Abstract
ObjectivesTo use 4D-flow MRI to describe systemic and non-systemic ventricular flow organisation and energy loss in patients with repaired d-transposition of the great arteries (d-TGA) and normal subjects.MethodsPathline tracking of ventricular volumes was performed using 4D-flow MRI data from a 1.5-T GE Discovery MR450 scanner. D-TGA patients following arterial switch (n = 17, mean age 14 ± 5 years) and atrial switch (n = 15, 35 ± 6 years) procedures were examined and compared with subjects with normal cardiac anatomy and ventricular function (n = 12, 12 ± 3 years). Pathlines were classified by their passage through the ventricles as direct flow, retained inflow, delayed ejection flow, and residual volume and visually and quantitatively assessed. Additionally, viscous energy losses (ELv) were calculated.ResultsIn normal subjects, the ventricular flow paths were well ordered following similar trajectories through the ventricles with very little mixing of flow components. The flow paths in all atrial and some arterial switch patients were more irregular with high mixing. Direct flow and delayed ejection flow were decreased in atrial switch patients’ systemic ventricles with a corresponding increase in residual volume compared with normal subjects (p = 0.003 and p < 0.001 respectively) and arterial switch patients (p < 0.0001 and p < 0.001 respectively). In non-systemic ventricles, arterial switch patients had increased direct flow and decreased delayed ejection fractions compared to normal (p = 0.007 and p < 0.001 respectively) and atrial switch patients (p = 0.01 and p < 0.001 respectively). Regions of high levels of mixing of ventricular flow components showed elevated ELv.Conclusions4D-flow MRI pathline tracking reveals disordered ventricular flow patterns and associated ELv in d-TGA patients.Key Points• 4D-flow MRI can be used to assess intraventricular flow dynamics in d-TGA patients.• d-TGA arterial switch patients mostly show intraventricular flow dynamics representative of normal subjects, while atrial switch patients show increased flow disorder and different proportions of intraventricular flow volumes.• Flow disruption and disorder increase viscous energy losses.
Highlights
MethodsDextro-transposition of the great arteries (d-TGA) is a congenital heart defect characterised by the transposition of the primary arteries exiting the heart resulting in deoxygenated blood being passed to the aorta and returned to the body, while oxygenated blood is returned from the left ventricle to the lungs in a closed circuit
Atrial switch subjects had significantly larger, normalised, systemic ventricle enddiastolic volume (EDV) and lower systemic ventricle ejection fraction (EF) compared with patients after arterial switch procedure and those with normal anatomy
This study investigated the intraventricular flow volumes and dynamics in d-transposition of the great arteries (d-TGA) patients after surgical repair of either atrial switch operation (Senning procedure) or arterial switch operation, in comparison with patients having normal cardiovascular anatomy
Summary
MethodsDextro-transposition of the great arteries (d-TGA) is a congenital heart defect characterised by the transposition of the primary arteries exiting the heart resulting in deoxygenated blood being passed to the aorta and returned to the body, while oxygenated blood is returned from the left ventricle to the lungs in a closed circuit. Patients have been treated with an atrial switch procedure, redirecting pulmonary blood from the lungs to the right ventricle and to the transposed aorta and body; this has been gradually replaced by the arterial switch procedure, which transects the aorta and main pulmonary artery, returning them to their natural position and resulting in improved survival rates [2]. After a Senning procedure, face a higher risk of atrial or ventricular arrhythmia as the right ventricle must maintain systemic circulation [3, 4]. This patient cohort requires regular follow-up imaging by echocardiography and MRI to recognise pathologies that need re-interventions, mostly concerning the right ventricular outflow tract [1, 2, 7, 8]
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