Download Cardiac Anatomy and Physiologic Correlates

Cardiac Anatomy and Physiologic Correlates for the Echocardiographer
Understanding of cardiac anatomy and how anatomy relates to physiologic function both in normal and abnormal hearts
continues to evolve. Research the past 10 years have added to our understanding of these anatomical/physiologic
interactions. The use of sonomicrometry crystals in animals to study valvular function and interactions have been
pioneered by a number of laboratories (Miller, Gorman, Duran). Mathematical modeling of these same interactions
have provided insight into how anatomical alterations can influence these anatomic/physiologic interactions. The
development and application of matrix array 3D TTE and TEE transducers now allows capture of human cardiac
anatomy/physiologic function in real time. Post processing analysis packages have been and continue to be developed
to study both cardiac anatomy and function ―hidden’ in these matrix array data sets. Studies in humans using 3D matrix
array data sets have now been published beginning to confirm data found in animals using sonomicrometry crystals.
3D echo both allows us to become superior 2D echo cardiographer (2D still provides greater frame rate for resolution),
and begins to provide us insight to physiologic function in our patients.
The following anatomical discussion and references are meant to introduce the novice to these topics, yet challenge the
experienced echocardiographer to develop a greater understanding of cardiac anatomy and physiologic function.
2D and 3D echo measurements will be included to assist the practitioner in understanding past, current and future
published articles on this subject.
Fibrous Skeleton of the Heart
The true fibrous skeleton of the heart is formed by the U-shaped cords of the aortic annulus and their extensions
forming the right trigone, left trigone and a smaller fibrous structure from the right aortic coronary cusp to the root
of the pulmonary artery1. This "skeleton" plays a primary function of supporting the heart within the pericardium.
A continuum of fibrous tissue extends from the fibrous skeleton providing attachments for the atriums, ventricles
and valve leaflets.
Figure 1.
Fibrous skeleton of the heart consisting of
3 U-shaped cords of the aortic annulus, the right and left
trigones, and fibrous structure from right coronary cusp to the
root of the pulmonary artery. Extensions from skeleton
include the aortic curtain, mitral and tricuspid annulus, and
anterior leaflet of the mitral valve and pulmonic valve.
Three U-shaped cords of the aortic annulus join to each other at the commissures of the aortic valve forming a scalloped
fibrous crown-like skeleton of the aortic valve. The right fibrous trigone extends from the base of the noncoronary
cusp, and is more substantial than the left fibrous trigone. The left fibrous trigone extends from the base of the left
coronary cusp. A scalloped area is formed between the right and left trigone and the annular attachment of the left and
noncoronary cusp. This is called the intertrigonal space and has no proper skeletal structure. A broad membranous
curtain extending from the aortic annulus to the mitral annulus covers this space. This broad membrane is often referred
to as the aortic curtain and the space as the mitral aortic interstitial fibrosis or intervascular space. This membrane
merges with the anterior third of the mitral annulus becoming the middle portion of the anterior leaflet of the mitral
valve.
From the left and right fibrous trigone, a fibrous tissue continuum extends around the left and right atrioventricular
orifices forming the annuli fibrosi of the mitral and tricuspid annulus. The mitral annulus is the transition area where the
left atrium, mitral valve leaflets, and left ventricle come together. The mitral valve leaflets form a membranous curtain
attaching to the mitral annulus. The anterior circumferential portion of the mitral annulus associated with the left
trigone, intertrigonal space, and right trigone area is the attachment point of the anterior leaflet of the mitral valve.
This anterior portion of the mitral annulus is less prone to dilation. The trigonal margins are defined surgically by two
dimples raised at the border of the right and left trigone when lifting the anterior leaflet.
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Bruce Bollen, MD
The annuli fibrosi of the mitral annulus becomes thinner and poorly defined as it extends posteriorly from the left and
right trigones. This portion of the annulus is poorly supported and is prone to dilation in pathologic states. The
posterior leaflet of the mitral valve attaches to this portion of the annulus. Dilation of the annular attachment of the
posterior leaflet creates increased tension on the middle scallop of the posterior leaflet explaining the 60% occurrence of
chordal tears in the middle scallop of the posterior leaflet2.
From the base of the annular cord of the noncoronary cusp a membrane extends becoming continuous with the
interventricular septum. Its downward extension forms the membranous septum. This relationship is important in
understanding the anatomy of the left ventricular outflow tract (LVOT).
Aortic Root and LVOT
Aortic Root
The aortic root and left ventricular outflow tract are include together because it is important to understand their close
anatomical relations and coordinated physiologic function. The interleaflet triangles although considered part of the
aortic root are beneath the leaflet annulus and are in fact ventricular being exposed to ventricular/LVOT pressure and
filling. The left/non coronary interleaflet triangle is exposed to the left atrium, aortic curtain (mitral aortic interstitial
fibrosa), and anterior annulus of the mitral valve. The importance of aorto/LVOT/mitral interactions will be dealt with
in a separate section.
The aortic root is the portion of the ventricular outflow that supports the leaflets of the aortic valve. The superior
boundary of the aortic root is the sinotubular junction and the inferior boundary is the plane defined by the bases of the
aortic semilunar valves attaching to the crown shaped aortic annulus. Within these boundaries the aortic root is
composed of the aortic valve leaflets, the sinuses of valsalva and the interleaflet triangles.
There are three functional semilunar leaflets of the
normal aortic valve. Each leaflet has (1) a functional
hinge point where it attaches to the aortic root, (2) a
body of the semilunar valve and (3) a coaptation
surface of the leaflet with a thickened central nodule
(nodule of Aranti). The hinge point of the aortic leaflets
attach to the aortic root in a semilunar fashion along
the crown shaped aortic annulus (annulus fibrosus).
