Mechanical Properties of the Heart - 2 Flashcards
What is diastole and how many sub phases can it be split into?
ventricular relaxation during which the ventricles fill with blood
Split into four sub-phases
What is systole and how many sub-phases is it split into?
ventricular contraction when blood is pumped into the arteries
Split into two sub-phases
How do you calculate stroke volume?
STROKE VOLUME (SV) = EDV - ESV
End-systolic volume
End-diastolic volume
How do you calculate ejection fraction?
Ejection fraction (EF) = SV / EDV
Stroke volume
END DIASTOLIC VOLUME (EDV)
What is end diastolic volume?
END DIASTOLIC VOLUME (EDV) = the volume in the ventricles just before
What is end systolic volume?
END SYSTOLIC VOLUME (ESV) = the volume in the ventricles after the ventricle has completely contracted and expelled as much blood as it is going to
Define ejection fraction?
EJECTION FRACTION (EF) = the proportion of the end diastolic volume that is pumped out of the heart (Ejection Fraction = SV/EDV)
In normal people the ejection fraction at rest is about 65%
In patients with heart failure, the ejection fraction can drop to around 35%
The cardiac cycle can be split into SEVEN events
Name these 7 events?
Atrial Systole
Isovolumic Contraction
Rapid Ejection
Reduced Ejection
Isovolumic Relaxation
Rapid Ventricular Filling
Reduced Ventricular Filling
What is isovolumetric contraction and isovolumertic relaxation?
isovolumetric contraction is an event occurring in early systole during which theventricles contract with no corresponding volume change (isovolumetrically)
isovolumic relaxation-that part of the cardiac cycle between the time of aortic valve closure and mitral opening, during which the ventricularmuscle decreases its tension without lengthening so that ventricular volume remains unaltered; the heart is neverprecisely isovolumetric (vs. isovolumic) except during long diastoles with a midiastolic period of diastasis.
What happens to the blood just before an atrial systole?
Just before atrial systole, the blood will flow PASSIVELY through the open AV valves into the ventricles
Atrial Systole tops off the volume of blood in the ventricles
What type of wave is seen on an ECG when there is atrial systole?
ECG - atrial systole is seen as a P wave - indicates atrial excitation
During atrial systole you occasionally hear an abnormal heart sound. What is the name of this sound?
What causes this abnormal sound?
Name 3 conditions that can cause S4?
During this time you occasionally hear an abnormal heart sound called S4- usually associated with pathollogical issues
S4 is usually caused by Atrial contraction to a non complient ventricle and valve incompetency (valves don’t shut properly making the blood flow become turbulent) - ventricle fail to relax
S4 occurs with:
Pulmonary Embolism
Congestive Heart Failure
Tricuspid Incompetence
In which vein may you feel a small pulse in when the atria contracts?
JUGULAR PULSE - you may feel a small pulse in the jugular at this time due to the atrial contraction pushing some blood back up the jugular vein
At this point there is very little change in the pressure in the aorta and the ventricles
P wave = ATRIAL DEPOLARISATION
Isovolumic Contraction
This happens in between the ……… ……………. valves closing and the …………. ……….. valves opening
This happens in between the Atrio Ventriccular valves closing and the semi-lunar valves opening
The interval between AV valves (tricuspid & mitral) closing and semi-lunar valves (pulmonary & aortic) opening
Contraction of ventricles with no change in volume
What is isovolumetric contraction?
The interval between AV valves (tricuspid & mitral) closing and semi-lunar valves (pulmonary & aortic) opening
Contraction of ventricles with no change in volume
Isovolumetric Contraction
This happens in between the AV valves closing and the semi-lunar valves opening
The ventricles are completely sealed off during this period
The ventricles start to contract AGAINST CLOSED VALVES
So the ventricles contract with NO CHANGE IN VOLUME hence it is isovolumic
This contraction against closed valves leads to a rapid increase in pressure
What is happening during the the QRS complex ?
QRS complex marks ventricular depolarization
What on an ECG marks isovolumetric contraction?
ECG - seen as the QRS complex = signified ventricular excitation
AV valves close as ventricular pressure (red) exceeds atrial pressure (orange)
Pressure in ventricles increases without a volume change and approaches aortic pressure (green)
What heart sound is heard during isovolumetric contraction and what causes this sound?
The first heart sound occurs during this period - caused by the closing of the AV valves
S1 is the first heart sound - caused by the closing of the AV valves (this is the ‘lub’)
When does isovolumic contraction end?
Once blood begins to be ejected, isovolumic contraction ends
The ventricles are contracting ISOMETRICALLY so the muscle fibres ARE NOT CHANGING IN LENGTH but they are generating force and the pressure increases
What happens when the ventricular pressure exceeds aortic pressure?
You reach a point at which the ventricular pressure EXCEEDS aortic pressure (afterload) and at this point the aortic valve opens and blood starts to be ejected from the ventricles
QRS complex = VENTRICULAR DEPOLARISATION
semilunar valve
noun
ANATOMY
plural noun: semilunar valves
each of a pair of valves in the heart, at the bases of the aorta and the pulmonary artery, consisting of three cusps or flaps which prevent the flow of blood back into the heart.
