Anatomy clinical scenarios (cardio)

Question 1

What structures are in the superior mediastinum?

Answer 1

trachea
oesophagus
arch of aorta + branches
SVC + tributaries
vagus nerves
phrenic nerves
left recurrent laryngeal nerve

Question 2

What structure is in the inferior anterior mediastinum?

Answer 2

thymus

Question 3

What structures are in the inferior middle mediastinum?

Answer 3

heart
pericardium
phrenic nerves
ascending aorta
pulmonary trunk

Question 4

What structures are in the inferior posterior mediastinum?

Answer 4

oesophagus
sympathetic chain
azygos vein
thoracic duct
descending aorta
vagus nerves

Question 5

What is the function of the pericardium?

Answer 5

outer fibrous layer + parietal serous layer + visceral serous layer
fibrous = supports heart in middle of inferior mediastinum and prevents excessive movement
if pressure builds in pleural cavity, pushing heart to one side, could damage heart or kink great vessels causing decreased blood flow to and from heart
fibrous prevents acutely over filling and stretching the cardiac muscle beyond its optimal functional capacity on Starling’s curve

Question 6

How can elevated JVP and swollen ankles link to fluid in the pericardial sac?

Answer 6

fluid in pericardial sac is reducing the remaining volume in the sac, reducing the volume available for venous blood to return to the heart
increases venous pressure in peripheral vascular system as blood cannot return to the heart and remains in peripheral veins
to decrease the pressure in the peripheral vascular system, water will be moved from the venous blood into the surrounding tissues, causing oedema, ankles = due to gravity

Question 7

What causes SOB and basal crepitations when there is fluid in the pericardial sac?

Answer 7

decreased blood flow through the heart means there is decreased output of oxygenated blood
reduced volume in pericardial sac, reduce venous return from lungs into left side of heart, causing increased pulmonary venous pressure
water will move from veins into surrounding tissues causing pulmonary oedema

Question 8

Which vein can be used to insert a central venous line to measure central venous pressure?

Answer 8

internal jugular vein
generally in the right side as it has a more direct route into the right atrium

Question 9

Are there valves in the internal jugular vein?

Answer 9

no

Question 10

What structures are at risk when inserting a central venous pressure line?

Answer 10

carotid arteries
vagus nerve
thoracic duct (on left)
parietal pleura
apex of lung

Question 11

What should you look for on an CXR post central venous pressure line insertion?

Answer 11

position of catheter in right atrium and to see if there is a pneumothorax

Question 12

During a CABG procedure, the pulmonary trunk and aorta need to be occluded, which pericardial sinus can be used to pass a temporary ligature around these vessels?

Answer 12

transverse sinus (passes posterior to pulmonary trunk + aorta)

Question 13

What vessel in the thoracic cavity can be used for the autograft in a CABG procedure?

Answer 13

internal thoracic/internal mammary artery

Question 14

Why is it advantageous to use a thoracic artery over a lower limb vein as the autograft in a CABG procedure?

Answer 14

an artery is adapted for carrying high pressure blood so compared to a vein it is less likely to become dilated
also, a vein can only be used to bypass the blockage however an artery can be used to provide an alternative source of blood to the region

Question 15

What are the 3 most common dominance patterns of the coronary arteries?

Answer 15

right dominant
left dominant
co-dominant

Question 16

What is myocardial infarction?

Answer 16

heart attack
caused by blockage of blood supply to muscle tissue of heart generally associated with blockage of a coronary artery

Question 17

How can the dominance pattern of a patient’s coronary arteries factor in their prognosis if they had an MI?

Answer 17

right dominant heart has separate supplies to the anterior and posterior interventricular arteries
if a coronary artery is blocked, there is still an alternate blood supply to part of the ventricles

left dominant heart = both interventricular arteries are branches of left coronary artery therefore a blockage in the left coronary artery will entirely cut off blood supply to the ventricles resulting in a poorer prognosis

Question 18

What type of valves stop backflow from the ventricles into the atria?