The apice of the leaflets attaching to the annulus
fibrosus attach to the sinotubular junction. The bases
of the aortic leaflets attach to the annulus at or below
the anatomic ventricular arterial junction. The three
cusps are referred to as right coronary, left coronary
and non-coronary cusps based on the coronary ostium
associated with the cusp. The cusps are of similar but
not equal sizes.
Figure 2. Diagram of the aortic root. (Inset) The coronet
like arrangement of the valvar attachments.
Corresponding with each cusp of the aortic valve, the aortic root is expanded forming the three sinuses of valsalva.
The sinuses of valsalva are defined inferiorly by the attachments of the aortic valve leaflets and superiorly by the
sinotubular junction.
The sinotubular junction is thicker than the adjacent sinuses and is circular, defining the beginning of the aorta proper.
The thickness and circular nature of the sinotubular junction plays an important role in supporting the aortic valve
leaflets. Dilation of the sinotubular junction can cause aortic insufficiency and may be a contraindication for placing a
stentless aortic valve.
The interleaflet triangles are the portion of the aortic root between the attachments
of the aortic valve leaflets along the
annulus fibrosus and the plane defined by the three bases of the aortic annulus 3. These interleaflet triangles, although
part of the aortic root, are exposed to left ventricular pressures in that they lay below the basal attachment of the aortic
leaflets.
Understanding the anatomic relationships of the aortic root to other cardiac structures is critical when evaluating
abnormal cardiac shunts and fistulas. These relationships are summarized in Table 1. Measurement of the diameter of
the base of the aortic annulus, sinus of valsalva, sinotubular junction and ascending aorta provide important data for
surgical decision making4.
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Bruce Bollen, MD
Table 1. Relationship of Various Portions of the Aortic Root to Surrounding Structures
Portion of Aortic Root
Related Structure
Noncoronary sinus
Left and right atriums, transverse sinus
Right coronary sinus
Right atrium, free pericardial space
Left coronary sinus
Left atrium, free pericardium
Non-/right coronary interleaflet triangle (membranous
spetum)
Right atrium, conduction system, septal leaflet of tricuspid
valve, right ventricle
Right/left coronary interleaflet triangle
Potential space between aorta and pulmonary trunk or
infundibulum
Left/noncoronary interleaflet triangle (subaortic curtain)
Left atrium, aortic curtain (mitral aortic interstitial fibrosa)
Figure 3. Schematic representation of four levels of aortic root
where measurements were taken.
Figure 4. Enfosse View of Fibrous Skeleton of Heart
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Bruce Bollen, MD
Figure 5. 3D Matrix array section, long axis view of LVOT and Mitral Valve
LVOT
The left ventricular outflow tract (LVOT) is defined anteriorly by the membranous and the muscular portion of the
interventricular septum5. The superior part of the membranous septum is directly continuous with the right wall of the
aortic root. The membranous septum is beneath the non-coronary cusp and right/non interleaflet triangle.
The posterior portion of the LVOT is defined by the anterior leaflet of the mitral valve.
The membranous septum is the fibrous part of the cardiac septum separating the LVOT from: 1) right ventricle and right
atrium. The line of attachment of the tricuspid annulus to the membranous septum determines the line of division
between the right ventricle and right atrium. The membranous septum also attaches to the infundibular (conal) portion
of the right ventricular RVOT22.
Expanding on this:
1) From the fibrous skeleton at the base of the noncoronary cusp a membrane extends becoming contiguous
with the interventricular septum and right trigone.
2) The right/non interleaflet triangle covering of the aortic root is membranous extending to the membranous
septum. Membrane extends inferiorly to join the LV septum.
3) From the fibrous skeleton at the base of the right coronary cusp the LV ventricular septum connects
directly.
4) The right/left interleaflet triangle covering of the aortic root is membranous, its base merging with the
interventriculae septum. However its base to apex is adjacent to the pulmonary trunk and infundibulum of
the RVOT. This intricate relationship between RVOT and LVOT is seen well by 3D echo and reflects
their development from the same tubular structure embryologically. (see Figure 4 and 5)
5) From the fibrous skeleton at the base of the left coronary cusp extends tissue connecting to the left trigone
6) The left/non interleaflet triangle covering of the aortic root is the aortic curtain (mitral aortic interstitial
fibrosa), merging with the anterio 1/3 of the mitral annulus becoming the anterior leaflet. Forms the
posterior portion of the LVOT.
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Bruce Bollen, MD
Anatomy of the Aortic Root
Leaflets and coronary ostia
a- interleaflet
triangles
b – valve
leaflets
Figure 6. Anatomy of the Aortic Root
Leaflets and coronary ostia,
interleaflet triangles
Understanding pathologic geometric changes in left ventricular and mitral valve apparatus relations is important in
conceptualizing abnormal mitral valve function. The concept of ―anterior displacement‖ of the mitral valve apparatus
resulting in SAM has been proposed in IHSS and post mitral valve annuloplasty where SAM is present. Left ventricular
dysfunction resulting in LV geometric change causing posterior and / or lateral displacement of the papillary muscles
causing altered mitral valve chordal tethering and mitral regurgitation has been proposed as the mechanism of
cardiomyopathic and ischemic mitral regurgitation.
Mitral Valve Apparatus
The mitral valve apparatus consists of the mitral annulus (with its atrial and ventricular attachments), mitral leaflets,
chordae, papillary muscles and the ventricular/papillary muscle interactions12-17. The important role of TEE
in mitral valve repair makes it imperative that the echocardiographer understands mitral valve anatomy. This
understanding of anatomy is then used to define the mitral valve anatomy visualized by multiplane/3D/ TEE imaging of
the mitral valve. The echocardiographer must be able to communicate his/her anatomic/pathological findings to the
surgeon performing a mitral valve repair. In addition to the anatomical terms for portions of the mitral valve, there are
two surgical nomenclatures used: the Carpentier terminology (adopted by ASE/SCA) 9,18 and the Duran
terminology19,20. Ideally the echocardiographer should be familiar with both of these different terminologies.
