Cvs 3: Cardiac Anatomy

Front 1

What is the mediastinum?

Back 1

- The space between the two lungs and pleurae
- Contains all the structures of the chest except the lungs and pleurae
- Extends from the superior thoracic aperture to the diaphragm, and from the sternum to the vertebrae
- Mediastinum divided into superior and inferior parts, and the inferior part divided into anterior, middle and posterior parts

Front 2

Describe the contents of the divisions of the mediastinum

Back 2

- Superior mediastinum found between the transverse thoracic plane (sternal angle to T4-T5) to the thoracic inlet:
→ Thymus anteriorly
→ The great vessels in the middle
→ The oesophagus, trachea and thoracic duct posteriorly
- Inferior mediastinum between the transverse thoracic plane divided into:
→ Anterior inferior mediastinum = posterior to the sternum and anterior to the pericardium
• Inferior thymus
→ Middle mediastinum
• Heart and pericardium
• Great arteries
• Phrenic nerve
• Main bronchi
→ Posterior mediastinum
• Oesophagus
• Thoracic aorta
• Vertebral bodies

Front 3

What is the pericardium? Describe its layers

Back 3

- A fibroserous sac that covers the heart and the beginning of its great vessels
- Composed of an outer fibrous layer
- Inner serous part composed of 2 layers - a parietal pericardium close to the fibrous paricardium, and a visceral pericardium closest to the heart. Between these layers is secreted a layer of pericardial fluid
- The pericardium helps anchor the heart and helps allow the heart to beat without friction (using the pericardial fluid)

Front 4

Describe the attachments of the pericardium

Back 4

- Base fused with the central tendon of the diaphragm
- Fused with the tunica adventitia of the great vessels entering and leaving the heart
- Anterior joined to the sternum via sternopericardial ligaments

Front 5

What are the 2 sinuses found in the pericardium?

Back 5

- Formed by folding of the embryologial heart
- Transverse pericardial sinus is a recess within the pericardium, posterior to the aorta and the pulmonary trunk and anterior to the superior vena cava
- The oblique pericardial sinus is a blind recess formed by the inferior vena cava and pulmonary veins

Front 6

Where is the base of the heart?

Back 6

Located posteriorly and formed mainly by the left atrium

Front 7

Where is the apex of the heart?

Back 7

- Formed by the left ventricle and is posterior to the 5th intercostal space

Front 8

What forms the sternocostal surface of the heart?

Back 8

Mainly the right ventricle

Front 9

What forms the diaphragmatic surface of the heart?

Back 9

Mainly by the left ventricle, and part of the right ventricle

Front 10

What forms the pulmonary surface of the heart?

Back 10

Mainly the left ventricle

Front 11

What makes up the borders of the anterior heart?

Back 11

- Right = right atrium →venous side of the heart (SVC and IVC)
- Left = left ventricle and left auricle → arterial side of the heart (aortic arch, pulmonary artery)
- Inferior = mainly right ventricle, and small part of left ventricle
- Superior = right and left auricles

Front 12

What is pericardial effusion?

Back 12

- Passage of fluid from pericardial capillaries into the pericardial cavity, or an accumulation of pus
- As a result, the heart becomes compressed and unable to expand or fill full because the fibrous pericardium can only stretch a little. This reduces cardiac output.
- May also result from congestive heart failure = heart that fails to pump blood out at the same rate that it receives blood

Front 13

What is cardiac tamponade?

Back 13

- Heart compression
- May be caused by pericardial effusion or haemopericardium (e.g due to a myocardial infarction or stab wounds).
- Haemopericardium is more likely to be fatal because of the high pressure involved and the rapidity of the accumulation of fluids
- Potentially lethal as the heart volume is increasingly compromised by the fluid outside the heart but inside the pericardial cavity
- Treatment = pericardiocentesis → syringe at 15 degrees from surface of skin

Front 14

Describe the features of the right atrium

Back 14

- Has the right auricle = conical muscular pouch that projects from the chamber, increasing its capacity
- Has a smooth, thin-walled posterior part, onto which the SVC, IVC and coronary sinus (between the right AV orifice and the IVC orifice) empty
- Rough anterior wall composed of pectinate muscles
- Smooth and rough parts of the wall separated by a vertical ridge, the crista terminalis, internally (sulcus terminalis externally)
- Interarterial septim has the fossa ovalis
- Tricuspid valve to the right ventricle

Front 15

Describe the features of the right ventricle

Back 15

- Contains irregular muscular elevations = trabeculae carneae
- Thick muscular ridge, the supraventricular crest, separates the ridged muscular wall of the inflow part of the chamber from the smooth wall of the outflow part (conus arteriosus)
- Papillary muscles = 3 conical muscular projections which pull chordae tendinae, which are attached to the cusps of the tricuspid valve. This closes the valve and helps prevent regurgitation
- Septomarginal trabeculae (moderator band) is a curved muscular bundle that carries part of the right branch of the AV bundle
- Pulmonary valve

Front 16

Describe the features of the left atrium

Back 16

- Left muscular auricle which contains pectinate muscles
- Larger, smooth-walled part
- Valveless pairs of right and left pulmonary veins enter
- Thicker wall that the right atrium
- Left mitral valve
- Fossa ovalis with surrounding annulus ovalis (remnant of valve)

Front 17

Describe the features of the left ventricle

Back 17

- Walls 3 times as thick as right ventricle
- Walls covered with trabeculae carneae which are more numerous and finer than those on the right
- 2 papillary muscles, which are larger than the right, with cordae tendinae attached, to the aortic valve
- Aortic vestibule, leading to the aortic valve

Front 18

Where do the coronary arteries arise?

