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Topic

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Right fibrous trigone

The right fibrous trigone is a dense, triangular portion of the cardiac fibrous skeleton, located between the aortic valve annulus and the atrioventricular valves. It connects the aortic valve (right coronary cusp) with the mitral valve annulus and tricuspid valve annulus, forming a critical part of the central fibrous body of the heart.

It serves as an important structural support, anchoring the valve annuli, and electrically insulates the atria from the ventricles except at the atrioventricular (AV) node and His bundle. This region is also clinically significant as a site of calcification (as in aortic stenosis), prosthetic valve anchoring, and electrophysiological conduction pathways.

Synonyms

  • Right central fibrous body

  • Fibrous trigone of heart (right side)

  • Right atrioventricular fibrous trigone

Function

  • Provides structural stability to the cardiac skeleton by linking the aortic, mitral, and tricuspid annuli

  • Serves as the anchor point for valve cusps

  • Maintains spatial integrity of the heart’s outflow and inflow tracts

  • Electrically insulates atria from ventricles, except via the AV node–His bundle pathway

  • Serves as a landmark in cardiac surgery and electrophysiology

MRI Appearance

T1-weighted images:

  • Appears as a low-signal intensity structure due to dense fibrous tissue

  • Surrounded by higher-signal myocardium and blood pool, providing contrast

  • Calcification (if present) appears as a signal void

T2 Cine (Cardiac-gated):

  • Appears consistently as a dark hypointense triangular region between the aortic root and AV valves

  • Provides visualization of movement and spatial relationships of valve annuli during the cardiac cycle

  • Useful in identifying mass lesions or abnormal thickening versus normal fibrous tissue

STIR (Short Tau Inversion Recovery):

  • Fibrous tissue remains low signal

  • Pathological changes such as edema or inflammatory infiltration would appear hyperintense (rare in this region)

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Normal fibrous trigone shows little or no enhancement

  • Abnormal enhancement may indicate fibrosis, inflammation, tumor infiltration, or post-surgical scarring

  • Helpful for evaluating prosthetic valve-related complications

MRI Non-Contrast Cardiac-Gated 3D Imaging:

  • Provides high-resolution anatomical visualization of the fibrous skeleton of the heart

  • Demonstrates the spatial relationship of the right fibrous trigone with the aortic root, mitral annulus, and tricuspid annulus

CT Appearance

CT Coronary Angiography (CCTA):

  • Seen as a triangular, dense fibrous tissue area between the aortic root and AV valves

  • In patients with calcification, appears as a hyperdense, calcified region within the central fibrous body

  • Important for preoperative planning of valve replacement, TAVR, and electrophysiological procedures

  • Multiplanar and 3D reconstructions highlight valve annular relationships

CT image

Right fibrous trigone CT axial image -img-00000-00000

MRI image

Right fibrous trigone mri image