Mitral Valve Leaflets: Carpentier Terminology
The Carpentier terminology is solely a terminology of the mitral leaflets and does not involve naming chordae or
papillary muscles18. The lateral scallop of the posterior leaflet is named P1, middle scallop named P2, and medial
scallop named P3. The anterior leaflet is divided into A1, A2, A3 based upon the portion of the anterior leaflet making
contact to P1, P2, and P3 during systole. This terminology is used to define mitral leaflet abnormality as restricted,
normal or prolapsed.
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Bruce Bollen, MD
Figure 7.
Chordal Relationships – ASE/SCA Terminology
Anterior leaflet divided into A1, A2, A3. Posterior leaflet divided into P1 (anterolateral scallop), P2 (middle scallop),
P3 (posterolmedial scallop). Commissural clefts not named anterior or posterior. Chordae arising from the anterior papillary muscle
attach to A1, AC, P1, and latereral half of P2, A2. Chordae rising from the posterior papillary muscle attach to A3, PC, P3,
and medial half of P2, A2.
The Carpentier terminology does not in fact define chordal attachment to the leaflets. However it is important for the
echocardiographer to understand the orientation of chordae as related to this terminology. For this purpose their
attachments are explained and related to the Carpentier terminology (Figure 7). The chordae tendinae are fibrous
strings radiating from the left ventricular papillary muscles or the ventricular free wall (posterior leaflet only) and
attaching to the mitral leaflets in an organized manner13. Chordae from the papillary muscle radiate upward attaching to
the corresponding halves of the anterior and posterior leaflets. Chordae arising from the anterior papillary muscle attach
to A1, AC, P1, and the lateral half of P2 and A2. Chordae arising from the posterior papillary muscle attach to, A3, PC,
P3, and medial half of P2, and A2. This relation aids in defining the portion of the mitral valve visualized
echocardiographically.
There are two chordae attaching to the ventricular surface of the anterior leaflet which is by far the thickest and largest
of the chordae to the mitral valve. They have been called strut or stay chordae. One arises from the anterior papillary
muscle and attaches to A1/A2 area of the anterior leaflet; one arises from the posterior papillary muscle and attaches to
the A2/A3 portion of the anterior leaflet.
Figure 8. Three types of mitral chords. Illustrated from the DuranAncore Annuloplasty System
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Bruce Bollen, MD
ASE/SCA Mitral Valve Terminology
The American Society of Echocardiography/Society of Cardiovascular Anesthesiologists in their 1999
―Guidelines for Performing a Comprehensive Intraoperative Multiplane Transesophageal Echocardiography
Examination‖ defined terminology nomenclature for the mitral valve (Figure 9).
They elected to use the Carpentier numbering system (A1, A2, A3, P1, P2, P3) of the mitral leaflet, but made significant
changes in how the anterior leaflet portions were defined. The ASE/SCA anatomic nomenclature of the mitral valve:
A1, the lateral third of the anterior leaflet; A2, the middle third of the anterior leaflet; A3, the midial third of anterior
leaflet; P1, lateral scallop of posterior leaflet; P2, middle scallop of posterior leaflet; P3 medial scallop of posterior
leaflet (Figure 9). The commissural portions are termed anterolateral commissure and posteromedial commissure.
Note that this differs from Carpentier terminology. In Carpentier’s terminology A1, A2, and A3, are defined by where
P1, P2, and P3, co-apt with the anterior leaflet, not a random division of the anterior leaflet into thirds (see section on
Carpentier terminology). A subtle, but significant difference.
The ASE/SCA terminology is primarily a mitral valve leaflet terminology and does not address LV-Papillary-ChordalLeaflet relationships.
Figure 9. Anatomy of mitral valve. A1, Lateral third of the anterior leaflet; A2, middle third of the anterior leaflet;
A3, medial third of the anterior leaflet; P1, lateral scallop of the posterior leaflet; P2, middle scallop of the posterior
leaflet; P3, medial scallop of the posterior leaflet.
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Bruce Bollen, MD
The echocardiographer performing TEE is able to measure the height of the anterior leaflet and the three scallops of the
posterior leaflet. Anatomic measurements of normal heights of these leaflets are given in Tables 2.
Table 2. Height and Width of the Anterior and Posterior Leaflets of the Mitral Valve, Compared the Data of Rusted,
Scheifley, and Edwards (1952) and of Cheichi and Lees (1956)
Present study
Height
and Width
Male
(26)
Anterior
Height
(cm)
Width
(cm)
2.4
(2.0-3.0)
3.6
(2.5-4.8)
Posterior
middle
Height
(cm)
Width
(cm)
1.4
(0.9-2.0)
2.3
(1.3-3.8)
Anterolateral
commissural
Height
(cm)
Width
(cm)
1.1
(0.9-2.0)
1.6
(0.9-4.0)
Posteromedial
scallop
Height
(cm)
Width
(cm)
1.0
(0.6-1.7)
1.5
(0.9-3.1
Female
(24)
Cusp
2.2
(1.8-3.5)
2.9
(1.8-4.2)
Leaflet
scallop
1.2
(0.7-1.8)
1.8
(0.6-2.6)
Rusted, Scheifley and Edwards
(1952)
Male
(25)
Anterior
2.3
(1.6-2.9)
Posterior
1.3
(0.8-1.8)
--
Female
(25)
Cusp
2.1
(1.6-2.5)
-Cusp
2.1
(1.9-3.2)
3.7
(2.5-4.5)
Ventricular
1.2
(0.7-2.4)
--
1.4
(1.8-2.5)
3.3
(2.5-4.1)
Anterior
accessory
--
--
Commissural
0.8
(0.5-1.1)
1.1
(0.5-2.2)
Male
(60)
Aortic
scallop
1.0
(0.8-1.4)
1.4
(0.9-2.0)
Cheichi and Lees
(1956)
1.1
(0.8-1.8)
1.5
(1.1-1.8)
Posterior
leaflet
--
--
0.9
(0.6-1.2)
1.1
(0.8-1.5)
Female
(25)
Leaflet
2.2
(1.8-2.7)
3.3
(2.4-4.2)
Leaflet
1.2
(0.8-2.4)
3.0
(2.3-3.6)
leaflet
1.0
(0.7-1.3)
1.2
(1.0-1.6)
accessory
09
(0.7-1.0)
0.8
(0.7-1.2)
Papillary Muscles
The papillary muscles are large trabeculae originating from the junction of the middle and apical third of the left
ventricular wall in a plane posterior to the intercommissural plane in diastole. Rusted, et al, suggested the nomenclature
anterior (anterolateral) and posterior (posterior lateral) based upon the consistent relationship that each papillary muscle
bears with its respective commissural area (Carpentier Ac, Pc).
