Lancet 2004;363:1295; Circ 2003;108:2726,2834

Cause: Thrombi from deep veins of the legs, pelvis, or arms embolize to the pulmonary arteries, producing pulmonary arterial obstruction

Nurses’ Health Study: Highest rates of PE seen in nurses > 60 yr old who were in highest quintile of body mass index; cigarette smoking, high BP also risk factors; hormone replacement rx doubles risk of venous thromboembolism and hence of PE; surgery increases risk of PE

Epidem: Up to 40% ofpts with DVT will have evidence of PE on lung scan; 29% ofpts with PE have abnormal scans of leg veins (Jama 1994;271:223; Ann IM 1997;12:775).

Among patients ≥ 50 yr old, incidence of PE was higher among women. Only a trivial difference in incidence was observed among African Americans compared to whites (Chest 1999;116:909).

Pathophys: Thrombi produce pulmonary arterial obstruction and hypoxic vasoconstriction. Release of vasoactive agents also increases pulmonary vascular resistance. An increase in alveolar dead space and redistribution of blood flow impair gas exchange. Reflex bronchoconstriction augments airway resistance. Edema
decreases pulmonary compliance, and RV afterload increases. RV enlargement shifts intraventricular septum, impairing LV diastolic function.

If patent foramen ovale or ASD is present, paradoxical embolism and/or right to left shunting and further hypoxemia can occur.

Sx: Dyspnea is the most frequent sx. Pleuritic chest pain, cough, hemoptysis, syncope, and cyanosis may also occur. In data from a multicenter registry, sx were acute in 63% ofpts.

The differential dx includes acute MI, CHF, dilated cardiomyopathy, pericarditis, pneumonia, asthma, primary pulmonary HT, pneumothorax, malignancy, rib fx, and costochondritis.

Si: JVD, parasternal lift, increased P₂, systolic murmur of TR at LLSB that increases in intensity during inspiration

Crs: The reported 3-mon mortality rate after PE is 13-17.5%. 30-day case fatality rates in Medicarepts with PE were 13.7% for men and 12.8% for women, 16.1% for blacks and 12.9% for whites (Nejm 1998;33:93).

ABGs: Hypoxemia raises suspicion for PE, but ABGs alone are neither sensitive nor specific enough to confirm or disprove the dx by themselves.

EKG: Anterior T-wave inversion is most frequent abnormality. Occasionally new RBBB, S₁Q₃T₃ pattern, T-wave inversion in leads V1-V4, or Afib is observed.

Echocardiogram: RV hypokinesis is seen in ˜ 40% ofpts and is associated with a twofold increase in the 14-d mortality rate and a 1.5-fold increase at 3 mon (Circ 1997;96:I-159). Normotensivepts with acute PE who present with RV dysfunction have a 10% rate of PE-related shock and 5% in-hospital mortality, while normotensivepts without echocardiographic RV dysfunction have a benign short-term
prognosis (Circ 2000;101:2817). Other nonspecific echo signs include RV dilation, abnormal septal motion, dilated PA, tricuspid regurgitation, and decreased/absent collapse of IVC during inspiration. Echo may be useful in excluding other conditions, such as acute MI or pericardial tamponade.

In a study of 1177pts with suspected PE, a D-dimer assay had a sensitivity of 85%, but a specificity of 69%; this suggests that a negative test is useful in excluding PE inpts with a low pretest probability of this condition (Mayo Clin Proc 2004;79:164; J Am Coll Cardiol 2002;40:1475; Ann EM 2002;39:144). Levels of D-dimer are elevated in acute MI, pneumonia, CHF, malignancy, and after surgery. The latex agglutination test is less sensitive than immunosorbent assay.

X-ray: CXR may show enlarged pulmonary arteries with pulmonary HT. Lung scan: In the PIOPED study, 933pts were studied prospectively. Few had negative lung scans; 88% ofpts with high-probability scans, 33% ofpts with intermediate-probability scans, and 12% ofpts with low-probability scans had PE by angiogram, but a minority of thepts with PE by angiogram had high-probability scans (sensitivity, 41%; specificity, 97%). Hence, a high-probability scan makes PE likely, but the absence of a high-probability scan does not exclude PE (Jama 1990;263:2753).