View source for Mitral valve

{{Short description|Valve in the heart connecting the left atrium and left ventricle}}
{{distinguish|text=a [[bicuspid aortic valve]], a congenital abnormality of the aortic valve}}
{{Infobox anatomy
| Name        = Mitral valve
| Latin       = valva atrioventricularis sinistra,<br>valva mitralis,<br>valvula bicuspidalis
| Greek       = 
| Image       = Diagram of the human heart (cropped).svg
| Caption     = Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow. (Mitral valve labeled at center right.)
| Width       = 
| Image2      = Gray495.png
| Caption2    = Base of ventricles exposed by removal of the [[Atrium (heart)|atria]]. (Bicuspid (mitral) valve visible at bottom left. 
[[Tricuspid valve]] visible at bottom right.)
| Precursor   = 
| System      = 
| Artery      = 
| Vein        = 
| Nerve       = 
| Lymph       = 
}}

The '''mitral valve''' ({{IPAc-en|ˈ|m|aɪ|t|r|ə|l}} {{respell|MY|trəl}}), also known as the '''bicuspid valve''' or '''left atrioventricular valve''', is one of the four [[heart valve]]s. It has two [[Cusps of heart valves|cusps]] or flaps and lies between the [[atrium (heart)|left atrium]] and the [[ventricle (heart)|left ventricle]] of the [[heart]]. The heart valves are all [[one-way valve]]s allowing blood flow in just one direction. The mitral valve and the [[tricuspid valve]] are known as the [[Heart valve#Atrioventricular valves|atrioventricular valves]] because they lie between the atria and the ventricles.<ref>{{Cite book|title=Gray's Anatomy: The Anatomical Basis of Clinical Practice|editor-last=Standring|editor-first=Susan|isbn=9780702052309|location=Philadelphia|oclc=920806541|year=2016}}</ref>

In normal conditions, blood flows through an open mitral valve during [[diastole]] with contraction of the left atrium, and the mitral valve closes during [[systole]] with contraction of the left ventricle. The valve opens and closes because of pressure differences, opening when there is greater pressure in the left atrium than ventricle and closing when there is greater pressure in the left ventricle than atrium.<ref>{{Cite book|title=Guyton and Hall's Textbook of medical physiology|last2=Hall|first2=John E.|last1=Guyton|first1=Arthur C.|year=2011|isbn=9781416045748|edition= Twelfth |location=Philadelphia, Pa.|oclc=434319356}}</ref>

In abnormal conditions, blood may flow backward through the valve ([[mitral regurgitation]]) or the mitral valve may be narrowed ([[mitral stenosis]]). [[Rheumatic heart disease]] often affects the mitral valve; the valve may also [[mitral valve prolapse|prolapse]] with age and be affected by [[infective endocarditis]]. 

The name of the mitral valve is derived from the word ''mitre'', referencing the ceremonial headdress worn by Roman Catholic bishops, due to the resemblance between the two leaflets of the valve and the distinctive shape of the headdress.<ref>{{Cite book|title=Porth's Pathophysiology: concepts of altered health states.|vauthors=Noriss TL|date=2018|publisher=Wolters Kluwer Health|isbn=978-1496377593|location=Amsterdam|oclc=1054224262}}</ref><ref>{{Cite book|title=Harrison's principles of internal medicine|publisher=McGraw Hill|vauthors=Kasper DL, Fauci AS, Hauser SL, et al.|isbn=9780071802154|edition= 19th |location=New York|oclc=893557976|date = 2015-04-08}}</ref>

