Mitral annular calcification (MAC) is a common degenerative process involving the
fibrous annulus of the mitral valve. It is generally an incidental finding associated with
aging although it is occasionally associated with significant mitral regurgitation and can
rarely cause symptomatic mitral stenosis. In addition, MAC is associated with atrial
fibrillation, conduction system disease, atherosclerotic disease and adverse cardiovascular
events, including stroke and mortality (Harpaz et al., 2001).
The mitral valve annulus is the C-shaped segment of the fibrous skeleton at the base
of the left ventricle at its junction with the left atrium. The leaflets of the mitral valve are
attached to and suspended from the mitral annulus which provides structural support to the
valve apparatus along the medial, posterior, and lateral aspects of the valve. Anteriorly, the
mid-section of the anterior mitral leaflet is in fibrous continuity (via the intervalvular
fibrosa) with the posterior aortic root without intervening annular tissue
(Deluca et al., 2008).
Mitral annular calcification (MAC) develops from progressive calcium deposition
along and beneath the mitral valve annulus (Bittrick et al., 2002). MAC generally follows
the C-shape of the mitral annulus so the base of the anterior mitral leaflet is generally but
not always spared (Bittrick et al., 2002). MAC is most commonly identified by
echocardiography as an echo dense shelf-like structure involving the mitral valve annulus
with associated acoustic shadowing. The calcification frequently has an irregular, lumpy
appearance. Although mitral valve leaflets and chordae tendinae are generally not involved,
calcification may progressively accumulate in the subvalvular region beneath the posterior
leaflet with encroachment on the leaflet. Usual sparing of the leaflet commissures and
anterior leaflet distinguishes MAC from rheumatic mitral involvement (Bittrick et al.2002).