A 69-year old woman presents with crushing substernal chest pain and nausea. She is treated with plasminogen activator, oxygen, and morphine sulfate. Laboratory studies show a WBC count of 13,000/μL, CK-MB of 6.6 ng/mL, and troponin I of 2.5 ng/mL. An ECG shows ST segment elevation. Cardiac catheterization reveals diffuse atherosclerosis of all major coronary arteries. The patient subsequently becomes acutely hypotensive and undergoes cardiac arrest. The surface of the heart at autopsy is shown in the image. At what point in time following acute myocardial infarction did this pathologic condition most likely occur?