CVS 146 Aortic Stenosis

Question 1

Describe what happens to the heart during diastole

Answer 1

Ventricles are rapidly relaxing

AV valves remain closed until the pressure drops sufficiently

Question 2

Describe what happens during atrial systole

Answer 2

Atrial depolarisation causing atrial contraction which fills the ventricles with blood

Question 3

What waves on the JVP tracing and ECG account for atrial systole?

Answer 3

a wave and P wave

Question 4

What is the End Diastolic Volume and what is its normal value?

Answer 4

Volume of blood inside the ventricles once they have been filled
Normally 120-140mls

Question 5

What is the end diastolic pressure and what is its normal value?

Answer 5

Pressure inside the ventricles after filling and is normally 10mmHg

Question 6

Why is the EDP in the left ventricle slightly higher than the right?

Answer 6

It is larger with increased wall thickness and stiffness

Question 7

Why is EDV important?

Answer 7

It is an important determinant of the strength of the subsequent contraction - Starlings Law of the Heart

Question 8

Describe what happens during ventricular systole?

Answer 8

Ventricles contract - sharp rise in pressure
the AV valves close
Once pressure inside the ventricles exceed that of the outflow vessels the pulmonary and aortic valves open

Question 9

What waves on ECG and JVP tracing are seen in ventricular systole

Answer 9

QRS complex
c wave = the wave when the pressure inside the ventricles rises but not sufficiently for outflow valves to open but causes the mitral valve to bulge into the atria

Question 10

What is the difference in pressure between the pulmonary artery and the aorta?

Answer 10

Aorta is ~80mmHg and the pulmonary artery = ~15mmHg

these are pressures in diastole

Question 11

What wave on ECG accounts for muscle repolarisation during the second half of ventricular systole?

Answer 11

T wave

Question 12

What makes the first and second heart sounds?

Answer 12

1st = AV valves closing (mitral and tricuspid) at beginning of ventricular systole
2nd = Closure of pulmonary and aortic valves at end of ventricular systole

Question 13

In the normal heart what is stroke volume? And therefore what usually is the end-diastolic volume?

Answer 13

~70mmHg

EDV ~ 50mmHg

Question 14

What is the ejection fraction of the heart?

Answer 14

The proportion of the blood in the heart that is ejected = stroke volume/ end diastolic volume

Question 15

What accounts for the v wave on JVP tracing?

Answer 15

An increased in atrial pressure as the veins fill the atria

Question 16

What proportionately to systole is the length of diastole at rest?

Answer 16

Double the length of systole

Question 17

What accounts or the y descent on JVP tracing?

Answer 17

As ventricular pressure decreased the AV valves open causing a decrease in atrial pressure

Question 18

What is the JVP tracing a measure of?

Answer 18

Right atrial pressure

Question 19

What accounts for the x descent on JVP tracing?

Answer 19

Downward motion of the heart in ventricular systole

Question 20

What is the pressure volume loop?

Answer 20

Ventricular pressure plotted against volume - generates a loop

Question 21

What is the shape of the pressure volume loop affected by?

Answer 21

Contractility, compliance of the ventricles and factors affecting refilling or ejection

Question 22

What does the volume inside of the pressure volume loop account for?

Answer 22

measure of the work done during a heart beat - an indicator of cardiac function

Question 23

What may be seen on JVP tracing in atrial hypertrophy? What is a common cause behind this?

Answer 23

Large a wave - pulmonary hypertension

Question 24

What may be seen on JVP tracing in tricuspid regurgitation?

Answer 24

Giant v wave

Question 25

What are the three main pathologies of aortic stenosis?

Answer 25

Acquired calcification Rheumatic fever Congenital - biscuspid valve

Question 26

What is the pathophysiological mechanism behind Aortic Stenosis?

Answer 26

There is a chronic inflammatory response to epithelial damage = inflammation, lipid plaques and leukocyte infiltration leukocytes cause insterstitial cells to differentiate into osteoblasts = bone nodule synthesis and calcification = stenosis due to decreased compliance of leaflets = reduced aortic vave area

Question 27

Why is there LVH in aortic stenosis?

Answer 27

The increased pressure required in the LV to maintain stroke volume and the pressure difference causes increased recruitment of myocytes and hypertrophy

Question 28

When do symptoms tend to develop in AS?

Answer 28

When valve surface area is down to about 1-1.5 cm^2 | = late presentation

Question 29

Why does angina develop in AS?

Answer 29

Increased demand for oxygen but decreased supply Increased demand: increased work due to greater pressures needed and increased number of myocytes Decreased supply: shortened diastole ( increased systole as LV takes longer to eject same SV); lower aortic pressures ( pressure required to fill CA's); reduced capilliary density ( hypertrophy squashes CA's = reduced myocardial perfusion)

Question 30

What are the possible mechanisms behind development of syncope in AS?

Answer 30

Failure to meet O2 demand - mostly during exertion Aortic hypotension - vasodilation in exercise but can't overcome low BP High ventricular pressure stimulates mechanoreceptors = bradycardia Ventricular arrhythmias

Question 31

What does dyspnoea develop in AS?

Answer 31

Due to LVH - decreased filling pressure = higher left atrium pressure = higher pulmonary BP due to back pressure into veins = left sided heart failure

Question 32

Why may there be GI bleeding in AS?

Answer 32

Angiodysplasia in GI tract, denatured clotting factors, platelets disturbed by turbulent flow

Question 33

What are some of the signs of AS?

Answer 33

Heaving apex beat (due to LVH) Slow rising pulse with reduced pulse pressure (slow passage of blood through stenosis and blood loss to arterioles) Ejection systolic murmur

Question 34

What are the 3rd and 4th heart sounds?

Answer 34

Not usually heard: 3: blood passively rushing into ventricles in diastole 4: turbulent blood flow during atrial systole

Question 35

When does an ejection systolic murmur occur? And why in AS?

Answer 35

between 1st and 2nd heart sounds and due to turbulent blood flow through stenosed AV