Adult C57BL/6J mice were obtained from Jackson Laboratory at 8 weeks of age, placed on a standard mouse chow diet and water ad libitum, and housed in a temperature-controlled environment under an alternating 12-hour light-dark cycle. All animal handling procedures adhered strictly to the approved guidelines of the Institutional Animal Care and Use Committee. A total of 16 mice (mean weight, 26.3±1.7 g) were randomly assigned to 1 of the following 3 groups: a group that underwent open thoractomy without coronary ligation (“sham”, N=5); a group that underwent permanent left anterior descending artery (LAD) ligation without subsequent treatment (“MI”, N=6); and, a group that underwent permanent LAD ligation followed by oral administration of an angiotensin converting enzyme inhibitor (ACEi) (captopril 20 mg/kg/day) in the drinking water starting on day 7 following surgery (“MI+ACEi”, N=5). Coronary ligation was performed as previously described.10 (link) Echocardiography was performed on all mice under light sedation (1% isoflurane in oxygen) prior to surgery (baseline) and at 1 week following surgery (prior to starting any treatment with ACEi), at 3 weeks, and at 7 weeks following surgery. Echocardiography was performed using a 18–38 MHz linear-array transducer with a digital ultrasound system (Vevo 2100 Imaging System, VisualSonics, Toronto, Canada). Standard parasternal long- and short-axis views were obtained during each echocardiographic exam. Conventional and novel echocardiographic image measurements were performed offline. All image acquisitions and offline measurements included in the present analysis were conducted by a single investigator who was blinded to animal groups. At 7 weeks, mice were sacrificed for pathologic assessment of cardiac remodeling and infarct size.