Studies on cardiac regeneration require large mammalian models of dilated cardiomyopathy (DCM) after acute myocardial infarction (AMI), and pig and sheep models are increasingly used in this field of preclinical research. Given the large interindividual variability in ovine left anterior descending artery (LAD) anatomy, protocols based on the coronary arteries to be ligated often lead to significant variation in infarct sizes and hence to heterogeneous results, ranging from no ventricular remodeling to acute, lethal left ventricular (LV) failure. We designed an ovine model of postinfarction DCM based on estimated infarct size rather than on a predetermined menu of coronary artery ligatures. In seven adult sheep we induced an anterolateral AMI of approximately 25% of the LV mass by ligating the branches of the LAD that, by visual inspection, would lead to such an infarct size. In 10 to 12 weeks, LV end-diastolic volume more than doubled and LV end-systolic volume almost tripled. LV ejection fraction decreased dramatically, as did LV percent fractional shortening and LV percent wall thickening. Infarct size (planimetry) was approximately 25% of the LV endocardial surface. We conclude that in sheep, an anterolateral AMI of approximately 25% of the LV mass--regardless of the coronary branches ligated to attain that infarct size--results in a model of postinfarction DCM that may prove useful in preclinical research on myocardial regeneration.Fil: Locatelli, Paola. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Favaloro; ArgentinaFil: Olea, Fernanda Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Favaloro; ArgentinaFil: Mendiz, Oscar. Fundación Favaloro; ArgentinaFil: Salmo, Fabián. Fundación Favaloro; ArgentinaFil: Fazzi, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación Favaloro; ArgentinaFil: Hnatiuk, Anna. Universidad Favaloro; ArgentinaFil: Laguens, Rubén. Fundación Favaloro; ArgentinaFil: Crottogini, Alberto Jose. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Favaloro; Argentina