In humans, cardiovascular disease (CVD) is the most frequent cause of death worldwide. Myocardial infarction (MI) is a leading cause of heart failure due to myocardial impairment, yet the progression of the resultant dysfunction is often undetected after incidental or induced myocardial infarction. In this study we tracked the progression of left-sided heart failure in 6-mo-old male castrated sheep in which we created 2 models of myocardial infarction, small and large. Myocardial infarction was induced through ligation of a single branch (obtuse marginal [OM] 1) of the left circumflex coronary artery to create small (mild) infarcts and of 2 branches (OM1 and OM2) for large (severe) infarcts. Progression of heart failure was evaluated by assessing scar size, the left ventricular ejection fraction, hematology, cardiac serum biochemical biomarkers, ST elevation, and clinical observation. All parameters were assessed at baseline and at 3 wk and 3 mo after infarction, except that clinical observation of the animals was conducted daily. The different parameters differed in their usefulness: some verified appropriate creation of the model, whereas others enabled assessment of the progression of heart disease. We hypothesize that myocardial scar size, as a function of induced ischemia, coupled with left ventricular ejection fraction are predictive indicators of postinfarction cardiac dysfunction.