This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
A patient developed breathlessness and chest pain, on second postoperative after a total hip replacement. Echo-cardiography showed right ventricular dilatation and tricuspid regurgitation. What is the most likely diagnosis. 
Select and explain. 
A. Acute MI, B. Pulmonary embolism, C. Hyptensive shock, D. Cardiac tamponade
B: Pulmonary embolism
Answer: B: Pulmonary embolism 
Explanation: B i.e. Pulmonary embolism Onset of chest pain and breathlessness, together with echocardiographic evidence of right ventricular dilatation and tricuspid regurgitation after a high risk procedure (for thromboembolism) like total hip replacement suggests a diagnosis of pulmonary embolism. For a patient presenting with acute breathlessness and chest pain, and in whom right ventricular dilatation with tricuspid regurgitation and mild elevation of pulmonary aery pressure is noted, a pulmonary embolus should be the initial diagnosis to be considered.