The anterior papillary muscle is located on the anterior-lateral free wall of the left ventricle. The posterior papillary
muscle originates at the junction of the inferior left ventricular free wall and the muscular ventricular septum. They
extend into the upper third of the ventricular cavity below the commissural tissue (Ac, Pc) of the left ventricle. The
papillary muscles most commonly have one head, but may have double, triple or multiple heads.
The anterior papillary muscle is more commonly supplied by two separate arteries: the first obtuse marginal arising
from the left circumflex and the first diagonal arising from the anterior descending artery. A single artery (usually form
the right coronary artery or the third obtuse marginal of the left circumflex) perfuses the posterior papillary muscle. The
greater incidence of posterior papillary muscle dysfunction or rupture in myocardial ischemia has been associated with
the single arterial supply to it vs. the common dual supply to the anterior papillary muscle.
The geometric distortion of the ventriculo-papillary-chordal-leaflet relationships has been shown to be the cause of
Carpentier type IIIb (restrictive motion in systole) leaflet dysfunction causing regurgitation in ischemic and
nonischemic myopathy. Focus on interpapillary muscle distance, papillary muscle activation dysynchrony, viable
myocardium (presence or absence) prior to bypass as risk factors for progression of type IIIb mitral regurgitation, and as
a cause of failure of ring annuloplasty alone in preventing recurrence of regurgitation is the subject of current research.
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Bruce Bollen, MD
Mitral Annulus
The mitral valve annulus is a three dimensional (3D), not a two dimensional (2D) structure. This was first described by
Weyman and Levine in 1987. Okada expanded the knowledge of 3D mitral valve annular structure in 1995 using
transesophageal echocardiography of surgical mitral valve repairs using flexible Duran or rigid Carpentier.28
Okada showed the 3D structure of the mitral valve annulus and suggested that the Duran flexible ring maintained the
patient’s 3D annular function better than the rigid Carpentier ring. (Figure 10-12)
Y. Yamaura, Okada et al.
J Heart Valve Disease;1995;4:618-622
Figure 10. Three-dimensional reconstruction of
the mitral annulus in normal subjects.
Figure 11. Three-dimensional reconstruction of the
mitral annulus in patients with a flexible
Duran Ring. Note apical movement of the
annulus in systole.
Figure 12. Three-dimensional reconstruction of the mitral
annulus in patients with a rigid Carpentier Ring.
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Bruce Bollen, MD
In 2000, Levine et al, expanded on their previous work and described the non-planimetry (annulus not lying in one 2D
plane) and referred to the mitral annulus as being ―saddle shaped‖29. Note the apical movement of the annulus in
systole. (Figure 13)
Flachscampf, Levine, Thomas et al.
J Am Soc Echocardiogr;13:277-287
Figure 13. Schematic drawings of parameters analyzed to quantitate the following. A, Nonplanarity: z-deviation
from least squares plane. B, Apico-basal excursion; excursion of temporally adjusted least squares plane centroid
from global least squares plane centroid. The absolute excursion in both directions from the global centroid was
taken as the total apico-basal excursion of the mitral annulus. C, Mitral annular area as projection of the annulus on
its temporally adjusted least square plane.
Modeling of Mitral Annulus
Engineers began to apply finite-element analysis computer modeling to describe strain, stresses and tensions in mitral
valve models. Models described were strictly defined. Modeling might use all, some or one of the mitral valve
apparatus components (annulus, leaflet, chordate, papillary muscles).
Kunzelman in the 1990’s developed a finite-element model modeling the annulus, leaflets and chordae. This model
suggested that annular tension was greatest at the trigones, and in the dilated annulus chordal tension was greatest in
marginal chordal closest to midline (A2/P2)2. This might explain greater tendency for ruptured chordae in these
regions. Her modeling suggested that mitral annular reduction annuloplasty helped to normalize leaflet, annular and
chordal stresses (flexible Duran superior to rigid Carpentier). This was supported by Cleveland Clinic data (1998)
suggesting that lack of ring annuloplasty was risk factor for failed repair. Kunzelman has expanded this modeling to
include the complete heart and examine the role of inflow fluid dynamics. (2010)26
Kuhl and Miller at Stanford recently published an excellent paper describing annular dynamics and tension in sheep.
They pointed also to the remarkable ―normal‖ variation of annular dynamics. 27
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Bruce Bollen, MD
The Gorman group in 2002 published their classic work modeling the saddle shaped mitral annulus as a hyperbolic
paraboloid (Figures 14-16). Their model was a mitral annular and leaflet model. No attempt was made to model
chordae. They showed in this nonplanar annulus the important role of annular height to commissural width ratio
(AHCWR) in minimizing leaflet tension. Optimal reduction of leaflet tension at a 25% AHWCR. Using TEE they
showed AHCWR in humans (14-16), sheep (7-19) and baboons (14-17). Hence the interest in measuring this height
and midcommissural diameter using 3D echocardiography31. They also suggested the role of saddle shaped annular
rings based on these findings. Hence the current interest in saddle shaped rings. Gorman’s laboratory has recently
reported 3D echo clinical studies relating annular and leaflet dynamics in patients receiving saddle shaped rings vs
Carpentier Physio Ring.
