CMR was performed at 3T (MAGNETOM Verio, Siemens AG, Healthcare Sector, Erlangen, Germany) according to the study protocol (Supplementary data online). Short-axis cine images were obtained using a balanced steady-state free precession sequence (8-mm parallel slices with 2-mm spacing) for the assessment of left ventricular function and volumes.
T1 mapping was performed using the MOdified Look-Locker Inversion recovery (MOLLI; flip angle 35°; minimum TI 100 ms; TI increment of 80 ms; time delay of 150 ms with a heart beat acquisition scheme of 3-3-5) with built-in motion correction.27 (link) A gradient echo field map and associated shim were performed to minimize off-frequency artefact. Short-axis T1 maps of the mid-cavity slice were acquired in diastole before and at 2, 5, 10, 15, 20, and 30 min following the administration of 0.1 mmol/kg of gadobutrol (Gadovist/Gadavist, Bayer Pharma AG, Germany). Additional basal and apical T1 maps were obtained in diastole at 0, 15, 20, and 30 min (see Supplementary data online). The basal slice was defined as the first complete ring of myocardium below the aortic outflow tract, and the mid-cavity slice as the most basal slice to include both papillary muscles. The apical slice was selected between the apex and the mid-cavity on the image least affected by trabeculations and partial volume averaging.

Methodology for measuring myocardial T1 at multiple time points and in multiple segments of the left ventricle (A) Measurement of myocardial T1 at multiple time points. ROI were drawn within the borders on the pre-contrast myocardial T1 maps and then copied onto the corresponding post-contrast images at all time points. Minor adjustments were made to avoid artefact and blood pool. An ROI was also drawn in the left ventricular blood pool in order to calculate the partition coefficient (λ) and extracellular volume fraction (ECV) at each time point. This approach demonstrated excellent intra- and inter-observer reproducibility. (B) Assessment of regional variation in T1 measures. Using the anterior and inferior ventricular insertion points as well as the mid-point of the ventricular cavity as reference points, three intersecting lines were drawn to divide the left ventricle into 16 segments. ROI were drawn onto the basal (six segments), mid-cavity (six segments), and apical (four segments) pre-contrast T1 maps with the standardized approach described above. Subsequently, the ROI were copied onto the 20-min post-contrast T1 maps. Pre- and post-contrast T1, λ, and ECV values were assessed in each segment

LGE imaging was performed between 8 and 15 min using two approaches: an inversion-recovery fast gradient-echo sequence and a phase-sensitive inversion recovery sequence, performed in two phase-encoding directions to differentiate true enhancement from artefact.28 (link),29 (link) The inversion time was optimized for each slice to achieve satisfactory nulling of the myocardium.