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Mitral Valve

Like with the aortic valve, in this chapter we will be primarily interested in the identification of catastrophic, gross valve failure or dysfunction that is severe enough to impact patient hemodynamics. This is the primary goal of the focused cardiac ultrasound (FoCUS) assessment and heavily relies on 2D ultrasound technology. A comprehensive evaluation of the valves involves color flow doppler (CFD), pulsed wave doppler (PWD) and continuous wave doppler (CWD) which are out of the scope of FoCUS but that we will briefly touch base. It is through these other techniques that we can have a better and more precise assessment of the different degrees of valve dysfunction. 

Mitral Valve Anatomy and Function Recap

The mitral valve is a bicuspid structure that allows directional flow of blood. Both the posterior and the anterior mitral valve leaflets are divided into eight segments with a thickness ranging between 1 to 5mm. On diastole, the mitral valve opens on the early filling stage when the left atrial pressure is greater than that of the left ventricle allowing it to fill with blood. Most of the blood flows during this initial phase of left ventricular relaxation. Atrial contraction contributes up to 25% of the cardiac output before the onset of systole. On systole, the pressure generated by the LV moves the scallops back to their closed position. The chordae tendinea prevent the valve from prolapsing into the atrium. The mitral annulus is the fibrous ring that supports the mitral valve leaflets and changes its shape throughout the cardiac cycle. 

MV anatomy.png
MV movement.gif

Mitral valve. On the left, its bileaflet structure with their corresponding scallops as seen from the left atrium. On the right we appreciate a 3D cine of the MV viewed from the left ventricle. Notice the movement of anterior mitral valve on early and late diastole as the anterior mitral valve appears to flicker. Also notice the shape of the MV annulus on systole and diastole. Images courtesy of Innotata and Kjetil Lenes.

MV stenosis

Mitral Valve Stenosis

The most common cause of mitral valve stenosis is rheumatic heart disease. The typical immobility of the valve tips creates a typical hokey stick configuration. 

On ultrasound we typically observe a hyperechoic and heavily calcified valve with significant reduction of movement. The diagrams display the movement of the valve on systole without and with stenosis.

Normal valve function on diastole

Mitral valve stenosis

2D Views

We can appreciate the restriction of movement of the anterior leaflet of the mitral valve in a hockey stick configuration on diastole when seen on the parasternal long axis and apical 4 chamber views. Compare the normal findings with that of a patient with MS.