==Structure==
[[File:Preop_view_Mitral_valve_Dr_Sáez_de_Ibarra.jpg|thumb|Operative view of the mitral valve with a chordal rupture "fail" of the anterior leaflet]]
[[File:3D Medical Animation Mitral Valve Prolapse.jpg|alt=3D Medical Animation still shot of Mitral Valve Prolapse|thumb|226x226px|3D medical animation still shot of mitral valve prolapse]]
{{See also|Heart valve}}
The mitral valve is typically {{convert|4|to|6|cm2}} in area and sits in the left heart between the left atrium and the left ventricle.<ref name="Donal">{{cite journal |last1=Donal |first1=E |last2=Panis |first2=V |title=Interaction between mitral valve apparatus and left ventricle. Functional mitral regurgitation: A brief state-of-the-art overview. |journal=Advances in Clinical and Experimental Medicine |date=October 2021 |volume=30 |issue=10 |pages=991–997 |doi=10.17219/acem/143324 |pmid=34714608|s2cid=240154628 |doi-access=free }}</ref> It has two cusps: an anterior one, and a posterior one.'''<ref name="Sinnatamby-2011">{{Cite book |last=Sinnatamby |first=Chummy S. |title=Last's Anatomy |publisher= Elsevier Australia|year=2011 |isbn=978-0-7295-3752-0 |edition=12th |pages=201}}</ref>''' The opening of the mitral valve is surrounded by a fibrous ring known as the [[Mitral valve#Annulus|mitral annulus]]. The anterior cusp attaches to one third of the circumference of the annulus, and the posterior cusp attaches to the remaining two thirds of its circumference. The anterior cusp is thicker and more rigid than the posterior one,'''<ref name="Sinnatamby-2011" />''' and covers approximately two-thirds of the valve.{{Citation needed|date=June 2023}} The anterior cusp intervenes between the mitral and aortic orifices.'''<ref name="Sinnatamby-2011" />''' Although the anterior leaflet takes up a larger part of the ring and rises higher, the posterior leaflet has a larger surface area.{{Citation needed|date=June 2023}}

===Leaflets===
[[File:Posterior leaflet of left atrioventricular valve.png|thumb|301x301px]]
In Carpentier's classification of a mitral valve, both the posterior and anterior mitral valve leaflets are divided into eight segments: P3 (medial scallop), P2 (central scallop), P1 (lateral scallop), A3 (anteromedial segment), A2 (anterocentral), A1 (anterolateral), PMC (posteromedial commissure), ALC (anterolateral commissure).<ref name="https://eurointervention.pcronline.com/article/mitral-valve-anatomy-implications-for-transcatheter-mitral-valve-interventions"/> Mitral leaflet thickness is usually about 1 mm but sometimes can range from 3–5 mm.<ref name="Omran-2010">{{Cite journal|last1=Omran|first1=A. S.|last2=Arifi|first2=A. A.|last3=Mohamed|first3=A. A.|date=2010-07-01|title=Echocardiography of the mitral valve|journal=Journal of the Saudi Heart Association|language=en|volume=22|issue=3|pages=165–170|doi=10.1016/j.jsha.2010.04.001|pmid=23960615|pmc=3727372|issn=1016-7315}}</ref><ref>{{Cite journal|last1=Lancellotti|first1=P.|last2=Moura|first2=L.|last3=Pierard|first3=L. A.|last4=Agricola|first4=E.|last5=Popescu|first5=B. A.|last6=Tribouilloy|first6=C.|last7=Hagendorff|first7=A.|last8=Monin|first8=J. L.|last9=Badano|first9=L.|last10=Zamorano|first10=J. L.|last11=on behalf of the European Association of Echocardiography|date=2010-05-01|title=European Association of Echocardiography recommendations for the assessment of valvular regurgitation. Part 2: mitral and tricuspid regurgitation (native valve disease)|url=https://academic.oup.com/ehjcimaging/article-lookup/doi/10.1093/ejechocard/jeq031|journal=European Journal of Echocardiography|language=en|volume=11|issue=4|pages=307–332|doi=10.1093/ejechocard/jeq031|pmid=20435783|issn=1525-2167|doi-access=free|url-access=subscription|hdl=1765/28539|hdl-access=free}}</ref>

===Chordae tendineae===
[[File:Heart left atrial appendage tee view.jpg|thumb|200px|The left side of the heart. The mitral valve, as well as the chordae tendinae are visible as white strings. These connect to the papillary muscles visible attaching to the muscular ventricle.]]
[[File:Chordae tendineae of left atrioventricular valve.png|thumb]]
The valve leaflets are prevented from prolapsing into the left atrium by the action of [[chordae tendineae]]. The chordae tendineae are inelastic [[tendon]]s attached at one end to [[papillary muscle]]s in the left ventricle, and at the other to the valve cusps. Papillary muscles are finger-like projections from the wall of the left ventricle.

