cardiac structure

details of heart location

oblique position

• base posterior and inferior

• anterior and superior

• superior to diaphragm

• inferior to the carina

• medial to pleural cavities

• posterior/deep to sternum

• anterior to esophagus

pericardium attachments

anteriorly - sternum

posteriorly - posterior mediastinum structures

laterally - mediastinal parietal pleura

inferiorly - diaphragm

function of the pericardium

1) fix heart within mediastinum ?

2) limit cardiac distention?

3) limit spread of infection?

do they always close the pericardium post surgery?

not always…does it actually serve all the aforementioned purposes?

what are the different sinuses located on the heart?

oblique pericardial sinus, transverse pericardial sinus

oblique pericardial sinus

formed from venous reflection of the IVC and pulmonary veins

transverse pericardial sinus

formed between the arterial reflections above the venous reflections of the SVC and pulmonary veins

how are the sinuses used in a clinical sense?

used during various surgeries to stop or divert blood

what is the crux?

the center of the posterior portion of the heart

implications of epicardial adipose tissue…

interaction of EAT with myocardial tissue can lead to arrhythmias » if you’re pacing through one of the veins then the fat tissue may change the threshold of voltage

instead of doing trans septal into the left atrium…

a physician may go through the watterston’s groove » where right atrium and left atrium come together, medial to superior and inferior vena cava » posteriorly in-between vena cava and pulmonary veins

what are all the features of the left atrium?

dome/roof, septopulmonary region, vestibule, coronary sinus, Bachmann’s bundle

what about the septopulmonary region is thought to contribute to arrhythmia?

the orientation of the muscle fibers here is potentially substrate for arrhythmia

what are the four components of the atria?

1) venous component » right atrium: SVC/IVC, left atrium: pulmonary veins

2) vestibule/outflow track

3) body

4) appendage/auricle

*5) septal

what is the crista terminalis externally aligned with?

the sulcus terminals/terminal groove

what originates from the right atrial anterolateral free wall?

pectinate muscle

what does the change in orientation of muscle fibers at terminal crest account for…?

changes in electrical conduction and atrial arrhythmia

what is the arcuate ridge?

muscular fold of tissue that originates from CT near junction of SVC and can extend towards the limbus of the fossa ovalis

what is the cavotricuspid isthmus (CTI)/inferior isthmus?

extends from the tricuspid valve to the IVC

why is ablating at CTI for atrial flutter high risk/high reward?

not only can you hit RCA but also you could cause arterial spasms

where is a spot for difficult ablation?

sub-eustachian sinus/sinus of Keith/sub-thebesian recess

what are thebesian veins?

small openings in endocardial surface on lateral wall and septal walls -- drain deoxygenated blood from myocardium

what about the structure of the SA node?

posterior/superior location in right atrium, crescent shaped structure

subepicardially within sulcus terminals » if endocardial ablation of SA node requires more energy

what is major component of the AV node structure?

koch’s triangle

triangle of koch

posterior border: fibrous extension of eustachian valve fusing with thebesian valve = tendon of todaro

anterior border: annulus/hinge of tricuspid valve septal leaflet

inferior border: coronary sinus orifice

apex of the triangle = AV node & central fibrous body of septum - where bundle of His penetrates inferiorly

inferior extensions of the AV node…

are thought to account for slow pathway of nodal reentry pathway

what are the structural components of the fossa ovalis?

thin fibrous portion with thicker muscular portion on the outer rim = limbus of fossa ovalis

what are notable septal closure devices?

1) septal occluder

2) Gore cardioform

what is considered to be the most posterior chamber?

left atrium

which atrial walls are typically thicker?

left atrium

what is just posterior to left atrial vestibule?

the coronary sinus

clots that are formed in relation to afib are typically found…

in left atrial appendage

what is located at the aterosuperior wall of left atrium?

Bachmann’s bundle

tell me about the mitral isthmus…

between mitral annulus & left inferior pulmonary vein ostium » most common linear ablation

why should you proceed with caution within/near the mitral isthmus?

