CVS 146 Aortic Stenosis Flashcards
Describe what happens to the heart during diastole
Ventricles are rapidly relaxing
AV valves remain closed until the pressure drops sufficiently
Describe what happens during atrial systole
Atrial depolarisation causing atrial contraction which fills the ventricles with blood
What waves on the JVP tracing and ECG account for atrial systole?
a wave and P wave
What is the End Diastolic Volume and what is its normal value?
Volume of blood inside the ventricles once they have been filled
Normally 120-140mls
What is the end diastolic pressure and what is its normal value?
Pressure inside the ventricles after filling and is normally 10mmHg
Why is the EDP in the left ventricle slightly higher than the right?
It is larger with increased wall thickness and stiffness
Why is EDV important?
It is an important determinant of the strength of the subsequent contraction - Starlings Law of the Heart
Describe what happens during ventricular systole?
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
What waves on ECG and JVP tracing are seen in ventricular systole
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
What is the difference in pressure between the pulmonary artery and the aorta?
Aorta is ~80mmHg and the pulmonary artery = ~15mmHg
these are pressures in diastole
What wave on ECG accounts for muscle repolarisation during the second half of ventricular systole?
T wave
What makes the first and second heart sounds?
1st = AV valves closing (mitral and tricuspid) at beginning of ventricular systole 2nd = Closure of pulmonary and aortic valves at end of ventricular systole
In the normal heart what is stroke volume? And therefore what usually is the end-diastolic volume?
~70mmHg
EDV ~ 50mmHg
What is the ejection fraction of the heart?
The proportion of the blood in the heart that is ejected = stroke volume/ end diastolic volume
What accounts for the v wave on JVP tracing?
An increased in atrial pressure as the veins fill the atria
What proportionately to systole is the length of diastole at rest?
Double the length of systole
What accounts or the y descent on JVP tracing?
As ventricular pressure decreased the AV valves open causing a decrease in atrial pressure
What is the JVP tracing a measure of?
Right atrial pressure
What accounts for the x descent on JVP tracing?
Downward motion of the heart in ventricular systole
What is the pressure volume loop?
Ventricular pressure plotted against volume - generates a loop
What is the shape of the pressure volume loop affected by?
Contractility, compliance of the ventricles and factors affecting refilling or ejection
What does the volume inside of the pressure volume loop account for?
measure of the work done during a heart beat - an indicator of cardiac function
What may be seen on JVP tracing in atrial hypertrophy? What is a common cause behind this?
Large a wave - pulmonary hypertension
What may be seen on JVP tracing in tricuspid regurgitation?
Giant v wave
What are the three main pathologies of aortic stenosis?
Acquired calcification
Rheumatic fever
Congenital - biscuspid valve
What is the pathophysiological mechanism behind Aortic Stenosis?
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
Why is there LVH in aortic stenosis?
The increased pressure required in the LV to maintain stroke volume and the pressure difference causes increased recruitment of myocytes and hypertrophy
When do symptoms tend to develop in AS?
When valve surface area is down to about 1-1.5 cm^2
= late presentation
Why does angina develop in AS?
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)
What are the possible mechanisms behind development of syncope in AS?
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
What does dyspnoea develop in AS?
Due to LVH - decreased filling pressure = higher left atrium pressure = higher pulmonary BP due to back pressure into veins = left sided heart failure
Why may there be GI bleeding in AS?
Angiodysplasia in GI tract, denatured clotting factors, platelets disturbed by turbulent flow
What are some of the signs of AS?
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
What are the 3rd and 4th heart sounds?
Not usually heard:
3: blood passively rushing into ventricles in diastole
4: turbulent blood flow during atrial systole
When does an ejection systolic murmur occur? And why in AS?
between 1st and 2nd heart sounds and due to turbulent blood flow through stenosed AV