Rapid Ejection
………… and …………….. valves open marking the start of rapid ejection
As the ventricles contract in the closed ventricular chamber the ventricular pressure rapidly increases until it exceeds the pressure in the ……… and ……………….. arteries (afterload)
At this point the …………….. valves open and the ventricular volume ………………
Aortic and pulmonary valves open marking the start of rapid ejection
As the ventricles contract in the closed ventricular chamber the ventricular pressure rapidly increases until it exceeds the pressure in the aorta and pulmonary arteries (afterload)
At this point the semi-lunar valves open and the ventricular volume decreases
What causes the c wave in the image below and what stage in the cardiac cycle causes this c wave?
RAPID EJECTION
The ‘c wave’ seen in the atrial pressure is caused by the right ventricular contraction pushing the tricuspid valve into the atrium and this creates a small wave into the jugular vein
Once the valves are open, aortic pressure increases in line with the ventricular pressure
ECG - as the excitation process has happened, there is NO ELECTRICAL ACTIVITY on the ECG and there are NO HEART SOUNDS because no valves are closing
Rapid Ejection = NO wave on ECG
What does the phase of reduced ejection mark the end of?
This phase marks the end of systole
What happens to the valves during reduced ejection?
Blood leaves the ventricles and ventricular pressure begins to fall, eventually aortic and pulmonary pressure will exceed the ventricular pressure and so the VALVES WILL BEGIN TO CLOSE
What letter in the PQRST wave correspndes to reduced ejection?
ECG - cardiac cells begin to REPOLARISE (action potential went very positive and is now returning to resting potential) - this is seen as a T wave
NO heart sounds because no valves are shutting
T wave = VENTRICULAR REPOLARISATION
What happens to the valves during isovolumic relaxation?
Aortic and pulmonary valves have shut and the AV valves remain shut
What is isovolumic relaxation the beggining of?
Beginning of diastole
Beginning of ………………
Semi-lunar valves have shut and the ……………. valves remain shut
As the …………….. valves are closed there is NO CHANGE IN VENTRICULAR VOLUME hence it is …………….. ……………….
Atria fill but the ………………..r valves are shut hence there is an increase in atrial pressure
Beginning of diastole
Semi-lunar valves have shut and the Atrioventricula valves remain shut
As the Atrioventricular valves are closed there is NO CHANGE IN VENTRICULAR VOLUME hence it is isovolumic relaxation
Atria fill but the Atrioventricular valves are shut hence there is an increase in atrial pressure
What causes the v wave in the diagram below and what stage of the cardiac cycle is this?
Isovolumic Relaxation
‘v wave’ in the atrial pressure is caused by blood pushing the tricuspid valve and giving a second jugular pulse
What is happening in the image below in the area highlighted in a dark blue?
Refer to the atria and valves
Atria have now filled with blood but AV valves shut hence atrial pressure rises (orange). Blood pushing tricuspid valve gives second jugular pulse (“v” wave).
In what cardiac cycle does a dichrotic notch occurs and what causes it?
Dichrotic notch due to rebound pressure wave against aortic valve as distended aortic wall relaxes.
What heart sound is heard during isovolumic relaxation?
2nd heart sound (dub) occurs when aortic & pulmonary valves close
What happens to the valves in Rapid Ventricular Filling?
What happens to the ventricular volume and atrial pressure during rapid ventirclar filling?
AV valves open again and the blood flows rapidly from the atria in to the ventricles
Ventricular Volume INCREASES
Atrial Pressure DECREASES
REMEMBER: This filling of the ventricles is PASSIVE as it is not due to atrial systole
What heart sound may be heard during rapid ventricular filling?
Name 2 conditions that can cause this sound?
What is other term is this heart sound known as?
During this period you may hear a THIRD HEART SOUND (S3) which is ABNORMAL and can signify turbulent ventricular filling due to the valves not closing properly so the blood flows turbulently
S3 can be due to severe hypertension or mitral incompetence
S3 is often referred to as VENTRICULAR GALLOP
Reduced Ventricular filling
This slow filling of the ventricles is also called …………………..
