A 52-year-old woman developed acute shortness of breath 3 weeks after a hysterectomy. She denied leg pain or swelling. She has no chronic medical problems and takes no medications. Her pulse is 105 beats/min, respiratory rate is 20 breaths/min, and the rest of her examination is unremarkable. She had an elevated hemidiaphragm on chest X-ray (CXR). These findings placed her at moderate risk for pulmonary embolism (PE) based on the Geneva score. Chest CT demonstrated a moderate-sized PE similar to the one shown in Figure 57-1. She was treated with anticoagulation without complications.
CXR showing a wedge-shaped pulmonary infarction with the base on the pleural surface and the apex at the tip of a pulmonary artery catheter; the catheter caused the occlusion of a peripheral artery. (From Miller WT Jr. Diagnostic Thoracic Imaging. New York: McGraw-Hill; 2006:272, Figure 5-61. Copyright 2006.)
PE is a thromboembolic occlusion (total or partial) of one or more pulmonary arteries, usually arising from a deep venous thrombosis (DVT).
- Population estimate of the age- and sex-adjusted annual incidence of DVT is 48 per 100,000 and 69 per 100,000 for PE; the incidence increases with age.1
- PEs are noted as incidental findings in 1% to 4% of chest CT studies.2
- One metaanalysis concluded that nearly 1 in every 4 to 5 patients presenting with an exacerbation of chronic obstructive pulmonary disease has a PE; presenting signs and symptoms did not distinguish patients with and without PE.3
- In a metaanalysis of randomized controlled trials (RCTs) of patients on venous thromboembolism (VTE) prophylaxis, the pooled rates of symptomatic DVT were 0.63% (95% confidence interval [CI], 0.47% to 0.78%) following knee arthroplasty and 0.26% (95% CI, 0.14% to 0.37%) following hip arthroplasty. The pooled rates for PE were 0.27% (95% CI, 0.16% to 0.38%) following knee arthroplasty and 0.14% (95% CI, 0.07% to 0.21%) following hip arthroplasty.4
- PE is most commonly caused by embolization of a thrombus from a proximal leg or pelvic vein that enters the pulmonary artery circulation and obstructs a vessel. PE may also be caused by:1
- An upper-extremity thrombus (from indwelling catheters or pacemakers) (Figure 57-1).
- Fat embolus (following surgery or trauma).
- Hair/talc/cotton embolus (from intravenous drug use).
- Amniotic fluid embolus (from a tear at the placental margin in a pregnant woman).
- PE results from vascular endothelial injury, which promotes platelet adhesion, blood flow stasis, and/or hypercoagulation causing more coagulants to accumulate than usual and resulting obstruction. Although most PEs are asymptomatic and do not alter physiology, PE can cause:
- Increased pulmonary, vascular, and airway resistance (from obstruction of vessels or distal airways).
- Impaired gas exchange (from increased dead space and right to left shunting).
- Alveolar hyperventilation (from stimulation of irritant receptors).
- Decreased pulmonary compliance (from lung edema, hemorrhage, or loss of surfactant).
- Right ventricular (RV) dysfunction ...