Self-navigated free-breathing isotropic 3D whole heart MRI for the characterization of complex cardiac anatomy in patients with congenital heart malformations

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Introduction: Cardiac anatomy of patients with congenital heart disease (CHD) is often complex and accurate evaluation mandates MR image acquisition in several non-standardized planes requiring considerable operator involvement and multiple breath-holds. The utility of self-navigated isotropic 3D-free-breathing whole-heart MRI (SN-3D) was assessed for the visualization of the heart, coronary arteries (CA) and great vessels (GV) in CHD patients. Methods: Data acquisition was performed during free breathing on a 1.5T-MRI scanner with a 3D-radial trajectory modified for respiratory self-navigation after gadobutrol injection; it was ECG-triggered, with a T2-preparation pulse and fat-saturated SSFP readout. The isotropic image data were reformatted offline. Image quality was graded and GV diameters were measured at several levels in all patients. 3D MR-angiography (MRA) was performed in a subset of patients and the GV diameters were also measured for comparison. Results: 38 patients (66% male, age 23±10y) were included. Heart rate was 71±13 bpm, scan duration 9.1±4.2 min, isotropic resolution 1.1×1.1×1.1 mm3. Image quality was good in 23, moderate in 10, mediocre in 2, and poor in 3. 3D datasets allowed the assessment of the arrangement of heart chambers and great vessels, the venous return anatomy after atrial switch for transposition of the great arteries (TGA), the morphology of cavo-pulmonary connections after Fontan operation, the morphology of the pulmonary arteries in tetralogy of Fallot or morphology of the great vessels after arterial switch for TGA. GV diameters with SN-3D were accurate using conventional MRA as the gold standard (n=25, r2=0.91, bias 0.1±2.2 mm), with a low intra- and inter-observer variability (3.7% and 5.4%). Moreover, the proximal 3 cm of the CA could be well visualized and its 3D course followed in most of the patients with moderate or good image quality (n=33: LAD 97%, LCx 73%, RCA 91%), making SN-3D useful to detect anomalous CA. Conclusion: The SN-3D methodology enables time-efficient whole-heart coverage during free breathing. The high isotropic resolution supports multi-planar offline reformatting in any plane orientation, which is particularly useful in CHD patients with complex anatomy. Self-navigation and the absence of fold-over artifacts enhance the ease of use and favor a fast acquisition planning. Reformatted images allow accurate measurement of the GV, and even small anatomical structures could be precisely identified illustrating the potential of this methodology to assess the anatomy of the proximal course of CA.

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