Ventricular volume ………………. more slowly
This slow filling of the ventricles is also called DIASTASIS
Ventricular volume increases more slowly
There are NO changes in the ECG and there are NO heart sounds
Good heart website
Image that puts everything together
http://www.blaufuss.org/
Pulmonary Circulation Pressures
The SAME PATTERNS OF PRESSURE CHANGES occur in the RIGHT side of the heart
BUT, everything on the right side of the heart occurs at LOWER PRESSURES
Despite this lower pressure, the right ventricle ejects the same volume of blood as the left ventricle
Blood Pressure Values:
SYSTEMIC = 120/80 mmHg
Pulmonary = 25/5 mmHg
A catheter can be inserted into a large vein and worked up into the right atrium and the right ventricle and you can have a pressure tip on it which allows you to measure changes in pressure
In the pulmonary artery, as you have the valve closing, the diastolic pressure rises in the pulmonary artery
You can insert a catheter with a balloon on the end into the pulmonary artery and inflate the balloon so that no blood can go past it
Distal to the balloon, you can measure pressure changes further up the pulmonary system which is linked to the left atrium
So by measuring on the right side of the heart, you can measure the preload on the LEFT side of the heart
This is PULMONARY ARTERY WEDGE PRESSURE (PAWP)
PAWP is elevated if you’ve got problems on the left side of the heart (particularly the left atrium) or problems with the mitral valve
When is Pulmonary Artery wedge pressure (PAWP) elevated in?
What are the systemic and pulmonary pressures?
LV Failure, Mitrial insufficiency, mitrial stenosis
Mitral insufficiency (MI), mitral regurgitation ormitral incompetence is a disorder of the heart in which the mitral valve does not close properly when the heart pumps out blood.
Mitral stenosis is a narrowing of the mitral valve opening that blocks (obstructs) blood flow from the left atrium to the left ventricle. Mitral stenosis usually results from rheumatic fever, but infants can be born with the condition. Mitral stenosis does not cause symptoms unless it is severe.
What does point 1 mean?
What does point 2 mean?
What does between point 2 and 3 mean?
What does point 3 mean?
Why is there a straight line between point 3 and 4?
You plot VENTRICULAR PRESSURE against VENTRICULAR VOLUME
Point 1 = End Diastolic Volume (EDV) - the ventricle has a large volume but hasn’t generated any pressure yet
Point 2 = Isovolumic Contraction - the volume in the ventricle hasn’t changed but there is a large increase in pressure
At this point, the ventricular pressure has got to the same point as the aortic pressure (afterload) and is just about to overcome it
Between Point 2 and Point 3 = the ventricle starts to expel blood so the volume of blood in the ventricle falls and the ventricular pressure rises then falls
This ends on Point 3 which is the End Systolic Volume (ESV)
THE DIFFERENCE BETWEEN POINT 3 and POINT 2 IS THE STROKE VOLUME
Pressure falls in the ventricles due to Isovolumic Relaxation but the volume stays the same so there is a straight line downwards between Point 3 and Point 4
Circle on the diagram below where preload and afterload are?
Preload - determines the stretch on the muscle fibres
Blood filling the ventricles during diastole determines the preload
Therefore, Point 1 which is End Diastolic Volume gives an idea of preload because it is the volume of blood filling the ventricles and stretching the resting ventricular muscle
Afterload is the pressure in the aorta that the ventricle has to overcome to eject blood
Afterload is realised just after point 2 - this is when the left ventricle encounters the aortic pressure when the aortic valve begins to open
Why does point 1 and 2 move further to the right?
If we increase the amount of blood flowing back to the heart and hence increase the stretch on the muscle we would move from the smaller PV loop to the bigger one
Point 1 and 2 move further to the right because there is more volume returning to the heart and hence the preload increases and End Diastolic Volume increases
Greater preload allows us to produce more contraction and therefore more stroke volume
The increase in stroke volume is shown by an increase in the distance between point 3 and point 2
Increasing preload ……………. stroke volume
Increasing preload increases stroke volume
Increasing afterload ……………… stroke volume
Increasing afterload decreases stroke volume
Why does point 2 move in the positive y direction?
When you increase the afterload you decrease the amount of shortening
So if you have high blood pressure, the afterload is increased so the ventricular muscle has to work harder to eject the blood against the higher pressure
Therefore, when we increase the afterload, more pressure is needed to open the aortic valve so Point 2 moves in a positive y direction
Point 1 remains the same because the End Diastolic Volume is the same
The increase in afterload also means that less shortening can occur and so the stroke volume decrease
How do you calculate cardiac output?
Stroke volume can be changed by changing the amount of blood that returns to the heart and by changing the arterial pressure - i.e. changing preload and afterload
Cardiac output can also be changed by altering the contractility (how forcefully it contracts) of the heart e.g. by using adrenaline
Cardiac output = heart rate x stroke volume
Define Cardiac Contractility
What is a simple measure if cardiac contractility
Contractility is increased by ……………. stimulation
- Definition: Contractile capability (or strength of contraction) of the heart
- Simple measure of cardiac contractility is ejection fraction
- Contractility is increased by sympathetic stimulation
- Family of different Frank-Starling relations as cardiac contractility changes
Increase in contractility means that more blood is pumped out hence the stroke volume increases and Point 3 moves further to the left
- During exercise contractility is …………….. due to increased sympathetic activity
- During exercise end …………….. volume is increased due to changes in the peripheral circulation (venoconstriction and muscle pump)
- During exercise contractility is increased due to increased sympathetic activity
- During exercise end diastolic volume is increased due to changes in the peripheral circulation (venoconstriction and muscle pump)
