Pulmonary embolism

Pulmonary embolism is a common medical problem whose incidence is likely to increase in our aging population. Although it is life-threatening, effective therapy exists. The treatment is not, however, without significant complications. Thus, accurate diagnosis is important. Unfortunately, the clinical manifestations of pulmonary embolism are nonspecific. Furthermore, in many patients the symptoms of an acute embolism are superimposed on underlying chronic heart or lung disease. Thus, a high index of suspicion is needed to identify pulmonary emboli. Laboratory parameters, including arterial oxygen tensions and electrocardiography, are as nonspecific as the clinical signs. They may be more useful in excluding another process than in diagnosing pulmonary embolism. The first radiologic examination is the chest radiograph, but the clinical symptoms are frequently out of proportion to the findings on the chest films. Classic manifestations of pulmonary embolism on the chest radiograph include a wedge-shaped peripheral opacity and a segmental or lobar diminution in vascularity with prominent central arteries. However, these findings are not commonly seen and, even when present, are not specific. Even less specific findings include cardiomegaly, pulmonary infiltrate, elevation of a hemidiaphragm, and pleural effusion. Many patients with pulmonary embolism may have a normal chest radiograph. The chest radiograph is essential, however, for two purposes. First, it may identify another cause of the patient's symptoms, such as a rib fracture, dissecting aortic aneurysm, or pneumothorax. Second, a chest radiograph is essential to interpretation of the radionuclide V/Q scan. The perfusion scan accurately reflects the perfusion of the lung. However, a perfusion defect may result from a variety of etiologies. Any process such as vascular stenosis or compression by tumor may restrict blood flow. 84 references