CMR exams were performed in the reference CMR center of the E-MIOT Network (Pisa) using a 1.5 T CMR scanner (Signa Artist; General Electric Healthcare, Waukesha, Wisconsin, USA). A 30-element cardiac phased-array receiver surface coil with breath-holding and electrocardiographic (ECG)-gating was used.

For T1 mapping, three parallel short-axis slices (basal, medium and apical) of the LV were acquired in end-diastole using a modified Look-Locker inversion recovery (MOLLI) sequence [26] with a 3 (3 s) 3 (3 s) 5 scheme. Other sequence parameters were: slice thickness = 8 mm, flip angle = 35°, matrix = 172 × 172 pixels, partial Fourier = 0.75. Starting from the 11 motion-corrected images with different inversion times, pixel-wise T1 maps were generated on the scanner using a three-parameter fitting model [26]. T1 maps were transferred to a dedicated workstation for offline post-processing, that involved manual tracing of endocardial and epicardial borders, with care taken to avoid blood pool and epicardial fat. Basal and medium slices were divided into 6 equiangular segments and the apical slice in 4 segments, according to the American Heart Association/American College of Cardiology model [27]. The T1 in each segment was obtained by averaging the T1 value for all the pixels within the segment. For blood analysis, a region was drawn in the LV blood pool of each short axis slice avoiding papillary muscles.

T2* multiecho images were acquired in the same 3 slice locations used for T1 mapping by a multi-echo gradient-echo T2* sequence (10 echo times-TEs). Sequence parameters and T2* images analysis, performed using a custom-written and validated software (HIPPOMIOT®), have been already described [19]. After the calculation of T2* values in all myocardial segments, an appropriate correction map compensated for cardiac/visceral geometrical and susceptibility artifacts [28].

Global T1 and T2* values were obtained by averaging all segmental T1 and T2* values, respectively. Mid-septum T1 and T2* values were obtained by averaging the values in segments 8 and 9.

Balanced steady-state free precession cine images were acquired in sequential 8-mm short-axis slices from the atrio-ventricular ring to the apex to quantify LV function parameters in a standard way using MASS® software (Medis, Leiden, The Netherlands) [29]. LV volumes and mass were normalized for the body surface area. Segmental wall motion was visually assessed in cine images.

To detect the presence of replacement myocardial fibrosis, LGE short-axis, vertical, horizontal, and oblique long-axis images were acquired 10–18 min after gadobutrol (Gadovist®; Bayer Healthcare; Berlin, Germany) intravenous administration (0.2 mmoL/kg). LGE images were not acquired in patients with an estimated glomerular filtration rate < 30 mL/min/1.73 m2 and in patients who declined contrast. LGE was considered present when visualized in two different views [22, 30].

Post-contrast T1 images were acquired 10 min after contrast medium administration and image analysis was performed by using the same approach employed for native T1 images. Segmental ECV values were calculated with input of native and post-contrast myocardial segmental and blood pool T1 values and same-day hematocrit [31].

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