CARDIAC ANATOMY

CARDIAC ANATOMY

1. Surface Anatomy
A. Right atrium anterior and to the right of left atrium
B. Left atrium a midline structure
C. Right ventricle anterior and to the right of left ventricle
D. Pulmonary artery anterior and to the left of aorta
E. Coronary arteries on surface follow A-V groove and interventricular septum

2. Cardiac Chambers
A. Right atrium
1) Wide based blunt appendage, crista terminalis separates trabeculated from non-trabeculated portion
B. Left atrium
1) Long, narrow appendage, smooth walls
C. Right ventricle
1) Coarsely trabeculated inlet/sinus, outlet portion
D. Left ventricle
1) Fine trabeculations inlet/sinus and outlet portions

3. Right Atrium
A. SVC - IVC
B. Crista terminalis
C. Coronary sinus
D. Tricuspid valve
E. Fossa ovalis
F. Triangle of Koch
G. Tendon of Todaro
H. Inferior isthmusTendon of Todaro

4. Right Ventricle
A. Inlet portion supports tricuspid valve
B. Trabecular sinus portion (main body of the RV)
1) Moderator band
2) Medial papillary muscle (of conus)
C. Outlet portion
1) Infundibular (Conal) septum (separates semilunar valves)
2) Crista supra ventricularis - seperates sinus (chamber) from outlet portion of the ventricle
3) Septal band (trabecula septomarginalis)
4) Parietal band (ventriculo-infundibular fold)
5) Pulmonary valve

5. Left Ventricle
A. Thick wall
B. Inlet portion supports mitral valve
C. Anterior and posterior papillary muscles
D. Outlet portion beneath aortic valve

6. Conduction System
A. Sinoatrial node - anterolateral RA
B. Interatrial conduction pathways - not well defined and somewhat controversial
C. Atrioventricular node - triangle of Koch
D. Bundle of His - AV node to membranous septum, usually located on the inferior/posterior wall of the membranous septum
E. Left bundle branch - left ventricular septal surface into multiple branches
F. Right bundle branch - below medial papillary muscle via septal and moderator bands to anterior papillary muscle
G. Inferior isthmus (right atrium)
H. Bachman's bundle (left atrium)
See Arrhythmia- Tachycardia
See Arrhythmia- Bradycardia

7. Cardiac Valves
A. Aortic valve wedged between mitral and tricuspid, pulmonary valve separated
B. Mitral valve
1) Anterior leaflet wide, short, 1/3 of annular circumference
2) Posterior leaflet narrow, long, 2/3 of annular circumference
3) Papillary muscles and chordae tendineae
C. Tricuspid valve
1) Anterior, posterior, septal leaflets
D. Aortic and pulmonary valves
1) 3 cusp, semilunar
2) Sinuses of Valsalva
3) Nodulus Aranti and lunulae

8. Left Ventricular Outflow Tract
A. Semilunar aortic valve
B. Fibrous annulus is not a ring
C. Interleaflet triangles
D. Aortoventricular junction
E. Sinuses of Valsalva
F. Sinotubular junction (sinus rim) = junction of sinus of Valsalva and ascending aorta
G. Posterior commissure relates to mid point of anterior leaflet of mitral valve

9. Ventricular Band (Torrent-Guasp)
A. Biventricular myocardial band extending from pulmonary artery to aorta
B. Two loops: basal and apical
C. Double helix derived from spiral fold
D. Apex has figure-8 configuration

10. Coronary Arteries
A. Right and left coronary arteries
B. Dominant pattern determined by origin of posterior descending
C. Dominance is usually right or balanced; 10-15% prevalence of left dominance
D. Balanced pattern occurs when there is no particular dominance
E. Septal blood supply 2/3 left anterior descending, 1/3 posterior descending
F. Sinus node artery from RCA - 55%
G. AV node artery from U bend at crux, just beyond the takeoff of the PDA if circulation is right dominant

11. Descriptive Variables
A. Situs of thoracic viscera and atria
1) This is best identified from the bronchial anatomy (3 bronchi on the right, 2 on the left)
2) Solitus, inversus, ambiguous
B. Situs of ventricles
1) Usual, concordant, D-loop, right-handedness
2) Inverted, discordant, L-loop, left-handedness
C. Dominance of ventricles
1) Balanced (usual), right (left small), left (right small)

12. Descriptive Variables
A. Cardiac connections
1) Atrioventricular and ventriculoarterial
2) Concordant or discordant (transposed)
B. Cardiac and arterial position
1) Cardiac apex; levo-, dextro-, mesocardia
2) Great arteries; transposition, malposition
3) The patient can have completely normal cardiac structures and still have dextrocardia - this only refers to the position of the cardiac apex
C. Conventional diagnosis; e.g., tetralogy of Fallot

Extended Outline

1. Cardiac Skeleton
A. Fibrous body
B. Right and left trigones

2. Coronary Arteries
A. Right and Left coronary arteries originate from proximal aorta via respective ostia
B. Common branches from main coronary arteries
1) Left main-- diagonal branches
2) Left anterior descending-- septal and diagonal arteries
3) Circumflex-- marginal arteries (and PDA in left dominant hearts)
4) Right coronary artery-- acute marginal, AV nodal, sinus node arteries (and PDA in right dominant hearts)

3. Cardiovascular Silhouette
A. Mediastinal Border
1) Right atrium
2) Superior vena cava
B. Left Border
1) Aortic arch
2) Pulmonary trunk
3) Left atrial appendage
4) Left ventricle

Surgical Anatomy Of The Mitral Valve

The mitral apparatus includes the leaflets, annulus, chordae tendineae, papillary muscles, and left ventricle.

