僧帽弁 MV

WordNet

control consisting of a mechanical device for controlling the flow of a fluid
device in a brass wind instrument for varying the length of the air column to alter the pitch of a tone
one of the paired hinged shells of certain molluscs and of brachiopods
the entire one-piece shell of a snail and certain other molluscs
a structure in a hollow organ (like the heart) with a flap to insure one-way flow of fluid through it
relating to or resembling the miter worn by some clerics
of or relating to or located in or near the mitral valve; "mitral insufficiency"
(of brass instruments) having valves

PrepTutorEJDIC

(液体・ガスなどの流れを調節する)『バルブ』,弁 / (血液の流れを調節する)弁,弁膜 / (管楽器の)バルブ / (2枚貝の)から,貝がら / 《英》真空管

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/10/12 10:18:36」(JST)

wiki en

The mitral valve (also known as the bicuspid valve or left atrioventricular valve) is a dual-flap (bi- from the Latin, meaning double, and mitral- from the Latin, meaning shaped like a mitre) valve in the heart that lies between the left atrium (LA) and the left ventricle (LV). The mitral valve (not to be confused with the congenital bicuspid aortic valve) and the tricuspid valve are known collectively as the atrioventricular valves because they lie between the atria and the ventricles of the heart and control the flow of blood.

During diastole, a normally-functioning mitral valve opens as a result of increased pressure from the left atrium as it fills with blood (preloading). As atrial pressure increases above that of the left ventricle, the mitral valve opens. Opening facilitates the passive flow of blood into the left ventricle. Diastole ends with atrial contraction, which ejects the final 20% of blood that is transferred from the left atrium to the left ventricle. This amount of blood is known as end-diastolic volume (EDV), and the mitral valve closes at the end of atrial contraction to prevent a reversal of blood flow.

Structure

Operative view of the mitral valve with a chordal rupture "fail" of the anterior leaflet

The mitral valve is typically 4–6 cm² in area. It has two cusps, or leaflets, (the anteromedial leaflet and the posterolateral leaflet) that guard the opening. The opening is surrounded by a fibrous ring known as the mitral valve annulus. (The orientation of the two leaflets resemble a bishop's mitre, whence the valve receives its name.^[1]) The anterior cusp protects approximately two-thirds of the valve (imagine a crescent moon within the circle, where the crescent represents the posterior cusp). Note that although the anterior leaflet takes up a larger part of the ring and rises higher, the posterior leaflet has a larger surface area. These valve leaflets are prevented from prolapsing into the left atrium by the action of tendons attached to the posterior surface of the valve, chordae tendineae.

The inelastic chordae tendineae are attached at one end to the papillary muscles and the other to the valve cusps. Papillary muscles are fingerlike projections from the wall of the left ventricle. Chordae tendineae from each muscle are attached to both leaflets of the mitral valve. Thus, when the left ventricle contracts, the intraventricular pressure forces the valve to close, while the tendons keep the leaflets coapting together and prevent the valve from opening in the wrong direction (thus preventing blood to flow back to the left atrium). Each chord has a different thickness. The thinnest ones are attached to the free leaflet margin, whereas thickest ones (strut chords) are attached quite away from the free margin. This disposition has important effects on systolic stress distribution physiology ^[2]

Function

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 to 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.

The mitral annulus changes in shape and size during the cardiac cycle. It is smaller at the end of atrial systole due to the contraction of the left atrium around it, like a sphincter. This reduction in annulus size at the end of atrial systole may be important for the proper coapting of the leaflets of the mitral valve when the left ventricle contracts and pumps blood.^[3] Leaking valves can be corrected by mitral valve annuloplasty, a common surgical procedure that aims at restoring proper leaflet adjustment.

Clinical significance

The closing of the mitral valve and the tricuspid valve constitutes the first heart sound (S1). It is not the valve closure itself which produces the sound but the sudden cessation of blood flow, when the mitral and tricuspid valves close.

There are some valvular heart diseases that affect the mitral valve. Mitral stenosis is a narrowing of the valve. This can be heard as an opening snap in a heart sound which is not normally present.

