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Question 11#

A 57-year-old man is admitted to the hospital because of acute shortness of breath shortly after a 12-hour automobile ride. Findings on physical examination are normal except for tachypnea and tachycardia. He does not have edema or popliteal tenderness. An electrocardiogram reveals sinus tachycardia but is otherwise normal. Which of the following statements is correct? 

A. . A normal D-dimer level excludes pulmonary embolus
B. If there is no contraindication to anticoagulation, full-dose heparin or enoxaparin should be started pending further testing
C. Normal findings on examination of the lower extremities make pulmonary embolism unlikely
D. Early treatment of pulmonary embolism has little effect on overall mortality
E. A normal lower extremity venous Doppler study will rule out a pulmonary embolus

Correct Answer is B

Comment:

The clinical situation strongly suggests pulmonary embolism. In greater than 80% of cases, pulmonary emboli arise from thrombosis in the deep venous circulation (DVT) of the lower extremities, but a normal lower extremity Doppler does not exclude the diagnosis. DVTs often begin in the calf, where they rarely if ever cause clinically significant pulmonary embolic disease. However, thromboses that begin below the knee frequently “grow,” or propagate, above the knee; clots that dislodge from above the knee cause clinically significant pulmonary emboli. Untreated pulmonary embolism is associated with a 30% mortality rate. Interestingly, only about 50% of patients with DVT of the lower extremities have clinical findings of swelling, warmth, erythema, pain, or palpable “cord.” When a clot does dislodge from the deep venous system and travels into the pulmonary vasculature, the most common clinical findings are tachypnea and tachycardia; chest pain is less likely and usually indicates pulmonary infarction. The ABG is usually abnormal, and a high percentage of patients exhibit low P CO2 with respiratory alkalosis, and a widening of the alveolar-arterial oxygen gradient. The ECG usually shows sinus tachycardia, but atrial fibrillation, pseudoinfarction in the inferior leads, and acute right heart strain are also seen. Initial treatment for suspected pulmonary embolic disease includes prompt hospitalization and institution of intravenous heparin or therapeutic dose subcutaneous lowmolecular-weight heparin. It is particularly important to make an early diagnosis of pulmonary embolus, as intervention can decrease the mortality rate from 30% down to 5%. A normal D-dimer level helps exclude pulmonary embolus in the low-risk setting. This patient, however, has a high pretest probability of PE; further testing (CT pulmonary angiogram, V/Q lung scan) must be done to exclude this important diagnosis.