Role of Cardiovascular Magnetic Resonance Imaging in Postoperative Follow-Up After the Arterial Switch Operation for Transposition of the Great Arteries

Multimodality Imaging of Transposition of the Great Arteries

Transposition of the great arteries (TGA) is a congenital conotruncal abnormality characterized by discordant connections between the ventricles and great arteries, with the aorta originating from the right ventricle (RV), and the pulmonary artery (PA) originating from the left ventricle (LV). The two main types of TGA are complete transposition or dextro-transposition of the great arteries (D-TGA), commonly referred to as d-loop, and congenitally corrected transposition (CCTGA), commonly referred to as l-loop or L-TGA. In D-TGA, the connections between the ventricles and atria are concordant, whereas in CCTGA they are discordant, with the left atrium connected to the RV, and the right atrium connected to the LV. D-TGA manifests during the neonatal period and can be surgically managed by atrial switch operation (AtrSO), arterial switch operation (ASO), Rastelli procedure, or Nikaidoh procedure. Arrhythmia, systemic ventricular dysfunction, baffle stenosis, and baffle leak are the common complications of AtrSO, whereas supravalvular pulmonary or branch PA stenosis, neoaortic dilatation, and coronary artery narrowing are the common complications of ASO. CCTGA may manifest late in life, even in adulthood. Surgeries for associated lesions such as tricuspid regurgitation, subpulmonic stenosis, and ventricular septal defect may be performed. A double-switch operation that includes both the atrial and arterial switch operations constitutes anatomic correction for CCTGA. Imaging plays an important role in the evaluation of TGA, both before and after surgery, for helping define the anatomy, quantify hemodynamics, and evaluate complications. Transthoracic echocardiography is the first-line imaging modality for presurgical planning in children with TGA. MRI provides comprehensive morphologic and functional information, particularly in adults after surgery. CT is performed when MRI is contraindicated or expected to generate artifacts. The authors review the imaging appearances of TGA, with a focus on pre- and postsurgical imaging. Online supplemental material is available for this article. ^©RSNA, 2021.

Feasibility of Transthoracic Echocardiography Evaluation of Pulmonary Arteries Following Arterial Switch Operation

Pulmonary artery (PA) stenosis is the most common late sequela following arterial switch for d-transposition of the great arteries. The purpose of this study was to assess the effectiveness of transthoracic echocardiography in evaluating the pulmonary arteries following repair. This was a retrospective, cross-sectional analysis of all echocardiograms performed on patients following arterial switch operation. A numerical scoring system was devised and used to quantify PA visualization based on 2D images, color mapping, and spectral Doppler. The study cohort included 150 patients. The ability to visualize at least one PA was poorer in patients who were older [> 10 years (47%) vs ≤ 10 years (89%) (p < 0.001)], and who had larger body surface area (BSA) (> 1.25 m² (40%) vs ≤ 1.25 m² (90%) (p < 0.001)]. Regardless of age, 2D visualization of the pulmonary arteries was poor for the entire cohort. Of those with at least one non-visualized PA, only 54% had alternative imaging performed or ordered within the 5 years at or prior to their last echocardiogram. In conclusion, PA visualization following arterial switch is worse in patients who are older and in those with larger BSA. In such patients, alternative forms of imaging are more likely to be necessary.