Classic mitral valve prolapse is caused by an excess of connective tissue that thickens the spongiosa layer of the cusp and separates collagen bundles in the fibrosa. This weakens the cusps and adjacent tissue, resulting in an increased cuspal area and lengthening of the chordae tendineae. Elongation of the chordae tendineae often causes rupture, commonly to the chordae attached to the posterior cusp. Advanced lesions—also commonly involving the posterior leaflet—lead to leaflet folding, inversion, and displacement toward the left atrium.^[4]

A valve prolapse can result in mitral insufficiency which is a regurgitation or backflow of blood due to the incomplete closure of the valve. Surgery can be performed to replace or repair a damaged valve. A less invasive method is that of mitral valvuloplasty which uses a balloon catheter to open up a stenotic valve.

Additional images

Section of the heart showing the ventricular septum. (Bicuspid valve visible at center.)
Front of thorax, showing surface relations of bones, lungs (purple), pleura (blue), and heart (red outline). Heart valves are labeled with "B", "T", "A", and "P".
Apical view of valves
Cross-sectional view of mitral valve between left atrium (upper chamber) and left ventricle (lower chamber), which shows parts of walls of left atrium and left ventricle that are next to the mitral valve.
Mitral valve
Mitral valve

References

^ mitral valve, Stedman's Online Medical Dictionary at Lippincott Williams and Wilkins
^ Nazari S, Carli F, Salvi S, et al. (Apr 2000). "Patterns of systolic stress distribution on mitral valve anterior leaflet chordal apparatus. A structural mechanical theoretical analysis". J Cardiovasc Surg (Torino) 41 (2): 193–202. PMID 10901521.
^ Pai RG, Varadarajan P, Tanimoto M (2003). "Effect of atrial fibrillation on the dynamics of mitral annular area". The Journal of Heart Valve Disease 12 (1): 31–7. PMID 12578332. Retrieved 2010-03-04.
^ Playford, David; Weyman, Arthur (2001). "Mitral valve prolapse: time for a fresh look". Reviews in Cardiovascular Medicine 2 (2): 73–81. PMID 12439384.

External links

Anatomy figure: 20:07-03 at Human Anatomy Online, SUNY Downstate Medical Center — "Valves of the heart"
Cardiac Valve Animations - Perioperative Interactive Education Group — Cardiac valve animations

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 慢性僧帽弁閉鎖不全症のマネージメントの概要 overview of the management of chronic mitral regurgitation
2. 僧帽弁の心エコー評価 echocardiographic evaluation of the mitral valve
3. 僧帽弁逸脱の定義および診断 definition and diagnosis of mitral valve prolapse
4. 僧帽弁逸脱症候群 mitral valve prolapse syndrome
5. 大動脈弁および僧帽弁の低侵襲性手術 minimally invasive aortic and mitral valve surgery

English Journal

Transthoracic echocardiography in women with treated severe pre-eclampsia.

Dennis AT1, Castro JM.Author information 1Director of Anaesthesia Research, Department of Anaesthesia, The Royal Women's Hospital Parkville, Parkville, Victoria, Australia; Department of Pharmacology and Department of Obstetrics and Gynaecology, The University of Melbourne, Melbourne, Victoria, Australia.AbstractThe aim of this study was to investigate cardiac function and haemodynamic indices using transthoracic echocardiography in women with severe pre-eclampsia who had already received treatment interventions. Fifteen women with treated severe pre-eclampsia were studied using transthoracic echocardiography. Mean (SD) cardiac output in women with treated disease was 5690 (1708) ml.min(-1) . Systolic function was preserved in women with treated disease evidenced by mean (SD) fractional shortening 41 (9)%, fractional area change 62 (12)% and septal s' velocities 9.0 (2.1) cm.s(-1) . Left ventricle end-diastolic diameters were within healthy reference ranges at 4.7 (0.3) cm and the left ventricle was not dilated. Diastolic function was reduced, with a mean (SD) mitral valve E/septal e' ratio of 12.6 (4.1). Left ventricular mass was increased at 182.0 (44.4) g. There was large variability in haemodynamics in women with treated severe pre-eclampsia. Transthoracic echocardiography is acceptable and applicable and enables quantification of cardiac function in women with severe pre-eclampsia.
Anaesthesia.Anaesthesia.2014 May;69(5):436-44. doi: 10.1111/anae.12623. Epub 2014 Mar 27.
The aim of this study was to investigate cardiac function and haemodynamic indices using transthoracic echocardiography in women with severe pre-eclampsia who had already received treatment interventions. Fifteen women with treated severe pre-eclampsia were studied using transthoracic echocardiograp
PMID 24673113

Cardiac magnetic resonance imaging in patients undergoing percutaneous mitral valve repair with the MitraClip system.

