Pericardial Effusion

 

 

• Normal anatomy
  • Inner serous layer  is the epicardium
  • Outer fibrous layer is pericardium
  • Space between the two is pericardial space
  • Normally contains about 20-50cc of fluid
  • Fat covers outside of heart and outside of pericardium sandwiching pericardial space between the two layers
    • Normal thickness of pericardium (parietal pericardium and fluid in space) is 2-4 mm
• Requires about 150-250cc before cardiac tamponade occurs
  • Tamponade compresses heart and causes low cardiac output
  • Most effusions do not lead to cardiac tamponade
  • Size of cardiac silhouette is frequently increased
  • Tamponade is rarely seen in association with pulmonary edema in the lungs

 

 

 

• Other causes
  • Serous fluid = transudate
    • Congestive heart failure
    • Hypoalbuminemia
    • Irradiation
  • Blood = hemopericardium
    • Rupture of ascending aorta or pulmonary trunk
    • Coagulopathy
  • Fibrin = exudate
    • Pyogenic infection, e.g. staph
    • Uremia: 18% in acute uremia; 51% in chronic uremia; dialysis patient
• Imaging findings
  • "Water bottle configuration" is symmetrically enlarged cardiac silhouette
    • Major DDX is cardiomegaly
  • Loss of retrosternal clear space
    • Non-specific and frequently not valid
  • "Fat-pad sign" from separation of retrosternal from epicardial fat line >2 mm (15%)

Pericardial effusion on both lateral chest radiograph and axial CT. Red arrow points to fat outside of pericardium. Green arrow points to pericardial space which is 8 mm in this patient (<4 mm is normal.)  The  yellow arrow  points to fat outside of heart and the blue arrow to the myocardium.

• Rapidly appearing cardiomegaly with normal pulmonary vascularity
• "Differential density sign" is increase in lucency at heart margin secondary to slight difference in contrast between pericardial fluid and heart muscle
• Diminished cardiac pulsations

• Echo
  • Separation of epi- and pericardial echoes extending into diastole (rarely behind LA)