• Common disease, any hospitalized patient at risk
  
• Chest radiograph nonspecific, 10% normal
  
• Pulmonary infarcts may be any shape or size

Chest radiograph

• 10% normal
  
• Most abnormalities nonspecific
  
• Vascular enlargement central pulmonary artery (knuckle sign)
  
• Focal oligemia (Westermark sign)
  
• Pulmonary infarct
  
  • 10% embolic episodes result in infarction
    
  • Infarction more common in those with underlying cardiopulmonary disease
    
  • May develop immediately or delayed 2-3 days following embolus
    
  • Any size or shape but classically cone shaped in periphery of lower lobes
    
  • Often associated with small pleural effusion
    
  • Evolution: initially ill-defined, over time become sharply defined
    
  • 50% clear completely usually within 3 weeks
    
  • May leave linear scars (Fleischner lines)

CT/HRCT

• Directly visualize clot in central pulmonary artery
• CT angiograms highly sensitive and specific
  
• High observer agreement
  
• Outcomes of negative CT angiograms excellent
• Mosaic perfusion, usually less well defined than pattern with small airways disease
  
  • Due to vascular obstruction with areas of hypoperfusion and overperfusion
    
  • No air trapping with expiratory scanning

• Mosaic pattern
  
  • Small airways disease
    
  • Viral or PCP pneumonia
    
  • Pulmonary alveolar proteinosis

• Pulmonary emboli end result of thrombosis in peripheral veins generally in the legs or pelvis
  

• No telltale signs, symptoms, or laboratory studies that strongly suggest PE
• Treatment
  • Anticoagulation and fibrinolysis
  • IVC filters if contraindications to drug therapy
• Prognosis
  • Good with appropriate therapy
  • Mortality of untreated disease 20%

Remy-Jardin M et al: Spiral CT angiography of the pulmonary circulation. Radiology 212: 615-36, 1999