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Topic

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Endocardium

The endocardium is the innermost layer of the heart wall, lining the atria, ventricles, and cardiac valves. It consists of a thin layer of endothelium supported by connective tissue, elastic fibers, and small blood vessels. Beneath it lies the myocardium, the contractile layer of the heart.

The endocardium provides a smooth, non-thrombogenic surface for blood flow and plays an important role in valve architecture and the cardiac conduction system, with Purkinje fibers running within the subendocardial zone. It is a key site for pathological changes in ischemic heart disease, endocarditis, mural thrombus, and endocardial fibrosis.

Synonyms

  • Cardiac endocardium

  • Inner lining of the heart

  • Tunica intima of the heart

Function

  • Maintains a smooth endothelial lining for cardiac chambers

  • Prevents thrombosis by producing anticoagulant mediators

  • Supports and contributes to valvular structure

  • Houses the subendocardial Purkinje fibers for impulse conduction

  • Serves as a marker for ischemic injury patterns in imaging

MRI Appearance

T1-weighted images:

  • Endocardium itself is too thin for direct visualization

  • Appears as a hypointense border between bright blood and myocardium

T2 Cine (Cardiac-gated):

  • Cine balanced SSFP (steady-state free precession) images show the endocardial border as a sharp interface between bright blood pool and myocardium

  • Allows clear assessment of endocardial motion, wall thickening, and systolic/diastolic function

  • Abnormalities include endocardial hypokinesia, akinesia, or dyskinesia in ischemic disease

  • Provides high temporal resolution for functional evaluation of chambers and valves

STIR (Short Tau Inversion Recovery):

  • Suppresses fat to highlight subendocardial edema or inflammation

  • Useful in acute ischemia, myocarditis, and endocardial involvement in infiltrative diseases

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • First-pass perfusion: endocardium visualized for blood supply defects

  • Late gadolinium enhancement (LGE): Subendocardial hyperenhancement indicates ischemic infarction; distinguishes from non-ischemic midwall or epicardial involvement

  • Critical for myocardial viability assessment

MRA (Magnetic Resonance Angiography):

  • Not used to directly assess endocardium

  • Indirectly maps coronary arteries, defining vascular territories affecting subendocardial viability

CT Appearance

Contrast-Enhanced CT (Cardiac CTA):

  • Endocardium appears as a thin interface between contrast-filled chambers and myocardium

  • Endocardial thickening, calcification, or thrombus can be identified

  • Used in endocardial fibroelastosis, mural thrombus, or valve-associated lesions

CT Delayed Enhancement (CTDE):

  • Similar to MRI late enhancement: demonstrates subendocardial hypo- or hyperattenuation consistent with infarction or fibrosis

  • Alternative to MRI for myocardial viability imaging

CT Image

endocardium anatomy CT axial image -img-00000-00000

MRI image

Endocardium, Cardiac endocardium