Cardiac Imaging Studies

All cardiac imaging studies were performed with the animals under anesthesia. In the short‐term follow‐up groups, a computed tomography (CT) 64‐slice scanner (Brilliance iCT; Philips Medical Systems, Best, The Netherlands) was used to evaluate LAD patency before euthanizing the animals (Figure 1B). Analysis of CT images was performed on a dedicated advanced image processing workstation (Extended Brilliance Workspace 3.5; Philips Medical Systems, Cleveland, OH) by 2 independent blinded investigators using mainly multiplanar reconstructions. In the long‐term follow‐up groups, CMR study was performed at 7 and 60 days (Figure 1B) with an Achieva 3T‐TX whole‐body scanner (Philips Healthcare, Best, The Netherlands) equipped with a 32‐element phased‐array cardiac coil as previously described.20 Each study consisted of a cine steady‐state free‐precision sequence to determine left‐ventricular end‐diastolic volume, left‐ventricular end‐systolic volume, and left ventricular ejection fraction21; late gadolinium‐enhanced sequence to determine infarct size and microvascular obstruction (MVO); and (only at the 7‐day CMR) a T2‐weighted short‐tau inversion recovery sequence to determine the extent of myocardial edema.21 Absolute cardiac perfusion was estimated using dynamic acquisition with dual‐saturation (TS=20, 80 ms) technique to avoid signal saturation during gadolinium‐based contrast administration.22 After perfusion maps generation, region‐of‐interest analysis was done at the infarcted core, infarct borders (anterior wall and septum), and remote myocardium.

Images were analyzed by 2 independent blinded investigators, and processed with analysis software (QMass MR 7.5; Medis, Leiden, The Netherlands and MR Extended Work Space 2.6; Philips Healthcare) as previously described.21 In case of lack of agreement between the conclusions of the 2 investigators, the discordant images were reviewed by a third blinded investigator.