls) was found. Increased offset of the caval venous connection resulted in enhanced pulmonary flow asymmetry. Compared with controls, reduced pulsatility in pulmonary arteries (1.4±0.6 vs 4.1±0.6 in controls) and caval veins (1.2±0.4 vs 2.8±1.1 in controls) were observed. Peak flow was reduced in both superior (22±14mls^-1 vs 76±7mls^-1 in controls) and inferior vena cava (61±28mls^-1 vs 187±42mls^-1 in controls). Conclusions: This feasibility study demonstrated the potential of whole-heart three-dimensional magnetic resonance velocity mapping to reveal overt haemodynamic differences in surgically palliated congenital heart with similar extracardiac cavopulmonary connection geometry. Future studies are warranted to evaluate its diagnostic impact for improved evaluation of the pre- and postoperative status in the individual patient.