When the left ventricle contracts, the pressure in the ventricle 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 [[Regurgitation (circulation)|blood flowing back]] to the left atrium). Each chord has a different thickness. The thinnest ones are attached to the free leaflet margin, whereas the thickest ones (strut chords) are attached further from the free margin. This disposition has important effects on systolic stress distribution physiology.<ref>{{cite journal  |vauthors=Nazari S, Carli F, Salvi S, etal |title=Patterns of systolic stress distribution on mitral valve anterior leaflet chordal apparatus. A structural mechanical theoretical analysis |journal=J Cardiovasc Surg (Torino) |volume=41 |issue=2 |pages=193–202 |date=Apr 2000 |pmid=10901521 |url=http://www.fondazionecarrel.org/carrel/cardiac/files/physio/physiofulltext.htm}}</ref>

===Annulus===
The '''mitral annulus''' is a [[fibrous rings of heart|fibrous ring]] that is attached to the mitral valve leaflets. Unlike [[artificial heart valve|prosthetic valves]], it is not continuous. The mitral annulus is saddle shaped and changes in shape throughout the [[cardiac cycle]].<ref>{{cite journal|last1=Mahmood|first1=Feroze|last2=Shakil|first2=Omair|last3=Mahmood|first3=Bilal|last4=Chaudhry|first4=Maria|last5=Matyal|first5=Robina|last6=Khabbaz|first6=Kamal R.|title=Mitral Annulus: An Intraoperative Echocardiographic Perspective|journal=Journal of Cardiothoracic and Vascular Anesthesia|date=December 2013|volume=27|issue=6|pages=1355–1363|doi=10.1053/j.jvca.2013.02.008|pmid=23962462}}</ref> The annulus contracts and reduces its surface area during [[systole (medicine)|systole]] to help provide complete closure of the leaflets. Expansion of the annulus can result in leaflets that do not join soundly together, leading to functional [[mitral regurgitation]].<ref>{{cite journal|last1=Perloff|first1=J. K.|last2=Roberts|first2= W. C.|year=1972|title=The Mitral Apparatus: Functional Anatomy of Mitral Regurgitation|journal= Circulation|volume=46|issue= 2|pages=227–239|doi=10.1161/01.cir.46.2.227|pmid=5046018|doi-access= free}}</ref>

The normal diameter of the mitral annulus is {{convert|2.7|to|3.5|cm}}, and the circumference is {{convert|8|to|9|cm}}. Microscopically, there is no evidence of an annular structure anteriorly, where the mitral valve leaflet is contiguous with the posterior aortic root.<ref>{{cite book|last1= Otto|first1=Catherine M.|first2=Robert|last2=Bonow|url=https://books.google.com/books?id=JO9LAQAAIAAJ|title=Valvular Heart Disease: A Companion to Braunwald's Heart Disease|location=Philadelphia|publisher=[[Elsevier Health Sciences]]|date=September 2009|isbn=9781416058922}}</ref>

==Function==
{{See also|Heart valves}}
During [[left ventricle|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 ([[Systole (medicine)|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 left ventricle contributes about 20% to the volume in the left ventricle prior to ventricular systole and is known as the ''atrial kick''.

[[File:Mitral Valve RK.png|thumb|240px|Mitral annulus]]

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.<ref name='Pai2003'>{{cite journal|title=Effect of atrial fibrillation on the dynamics of mitral annular area|journal=The Journal of Heart Valve Disease|year=2003|volume=12|issue=1|pages=31–7|pmid=12578332|url=http://www.icr-heart.com/journal/content/2003/jan/abstracts/article.php?id=135|access-date=2010-03-04|vauthors=Pai RG, Varadarajan P, Tanimoto M|archive-date=2011-07-13|archive-url=https://web.archive.org/web/20110713001841/http://www.icr-heart.com/journal/content/2003/jan/abstracts/article.php?id=135|url-status=dead}}</ref> Leaking valves can be corrected by [[Mitral Valve Annuloplasty|mitral valve annuloplasty]], a common surgical procedure that aims at restoring proper leaflet adjustment.

