A hematology expert witness opines on post-operative anticoagulation in patients with multiple comorbidities. This case involves a fifty-four-year-old female patient with a past medical history of obesity and Atrial Fibrillation. The patient was being treated by her primary care physician and had been prescribed Coumadin for her arrhythmia. It was decided by her cardiologist that the patient required a cardiac ablation. The surgery was performed without complications; however in the post-operative recovery period the treating surgeons recognized that the patient required an emergent cholecystectomy. The procedure was initially intended to be performed laparascopically, however had to be converted to open technique due to complications intraoperatively. The surgery was completed and the patient was transferred to the PACU. Post-operatively, physicians had a difficult time controlling the patient’s PTT. The patient was given a large dose of Heparin on post-operative day six. She coded and died as a result of internal hemorrhaging.