Mitral valve
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The mitral valve, also known as the bicuspid valve, is a valve in the heart that lies between the left atrium (LA) and the left ventricle (LV). The mitral valve and the tricuspid valve are known as the atrioventricular valves because they lie between the atria and the ventricles of the heart.
Overview
A normally functioning mitral valve allows blood to flow into the left ventricle during ventricular diastole, and prevent blood from going retrograde from the ventricle to the left atrium during systole.
Anatomy
The mitral valve has two cusps/leaflets (the anteromedial leaflet and the posterolateral leaflet) and gaurds an opening that normally admits two fingers. The opening is surrounded by a fibrous ring known as the mitral valve annulus. (The orientation of the two leaflets resembles a bishop's miter, which is where the valve receives its name.) These valve leaflets are prevented from prolapsing into the left atrium by the chordae tendinae.
The inelastic chordae tendineaeare attached at one end to the papillary muscles and the other to the cusps. Papillary muscles are finger like projections from the wall of the left ventricle. Chordae tendinae from each muscle are attached to both leaflets of the mitral valve. Thus when the ventricle contracts the chorde pull the two cusps together closing the opening.
Normal physiology
During left ventricular diastole, after the pressure drops in the left ventricle due to relaxation of the ventricular myocardium, the mitral valve opens, and blood travels from the left atrium to the left ventricle. About 70-80% of the blood that travels across the mitral valve occurs during the early filling phase of the left ventricle. This early filling phase is due to active relaxation of the ventricular myocardium, causing a pressure gradient that allows a rapid flow of blood from the left atrium, across the mitral valve. This early filling across the mitral valve is seen on doppler echocardiography of the mitral valve as the E wave.
After the E wave, there is a period of slow filling of the ventricle.
Left atrial contraction (left atrial systole) (during left ventricular diastole) causes added blood to flow across the mitral valve immediately before left ventricular systole. This late flow across the open mitral valve is seen on doppler echocardiography of the mitral valve as the A wave. The late filling of the LV contributes about 20% to the volume in the left ventricle prior to ventricular systole, and is known as the atrial kick.
See also
- Anatomy
- Pathophysiology
- Procedures to fix the mitral valve
External links
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