Chapter 75: Pulmonary Embolism
The most common origin for pulmonary emboli related to venous thromboembolic disease is from which vascular territory?
A. Deep veins of the lower extremities in the thighs
B. Deep veins of the lower extremities in the calves
C. Deep veins of the lower extremities in the foot
D. Deep veins of the upper extremities, especially the arms
E. Deep veins of the upper extremities, especially the hands
The answer is B. (Hurst’s The Heart, 14th Edition, Chap. 75) The overwhelming majority of emboli originate from the deep veins of the lower extremities, although any venous bed can be involved. Although thrombi may form at any point along the vein wall, most originate in valve pockets. The veins of the calf are the most common site of origin, with subsequent extension of the clot proximally prior to embolization (option B). Eventually, the thrombus may expand to fill the vessel entirely, with both retrograde and proximal extension. If embolization does not occur, the thrombosis can partially or completely resolve via three mechanisms: recanalization, organization, and lysis. Upper extremity DVT has become an increasingly important clinical problem because of the increasing use of pacemakers; implantable defibrillators; and long-term, indwelling, central venous catheters. Symptomatic PE may originate from upper extremity thrombi, although it is much less common than embolization from lower extremity DVT (options D and E).
Which of the following is not a risk factor for venous thromboembolism?
A. Oral contraceptive use
B. Myocardial infarction and heart failure
C. Body mass index of 20 kg/m2
E. Antithrombin III deficiency
The answer is C. (Hurst’s The Heart, 14th Edition, Chap. 75) Recent studies implicate obesity as a risk factor for VTE, particularly in developed countries. The Nurses’ Health Study found that a body mass index of 29 kg/m2 or greater was an independent risk factor for PE (option C).1 Observational studies suggest that patients with myocardial infarction and heart failure are at higher risk for VTE (option B).2 Malignancy clearly increases the risk of VTE (option D). Oral contraception, pregnancy, and the postpartum period are the most common settings in which women younger than age 40 acquire thromboembolic disease. Venous thrombosis develops in these settings three to six times more often than in age-matched women who are not on oral contraceptives (option A). Inherited thrombophilias including antithrombin III deficiency (option E), antiphospholipid antibody syndrome, the presence ...