Postoperative pulmonary and aortic 3D haemodynamics in patients after repair of transposition of the great arteries.

OBJECTIVES: To characterise aortic and pulmonary haemodynamics and investigate the correlation with post-surgical anatomy in patients with dextro-transposition of the great arteries (d-TGA).
METHODS: Four-dimensional (4D) MRI was performed in 17 patients after switch repair of TGA and 12 healthy controls (age, 11.9 ± 5.4 vs 23.3 ± 1.6 years). Patients were divided according to the pulmonary trunk (TP) position in relation to the ascending aorta (AAo): anterior (n = 10) and right/left anterior position (n = 7). Analysis included visual grading (ranking 0-2) of pulmonary and aortic vortical and helical flow, flow velocity quantification, blood-flow distribution to the right and left pulmonary arteries (flow ratio rPA:lPA), and vessel lumen areas.
RESULTS: Anterior TP position was associated with increased vortices in six out of ten patients compared with right anterior TP position (one out of seven) and controls (none). Reduced systolic lPA and TP lumina in patients resulted in significantly increased peak systolic velocities (P < 0.001). Flow ratio rPA:lPA was more heterogeneous in patients (rPA:lPA = 1.56 ± 0.78 vs volunteers 1.09 ± 0.15; P < 0.05) with predominant flow to the rPA. Eleven patients presented increased helices in the AAo (grade 1.6).
CONCLUSIONS: Evaluation of post-surgical haemodynamics in TGA patients revealed increased vortical flow for anterior TP position, asymmetric flow and increased systolic flow velocity in the pulmonary arteries owing to reduced vascular lumina. KEY POINTS: • 3D phase contrast MRI with velocity encoding (4D MRI) has numerous cardiovascular applications • 4D MRI demonstrates postoperative haemodynamics following surgery for transposition of the great arteries • Flow visualisation depicted enhanced pulmonary vortices in the anterior pulmonary trunk • Narrow pulmonary arterial systolic lumina resulted in increased peak systolic velocities.