Data set from the article Lo Rito M, Raso I, Saracino A, Basile DP, Varrica A, Reali M, Carminati M, Frigiola A, Giamberti A. Primary Arterial Switch Operation for Late Presentation of Transposition of the Great Arteries With Intact Ventricular Septum. Semin Thorac Cardiovasc Surg. 2020 Nov 26:S1043-0679(20)30425-1. doi: 10.1053/j.semtcvs.2020.11.030. Epub ahead of print. PMID: 33249102. This is the abstract: Transposition of the great arteries (TGA) with intact ventricular septum (IVS) are subject to neonatal arterial switch operation (ASO) to avoid deconditioning of the left ventricle (LV). Often an early repair is not feasible in developing countries where late referral is frequent. We aim to explore ASO outcomes in late TGA-IVS and compare "unfavorable candidates" (LV myocardial mass <35gr/m2 unfavorable geometry. banana-like LV shape) with other late TGA-IVS. Single-center retrospective study on late TGA-IVS who underwent primary ASO between 2015 and 2018. We divide patients into 2 groups: unfavorable candidates and favorable candidates TGA. We report categorical variables as number and percentage and continuous variables as median with interquartile range. Differences were assessed with Chi-squared or Fisher exact tests, Wilcoxon sign-rank, and Wilcoxon-rank sum tests. 45 TGA-IVS were referred with a median age of 35 days. Pre-operative echocardiography identified banana-like LV shape in 66.7%; unfavorable LV geometry in 47.6% and LV mass <35gr/m2 in 51%. Only 1 death occurred related to myocardial ischemia. Five patients (11%) required ECMO for LV dysfunction, with unfavorable candidates having a higher but not significant use (18.7% vs 6.9%, P = 0.33). At discharge, echocardiography demonstrated significant LV mass improvement compared to pre-operative (58.6 vs 33.8 gr/m2, P < 0.0001) with no significant echocardiographic difference between unfavorable and favorable late-TGA. Primary ASO in late presenter TGA-IVS can be performed safely with low mortality having a low threshold to ECMO. Significantly unconditioned LV are amenable with primary ASO with good LV mass recovery.