Normal anatomy of tricuspid valve

Anatomy , embryology , histology and functioning of tricuspid valve

1. NORMAL ANATOMY OF TRICUSPID VALVE The forgotten valve “Cinderella” of all cardiac valves

2. Tricuspid valve The tricuspid valve is part of a complex functional system that also includes the right atrium, the right ventricle, and the pulmonary circulation. It is generally a three-leaflet valve with an annulus and its valvular plane facing toward the right ventricular apex

3. DEVELOPMENT

4. TRICUSPID VALVE DEVELOPEMENT DEVELOPMENT OCCURS IN TWO PHASES:- FIRST PHASE- CONNECTION OF RIGHT ATRIUM WITH RIGHT VENTRICLE SECOND PHASE- INVOLVES THE FORMATION OF THE VALVAR LEAFLET WITH THEIR TENSION APPARATUS

5. DEVELOPMENT OF TRICUSPID VALVE TV develops from two components - Endocardial tissue of AV canal. -Ventricular musculature( myocardial gully/ tricuspid gully)

6. Tricuspid gully complex Remodelling of the tissue of the right atrio-ventricular junction produces a myocardial gully that guards the inferior portion of the ventricular inlet The muscular conduit thus formed was initially termed the “tricuspid gully”

7. Inferior and lateral wall of this gully together with right endocardial cushion form the inferior leaflet. Septal leaflet develop from ventricular septum and postero -inferior part of endo- cardial cushion. Anterior leaflet formed from supraventricular crest

8. The separation of the trabecular layer sets the scene for formation :- Anterosuperior and inferior leaflets of the tricuspid valve, along with their supporting tension apparatus. Septal, leaflet of the tricuspid valve, along with its tension apparatus, is delaminated at a much later stage from the right ventricular aspect of the developing ventricular septum.

9. Developmental process leads to delamination of the underlying myocardium during 8-12 weeks. Delamination progress from posterior leaflet and development of this leaflet at 8 weeks to anterior leaflet (11 weeks) and finally to septal leaflet(12 weeks).

10. Congenital - EBSTEIN ANOMALY Characterized by Adherence of the septal and posterior leaflets to the underlying myocardium (failure of delamination, namely splitting of the tissue by detachment of the inner layer during embryologic development) Downward (apical) displacement of the functional annulus (septal> posterior> anterior)

11. TRICUSPID VALVE COMPLEX Annulus Three valve leaflets Supporting chordae tendineae Papillary muscles Part of Right atrium and right ventricular myocardium

12. ANNULUS

13. TV annulus -Annulus is a heterogeneous ,almost virtual ,structure composed of intermixed fibrotic and elastic fibers in continuity with the leaflet tissue , the atrium, and the ventricle . -Complex 3 D structure, Nonplaner , elliptical-saddle shaped annulus. -The annulus fibrosus is not visible from atrial view because it is deeper and 2mm external to the hinge.

14. More a landmark rather than fibrous ring Absence of encircling fibrotic structure explains the large changes in the tricuspid orifice continuously during cardiac cycle. Reduction in orifice perimeter is not uniform and annulus corresponding to septal leaflet reduces least while maximum reduction occur in posterior leaflet.

15. TV annulus DURING DIASTOLE –GROSSLY CIRCULAR DURING SYSTOLE – THE ATRIO-VALVULAR JUNCTION HAS AN OVOID SHAPE Normal circumference of TV annulus in adults is 11±2 c.m . Normal area of tricuspid valve is 7-10 cm2. Normal diameter in 4 chamber view is 28±5 c.m . Size of TV change dramatically during cardiac cycle Maximum size just before atrial systole In Mid systole reduced to 10±1 c.m . (19% reduction in circumference and 33 % reduction in area)

16. During disease conditions, the saddle-shaped annulus enlarges, becoming circular, and the corresponding change in the annulus area typically serves as a predictor of valve disorders such as tricuspid regurgitation .

