A 55-year-old man comes to the emergency department due to sudden-onset dyspnea. Medical history is significant for hypertension, hyperlipidemia, type 2 diabetes mellitus, and chronic kidney disease. The patient takes multiple medications and has no drug allergies. He works for an international bank and returned from a business trip in Australia a day ago. Blood pressure is 110/70 mm Hg and pulse is 110/min. Physical examination shows a moderately overweight man with tachypnea. The lungs are clear on auscultation. ECG shows sinus tachycardia. Ventilation/perfusion scanning is ordered. Which of the following findings would help confirm the suspected diagnosis in this patient?

Question

A 55-year-old man comes to the emergency department due to sudden-onset dyspnea.  Medical history is significant for hypertension, hyperlipidemia, type 2 diabetes mellitus, and chronic kidney disease.  The patient takes multiple medications and has no drug allergies.  He works for an international bank and returned from a business trip in Australia a day ago.  Blood pressure is 110/70 mm Hg and pulse is 110/min.  Physical examination shows a moderately overweight man with tachypnea.  The lungs are clear on auscultation.  ECG shows sinus tachycardia.  Ventilation/perfusion scanning is ordered.  Which of the following findings would help confirm the suspected diagnosis in this patient?

Quizplus · Accepted Answer

11ec160b_3b4b_1385_9249_29c569c82a9f_MD0001_00 Pulmonary embolism (PE) should be suspected in this patient with recent extended travel (prolonged immobilization) who now has acute-onset dyspnea and tachypnea, normal lung examination, and sinus tachycardia on ECG. In most patients, CT angiography, which requires intravenous contrast administration, is the diagnostic test of choice. However, the contrast used in CT studies should be avoided in patients with chronic kidney disease due to the increased risk of contrast-induced nephropathy; in such patients, a ventilation/perfusion (V/Q) scan is the preferred diagnostic study. A V/Q scan is a nuclear medicine study that uses a radioactive tracer placed in both inhaled gas and the bloodstream to visualize areas of ventilation and perfusion in the lung. In patients with PE, ventilation is preserved but the embolus prevents adequate blood perfusion to the affected areas of the lung. Therefore, the most definitive diagnostic finding for PE on V/Q scan is a large area showing a perfusion defect without ventilation defect (mismatched perfusion defect). (Choice A) The absence of perfusion abnormalities is a useful finding on V/Q scan, as it likely rules out significant PE. (Choices B and E) Matched ventilation and perfusion defects may result from chronic lung abnormalities (eg, airway inflammation or obstruction, atelectasis) that lead to localized areas of poor ventilation with corresponding hypoxic vasoconstriction, or they may represent a PE that happens to be in an area of poor ventilation. These results are often inconclusive and necessitate additional testing to confirm or rule out PE. (Choice D) An area of ventilation defect without perfusion defect is suggestive of conditions that lead to acute alveolar filling (eg, pneumonia, pulmonary edema). Educational objective: Ventilation/perfusion scanning can be useful for diagnosing pulmonary embolism. A large perfusion defect without ventilation defect is the characteristic positive test result. __________ References: Value of the ventilation/perfusion scan in acute pulmonary embolism: results of the prospective investigation of pulmonary embolism diagnosis (PIOPED). (http://www.ncbi.nlm.nih.gov/pubmed/2332918) Current status of ventilation-perfusion scintigraphy for suspected pulmonary embolism. (http://www.ncbi.nlm.nih.gov/pubmed/28095020)

A 55-Year-Old Man Comes to the Emergency Department Due to Sudden-Onset