Morphological anatomy of the heart.

1. Morphological anatomy of the
the heart
DR. KRISHNAPRASAD BASHYAL
MCH RESIDENT CTVS

2. PERICARDIUM
 Pericardial sac – freestanding
 Pericardial cavity – between 2 layers of serous pericardium
 Two recesses – oblique sinus, transverse sinus
 Transverse sinus – horse shoe shaped
 Oblique sinus

5.  Most cardiac surface facing surgeon – right heart
 Extensive right atrial appendage – superior caval vein
 Leftward – aorta & pulmonary trunk
 Ventricular mass – extends to cardiac apex
 Cardiac silhouette

6.  Ventricular mass – three sided pyramid
 Diaphragmatic
 Anterior/sternocostal
 Left/pulmonary

8.  Terminal sulcus / terminal groove
 Sinus node
 Waterston / Sondergaard groove

12. RIGHT ATRIUM
 Three components
 Appendage
 Venous sinus
 vestibule

14.  Terminal sulcus  terminal crest

16.  SA node
 Blood supply to SA node
 The true IAS – between right & left chambers, formed by the floor of the fossa
ovalis (derived from fetal flap valve), adjacent anteroinferior muscular rim.
 extensive superior rim – septum seccundum, formed by deep interatrial fold,
extending between systemic & pulmonary veins.

18.  AV node – triangle of Koch

19.  Tendon of Todaro - is a fibrous structure formed by the union of the eustachian and
thebesian valves. The fibrous extension of these two valvar remnants buries itself in
the tissue separating the oval fossa from the mouth of the coronary sinus, and it
runs medially as the tendon of Todaro, which inserts into the central fibrous body.

20.  The entire atrial component of the axis of atrioventricular conduction tissues is
contained within the confines of the triangle of Koch.
 The atrioventricular bundle, penetrates more or less directly at the apex of the
triangle of Koch

21.  Central fibrous body – an area where the membranous septum, leaflets of A-V and
aortic valves join in fibrous continuity
 Proximity Aortic, Mitral & LBB of conducting system

24. LEFT ATRIUM
 Due to its position, only the appendage of the left atrium may be immediately
evident
 three components
 Unlike RA, venous component of LA larger than appendage
 Junction between these two parts not marked by terminal groove / crest

25.  Pectinate muscles of LA only within appendage (only trabeculated surface)
 Permits differentiation
 LA firmly anchored due to the four PV – direct access difficult
 Septal surface characterized by flap valve of FO – septum primum

27. RIGHT VENTRICLE
 Three portions – inlet, trabecular
and outlet parts

28.  Inlet portion – contain and limited by the TV and its tension apparatus
 Leaflets of TV positioned septally, inferiorly (murally), anterosuperiorly
 Constant feature of valve – direct attachment to the septum of the cords of its
septal leaflets
 Anterosuperior and inferior leaflets attach to freewall of RV

30.  Trabecular component of the right ventricle extends out to the apex, where its wall
is particularly thin and is especially vulnerable to perforation by cardiac catheters
 The outlet component of the right ventricle is a complete muscular structure, the
infundibulum, which supports the pulmonary valve

31.  The three leaflets of the pulmonary valve do not have a ring or an annulus, instead
are attached to the infundibular musculature in semilunar fashion
 The semilunar hinge-points crossing the anatomic ventriculoarterial junction, which
does form a complete ring, as does the sinotubular junction

32.  The basal attachments of the leaflets are attached in the ventricle, upstream relative
to the anatomic ventriculoarterial junction, whereas the peripheral attachments are
to the arterial sinotubular junction.
 The overall valvar structure, therefore, takes the form of a three-pointed coronet

35.  A distinguishing feature of the right ventricle is the prominent muscular shelf
separating the tricuspid and pulmonary valves: the supraventricular crest
 Most of the crest is the infolded inner heart curve
 Incisions, or deep sutures through this part, run into the transverse sinus and right
atrioventricular groove and can jeopardize the right coronary artery

36.  The distal part of the crest is continuous with the freestanding subpulmonary
infundibulum, the presence of this muscular sleeve permits the valve to be removed
and used as an autograft
in the Ross procedure
 Medial papillary muscle arises from
inferior limb of smt