==Clinical significance==
===Disease===
{{listen|filename=Mitral Valve Prolapse.wav|title=Mitral Valve Prolapse murmur|description=Heart sounds of a 16 year old girl diagnosed with mitral valve prolapse and mitral regurgitation. Auscultating her heart, a systolic murmur and click is heard. Recorded with the stethoscope over the mitral valve.|format=[[wav]]}}There are some [[valvular heart disease]]s that affect the mitral valve. [[Mitral stenosis]] is a narrowing of the valve. This can be heard as an opening snap; 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.<ref name="freshlook">{{cite journal |first1=David |last1=Playford |first2=Arthur |last2=Weyman |title=Mitral valve prolapse: time for a fresh look |journal=Reviews in Cardiovascular Medicine |volume=2 |issue=2 |pages=73–81 |year=2001 |pmid=12439384 |url=http://www.medreviews.com/pubmed.cfm?j=2&v=2&i=2&p=73 |access-date=2015-01-01 |archive-url=https://web.archive.org/web/20140903102048/http://www.medreviews.com/pubmed.cfm?j=2&v=2&i=2&p=73 |archive-date=2014-09-03 |url-status=dead }}</ref>

A valve prolapse can result in [[mitral insufficiency]], which is the regurgitation or backflow of blood from the left ventricle to the left atrium due to the incomplete closure of the valve causing a systolic murmur heard at the apex of the heart. This increase in pressure in the left atrium and pulmonary circuit can lead to symptoms like fatigue, shortness of breath, and atrial fibrillation over time.<ref>{{Citation |last=Douedi |first=Steven |title=Mitral Regurgitation |date=2024 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK553135/ |access-date=2024-11-10 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=31985928 |last2=Douedi |first2=Hani}}</ref>

[[Rheumatic heart disease]] often affects the mitral valve. The valve may also be affected by [[infective endocarditis]].

There are also some rarer forms of congenital mitral valve disease that are often associated with other congenital heart anomalies. [[Parachute mitral valve]] occurs when all chordae tendineae of the mitral valve are abnormally attached to a single (or fused) papillary muscle. Straddling Mitral Valve occurs when the mitral valve's chordal attachments straddles, or goes through, a [[Ventricular septal defect|ventricular septal defect (VSD)]] and so has chordae originating on both sides of the ventricular septum. Mitral valve agenesis is very rare, defined as an absence or minimal presence of both mitral valve leaflets (complete agenesis) or one of the leaflets (partial agenesis).<ref>{{Cite journal |last1=Séguéla |first1=Pierre-Emmanuel |last2=Houyel |first2=Lucile |last3=Acar |first3=Philippe |date=2011-08-01 |title=Congenital malformations of the mitral valve |journal=Archives of Cardiovascular Diseases |language=en |volume=104 |issue=8 |pages=465–479 |doi=10.1016/j.acvd.2011.06.004 |pmid=21944149 |issn=1875-2136|doi-access=free }}</ref> 

Surgery can be performed to [[Mitral valve replacement|replace]] or [[mitral valve repair|repair a damaged valve]]. A less invasive method is that of [[mitral valvuloplasty]] which uses a balloon [[catheter]] to open up a stenotic valve. Alternatively, the Lawrie technique is an option for patients who have less valve tissue available for repair as they may have damaged or fragile valve leaflets. During the Lawrie technique, artificial fabric chordae are used to repair the valve which spares the existing valve leaflets and chordae during the repair.<ref>{{Citation |last=Salik |first=Irim |title=Mitral Valve Repair |date=2024 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK549879/ |access-date=2024-11-10 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=31751069 |last2=Lee |first2=Lawrence S. |last3=Sharma |first3=Sanjeev |last4=Widrich |first4=Jason}}</ref>

Rarely there can be a severe form of [[Mitral annular calcification|calcification of the mitral valve annulus]] that can be mistaken for an intracardiac mass or [[thrombus]].<ref>{{cite journal|last1=Kosior|first1=Dariusz A.|title=Mitral annulus caseous calcification mimicking cardiac mass in asymptomatic patient – multimodality imaging approach to incidental echocardiographic finding|journal=Polish Journal of Radiology|date=2014|volume=79|pages=88–90|doi=10.12659/PJR.889830|pmc=4005861|pmid=24791181}}</ref>

