of the mitral valve mike poullis 形态的二尖瓣麦克课件

MORPHOLOGY OF THE MITRAL VALVE M. Kuduvalli ELEMENTS OF MITRAL VALVE APPARATUS nAnnulus nLeaflets nSubvalvar apparatus - Chordae tendinae - Papillary muscles MITRAL ANNULUS nZone of junction which serves as attachment to the muscular fibres of the atrium, ventricle, and attachment of the mitral valve nAttached to two fibrous trigones -The right fibrous trigone which forms a dense junction between the mitral, tricuspid and aortic (non-coronary cusp) annuli, and the membranous septum -The left fibrous trigone which lies between the aortic (left cusp) and the mitral annuli nBetween the two trigones, the mitral valve is in continuity with the aortic wall and there is no fibrous mitral annulus in this region FIBROUS SKELETON OF THE HEART SPATIAL RELATIONSHIP BETWEEN MITRAL, AORTIC AND TRICUSPID VALVES MITRAL ANNULUS nMitral annulus is a dynamic structure nHas a sphincter like function, effectively decreasing the valve area by about a quarter during systole nThis is secondary to contraction and relaxation of the basoconstrictor muscles (bulbospiral and sinospiral) nDilatation of the annulus occurs posteriorly IMPORTANT STRUCTURES SURROUNDING THE MITRAL ANNULUS MITRAL LEAFLETS nForm a continuous veil attached to the circumference of the mitral annulus nFree edge hangs into the LV, and is split by indentations nTwo well defined and constant indentations: - Anterolateral commissure - Posteromedial commissure MITAL LEAFLETS nCommissural areas (identified by presence of commissural chordae) divide the continuous mitral veil into two leaflets: - Anterior (aortic) leaflet - Posterior (mural) leaflet MITRAL LEAFLETS nCovered with endocardium nDistinct ridge on atrial side which - defines line of leaflet closure - separates leaflets into two zones - rough zone distal to the ridge (represents surface of coaptation) - clear zone proximal to the ridge ANTERIOR MITRAL LEAFLET nSemicircular or triangular nAttached to around 3/8th of circumference of the mitral annulus nHas common attachment to the cardiac skeleton with - left coronary cusp of aortic valve - half of non-coronary cusp ANTERIOR MITRAL LEAFLET nRough zone receives the chordae tendinae nForms boundary dividing the outflow and inflow tracts of the left ventricle. ANTERIOR MITRAL LEAFLET nDirect continuity between AML and the aortic wall nGap between aortic and mitral valves is filled with an inter-valvular septum. Fibrous mitral annulus is absent here 1.Intervalvular septum 2. AML 3. PML POSTERIOR MITRAL LEAFLET nQuadrangular in shape nAttached to around 5/8th of the circumference of the mitral annulus nMargin has two indentations, forming three scallops: - Anterolateral - Middle - Posteromedial nCleft chordae insert into these indentations MITRAL LEAFLETS POSTERIOR MITRAL LEAFLET nAdditional third zone, k/a basal zone, which is between the clear zone and the annulus. It receives insertion of the basal chordae nBasal zone is most obvious in the middle scallop since the majority of basal chordae insert here SUBVALVAR APPARATUS PAPILLARY MUSCLES nTwo groups of LV papillary muscles - Anterolateral - Posteromedial nEach group supplies chordae to their respective halves of both leaflets nArise from the anterior and posterior walls of the left ventricle respectively SUBVALVAR APPARATUS PAPILLARY MUSCLES nMay have one or more bellies each. Anterolateral usually has one nTip points towards the respective commissure SUBVALVAR APPARATUS PAPILLARY MUSCLES SUBVALVAR APPARATUS CHORDAE TENDINAE nFibrous strings that originate from tiny nipples on the apical portion of the two papillary muscles nMajority have branching pattern, either soon after their origin from the papillary muscles, or just before their insertion into the leaflets SUBVALVAR APPARATUS CHORDAE TENDINAE COMMISSURAL CHORDAE nTwo in number, one for each commissure, with similar names nArise as a main stem which branches radially to insert into the free margins of the commissural regions nTheir attachment defines the extent of the commissural areas CHORDAE OF THE A.M.L nTypically splits into 3 cords soon after its origin from the papillary muscles MAIN CHORDAE OF THE A.M.L. nTwo in number, one from each papillary muscle nInserted at 4-5 Oclock posteromedially and 7-8 Oclock anterolaterally OTHER CHORDAE OF THE A.M.L. nParamedial chordae - Insert near the middle of the free edge nParacommissural chordae - Insert between the main chordae and the commissural chordae CHORDAE OF THE A.M.L. CHORDAE OF THE P.M.L. nBasal chordae - Unique to the PML - Arise directly as single strands from the left ventricular free wall or from the small trabeculum carnae nRough zone chordae tendinae - Similar to AML chordae, but shorter and thinner nCleft chordae - Insert into indentations on the PML CHORDAE OF THE P.M.L. BLOOD SUPPLY OF THE MITRAL VALVE nMitral leaflets and chordae are avascular nPapillary muscle supply - Anterolateral supplied by LAD and in addition, by the Diagonal or an OM from the Circumflex - Posterolateral variably supplied by branches of either the Lt. Circumflex or the RCA TYPES OF MITRAL VALVE PATHOLOGY nType I: Normal leaflet motion - Annular dilatation - Leaflet perforation nType II: Leaflet prolapse - Chordal rupture - Chordal elongation - Papillary muscle rupture - Papillary muscle elongation nType III: Restricted leaflet motion - Restricted opening: Commissural fusion, leaflet and chordal thickening - Restricted closure: Excess tension on chordae during systole TYPES OF MITRAL VALVE PATHOLOGY REFERENCE POINT RHEUMATIC MITRALVALVE MORPHOLOGY nCan manifest as - Stenosis - Regurgitation - Mixed nThree primary pathological processes - Leaflet thickening - Chordal thickening, shortening and fusion - Coaptation of the edges of the leaflets, especially near the commissures RHEUMATIC MITRALVALVE MORPHOLOGY nLeaflet thickening can progress to: - Calcification, first of leaflet, and then peri-annular - Retraction, leading to combined stenosis and regurgitation nSubvalvar apparatus involvment may lead to different degrees of subvalvar fusion ISCHEMIC MITRAL VALVE DISEASE nDue to a combination of left ventricular wall akinesia or dyskinesia and ischemia of the papillary muscle itself, affecting the integrity of the subvalvar apparatus nPapillary muscle necrosis can lead to rupture either at its attachment at the base to the LV wall or at its tip near the chordal attachments nLeaflets and chordae are avascular structures, and are not directly involved in ischemic MR MYXOMATOUS DEGENERATION MORPHOLOGY nChordal elongation and rupture nThickening of mitral leaflets nRedundancy of mitral leaflets, billowing into the left atrium in systole nDegeneration and abnormal collagen synthesis in the region close to the chordal attachments INFECTIVE ENDOCARDITIS OF MITRAL VALVE nLeaflet involvement, with vegetation formation and subsequent destruction of the leaflet nThickening and healing a