Krumm P1, Zuern CS, Wurster TH, Mangold S, Klumpp BD, Henning A, Mueller II, Bretschneider C, Bauer A, Kramer U, May AE.Author information 1Department of Diagnostic and Interventional Radiology, Eberhard Karls University Tuebingen, Hoppe-Seyler-Str. 3, 72076, Tuebingen, Germany.AbstractBACKGROUND: Percutaneous mitral valve repair (MVR) with the MitraClip(®) system in patients with mitral regurgitation (MR) is known to reduce symptoms and to improve cardiac morphology and function. MitraClip has been approved for cardiac magnetic resonance imaging (MRI). To date, however, no systematic analysis exists on cardiac MRI in patients undergoing the MitraClip procedure.
Clinical research in cardiology : official journal of the German Cardiac Society.Clin Res Cardiol.2014 May;103(5):397-404. doi: 10.1007/s00392-014-0670-x. Epub 2014 Jan 30.
BACKGROUND: Percutaneous mitral valve repair (MVR) with the MitraClip(®) system in patients with mitral regurgitation (MR) is known to reduce symptoms and to improve cardiac morphology and function. MitraClip has been approved for cardiac magnetic resonance imaging (MRI). To date, however, no syste
PMID 24477865

Isolated accessory mitral valve: identification and anatomic description using 3D transesophageal echocardiography.

Berkowitz E1, Kronzon I.
European heart journal cardiovascular Imaging.Eur Heart J Cardiovasc Imaging.2014 May;15(5):596. doi: 10.1093/ehjci/jet230. Epub 2013 Nov 14.
PMID 24243141

Japanese Journal

左室機能低下と僧帽弁閉鎖不全症を有する重症心不全に対する心拍動下手術 (特集重症心不全に対する外科治療)

木山宏,垣伸明,塩見大輔
胸部外科 66(1), 11-16, 2013-01
NAID 40019541614

Triggers for Surgical Referral in Degenerative Mitral Valve Regurgitation

Itagaki Shinobu,Adams David H.,Anyanwu Anelechi C.
Circulation Journal 77(1), 2013
… Degenerative mitral valve disease is the most common etiology of mitral regurgitation in developed countries. … Degenerative mitral valve disease should be distinguished from other valvular disease because most of the lesions caused by degenerative changes are amenable to valve repair as opposed to replacement, and successful durable repair with optimal timing can maintain the patient's normal life expectancy. …
NAID 130001870155

Structural Valve Deterioration in a Starr-Edwards Mitral Caged-Disk Valve Prosthesis

Aoyagi Shigeaki,Tayama Kei-ichiro,Okazaki Teiji,Shintani Yusuke,Kono Michitaka,Wada Kumiko,Kosuga Ken-ichi,Mori Ryusuke,Tanaka Hiroyuki
Circulation Journal 77(1), 2013
… Background: The durability of the Starr-Edwards (SE) mitral caged-disk valve, model 6520, is not clearly known, and structural valve deterioration in the SE disk valve is very rare. … Methods and Results: Replacement of the SE mitral disk valve was performed in 7 patients 23–40 years after implantation. …
NAID 130001870112

Related Pictures

★リンクテーブル★

リンク元	「僧帽弁」「MV」
拡張検索	「floppy mitral valve」「sistlic anterior motion of the mitral valve」「systolic anterior motion of the mitral valve」「mitral valve ostium」
関連記事	「mitral」「valve」

「僧帽弁」

Mitral valve
	Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow. (Mitral valve labeled at center right.)
	Base of ventricles exposed by removal of the atria. (Bicuspid (mitral) valve visible at bottom left.)
Details
Latin	Valva atrioventricularis sinistra,; valva mitralis
Identifiers
Gray's	p.534
MeSH	A07.541.510.507
Dorlands; /Elsevier	12843904
TA	A12.1.04.003
FMA	7235
	Anatomical terminology