17. Structurally, the annulus forms the base of the TV leaflets and is composed of two types of discontinuous segments—muscular annulus and collagen-rich fibrous annulus . The muscular annulus is formed of a circumferentially oriented myofiberous lamina and a second lamina formed of myofibers perpendicular to the circumferential myofibers . Racker et al. (1991)described that the anterior, lateral, and posterior regions of the TV annulus are completely encircled with circumferential myofibers with only a thin muscular connection at the medial region of the TV annulus. The fibrous annulus forms the antero-medial regions and continues with the connective tissues into the TV leaflets. Microscope-based study of the human TV annulus indicated the presence of myofibers in the posterior and anterior annulus and collagen bundles in the septal annulus

18. Fibrous Skeleton Rt fibrous trigone brings both MV and AOV into fibrous continuity with TV. This part of fibrous skeleton includes the membranous septum which separates the LVOT from right heart chamber. Septal leaflet inserts obliquely across the septum. This insertion of septal leaflet is 10-15 mm low(apically placed) compare to MV and divides membranous septum into atrioventricuar and interventricuar components.

19. Fibrous Skeleton

20. TV leaflets THREE LEAFLETS

21. The TV annulus transitions into three leaflets: Anterior leaflet Posterior leaflet Septal leaflet In general, the TV leaflets have a rough zone in the crescentic region where chordae tendineae are attached, a broad basal zone at the apex of the leaflet, and a clear zone.

22. The TV leaflet tissue layers are composed of extracellular matrix proteins—elastin, collagen, proteoglycans (PGs), and glycosaminoglycans (GAGs) populated with dynamic valvular interstitial cells (VICs). The connective tissue structure is organized into four morphologically and biomechanically distinct layers known as the: Atrialis (A) Spongiosa (S) Fibrosa (F) Ventricularis (V) HISTOLOGY

23. A dense, collagenous fiber network distinguishes the main load bearing layer of the leaflets, the fibrosa, from the surrounding tissue. The ventricularis , anatomically situated below the fibrosa and facing the ventricular side of the heart, is rich in circumferentially oriented elastin fibers that assist in the stretching and recoiling of the valve tissue.

24. The spongiosa layer is rich in hydrophilic GAGs and PGs that act as a dampening mechanism during rapid leaflet bending The atrialis layer—on the atrial side of the leaflet—is composed of elastin, collagen and GAGs, and this layer of the TV leaflets is reported to have a high innervation density

25. In addition, VICs are heterogeneous, dynamic cells distributed throughout the leaflets’ layers . VICs play a major role in maintaining the structural integrity of the leaflet tissues by regulating the extracellular matrix (ECM) scaffold remodeling. Different VIC phenotypes express molecular markers found in myofibroblast and smooth muscle cells (SMCs). The activated VICs produce myofibroblasts and express smooth muscle α-actin as well as other contractile proteins commonly found in the vascular SMCs . It has also been shown that the MV leaflet VICs are stiffer than the cells in the TV leaflets, implying a correlation between the VIC-regulated collagen biosynthesis and transvalvular pressure loading

26. Anterior leaflet- also known as infundibular leaflet, superior leaflet or greater leaflet. Semicircular but may be quadrangular. Largest in all leaflet , attached to right ventricular outflow tract LEAFLETS OF TV

27. Leaflets of TV Posterior leaflet - also known as marginal, dorsal or inferior leaflet Roughly trapezoidal shape. Inserted on one third of the circumference of the annulus Leaflet has several indentations or clefts in its free edge that give it a scalloped appearance. (predominantly three)

28. Leaflets of TV Septal leaflet - also called medial leaflet. Smallest leaflet. Semioval in shape. Attached to the right fibrous trigones and the atrial and ventricular septa. These fibrous attachments make this leaflet relatively immobile.

29. Leaflets of TV Because septal leaflet is relatively immobile most of the annular descent takes place along the margin of anterior and posterior cusp. During diastole anterior and posterior cusps move like sail to meet septal leaflet so functionally TV acts as bicuspid valve.

30. Leaflet of TV LEAFLET HAS THREE ZONES Rough zone -area between its free edge and line of closure. Basal zone - usually 2 mm wide area extends from the annulus to clear zone. 3. Clear zone - between these two zone.

31. Commisures Three commisures ANTERO SEPTAL COMMISURE- - Between anterior and septal leaflet -Chordae is short and arises directly from septal band or small papillary muscle. - Basal attachment of TV at this commisure is highest level at membranous septum.

32. Commisures ANTEROPOSTERIOR COMMISURE - Between anterior and posterior leaflet - Located roughly at acute margin of RV - Large anterior papillary muscle identifies this commisure . POSTEROSEPTAL COMMISURE -Between posterior and septal leaflet - Large chordae, papillary muscle and fold in septal leaflet - Posteroseptal commisure has the widest spread Free edge of commisural areas forms smooth arch.