Answer 18

atrioventricular cuspid valves
- mitral = left
- tricuspid = right

Question 19

How are the atrioventricular valves reinforced?

Answer 19

by chordae tendinae attached to papillary muscles
these muscles ‘contract’ and ‘brace’ the valve during ventricular systole

Question 20

What type of valves guard the exit from the ventricles?

Answer 20

semilunar valves
- aortic = left
- pulmonary = right

Question 21

Why do aortic and pulmonary valves not need to be reinforced?

Answer 21

the blood they are stopping is at a much lower pressure - passive backflow from the great arteries rather than high pressure blood being pushed out by the ventricles

Question 22

What is the function of the aortic sinus?

Answer 22

small swelling behind the semilunar aortic cusps that allows blood to pool after ventricular systole and then flow into coronary arteries
also stops cusps from sticking to aortic walls when fully open

Question 23

Why is there a difference in thickness between the wall of the right and left ventricles?

Answer 23

left ventricle has to pump the blood further therefore it has a thicker wall to generate greater force during systole

Question 24

Why can the fact that blood flows over the anterior (septal) cusp of the bicuspid (mitral) valve during atrial and ventricular systole be important clinically?

Answer 24

because blood flows over both sides of the cusp it is more likely to wear down

Question 25

What is the role of the sinoatrial node?

Answer 25

pacemaker of the heart
responsible for regulating + coordinating contraction of cardiac muscles

Question 26

Which part of the autonomic nervous system is predominantly responsible for innervating the SA node to generate an impulse?

Answer 26

sympathetic nervous system

Question 27

Why does the skeleton of the heart stop the electrical impulse passing directly from the atria to the ventricles?

Answer 27

electrical impulse travels across heart and stimulates cardiac muscle to contract
travels down atria so blood is pumped down into the ventricles
ventricles need to contract inferiorly to superiorly so blood is pumped up the great arteries
without impulse being stopped, the ventricles would attempt to contract top to bottom and force blood through the ventricle wall

Question 28

How does the electrical impulse pass from the atria to the ventricles?

Answer 28

via AV node - delays spread of wave of depolarisation from SA node so atria can fully empty before the ventricles contract
–> bundle of his (interventricular bundle)
–> Purkinje fibres

Question 29

What is the function of the moderator bands?

Answer 29

conduct impulse from interventricular bundle (in ventricular septum) to base of anterior papillary muscle
ensures impulse reaches papillary muscle at same time as apex of heart, allows papillary muscle to contract, ‘bracing’ tricuspid and mitral valves in advance of ventricular systole

Question 30

What is the clinical significance of moderator bands?

Answer 30

assist in stopping valves from everting, allowing backflow of blood into the atrium during systole

Question 31

Why does mitral valve stenosis cause jugular distention and right ventricular heave?

Answer 31

mitral stenosis decreases blood flow into left ventricle
as left atrial pressure increases, flow is decreased in pulmonary vessels, so right ventricle distends and JVP rises

Question 32

What causes ankle swelling in mitral stenosis?

Answer 32

blood cannot effectively leave left ventricle causing backup of blood in lungs
causes blood to build up in right side of heart and in systemic venous system
increased pressure and therefore JVP rises
water will move from veins into tissues, ankles because gravity

Question 33

Major complications of mitral stenosis

Answer 33

pulmonary hypertension - blood cannot move from lungs to heart causing pressure to increase
blood clot formation
cardiomegaly - heart attempts to decrease pressure by increasing chamber volumes
AF
heart failure

Question 34

What are the 4 main changes at birth that facilitate the change to normal postnatal circulation?

Answer 34

closure of umbilical arteries

closure of umbilical veins + ductus venosus - blood now passing through liver

closure of ductus arteriosus

closure of foramen ovale

Question 35

What is a key factor in the closure, and fusion, of septum primum and septum secundum?

Answer 35

relative increase in pressure within left atrium forces septum primum against septum secundum associated with the 1st breath