Chapter 19

• • Clinicians should be aware of individual risk factors for development of pulmonary embolism.
• • Pulmonary embolism should be considered in cases of unexplained hypoxemia.
• • Limitations exist for all current diagnostic studies.
• • All clinicians should have a diagnostic algorithm in cases of suspected pulmonary embolism.

Venous thromboembolism (VTE), a common medical problem, is the third most common vascular disease and carries a high morbidity and mortality. It is characterized by intravenous thrombus formation either as a deep venous thrombosis (DVT) in leg veins or as a pulmonary embolism (PE), a thrombus migrating to the lung circulation from proximal leg veins or the pelvis. Risk of venous thromboembolism rises with increasing age, up from 1:10,000 in childhood to 1:100 in the elderly. It is estimated that DVT occurs in 1 of 1000 adults and PE in 10–25% of these patients. Both conditions are difficult to diagnose due to their nonspecific symptoms and signs. As a result, many cases are recognized only postmortem or after a thrombus has migrated to the lung circulation. Therefore, it is extremely important to identify patients at risk to facilitate prompt diagnosis and management (Table 19–1). An algorithm can be instrumental in doing this. Because the thrombi originate in the legs, PE is potentially avoidable if preventive therapy, such as anticoagulation or compression stockings, is used in high-risk situations.

Table 19–1. Risk Factors for Venous Thromboembolism.

### Symptoms and Signs

Presenting signs and symptoms for pulmonary embolism are nonspecific, which makes clinical diagnosis difficult. The most common presenting symptoms noted in the patients from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study who had angiographically confirmed PE were dyspnea, pleuritic chest pain, and tachypnea. The findings on physical examination included increased respiratory rate, rales, tachycardia, a loud second heart sound, deep venous thrombosis, temperature above 38.5°C, wheeze, Homan’s sign (pain on palpation of the calf), pleural friction rub, an S3 gallop, and cyanosis. Syncope or hypotension may uncommonly be the presenting symptoms of pulmonary embolism and suggests severe hemodynamic compromise. The presence of the above clinical findings can heighten concern for PE but does not constitute a diagnosis.

Although clinical symptoms and signs are nonspecific, clinical models using findings from history and physical examination help focus clinical suspicion for PE. Recent clinical models use weighted clinical scores to assign low, moderate, or high clinical probability of a PE. Some use clinic assessment plus a noninvasive diagnostic test, such as the d-dimer assay that ...

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