33. Commissures Defined by the presence of Fan chords

34. Chordae tendinae Five types - FAN shaped chordae - Inserts into commisure and cleft - Rough zone chordae - inserts into rough zone of TV, divides into three prior to insertion. One at free edge, other at upper limit of rough zone and third between these two.

35. Chordae tendinae Free edge chordae - single, thread like, inserts at apex of leaflet. Deep chordae - long chordae inserts to rough or clear zone. Basal chordae - usually single, arises directly from myocardium or trabeculae . Inserts into zone approx. 2 mm wide extending into the leaflet from the annular region.

36. Chordae tendinae Average 25 chords inserts into the tricuspid valve. Seven to anterior, six to posterior, nine to septal and three into commisural areas. Fan shaped chordae inserts into cleft of posterior leaflet and at interleaflet commisure Other four are common to all three leaflets.

37. TANDLERS CLASSIFICATION

38. Papillary muscles Classically, three groups of papillary muscles – Anterior papillary muscle Posterior papillary muscle Septal papillary muscle These are present in the right ventricle, bearing fibrous chordae tendineae , which support the adjacent cusps of the tricuspid valve and prevent their reversion and re-gurgitation during systole. Trabeculae carneae , which are irregular muscular ridges and projections in the ventricular cavity, lined by the endocardium , are of varying type like free, fixed and papillary muscles.

39. The anterior papillary muscle is the largest and arises from the anterior wall The posterior papillary muscle is frequently bifid or trifid and arises from the inferior wall of right ventricle. Third smaller and most variable septal papillary muscle has a medial position, attached to the ventricular septum

40. According to a more recent functional terminology for the tricuspid valve, the papillary muscles can be grouped according to the distribution of their cords to a definite commissure and its contiguous main leaflets. Therefore, the APM becomes the anteroposterior , the PPM the posteroseptal and the SPM the anteroseptal papillary muscle, respectively ( Joudinaud et al., 2006).

41. TRICUSPID VERSUS MITRAL VALVE TRICUSPID VALVE MITRAL VALVE TRICUSPID BICUSPID VALVE 2) LARGE IN DIAMETER DIAMETER SMALL COMAPRE TO TV 3) MORE CHANGES DURING CARDIAC CYCLE BECAUSE OF FIBROUS SKELETON LESS CHANGES IN ANNULUS 4) EXTENSIVE CHORDAL SUPPORT BUT LESS UNIFORM MORE UNIFORM CHORDAL SUPPORT 5) PAPILLARY MUSCLE AT COMMISURE ARE INCONSISTENT PAPILLARY MUSCLE SUPPORT GOOD AND CONSISTENT 6) BASAL CHORDAE PRESENT IN ALL LEAFLETS BASAL CHORDAE PRESENT IN ONLY POSTERIOR LEAFLET 7) CHORDAE INSERTS AT VENTRICULAR WALL CHORDAE NEVER INSERTS TO VENTRICULAR WALL

42. TRICUSPID VERSUS MITRAL VALVE TRICUSPID VALVE MITRAL VALVE 8) RARELY AFFECT IN ISOLATION COMMONLY AFFECT IN ISOLATION 9) WORKS IN LOW PRESSURE SYSTEM WORKS IN HIGH PRESSURE SYSTEM

43. Relation with other structure Related to conduction system Right coronary artery Coronary sinus Aortic root

44. Conduction system – Triangle of Koch: The triangle of Koch is the home of the Atrioventricular node. Inferior border is Todaro's tendon Superior border is the septal leaflet of the tricuspid valve. The base is the coronary sinus.

45. Conduction system

46. Conduction system Bundle of HIS is direct continuation of AV node. Passes through the rightward part of central fibrous body to reach to the posteroinferior margin of membranous ventricular septum. This area is just inferior to commisure between septal and anterior leaflet of TV.

47. Conduction system When repairing the tricuspid valve, an open "C" ring avoids the necessity of suturing near the AV Node making complete heart block less likely

48. Coronary artery Right coronary artery runs parallel to the atrioventricular groove. Although injury to RCA is very rare but one should always careful while taking suture in this area.

49. CORONARY SINUS Coronary sinus situated above the posterosetal commisure and close to the right fibrous trigone . Place suture safely and avoid damage to coronary sinus.

