You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is A 55-year old man who has been on bed rest for the past 10 days, presents with sudden onset of breathlessness and chest pain. The chest x-ray is normal. Which of the following represents the next step in investigation? and explain in detail?
Ventilation-perfusion scan has a sensitivity and specificity of 90% if results of the scan correlate with clinical risk factor assessment. Lung scanning is the second-line diagnostic test for Pulmonary Embolism, used mostly in patients who cannot tolerate intravenous contrast. The perfusion scan defect is indicated by absent or decreased blood flow. A high-probability scan indicates two or more segmental perfusion defects in the presence of normal ventilation. Echocardiography: Is not a reliable diagnostic imaging tool for acute PE because most patients with PE have normal echocardiograms. It is used to detect conditions that may mimic PE. Pulmonary Angiography: Chest CT with contrast has viually replaced invasive pulmonary angiography as a diagnostic test. Ref: Current Diagnosis and Treatment: Surgery, 13th Edition, Chapter 35