Imaging procedures. CMR is considered the reference standard. CMR was performed on a 3.0 Tesla whole-body scanner (Achieva, Philips), using a phased array cardiac receiver coil. During repeated breath- holds, electrocardiogram-gated steady state free precession (SSFP) cine images were acquired in contiguous short-axis slices of 1 cm covering the entire LV. CMR scans (N=271) were assessed in an independent core laboratory by two experienced observers, using QMass (Medis, Leiden, the Netherlands). Endo- and epicardial borders were outlined in the end- systolic and end-diastolic phases. LV end-diastolic volume (LVEDV), end-systolic volume (LVESV), and LV mass were measured in addition to LVEF, which was the primary outcome measure of the GIPS-III study. Cohort-specific CMR characteristics have been described and compared with reference values previously [10]. LVESV, LVEDV, LVEF, and LV mass were determined using the Xxxxxxx method of disk summation. LV mass was determined at the end-diastolic phase, excluding papillary muscles. Infarct size was defined as fraction of LV mass showing hyperenhancement on late gadolinium enhancement series, determined using the full width at half maximum (FWHM) technique [11]. 2D TTE is considered the index test. 2D TTE was performed on the same day as the CMR assessment, in left decubital position, using a Vivid 7 echo system (General Electric, Xxxxxx, Norway). Post-processing analyses were performed in an independent core laboratory (Groningen Imaging Core Laboratory, Groningen, the Netherlands) by four experienced observers, on an Echopac BT 00 (Xxxxxxx Xxxxxxxx, Xxxxxx, Norway). LVEDV, LVESV, and LVEF were determined using the biplane summation of disks method (modified Xxxxxxx’x rule), which is the recommended method for 2D TTE volume calculations by the American Society of Echocardiography and the European Association of Cardiovascular Imaging [12]. The M-mode approach was not pursued, to avoid oblique sections of the ventricle. LV mass was estimated using the 2D linear dimension method [12,13]. Observers conducting CMR and 2D TTE post-processing analyses were blinded to all patient data, analyses were performed in accordance to contemporary guidelines [12,14].