Salgo et al.
Figure 14. Plot of an elliptic (A) and
hyperbolic (B) paraboloid as
fundamental shapes, not leaflets. The
annular dimensions are 38.75 mm
across the major axis and 30 mm on
the minor axis. The height is 15mm,
which corresponds to a dome-height
ratio of 39% (hb/2a) for A (billowing
leaflet model) and an AHCWR of 39%
(ha/a) for B (nonplanar annulus model).
The hue of the shapes varies by
curvature using differential geometry.
The configuration in B represents
minimal surface area.
Figure 15. A, Figure of wire frame used to construct the mitral annulus and leaflets.
The AHCWR was 20% for this case. The annulus shown here is saddle-shaped.
The apposition of the anterior and posterior leaflet is shown across the major axis
of the annulus. The central struts of the anterior and posterior leaflets are shown.
These were either curved for domed leaflets or flat for flattened leaflets. B,
Demonstration of nonuniform rational B-spline surfaces used to fit phantom leaflets.
Collagen orientation is not shown. C, Model of phantom after mesh generation for
optimal alignment of computational elements. Anatomic landmarks are labeled
(LAA indicates location of leaflet atrial appendage; Ao, aorta; A, anterior leaflet; P,
posterior leaflet; and 1, 2, and 3, lateral, middle, and medial areas of the leaflets).
The mesh shown was used numerically for the finite element solutions. D, Stress
plot of linear static analysis.
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Figure 16. Plot of peak stress versus percent height.
The elliptic paraboloid (A) and the hyperbolic
paraboloid (B;saddle) are shown. A, Peak stress for
the billowing leaflet model. B, Peak stress for the
nonplanar annulus model. A flat disc results when the
parameters for each model, hb and ha respectively,
are set to 0. The peak stress of the flat disc is 335
MPa in A and B.
Bruce Bollen, MD
The Cleveland Clinic group in 2004 suggested the use of the non-planimetry angle to define the saddle shape of the
mitral valve hence the interest in 3D echo of measuring the NPA angle. (Figure 17)30
Kwan et al.
Figure 17. Three-dimensional digram of saddle-shaped
mitral annulus describing nonplanar angle (NPA), which
was defined as an angle between two vectors from two
hinge points of annulus in anteroposterior plane (AD 1) to
the center of axis connecting two commissures in
commissure-commissure plane and represented
nonplanarity of annulus.
Cardiac Ventricles
The right ventricle has functionally two openings separated by a band of mycocardium, the crista supraventricularis.
The two openings are the tricuspid and pulmonic valves. The left ventricle (LV) has a common opening at its base
shared by the aortic root and the mitral valve (Figure 18)5. The aortic valve and mitral valve share a common opening
in the base of the muscular left ventricle. The aortic valve and mitral valve are set at an angle to each other in this
shared left ventricular opening (Figure 19).
Figure 18. Diagram to show that the tricuspid and pulmonary
valves occupy separate openings within the right
ventricle. Whereas the mitral and aortic valves share
a common opening in the base of the left ventricle.
Figure 19. Aortic Root/LVOT/MV
Understanding pathologic geometric changes in left ventricular and mitral valve apparatus relations is important in
conceptualizing abnormal mitral valve function. The concept of ―anterior displacement‖ of the mitral valve apparatus
resulting in SAM has been proposed in IHSS and post mitral valve annuloplasty where SAM is present. Left ventricular
dysfunction resulting in LV geometric change causing posterior and / or lateral displacement of the papillary muscles
causing altered mitral valve chordal tethering and mitral regurgitation has been proposed as the mechanism of
cardiomyopathic and ischemic mitral regurgitation.
To facilitate reporting of left ventricular function echocardiographically, the ventricle is divided into segments. Various
segmental classifications have been utilized. The American Society of Echocardiography (ASE) has developed a 16segment model of the LV based on the recommendations of the Subcommittee on Quantification of the ASE Standards
Committee. This model divides the LV into three levels: basal, mid and apical. The basal and mid levels are each
divided circumferentially into six segments and the apical into four9.
In 2002, a 17-segment model of the LV was proposed. This model takes into account the apex tip of the heart as a
single segment. The basal and mid portion of the LV is divided into 6 segments each, the apex into 4 segments and
apical tip as one segment10.
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Bruce Bollen, MD
Aortic Root/LVOT/Mitral Interactions
The aortic root/LVOT/mitral valve annulus-leaflets share the single muscular opening of the left ventricular muscular
cone. For years they were considered separately. In the 1990s it became apparent to some that to understand cardiac
function aortic root/LVOT/mitral annulus needed to be considered together. A brief summary is as follows from the
elegant work of Duran, Lansac et al published in 2002 using sonomicrometry crystals in sheep: (Figure 20 and 21)24
1) Maximal mitral valve annular area occurs during mid-diastole
2) Minimal mitral valve annular area occurs during the second half of systolic ejection
3) Mitral valve annular area contracts 16% from mid-diastole to the second half of systolic ejection
4) Majority of mitral annular area reduction occurs before systolic isovolemic contraction (70%)
a. 30% of annular area reduction occurs in systole in a complex deformational manner
5) The posterior mitral annulus contracts from mid-diastole to beginning of systole
a. The arched anterior mitral annulus undergoes a conformational change (flattening) from early
diastole to early systole resulting in increased linear intertrigonal distance.
b. Anterior/Posterior diameter of the mitral annulus is lease when the linear intetrigonal distance is
at its maximal expansion.
Duran, Lansac et al.
Figure 20. Dynamic changes of the mitral anulus area during
cardiac cycle (MA) and of the anterior (T1-T2) and posterior
(T2-P2-PM-P1-T1)
annulus lengths (sheep 7).