50. RIGHT VENTRICLE ANATOMY,PHYSIOLOGY, ASSESSM ENT & CLINICAL SIGNIFICANCE A N A T O MY Crescent shaped chamber As suggested by “Goor and Lillehi” , Inlet Trabecular Out f l o w / Conus/ Infundibulum

51. RIGHT VENTRICLE ANATOMY,PHYSIOLOGY, ASSESSMENT & CLINICAL SIGNIFICANCE

52. RIGHT VENTRICLE ANATOMY ,PHYSIOLOGY, ASSESSMENT & CLINICAL SIGNIFICANCE • Within the right ventricle, a nearly circular ring of muscle known as the crista supraventricularis (supraventricular crest) forms an unobstructed opening into the outlet region. It consists of – Parietal band Outlet septum • • • • Septal band, and Moderator band

53. RIGHT VENTRICLE ANATOMY,PHYSIOLOGY, ASSESSMENT & CLINICAL SIGNIFICANCE

54. Aortic valve Anteroseptal commisure is very close to the non coronary sinus of aortic valve, placing the aortic prosthesis prior to TV prosthesis at this level can lead to injury, which will be difficult to repair in presence of aortic prosthesis so that always So always perform tricuspid valve procedure first.

55. TV DISEASE Can be classified in two group 1) Functional 2) organic TV DISEASE

56. Tricuspid regurgitation Functional TR  -occurs in left heart disease -severe PAH Leaflet and chordae remains normal. TR because annulus dilated and fails to shortens during systole. septal leaflet affects least in functional TR because- fixed at right fibrous trigone Attached to ventricular septum posterior leaflet changed maximum in TR . Kings et al reported 66% of sev TR patient came for surgery had mild TR at MV surgery.

57. Disproportional dilation of tricuspid annulus in secondary tricuspid regurgitation. Dilation develops in the area of anterior and posterior leaflets. Annulus does not dilate in the area of septal leaflet.

58. TV regurgitation

59. ORGANIC TV disease

60. Organic TV disease Endocarditis  5-10 % of all cases of IE. - More common in IV drug abuser - because its located prior to lung filter so -lesion vary from isolated vegetation to total destruction of annulus. - vegetation usually present at the tip of leaflet or towards the atrial side( conservative surgery possible).

61. Organic TV disease Rheumatic  isolated TV involvement very rare . Typical lesion show leaflet thickening with commisural fusion. Subvalvular apparatus rarely affected and cacification very rare. Classical lesion is stenosis but regurgitation also equally present.

62. Organic TV disease TV

63. Congenital - EBSTEIN ANOMALY Characterized by Adherence of the septal and posterior leaflets to the underlying myocardium (failure of delamination, namely splitting of the tissue by detachment of the inner layer during embryologic development) Downward (apical) displacement of the functional annulus (septal> posterior> anterior)

64. Ebstein … (3) dilation of the “ atrialized ” portion of the right ventricle, with various degrees of hypertrophy and thinning of the wall. (4) redundancy, fenestrations, and tethering of the anterior leaflet . (5) dilation of the right atrioventricular junction (true tricuspid annulus)

65. Ebstein anomaly Anterior leaflet is usually large and billowy (sail like). its chordae are fused short and deformed. It is least displced as compared to septal and posterior leaflet. The downward displacement of the septal and posterior leaflets in relation to the anterior mitral valve leaflet is 8 mm/m2 body surface area in normal heart.

66. Ebstein anomaly In Ebstein’s anomaly, the RV is divided into 2 regions: 1) the inlet portion, which is functionally integrated with the right atrium, 2) trabecular and outlet portions, that constitute the functional right ventricle. There is often marked dilatation of the true tricuspid valve annulus, which is not displaced, and a large chamber separating this true annulusfrom the functional RV. The RCA demarcates the level of the true annulus and may become kinked during plication annuloplasty procedures.

67. Ebstein anomaly During atrial contraction atrialized portion of RV in diastole and balloon out( taking up a large portion of blood volume to be ejected) During ventricuar systole atrialized RV contracts and creates pressure wave in normal RA. OVERALL effect leads to gross RA dilatation  this dilatation increases TV incompetence.

68. ANOMALIES OF TV STRADDLING OF TV  when a part of tension apparatus of the valve crosses the VSD and attached to the septum or VSD of the opposite ventricle. OVERRIDING  when atriventricular junction is connected to both ventricles.