Mitral disease can be classified using Carpentier's classification which is based on the leaflet motion. Type I pertains to normal leaflet motion. Whereas, disease of the valve is categorized to primary mitral regurgitation or secondary mitral regurgitation based on the regurgitant etiology. Type II pertains to excessive leaflet motion leading to leaflet prolapse. Common causes include, but is not limited to, Barlow disease, myxomatous degeneration, inflammation, and papillary muscle rupture. Type III pertains to restrictive motion of the leaflets. Type IIIa pertains to restrictive motion during systole and diastole. Type IIIb pertains to restrictive motion during systole.<ref>Patrizio Lancellotti, Philippe Pibarot, John Chambers, Giovanni La Canna, Mauro Pepi, Raluca Dulgheru, Mark Dweck, Victoria Delgado, Madalina Garbi, Mani A Vannan, David Montaigne, Luigi Badano, Pal Maurovich-Horvat, Gianluca Pontone, Alec Vahanian, Erwan Donal, Bernard Cosyns, the Scientific Document Committee of the European Association of Cardiovascular Imaging, Multi-modality imaging assessment of native valvular regurgitation: an EACVI and ESC council of valvular heart disease position paper, European Heart Journal - Cardiovascular Imaging, Volume 23, Issue 5, May 2022, Pages e171–e232, https://doi.org/10.1093/ehjci/jeab253</ref>

===Investigation===
The closing of the mitral valve and the tricuspid valve constitutes the [[first heart sound]] (S1), which can be heard with a [[stethoscope]]. 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.{{citation needed|date=September 2017}}. Abnormalities associated with the mitral valve can often be heard when [[auscultation|listening with a stethoscope]].

The mitral valve is often also investigated using an [[Echocardiogram|ultrasound scan]], which can reveal the size, anatomy and flow of blood through the valve.

==Etymology==
The word ''mitral'' comes from [[Latin]], meaning "shaped like a [[mitre]]" (bishop's hat). The word ''bicuspid'' uses [[classical compound|combining forms]] of ''[[wikt:bi-#Prefix|bi-]]'', from Latin, meaning "double", and ''[[wikt:cusp#Noun|cusp]]'', meaning "point", reflecting the dual-flap shape of the valve.

==Additional images==
<gallery>
Image:Gray internal structure of heart.png|The human heart, viewed from the front. The mitral valve is visible on the right as the "bicuspid valve"
 Image:Gray1216.svg|The chest, showing surface relations of [[bone]]s, [[lungs]] (purple), [[pleura]] (blue), and [[heart]] (red). [[Heart valves]] are labeled with "[[Bicuspid valve|B]]", "[[Tricuspid valve|T]]", "[[Aortic valve|A]]", and "[[Pulmonary valve|P]]".
 Image:Mitral valve.jpg|Mitral valve, viewed in a [[cadaver]] specimen from within the left atrium.
</gallery>

==See also==
*[[Heart]]
*[[Heart rhythm]]
*[[Electrocardiography]]

==References==
{{Reflist}}

==Further reading==
*{{cite book|last1=Ingels|first1=Neil B.|last2=Karlsson|first2=Matts|title=Mitral Valve Mechanics|publisher=Linköping University Electronic Press|url-status=live|archive-url=https://web.archive.org/web/20220519032632/http://liu.diva-portal.org/smash/get/diva2:896325/FULLTEXT01.pdf|date=21 January 2016|isbn=9789176859520|url=http://liu.diva-portal.org/smash/get/diva2:896325/FULLTEXT01.pdf|archive-date=19 May 2022}}

==External links==
*{{SUNYAnatomyFigs|20|07|03}}—"Valves of the heart"
*[http://pie.med.utoronto.ca/PIE/PIE_whatWeDo_valves.html Cardiac Valve Animations—Perioperative Interactive Education Group]

{{Heart anatomy}}
{{Authority control}}

[[Category:Cardiac anatomy]]
[[Category:Heart valves]]