Figure 21. Location of the sonomicrometry crystals in the aortic
root base and in the mitral anulus. R, L, and NC, Base of the
right, left, and noncoronary sinuses of Valsalva; T1 and T2, left
and right trigones; AM, midpoint between T1 and T2; PM,
midpoint of posterior anulus; P1 and P2, widest mitral diameter.
Duran and Lansac findings corroborated previous findings of systolic annular folding related to posterior displacement
of the anterior mitral annulus towards the left atrium.
They concluded that the aortic and mitral valves are part of a single structure functioning in synchrony.
―During early diastole the mitral valve orifice becomes larger because of the very significant expansion of its
anterior/posterior and transverse diameters. The anterior/posterior enlargement is caused primarily by the
expansion of the posterior annulus but also by displacement of the intertrigonal area toward the aortic orifice.‖
―During systole, the aortic orifice expands, including a displacement of the intertrigonal space toward the
posterior annulus‖
―The synchronized movements of the mitral and aortic annuli are a complex mechanism designed to facilitate
the filling and emptying of the ventricle‖.
Miller et al, extending their large body of work on mitral annular dynamic motion reported on the pre-ejection septallateral (anterior/posterior) hinge motion of the mitral annulus, similar to Duran and Lansec. They also posed the
problematic aspect of echocardiographic measurement of mitral valve orifice area: 2 dimensional projections of area vs
true 3D calculations. (Figure 22 and 23) 25
13
Bruce Bollen, MD
Itoh et al.
Figure 22↑. Schematic representation of septal-lateral
reduction during isovolumic contraction with mean data of
change in hinge angle (∆Φ), hinge axis-midlateral dimension,
and hinge axis-saddle-horn dimension.
Figure 23. Schematic representation of marker array in left ventricle
(LV), mitral annulus, and leaflets. Best-fit plane is applied to fibrous
annulus and muscular annulus. Angle from muscular plane to fibrous
plane was defined as hinge angle (∆Φ). B, Mitral annular and leaflet
markers, annular dimensions. EA, anterior mitral leaflet midedge; EP,
posterior mitral leaflet midedge; H-S, hinge-saddle-horn dimension;
H-L, hinge-lateral (muscular dimension); S-L, septal-lateral dimension.
C, Schematic representations of 3-dimensional total mitral annular area
(a) and 3-dimensional muscular and fibrous areas (b), with
2-dimensional projections on least squares-fit plane.
2D Echocardiographic Evaluation of the Mitral Valve
The ability to echocardiographically study the anatomic structure of the mitral valve apparatus has proved important to
aid mitral valve repair and to detect presence of perivalvular leak after mitral valve replacement.
When studying diagrams of the mitral valve related to the echocardiography it is important to bear in mind their
anatomic orientation: ventricular view vs atrial view of the mitral valve. When viewed surgically it is the atrial view
most often visualized. Additionally, although it is common practice to show multiplane sections from 0-180with the
axis of rotation in the middle of the mitral valve; in fact the axis rotation is at the probe posterior to the heart. Thus
standard views are really ―landmark views‖ requiring performer interpretation to determine location of structures being
visualized.
Foster et al in 1998 provided a nice summary of TEE landmark views of the mitral and related them to leaflet anatomy
using Carpentier’s terminology. They used both ventricular and atrial view diagrams . (Figure 24a-b)21
Using their imaging diagram overlayed with degree rotation of the TEE probe, the orientation of the valve leaflet (left
vs right) on the echo monitor can be conceptualized. As the probe rotates from 1-180it is actually creating a circle of
rays encompassing 360. If the center of each ray is conceptualized a the middle of the mitral valve, then for each ray
(or cut) half is between 0-180and the other end lies between 180 and 360. The orientation on the echo screen left to
right is as follows: Left side of the screen are sections of the ray from 0-180, right side of the screen are ray sections
from 180-360.
Using these landmark views the echocardiographer can define the anatomy of the mitral valve apparatus. Carpentier
recommended classifying mitral valve dysfunction based on leaflet pathology being normal, related to annular dilation,
leaflet prolapse, or leaflet restriction. Although unclear, most functional mitral regurgitation probably has a leaflet
restriction mechanism that can be defined echocardiographically but not surgically. These point to the importance of
examining the complete mitral valve apparatus (annulus, leaflet, chordae, ventricular function) and relating the anatomy
to abnormal flow, function. Possible anatomic changes related to surgical repair and their risk for SAM can also be
assessed.
14
Bruce Bollen, MD
Figure 24a. Standard Midesophageal Position:
Ventricular View
Figure 24b. Standard Midesophageal Position:
Atrial (Surgical) View
2D and 3D Echo
Matrix array transducers provide the ability to obtain steering of 2D images not available with multiplane probes. The
x-plane application gives a bi-plane view, but allows steering within the first plane to obtain different plane cut images
on the second 2D plane view. This steering is very helpful to examine the aortic and mitral valve, providing high frame
rate images with excellent definition and special orientation. In fact the X-pane alone is reason to obtain matrix array
TEE probes and machines.
Matrix array also allows for 3D:
1) Cropping of images to allow conceptualization of valve prolapse
2) Cropping to allow definition of location of pathology and specific measurements.
3) Analysis packages to measure mitral valve dimensions, leaflet coaptation 2D, and 3D areas, non planimetry etc.
4) Commercial analysis packages are being developed to do the same for the aortic root.
Applications of these tools will be discussed in the 3D portion of the perioperative echo meeting.