37.  The body of the supraventricular crest inserts between the limbs of a prominent and
important right ventricular septal trabeculation.
 This structure, called the septomarginal trabeculation, has superior and inferior
limbs that clasp the crest.
 Superior limbs run upto leaflets of the pulmonary valve, whereas the inferior limb
extends backward inferior to the interventricular component of the membranous
septum

38.  The body of the septomarginal trabeculation runs to the apex of the ventricle,
where it breaks up into a sheath of smaller trabeculations
 Two trabeculations are particularly prominent
 One becomes the anterior papillary muscle of the tricuspid valve
 the other extends from the septomarginal trabeculation to the papillary muscle,
forming the moderator band.

42.  coarseness of the apical trabeculations is the most constant feature of the
morphologically right ventricle

43.  TV – annulus, leaflets, chordae and papillary muscles
 Contains very thin leaflets attached to the annulus
 Annulus more of a landmark than an actual fibrous ring
 Lack of this fibrous ring – large variations of the TVo in cardiac cycle, comfortable
dilatation in diseases

44.  TVoa expands and contracts twice during the cardiac cycle
 Contraction
 Begins during isovolumic relaxation and continue through first half of diastole
 Beginning of isovolumic contraction continues during ejection – reduces TVoa to its
minimum
 This contraction corresponds to closure of the valve completed at end of isovolumic
contraction

45.  Reduction in orifice perimeter not uniform
 septal – 12%
 Anterior – 15%
 Posterior – 17%
 Dilation of annulus – anterior and posterior segments, septal segment restricted due
to relationship with cadiac fibrous skeleton

47.  Narrowing of TVo – not only d/t perimeter contraction, also d/t change in shape of
annulus
 Contraction – more elliptical d/t displacement of AP commissure and bulging of the
septum

48.  TV annulus is saddle shaped
 Pommel  area of anteroseptal commissure
 Cantle  midpoint of base of posterior leaflet

49.  In cases of tricuspid regurgitation, besides an increase of tricuspid valve annulus
area, there is an increase in planarity or flattening of the normal annulus, which
induces leaflet tethering.
 Rigid structures, such as stented prostheses and rigid annuloplasty rings, destroy
this configuration and are likely to have a negative impact on the function of the
right ventricle

50.  Size of leaflets  anterior, posterior, septal
 Leaflet excursion (angle between free edge and annulus) is different for each
 Septal leaflet significantly smaller leaflet excursion comparatively
 Septal leaflet – plastered against the septum

52.  Leaflets – held by marginal and basal chords arising from three papillary muscle
groups
 Marginal – free margin
 Basal – ventricular surface
 Elongation / rupture of marginal chords  prolapse

53.  Three papillary muscles – anterior, posterior and septal
 Anterior and posterior aways present
 Septal PM absent in 20%
 APM largest head, usually single and sustains largest no. of chordae

55. LEFT VENTRICLE
 The left ventricle is also conveniently considered
in terms of inlet, trabecular, and
outlet components
 In contrast to the right ventricle, the inlet
and outlet components overlap considerably
in the morphologically left ventricle

56.  The inlet component surrounds, and is limited by, the mitral valve and its tension
apparatus.
 The two leaflets of the mitral valve, supported by two prominent papillary muscle
groups and their commissural cords and closing along a solitary zone of apposition,
have widely different appearances

58.  The aortic leaflet is short, squat, and relatively square.
 This leaflet, which is in fibrous continuity with two of the leaflets of the aortic valve,
is best termed the aortic leaflet, because it is not strictly in either an anterior or a
superior position
 Other leaflet – mural leaflet
 Aortic leaflet of the mitral valve also forms part of the outlet of the left ventricle the
distinction between inlet and outlet is somewhat blurred.

