Pulmonary Venous Thromboembolism

Key Features

Essentials of Diagnosis

• Predisposition to venous thrombosis, usually of the lower extremities

• Usually dyspnea, chest pain, hemoptysis, or syncope

• Tachypnea and a widened alveolar–arterial PO₂ difference

• Elevated rapid D-dimer and characteristic defects on CT pulmonary arteriography, ventilation-perfusion lung scan, or pulmonary angiogram

General Considerations

• Third most common cause of death in hospitalized patients

• Most cases are not recognized antemortem: < 10% with fatal emboli receive specific treatment

• Pulmonary thromboembolism (PE) and deep venous thrombosis (DVT) are manifestations of the same disease, with the same risk factors

  • Immobility (bed rest, stroke, obesity)

  • Hyperviscosity (polycythemia)

  • Increased central venous pressures (low cardiac output, pregnancy)

  • Vessel damage (prior DVT, orthopedic surgery, trauma)

  • Hypercoagulable states, either acquired or inherited

• Pulmonary thromboemboli most often originate in deep veins of the lower extremities

• PE develops in 50–60% of patients with proximal lower extremity DVT; 50% of these events are asymptomatic

• Hypoxemia results from vascular obstruction leading to dead space ventilation, right-to-left shunting, and decreased cardiac output

• Other types of pulmonary emboli

  • Fat embolism

  • Air embolism

  • Amniotic fluid embolism

  • Septic embolism (eg, endocarditis)

  • Tumor embolism (eg, renal cell carcinoma)

  • Foreign body embolism (eg, talc in injection drug use)

  • Parasite egg embolism (schistosomiasis)

Clinical Findings

Symptoms and Signs

• See Table 9–18

• Clinical findings depend on the size of the embolus and the patient's preexisting cardiopulmonary status

• Dyspnea occurs in 75–85% and chest pain in 65–75% of patients

• Tachypnea is the only sign reliably found in more than 50% of patients

• 97% of patients in the PIOPED study had at least one of the following

  • Dyspnea

  • Tachypnea

  • Chest pain with breathing