DESCRIPTION

Occlusion of a pulmonary vessel by a thrombus

EPIDEMIOLOGY

• Pulmonary embolism (PE) is seen more frequently in adults and tends to occur in postsurgical situations, especially when patients have been bedridden. Two patterns are described in children, classic thromboembolic PE (TE-PE) and in situ pulmonary artery thrombosis (ISPAT).
• Mean age for PE in children is 14.9 years, and 51% of cases are male.
• ~10% of adults who present with an acute PE die within 1 hour of onset.
• Increasing incidence is secondary to increased central catheter use.
• Mortality rate can be as high as 30% if diagnosis is delayed. Diagnostic delay averages 7 days from symptom presentation.
• The incidence of new cases of PE presenting to a large, urban pediatric emergency department was 2.1 cases per 100,000 visits.

ETIOLOGY

Blood clots appear as a result of deep vein thrombosis or other disease states.

RISK FACTORS

• In children
  • Presence of a central venous catheter
  • Lack of mobility
  • Congenital heart disease
  • Ventriculoatrial shunt
  • Trauma
  • Solid tumors or leukemia
  • After-surgical procedures (especially reparative intervention for scoliosis repair)
  • Hypercoagulable condition
  • Systemic infection
  • Elevated factor VIII or von Willebrand factor levels
  • Protein C deficiency
  • Factor V Leiden deficiency
  • Protein S deficiency
• In adults: most commonly due to the presence of a deep vein thrombosis, usually in the legs or pelvis

PATHOPHYSIOLOGY

• Thromboemboli may develop anywhere in the systemic venous system.
• PE is characterized by the triad of hypoxemia, pulmonary hypertension, and right ventricular failure.
  • Diminished pulmonary perfusion causes a ventilation–perfusion mismatch, resulting in hypoxemia.
  • Hyperventilation occurs secondary to stimulation of proprioceptors in the lung.
  • Hypercapnia is seen with severe occlusion of the pulmonary artery (often not seen with smaller emboli).
• Pulmonary infarction is uncommon due to the presence of collateral pulmonary and bronchial arteries along with the airways providing additional sources of oxygen to the tissues.
• Death occurs with 85% obstruction of the pulmonary arteries.