59.  The trabecular component of the left ventricle extends to the ventricular apex and
has characteristically fine trabeculations
 The apical myocardium is surprisingly thin
 outlet component of the left ventricle supports the aortic valve. Unlike its right
ventricular counterpart, it is not a complete muscular structure

60.  The septal wall is largely composed of muscle, but the membranous septum forms
part of the subaortic outflow tract.
 The posterior portion of the outflow tract is composed of the fibrous curtain joining
the apparatus of the aortic valve to the aortic leaflet of the mitral valve

62.  The muscular septal surface of the outflow tract is characteristically smooth, and
down this surface cascades the fanlike left bundle branch.
 The landmark of the descent of the left bundle branch is the membranous septum
immediately beneath the zone of apposition between the right coronary and
noncoronary leaflets of the aortic valve

64.  MV apparatus – annulus, leaflets, chordae tendinae, papillary muscles, left
ventricular free wall
 Chordae & papillary muscles – subvalvular apparatus
 Right fibrous trigone
 Left fibrous trigone

65.  The anterior leaflet is in fibrous continuity with the aortic valve through the aortic–
mitral anulus and forms a boundary of the left ventricular outflow tract
 The mitral valve leaflets are attached to an ovoid ring, or annulus of fibrous tissue,
that extends from the right and left fibrous trigones to form the junction between
the left atrium and ventricle

66.  In three-dimensional space, the annulus maintains a hyperbolic paraboloid shape
(saddle shape)
 The midanterior and mid-posterior annular segments are highest (farthest from
ventricular apex)
 The anterolateral and posteromedial commissures are lowest

67.  The mitral annulus is thinnest at the insertion site of the posterior leaflet.
 As this segment is not attached to any rigid cardiac structures, it is the most mobile
throughout the cardiac cycle and is the most prone to annular dilation

68.  As this segment is not attached to any rigid cardiac structures, it is the most mobile
throughout the cardiac cycle and is the most prone to annular dilation
 Depth of commissures in normal MV averaged 0.7 – 0.8 cm never exceeding 1.3cm

70.  Leaflets – anterior (larger), posterior (mural)
 Posterior leaflet – subcommissures
 Subcommissures divide MV into 8 segments

72.  The distance between the free edge of the commissures and the annulus is
approximately 8 mm
 The atrial surface of the leaflets is divided into two zones: a marginal rough zone
and central smooth zone.
 The rough zone is the coaptation surface of the valve and is the insertion site of
most of the chordae tendineae

73.  The chordae tendineae are collagenous leaflet extensions connecting the papillary
muscles and the ventricular side of the leaflets
 Tandler defined three orders of chordae

74.  Commissural chordae are shorter than the others and usually originate from the
highest tip of the papillary muscle
 There are usually 4 to 12 chordae originating from each papillary muscle group (2-
22)
 Chordal branching results in a number of chordae inserting to the mitral valve
leaflet, ranging from 12 to 80

75.  Two papillary muscles arise between the middle and apical thirds of the left
ventricle
 The anterolateral papillary muscle is typically composed of one muscle body while
the posteromedial papillary muscle usually arises from two muscle bodies
 Each papillary muscle supplies chordae to both leaflets.

76.  The anterolateral papillary muscle receives blood from both the left anterior
descending artery as well as a diagonal or obtuse marginal branch of the circumflex
artery
 Posteromedial papillary muscle receives blood from only one source: either the
circumflex or right coronary artery
 Acar and colleagues proposed a clinical morphologic classification of the papillary
muscles

77.  Type I a single undivided papillary muscle
 Type II refers to papillary muscles cleaved in a sagittal plane into two heads that
separately support the anterior and posterior leaflets of the mitral valve.
 Type III papillary muscles are cleaved in a coronal plane, forming an individual
head that supports the commissural chordae.

78.  Type IV refers to papillary muscles divided into multiple heads, with a separate
papillary muscle originating as a separate muscular band close to the mitral
which supports short chordae to the commissure.

81. AORTA
 The ascending aorta begins at the distal extremity of the three aortic sinuses, the
sinotubular junction, which lies at the line of opening of the free edge of the
of the aortic valve
 It is contained within the fibrous pericardial sac, so its surface is covered with
pericardium.

82.  The ascending aorta is related anteromedially to the right atrial appendage, and
posterolaterally to the right ventricular outflow tract and the pulmonary trunk
 The medial wall of the right atrium, the superior caval vein, and the right pleura
relate to its right side.
 On the left, its principal relationship is with the pulmonary trunk.

