Surgical Management of Mitral Valve Disease

Valve Anatomy

The mitral valve is composed of a number of structures that function together allowing the valve to open in diastole and close in systole. There are five main components to allowing the mitral valve to function correctly: The valve leaflets, annulus, chordae tendineae, papillary muscles and the left ventricular wall. As the heart progresses through the cardiac cycle these components move together allowing for a competent valve. Anatomic or physiological changes to one or more of these components may lead to valve dysfunction.

There are two leaflets that comprise the mitral valve - anterior and posterior (Ranganathan, Lam et al., 1970). The region where the leaflets meet in continuity is referred to as the commissures. Although the leaflets are shaped differently they comprise the same surface area. The leaflets coapt along the rough zone which is thicker compared to the thinner atrial zone. Where the leaflets insert into the atrium is known as the annulus of the valve. The anterior aspect of the annulus is supported by the fibrous skeleton of the heart and as one moves towards the posterior annulus in a counterclockwise direction the fibrous support diminishes and eventually is absent leading to a more fragile region along the posterior annulus which is prone to dilatation (Wilcox & Anderson, 2004).

The chordae tendineae of the valve attach the leaflets to the papillary muscles. The chordae are divided into three main types depending on where they attach onto the leaflets (Lam, Ranganathan et al., 1970).

The primary chordae insert very close to the free margin of the leaflet edge. Secondary chordae attach to the leaflets usually in their mid portion in the ventricular side. Finally basal chordae extend from the ventricular wall or papillary muscle and insert at the base of the posterior leaflet.