The mitral annulus/orifice depicted above as a 2D planar structure is in fact non-planar existing in a 3D X-Y-Z planar
axis. The classic diagram often shown is that the mitral valve is saddle shaped. The mid anterior annulus is the
elevated anterior horn, the mid elevated posterior annulus is the posterior horn. The anterolateral and posteromedial
commissural areas are the lower portions of the annulus and define a lower commissural plane. These are only four
points of an annulus. Connected with them, annular point and leaflets attached giving a saddle shape or hyperbolic
paraboloid shape. This shape amazingly enough is one that minimizes tension on the mitral valve apparatus when
functioning normally.
3D echo can examine the shape of the mitral annulus and it changes throughout the cardiac cycle. Annular shape differs
between normal and pathological states. The recent output of 3D echo papers on this subject will continue.
15
Bruce Bollen, MD
Measurement of the non-planimetry of the mitral valve is often referred to:
1) H: The vertical distance between the line connecting the anterior mitral annulus midpoint and posterior
annulus midpoint, and the line connecting the midcommissural transverse plane line.
2) The non-planimetry angle (NPA): Angle formed by vectors originating from midcommissural plane
(lowest planar projection of mitral annuls) to 1) Anterior mitral annulus and 2) Posterior mitral annulus.
Reflects nonplanar nature of mitral annular saddle shape.
Enriquez-Sarano and the Mayo Clinic group reported in 2010 3D echo annular dynamics for myxomatous mitral valves.
They showed flattened annular rings, reduced height, and increased circumference in myxomatous compared to
normals. (Figure 25,26, and Table 3)32
Grewal, Enriques-Sarano et al
Circulation 2002;106:711-717
Figure 25. Schematic representation of a
3-dinensional reconstructed mitral annulus. Standard
measurements are illustrated. Abbreviations as in
Figure 25.
16
Figure 26. Schematic profile view of a normal and a
myxomatous mitral valve annulus in late diastole (top
left and right, respectively) and early systole (bottom
left and right, respectively). Note that the saddle
shape is accentuated from late diastole to early
systole in the normal annulus but that this change is
blunted in MVD. Abbreviations as in Figure 26.
Bruce Bollen, MD
Table 3. Annular Dimensions Overall and Throughout the Cardiac Cycle Among Normal Subjects (n=15) and MVD Patients (n=32)
Grewal, Enriques-Sarano et al
Lawrie and Zoghbi reported 3D results in functional and myxomatous patients with prolapse. Both had increased mitral
annular enlargement, but this was greater in the myxomatous (prolapsed) group. (Figure 27 and 28)33
Little, Lawrie, Zoghbi et al
JASE 2010;23:872-9
Figure 27. Dynamic MA area throughout the
cardiac cycle. Compared with the normal
control group, the F-MR group demonstrated
mild increase in MA area with marked
reduction in dynamic area change. The P-MR
group had markedly increased MA area with
relatively preserved dynamic area change.
17
Figure 28. Annular was markedly increased for the P-MR
group and mildly increased for the F-MR group (A).
Annular area change was reduced in the F-MR group (B).
Annular displacement was mildly reduced in the P-MR
group but markedly reduced in the
F-MR group (C). *P<.05 versus normal controls. †P<.05
versus patients with F-MR.
Bruce Bollen, MD
Watanabe et al reported on the different patterns of leaflet tethering in anterior vs posterior left ventricular ischemia and
functional mitral regurgitation. (see Figure 29 and Table 4). Note in table—the difference between LV volumes in
anterior vs posterior ischemia groups34. Gorman’s laboratory has recently reported an elegant 3D TEE clinical study
further defining annular and leaflet dynamics in functional ischemic MR, pointing to different subgroups.
Watanbe et al
JASE 2006;19:71-75
Figure 29. Anatomic 3-dimensional images of mitral annulus and leaflets created to
observe actual configuration of annulus and leaflets with surface coloration. Inferior
(left) and anterior (right) myocardial infarction. Tenting of mitral leaflets, which were
tethered into left ventricle (LV), were seen in both groups of patients with ischemic
mitral regurgitation. For patients with anterior infarction, mitral valve leaflets are
widely tethered and bulged toward LV, in contrast with patients with inferior infarction
showing localized tenting of leaflet with less bulging. L, Lateral; LA, left atrium;
M, medial; A, anterior; P, posterior.
Table 4. EDVI, left ventricular end-diastolic
volume index; EF, ejection fraction; ESVI, left
ventricular end-systolic volume index; LV, left
ventricular; MI, myocardial infarction; ROA,
regurgitant orifice area.
Tricuspid Valve
The tricuspid valve of the right ventricle has three leaflets. Its orifice viewed from the right ventricle is triangular with
anterior, posterior, and septal sides. The tricuspid annulus is relatively indistinct especially in the septal region.
The tricuspid valve has three leaflets: anterior, posterior and septal. The anterior leaflet, the largest of the three, is
semicircular to quadrangular in shape. Chordae attaching to the anterior leaflet arise from the anterior and medial
papillary muscles. The posterior leaflet is usually the smallest. The leaflet has several indentations or clefts that give it
a scalloped appearance. Its chordae arise from the posterior and anterior papillary muscles. The septal leaflet is
primarily attached to the septum, the remainder attaching to the posterior wall of the right ventricle. Part of its basal
attachment is to the posterior wall of the right ventricle but most is to the septal wall. Its chordae arise from the
posterior and septal papillary muscles.
Silver et al. defined three commissures: anteroseptal commissure, anteroposterior commissure, and posteriorseptal
commissures11. These commissures define the margins of the leaflets of the tricuspid valve. The anteroseptal
commissure is defined by a deep indentation in the membranous interventricular septum where the anterior and septal
walls of the right ventricle join. The anteroposterior commissure is defined by fan shaped chorda at the acute margin of
the right ventricle and the anterior papillary muscle pointing to the commissure. The posteriorseptal commissure is
defined by attaching fan shaped chorda; the most medially placed posterior papillary muscle and a fold of tissue on the
septal leaflet.
