What is the mitral annulus?
The mitral annulus is a fibrous, ring-like structure that binds to and supports the two leaflets of the mitral valve and its surrounding anatomy. It enables proper function of the mitral valve (bicuspid valve) and facilitates blood flow within the heart.
In the average person, the mitral valve’s annulus has a circumference of about 3.34 inches (8.5 centimeters) and a diameter of approximately 1.22 inches (3.1 centimeters).
What does the mitral valve annulus look like?
Despite often being referred to as a “ring”, the mitral annulus is not actually round. Though unique in each person, it has a saddle-like shape (hyperbolic paraboloid) and is not continuous or complete.
There are two parts, the anterior and posterior. The anterior portion supports the anterior leaflet and is connected to the left and right trigones, the intertrigonal region and non-coronary and left cusps, and ultimately the aortic valve annulus, via a fibrous structure known as the aortomitral curtain. The posterior section supports the posterior leaflet of the valve and is generally less developed.
What is the function of the mitral annulus? How does it function?
The mitral ring plays an important role in cardiac valve function.
Its main functions are to support the mitral valve leaflets (and nearby structures) and ensure that they join neatly during closure by contracting, preventing mitral valve prolapse and mitral regurgitation.
What can go wrong with the mitral annulus?
A number of things can go wrong with the annulus.
An annulus that doesn’t attach well to the cusps of the bicuspid valve may cause dysfunction, which can lead to a variety of problems. Another concern is mitral annular calcification. This is a degenerative disease that occurs with age and tends to affect women and those over 70.
Complications of calcification include mitral regurgitation, mitral stenosis, and atrial fibrillation, infective endocarditis, coronary atherosclerosis, cardiac conduction system diseases, strokes, and more.