Back 18

- Left coronary artery arises from the left anterior cusp of the aortic valve
- Right coronary artery arises from the right anterior aortic sinus just above the right anterior cusp of the aortic valve

Front 19

Describe the 3 tissue layers of the heart wall

Back 19

- Epicardium aka visceral pericardium
- Myocardium = thickest layer and contains muscle cells which attach to the heart skeleton, providing a base for contraction. Atrial myocardium secretes ANP (atrial natriuretic peptide) when stretched, promoting salt and water excretion. Ventricular myocardium secretes BNP (brain natriuretic peptide) when stretched
- Endocardium = 3 layers. An outermost connective tissue layer (containing nerves, vessels and Purkinje fibres), an middle connective tissue layer, and a inner endothelium of flat endothelial cells

Front 20

What is the heart skeleton?

Back 20

- Consists of fibrocollagenous rings of dense connective tissue encircling the base of the aorta and pulmonary trunk and the atrioventricular openings
- The heart valves and muscles attach to these to form the base of muscle contraction
- Also electrically insulates the atria from the ventricles except along the interventricular septum, which contains the bundle of His

Front 21

What is the most important point to remember about heart valves?

Back 21

They are avascular so if bacteria invades the valves there will be little immune reaction and infective endocarditis may result. Also, serious problems healing

Front 22

Describe 3 cardiac-specific radiographic views

Back 22

1. Short axis
- Slices perpendicular to long axis of LV
- LV and RV chambers well seen
- Volume measurements
- Easy to see wall thickness

2. Horizontal long axis
- Perpendicular plane through vertical long axis
- 4 chamber view
- As seen from below looking upwards and see left and right
- Chamber size, septum, mitral and tricuspid valves well seen

3. Left ventricular outflow tract
- Through and perpendicular to plane of aortic valve
- Oblique coronal plane
- Thick wall LV, brachiocephalis trunk, common carotic artery → functional anatomy of heart

Front 23

Describe the anatomical positions of the heart sounds and where you would listen to heart sounds

Back 23

- Note that you listen to valves in the direction of the flow of blood from the valve

Front 24

Describe the 2 pericardial sinuses

Back 24

- Two sinuses:
1. Transverse sinus
- posterior to the pulmonary trunk and ascending aorta and anterior to the superior vena cava. Superior to the atria;
2. Oblique sinus of the pericardium
- posterior to the base of the heart, anterior to the oesophagus

Front 25

What is this and what is its cause?

Back 25

- GLobular heart shadow on CXR
- Heart loses shape due to pericardial effusion
- Pain worsens when sit forwards
- AXR shows large extra swelling of fluid within the pericardium of the heart

Front 26

How can radiography be used to assess cardiac hypertrophy?

Back 26

- Heart should occupy 50% of the maximum internal thoracic diameter on a standard PA erect view → if it is larger than this hypertrophy is present
- Cannot comment on heart size on AP view because magnification of the heart is seen

Front 27

What is dextrocardia?

Back 27

- Heart found on RHS
- Very rare = 1/20,000
- Usually associated with other situs invertus

Front 28

Describe the path of the phrenic nerve in the mediastinum

Back 28

- The right phrenic nerve travels down the SVC and across the LA to the diaphragm
- The left phrenic nerve travels more anteriorly, along ascending aorta and pulmonary trunk, to travel along the left ventricle to the diaphragm

Front 29

Describe the 2 types of cardiac vavles

Back 29

1. Semilunar vavles
- Passively opened and closed
- Pulmonary artery and aorita
- 3 cusps

2. Atrioventricular vavles
- Passively opened and closed
- Actively held closed by papillary muscles pulling on the chordae tendineae

Front 30

What is there problem here?

Back 30

- Calcification of the aortic valve → aortic stenosis and possible left sided hypertrophy

Front 31

Label 1, 4 and 7

Back 31

1 = Left anterior descending (anterior interventricular) artery
4 = Circumflex artery (NOT LAD)
7 = Left coronary artery

Front 32

What is the problem here and how may it be treated?

Back 32

- Coronary heart disease of right coronary artery
- Treatment
1. Coronary bypass graft (CABG = cabbage) = from internal thoracic artery or long saphenous vein
2. PTCA = coronary angioplasty → remodelling the artery through the skin
3. Stents = keeps the artery open