This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thromboembolism and Fat Embolism Syndrome, Subject name: Medicine
After total knee implant surgery, a 65-year-old woman complains of calf pain and swelling in the leg from last 2 days. Later she complains of breathlessness and dies suddenly in the ward. What is the probable cause? 
Select and explain. 
A. Pulmonary embolism, B. Myocardial infarction, C. Stroke, D. ARDS
A: Pulmonary embolism
Answer: A: Pulmonary embolism 
Explanation: PE and DVT occurring after total hip or knee replacement are prevented by giving subcutaneous fondaparinux. Pt with DVT has H/O cramp in the lower calf that persists for several days and becomes more uncomfoable as time progresses. Pt with PE often has the most common history of unexplained breathlessness. - ARDS is being ruled out as the presentation is acute with decrease in PCWP <18mmHg with B/L pulmonary infilteration on CXR - Stroke and MI has no H/O post op. breathlessness and such presentation.