90% - great cardiac vein

57% - circumflex artery

35% - vein of marshall

tell me about the left atrial appendage isthmus…

connects LAA orifice & lateral aspect of mitral annulus/adjacent to MI

variation in wall thickness - thus may need varying levels of energy

why should you proceed within/near the LAAI?

96.5% - 1 or 2 circumflex branches

77% - at least one coronary vein

what structure is a common source of supra ventricular arrhythmias due to unique morphology?

left atrial ridge » may over lie vein of marshall + autonomic nerve bundles

• direct connection with surrounding tissue

• considered most difficult ablation site for these reasons

where is the left atrial ridge? (left lateral ridge, warfarin ridge, Coumadin ridge, endocardial ridge)

between left sided pulmonary veins and LAA orifice

why pulmonary vein isolation or wide area circumferential ablation?

perhaps because of musculature of lA wall with myocardial sleeves extending over the outer surface of venous wall at venoatrial junction - complex architecture may facilitate micro reentry pathways

• are superior PV longer sleeves more arrythmogenic ?

what is high thrombogenicity associated with in the left atrial appendage?

unique morphology, multi lobular, heavily trabeculated

4 types of shapes: chicken wing, cauliflower (stroke predictor), windsock, cactus

what are the components of the ventricle?

inlet (inflow tract), apical trabecular, outlet (outflow tract)

morphologically, which ventricle has more coarse muscular trabeculations?

right ventricle

what are the shapes of the ventricles

LV = oral/barrel/bullet shaped

RV = crescent shaped

papillary muscles of the right ventricle

anterior (largest)

septal (smalles)

posterior (inferior)

FALSE

false papillary muscles are considered to be…

more arrythmogenic

what are the septomarginal trabeculations?

septal band, moderator band

what is the outflow track?

conus arteriosus » RVOT » infundibulum » usually smooth muscle

what muscle bundle separates the RVOT from the RA?

supraventricular crest

what are the possible functions of the moderator band?

1) carries RBB conduction to RV free wall & anterior papillary muscle

2) resists over filling

3) assists with systolic function

left ventricle characteristics

finer muscular trabeculations

papillary muscles: posteromedial/inferior, anterolateral/lateral

LVOT = left ventricular outflow tract AKA vestibule

LV summit arrhythmia is difficult to ablate…

because great cardiac vein, circumflex vein, posterior descending artery all behind it

recall cardiac skeleton functions

• attach atrial and ventricular myocardium

• foundation for heart valves

• prevents overstretching of valves

• electrically separates upper & lower chambers

central fibrous body of cardiac skeleton

right fibrous trigone

membranous septum

left fibrous trigone

aortic mitral continuity (aortic mitral curtain)

right fibrous trigone

triangular formation between aortic semilunar valve and medial parts of tricuspid and bicuspid valve

membranous septum

inferior extension of central fibrous body

left fibrous trigone

triangular formation between aortic valve and anterior/aortic cusp of mitral valve

aortic mitral continuity (aortic mitral curtain)

formation between aortic cusp of bicuspid valve and aortic valve (junction for the left and right fibrous trigones)

AV valve histology

fibrocytes, histocytes, collagen fibers, fibroblasts, smooth muscle cells and myocardial cells surrounded by endothelial cells

what kind of innervation do AV valves contain?

both sensory and autonomic innervation

AV valves contractile activity

1) twitch contraction during systole

2) tonic contraction during isovolumetric relaxation » we don’t want regurgitation

what are the chordae tendinae composed of?

various levels of collagen, elastin, and vascularization

what are the papillary muscles composed of?

parallel myocytes with complex intercalated discs, extensive innervation, and vascular system

semilunar valve histology: fibrous core

mixed with elastin with endothelial lining forming the backbone of the valve

what does the dense backbone of the semilunar valve histology give way to?

a looser structure called the spongiosa near the ventricular aspect of the leaflet cusps

where do all three leaflets coapt?

the free edge near the apposition zone with a thicker fibrous layer creating a node (modulus Arantii)