The basal attachment of the leaflets to the annulus are at different levels in the heart. The posterior leaflet and the
posteriorseptal half of the septal leaflet are roughly horizontal and about 15 mm lower than the highest part of the
valve’s attachment, which occurs at the anteroseptal commissure near the midpoint of the membranous interventricular
septum.
The chordae of the tricuspid valve originate from papillary muscles or directly from the muscle of the posterior or septal
walls of the right ventricle. Silver et al defined chordae as being rough zone, fan shaped, basal, free edge and deep
chordae.
Pulmonic Valve
The pulmonic valve is not part of the fibrous skeleton of the heart. Instead the pulmonic annulus is attached to cardiac
muscle. The pulmonic valve normally has three cusps with a nodule at the midpoint of each edge. The pocket behind the
cusp is the sinus.
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Bruce Bollen, MD
Coronary Anatomy
The left main and right coronary arteries (RCA) supplying the heart arise from ostia in the left and right sinus of valsalva
respectively. The left main coronary artery then divides into the left anterior descending (LAD) coronary artery and the
circumflex coronary artery. At the base of the heart the RCA and Circumflex artery form a circle around the heart in the
atrioventricular groove. A long axis loop is formed by the LAD and the posterior descending coronary artery. (Figure 30)22,23
Figure 30. Diagram of the anatomic segments of the coronary arteries for
use in locating lesions in individual patients.
(1, 2, 3,) Proximal, mid-, and distal portions of the right coronary artery. (4, 27)
Posterior descending coronary artery, which, as the dotted segments proximal
to it indicate, may arise from the right (4) or left (27) system. (5) Right
posterolateral segment, an extension of the right coronary artery in association
with right dominant systems. (6, 7, 8,) From it come several inferior surface
(marginal) branches, called right posterolateral arteries, to the back of the left
ventricle. Left dominant systems have a comparable left posterolateral
segment, leading to the posterior descending artery. (9) Inferior septal
branches of the posterior descending artery. (10) Acute marginal branches of
the coronary artery. (11) Left main coronary artery. (12, 13, 14) Proximal, mid, and distal portions of the left anterior descending coronary artery. (15, 16)
First and second diagonal branches. The first diagonal may originate almost
from the bifurcation of the left main coronary artery, and was formerly called a
ramus intermedius. Additional diagonal branches may be present. (17) First
septal branch of the anterior descending artery. (18, 19) The proximal and
distal portions of the left circumflex coronary artery. (20, 21, 22) The first,
second, and third obtuse marginal branches of the circumflex artery, the first
usually being a large vessel. (23) An extension of the circumflex artery, called
the left AV artery, present only in patients with a left dominant system. In such
patients, this vessel gives off further inferior surface (“marginal”) branches to
the back of the left ventricle, now called left posterolateral arteries (24,25,26),
before terminating in the left posterior descending coronary artery (27).
From The National Heart, Lung, and Blood Institute Coronary Artery Surgery
Study (CASS), and the American Heart Association, Inc 23
The posterior descending artery originates as a termination of the right coronary and or circumflex coronary artery. The term
dominance in regards to the coronary circulation defines which of these two vessels terminate to form the posterior
descending artery. A right dominant circulation is one in which the PDA is formed as a termination of the RCA. A left
dominant coronary circulation is one where the PDA is formed as a branch of the circumflex coronary artery. Left dominance
occurs in about 10-15% of hearts. Vessels may be co-dominant if the right coronary gives rise only to the posterior
descending artery and the circumflex to vessels supplying the posterior left ventricle.
The left main coronary artery originates from an ostium in the left sinus of valsalva. The left main coronary artery bifurcates
into the left anterior descending artery and the circumflex coronary artery. Occasionally an additional branch comes off which
parallels the diagonal arteries of the left anterior descending artery. Such a branch off the left main is called the ramus
intermedius.
The left anterior descending coronary artery originates from the left main and travels along the anterior interventricular sulcus
to the apex of the heart. In most cases the artery extends to the posterior aspect of the heart communicating with the posterior
descending artery. The LAD sends large septal perforating arteries perpendicularly into the interventricular septum, providing
most of the septal blood supply. Diagonal branches of the LAD course obliquely between the LAD and circumflex artery
supplying the left ventricular free wall anteriorly and laterally. The LAD supplies a few small branches to the right ventricular
free wall.
The left circumflex coronary artery originates from the left main coronary artery and then travels along the left atrial
ventricular groove on the left coursing posteriorly. In hearts that have a left dominant circulation, the circumflex gives rise to
the posterior descending artery. Obtuse marginal branches of the circumflex arterior supply the obtuse margin of the left
ventricle. In left dominant circulation the circumflex provides left posterolateral (marginal) arteries to the inferior portion of
the left ventricle.
The right coronary originates from an ostium in the right sinus of valsalva. Traveling in the right atrioventricular groove, the
RCA gives off branches to the anterior right ventricular free wall. Traveling in the region of the acute margin of the right
ventricle the RCA gives off acute marginal branches which course to the apex of the heart. In right dominant circulations the
RCA courses posteriorly terminating by bifurcating into the posterior descending and right posterolateral segment artery. The
posterior descending artery travels in the posterior interventricular sulcus giving rise to septal, right ventricular and left
ventricular branches. The right posterolateral segment artery gives rise to marginal branches supplying the inferior surface of
the left ventricle.
The general areas of the left ventricular wall supplied by the coronary arteries have been summarized in the standard
ASE/SCA Guidelines for Performing Intraoperative TEE according to the standardized 16 segmental views9,10. The LAD
supplies the basal, mid and apical septal segments; basal and mid anteroseptal segments; basal, mid, and apical anterior
segments. The circumflex artery supplies the basal, mid and apical lateral segments; basal and mid posterior segments. The
RCA in right dominant circulations provides basal, mid and apical inferior segments of the left ventricle.
19
Bruce Bollen, MD
ASE/SCA
Terminology
(per Carpentier)
20
Bruce Bollen, MD
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