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Pericardial cavity

The pericardial cavity is the potential space between the visceral pericardium (epicardium) and the parietal pericardium, normally containing a small amount of serous fluid (15–50 mL). This fluid acts as a lubricant, reducing friction between the heart and pericardial sac during the cardiac cycle.

The cavity is not a single uniform space; it includes recesses and sinuses formed by reflections of the serous pericardium, such as the transverse sinus (between venous inflow and arterial outflow tracts) and the oblique sinus (posterior to the left atrium).

Pathologically, the pericardial cavity is the site of pericardial effusion, hemopericardium, chylopericardium, and pericarditis, all of which can impair cardiac function, sometimes leading to cardiac tamponade.

Synonyms

  • Pericardial space

  • Cavitas pericardialis

  • Serous pericardial cavity

Function

  • Provides a frictionless environment for heart movement

  • Allows cardiac motion within the pericardial sac during systole/diastole

  • Acts as a barrier against infection or spread of mediastinal pathology

  • Can expand in disease states to accommodate fluid, blood, or exudates

MRI Appearance

T1-weighted images:

  • Normal pericardial cavity contains only a thin hypointense line (serous fluid not appreciable in physiologic amounts)

  • Large effusions appear as low-signal collections surrounding the heart

T2 Cine (Cardiac-gated):

  • Cavity normally not seen unless fluid is present

  • Pericardial effusion appears as a bright hyperintense rim around the heart

  • Cine sequences demonstrate hemodynamic effects (e.g., diastolic collapse of RA/RV in tamponade)

STIR (Short Tau Inversion Recovery):

  • Suppresses fat and highlights pericardial fluid or inflammation as hyperintense

  • Useful in detecting exudative effusion, pericarditis, or pericardial cysts

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Pericardium enhances, but cavity itself does not

  • Highlights pericardial inflammation, thickening, or enhancement in pericarditis

  • Differentiates transudative vs exudative effusions when combined with mapping techniques

MRA (Magnetic Resonance Angiography):

  • Not typically used for the cavity itself

  • Demonstrates relation of cavity and effusion to great vessels

CT Appearance

Contrast-Enhanced CT:

  • Normal pericardial cavity appears as a potential space, usually invisible

  • Effusion appears as a hypodense (0–20 HU) rim around the heart

  • Hemopericardium appears hyperdense (>30–45 HU)

  • CT is excellent for detecting pericardial thickening, calcification, tumors, and fluid collections

CT Coronary Angiography (CCTA):

  • Clearly delineates pericardial cavity when abnormal fluid is present

  • Provides detailed relationship of pericardial space with coronary arteries and great vessels

  • Useful in pericardial constriction, effusion, and post-surgical assessment

CT images

Pericardial cavity anatomy CT axial image -img-00000-00000

CT images

Pericardial cavity anatomy CT axial image -img-00000-00000_00001