A 66-year-old man comes to the emergency department with acute onset of severe chest pain and shortness of breath. The pain is in the right upper chest and is aggravated by deep breathing and coughing. Medical history is significant for hypertension and obstructive sleep apnea. The patient quit smoking 10 years ago and drinks beer on weekends. Blood pressure is 110/70 mm Hg, pulse is 116/min and regular, and respirations are 22/min. BMI is 30 kg/m². Normal vesicular breath sounds are heard on auscultation of the chest. Cardiac auscultation reveals tachycardia and an accentuated S2. Chest x-ray is unremarkable. ECG shows sinus tachycardia. CT angiogram of the chest reveals an embolus in the right pulmonary artery. Which of the following is the most likely origin of this embolus?

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Explanation: 11ec25c8_d433_6ebb_bc81_2171964e8461_MD0003_00 This patient's clinical presentation (eg, acute chest pain worse with inspiration, tachycardia, S2 suggestive of pulmonary hypertension) with CT angiogram findings of a thrombus in the right pulmonary artery is diagnostic of pulmonary embolus (PE). The deep veins of the lower extremities are the most frequent source. Lower extremity deep vein thrombosis (DVT) is divided into 2 categories: Proximal/thigh (eg, iliac, femoral, popliteal): These DVTs are the source of >90% of acute PEs, probably due to their large caliber and proximity to the lungs. Distal/calf: Although most DVTs occur in the calf vein, distal/calf DVTs are less likely than proximal/thigh DVTs to embolize to the lungs and cause PE and they are more likely to spontaneously resolve (Choice A). (Choice C) Thrombi originating from the renal veins are most common in patients with nephrotic syndrome. The prevalence of PE in patients with nephrotic syndrome is 10%-30%. (Choice D) Thrombi originating in the right atrium are more common in patients with intracardiac devices (eg, pacemaker) and are less likely to occur spontaneously. (Choice E) Spontaneous upper extremity DVT is generally uncommon (1%-4%) and even less likely to cause PE. Common risk factors for upper extremity DVT include prothrombotic state, indwelling catheter, and anatomical venous obstruction (eg, cervical rib, bony overgrowth after clavicular fracture). Educational objective: The proximal deep leg veins are the most common source of symptomatic pulmonary embolism. Other less common sources of emboli include the calf veins, renal veins, pelvic veins, upper extremity veins, and right heart. References: Comparison of the clinical history of symptomatic isolated distal deep-vein thrombosis vs. proximal deep vein thrombosis in 11 086 patients. (http://www.ncbi.nlm.nih.gov/pubmed/19793188)

A 66-Year-Old Man Comes to the Emergency Department with Acute