3.0T MR Coronary Angiography after Arterial Switch Operation for Transposition of The Great Arteries-Gd-FLASH Versus Non-Enhanced SSFP. A Feasibility Study

Background: Patency of the coronary arteries is an issue after reports of sudden cardiac death in patients with transposition of the great arteries (TGA) operated with arterial switch (ASO). Recent studies give rise to concern regarding the use of ionising radiation in congenital heart disease, and assessment of the coronary arteries with coronary MR angiography (CMRA) might be an attractive non-invasive, non-ionising imaging alternative in these patients. Theoretically, the use of 3.0T CMRA should improve the visualisation of the coronary arteries. The objective of this study was to assess feasibility of 3.0T CMRA at the coronary artery origins by comparing image quality with non-contrast CMRA in ASO TGA patients to healthy age-matched controls, and by comparing image quality with non-contrast CMRA to contrast enhanced CMRA in the patient group. Material and methods: Twelve patients, 9-15 years (mean 11.9 years, standard deviation 1.5 years), and 12 age-matched controls (mean 12.7 years, standard deviation 1.7 years) were examined with 3D balanced steady-state free precession (SSFP). Nine of twelve patients had Gadolinium-enhanced fast low-angle shot (Gd-FLASH) performed after SSFP. Image quality at the coronary artery origins was evaluated subjectively with a 10 cm figurative visual analogue scale (fVAS) and objectively by signal-to-noise and contrast-to-noise ratio (SNR, CNR). Results: All, but one, coronary artery origins were identified. No significant difference in image quality scores was found between patients and controls with SSFP (mean values 6.5 cm-9.1 cm in patients and 7.0 cm-8.0 cm in controls, p-values > 0.1). With SSFP, intra-observer fVAS mean score was 6.7 cm-8.6 cm and with Gd-FLASH 7.7 cm-8.7 cm. CNR was higher with Gd-FLASH (p < 0.03). Intra-observer agreement index (AI) with SSFP was moderate-to-good (0.43-0.71) and with Gd-FLASH good (0.64-0.79) in all origins. Inter-observer AI was good in the left main stem (LMS) with SSFP (0.65). With Gd-FLASH inter-observer AI was good in LMS (0.78) and moderate (0.5) in the left anterior descending artery, but lacking in the other origins though with a good agreement on Bland-Altman plots. Conclusions: Our findings indicate a better, more reproducible image quality with Gd-FLASH than with non-contrast SSFP CMRA on 3.0T for evaluation of the coronary artery origins in ASO TGA children and adolescents.