A. Leaflets

* The mitral valve has two leaflets, the anterior (aortic) and posterior (mural) leaflets.
* The leaflets are attached directly to the mitral annulus and to the papillary muscles by primary and secondary chordae.

1.Anterior mitral leaflet:

* Is in direct continuity with the fibrous skeleton of the heart.
* This leaflet is contiguous with the left and noncoronary cusps of the aortic valve and the area beneath the intervening aortic commissure, termed the fibrous subaortic curtain.
* Although the anterior leaflet occupies only 35% to 45% of the annular circumference, its leaflet area is almost identical to that of the posterior leaflet.

2.Posterior Leaflet:

* Has two variable indentations or clefts that divide the posterior leaflet into three scallops: the largest or middle scallop, the posteromedial scallop, and the anterolateral scallop.
* Fan-shaped chordae insert into and define the clefts between the individual posterior scallops.
* Motion of the posterior leaflet is more restricted than that of the anterior leaflet; however, both mitral leaflets contribute importantly to effective valve closure.


The surface of the mitral leaflet is divided into three zones corresponding to areas of chordal insertion and leaflet coaptation.

1. The rough zone: is the leading edge of the anterior and posterior mitral leaflets. This zone is the contact surface of the mitral leaflets during systole.
2. The clear zone: is peripheral to the rough zone and represents most of the body of the leaflet; this portion of the mitral valve billows into the atrium during ventricular contraction.
3. The basal zone: between the clear zone and the annulus, receives the insertion of the basal chordae tendineae (tertiary chordae), which originate directly from the trabeculae of the left ventricle. The basal zone is found only on the posterior leaflet.


B. Annulus

* The mitral annulus is the site of leaflet attachment to muscular fibers of the atrium and ventricle.
* The annulus is flexible and decreases in diameter during each systolic contraction by approximately 26%.
* The orifice of the mitral valve also changes shape, from elliptical during ventricular systole to circular during late diastole. This flexibility increases leaflet coaptation during systole and maximizes orifice area during diastole.
* Anteriorly, the annulus is attached to the fibrous skeleton of the heart. This limits its flexibility and its capacity to dilate with mitral regurgitation (MR). The posterior annulus is more flexible and is not attached to rigid surrounding structures. This accounts for the clinical observation that dilation of the annulus occurs posteriorly with MR.
* Important Anatomic Landmarks:

1. The circumflex coronary artery courses laterally around the mitral annulus in the posterior atrioventricular groove.
2. The coronary sinus runs more medially in the same groove.
3. The artery to the atrioventricular node, usually a branch of the right coronary artery, runs a course parallel and close to the annulus of the anterior leaflet near the posteromedial commissure.
4. The aortic valve is situated between the anterior and posterior fibrous trigones. The bundle of His is located near the posterior trigone.


C. Chordae Tendineae

* The chordae tendineae are chords of fibrous connective tissue that attach the mitral leaflets to either the papillary muscles or the left ventricular free wall.
* They often subdivide and interconnect before they attach to the leaflets. The chordae are divided into:

1. Primary chordae: attach directly to the fibrous band running along the free edge of the leaflets. These chordae ensure that the contact surfaces (rough zone) of the leaflets coapt without leaflet prolapse or flail.
2. Secondary chordae: attach to the ventricular surface of the leaflets at the junction between the rough and clear zones. These chordae contribute to ventricular function. Secondary chordae enable the ventricle to contract in an efficient cone-shaped fashion; when secondary chordae are excised, the left ventricle assumes a globular shape.
3. Tertiary chordae: are unique to the posterior leaflet. They arise as strands directly from the left ventricular wall or from small trabeculae to insert into the ventricular surface of the leaflet near the annulus.


D. Papillary Muscles

* The anterolateral and posteromedial papillary muscles each supply chordae tendineae to both leaflets.
* The two groups of papillary muscles subtend the anterolateral and posteromedial commissures and arise from the junction of the apical and middle thirds of the ventricular wall.
* The anterolateral papillary muscle receives a dual blood supply from the anterior descending coronary artery and either a diagonal branch or a marginal branch of the left circumflex artery.
* The posteromedial papillary muscle receives its blood supply from either the left circumflex artery or a distal branch of the right coronary artery.
* Because of the single blood supply to the posteromedial papillary muscle, infarction of the posteromedial papillary muscle is much more common.


E. Left Ventricle

* The posterior left ventricular wall and papillary muscles play an important role in leaflet coaptation and valve competence.
* Papillary muscles are aligned parallel to the ventricular wall and attach via chordae to the free edges of the valve leaflets. These muscles project from the trabeculae and may be single, bifid, or a row of muscles arising from the ventricular wall.
* During isovolumetric contraction the mitral leaflets are pulled downward and together by this interaction. Ventricular dilatation may affect the alignment and tension on the papillary muscles and valve competence.