83.  Posterior to the ascending aorta is the transverse sinus of the pericardium, which
separates it from the roof of the left atrium and the right pulmonary artery

84.  The aortic root is the anatomic segment between the left ventricle and the
ascending aorta.
 It contains the aortic valve and other anatomic elements, which function as a unit.
 The aortic root has several anatomic components: the subcommissural triangles, the
aortic annulus, the aortic cusps, the aortic sinuses or sinuses of Valsalva, and the
sinotubular junction.

85.  The subcommissural triangles are part of the left ventricular outflow tract, but they
play an important role in the function of the aortic valve.
 The subcommissural triangles of the noncoronary aortic cusp are fibrous extension
of the intervalvular fibrous body and membranous septum
 subcommissural triangle beneath the left and the right aortic cusps is an extension
of the muscular interventricular septum

87.  Aortic annulus attaches AV to the LV
 It is attached about 45% of its circumference directly to the myocardium
 55% - fibrous structures

88.  Histologic examination of the aortic annulus reveals that the aortic root has a
fibrous continuity with the anterior leaflet of the mitral valve and membranous
septum, and it is attached to the muscular interventricular septum by fibrous
strands

89.  An important structure immediately below the membranous septum is the bundle
of His.
 The atrioventricular node lies in the floor of the right atrium between the tricuspid
annulus and the coronary sinus orifice
 This node gives origin to the bundle of His, which travels through the right fibrous
trigone along the posterior edge of the membranous septum to the muscular
interventricular septum

90.  At this point, the bundle of His divides into left and right bundle branches, which
run subendocardially along both sides of the interventricular septum.

91.  The normal aortic valve has three cusps. Each cusp has a semilunar shape and has a
base and a free margin.
 The base is attached to the aortic annulus in a crescent fashion. The point at which
the free margin of a cusp joins its base is the commissure, and the ridge in the
aortic wall that lies immediately above the commissures is the sinotubular junction

92.  The spaces contained between the aortic annulus and the sinotubular junction are
the aortic sinuses, or sinuses of Valsalva.
 There are three cusps and three sinuses: left cusp and sinus, right cusp and sinus,
and noncoronary cusp and sinus.
 The left main coronary artery arises from the left aortic sinus, and the right coronary
artery arises from the right aortic sinus

93.  The normal aortic root has a fairly consistent shape, and the sizes of the cusps, the
aortic annulus, the aortic sinuses, and the sinotubular junction are somewhat
interdependent
 Thus, large cusps have a proportionally large annulus, sinus, and sinotubular
junction.
 The three aortic cusps often have different sizes in a person, and the right and
noncoronary cusps are usually larger than the left cusp

94.  The free margin of an aortic cusp extends from one of its commissures to the other.
The length of the free margin of an aortic cusp is approximately 1.5 times the length
of its base

96.  During diastole, the free margins and part of the body of the three cusps touch
each other approximately in the center of the aortic root to seal the aortic orifice.
 The average length of the free margins of three aortic cusps must exceed the
diameter of the sinotubular junction to allow the cusps to coapt centrally and
render the aortic valve competent

97.  If a pathologic process causes shortening of the length of the free margin of a cusp,
or if the sinotubular junction dilates, the cusps cannot coapt centrally, resulting in
aortic insufficiency

98.  If the length of a free margin is elongated, the cusp prolapses, and depending on
the degree of prolapse, aortic insufficiency ensues

99.  The diameter of the aortic annulus is 10% to 20% Larger than the diameter of the
sinotubular junction of the aortic root in young patients
 As the number of elastic fibers in the arterial wall decreases with age, the
sinotubular junction dilates, and its diameter tends to become equal to that of the
aortic annulus in older patients.

100.  Dilation of the aortic annulus pulls the belly of the aortic cusps apart, decreasing the
coaptation area, and it eventually causes aortic insufficiency.
 With dilation of the aortic annulus, the subcommissural triangles of the
noncoronary cusp tend to become more obtuse as the crescent shape of the aortic
annulus along its fibrous insertion flattens

102.  The aortic sinuses facilitate closure of the aortic valve by creating eddies and
currents between the cusps and arterial wall
 Also prevent cusps from occluding the coronary artery orifices during systole, thus
guaranteeing myocardial perfusion during the entire cardiac cycle