S1M3 Cardiac Cycle
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What happens in the rapid ventricular filling phase?
- After systole, the heart is relaxing (diastole)
- Mitral valve opens, LA pressure drops
- LV volume is doubled (50mL to 100mL, we start with 50 due to LVESV)
- LV pressure decreases* (counterintuitive, but think about it, heart just contracted, making that wringing motion, now it is relaxing and filling the ventricles with blood, so it's decreasing LV pressure, but doubling LV volume.
What is LVESV?
- Left ventricle end systolic volume
- Systole doesn't fully empty our left ventricle so we start diastole with about 50 mL blood in the ventricle.
- The LVESV is doubled during the rapid ventricular filling phase
What is diastasis?
- The period of slow ventricular fillingDuring diastole, when ventricle and atria are stil relaxing
What is occuring in the slow ventricular filling phase?
- Diastole Still so....
- The left atrium and ventricle are continuing to relax
- Very little LV filling taking place (only about 10 mL added)
- Rate of ventricular filling decreases towards the end of diastole***!
- Not a very important phase...if you got rid of it, no big deal!
- This phase is also known as Diastasis
Why in the slow ventricular filling phase is the LA pressure slightly higher than the LV pressure?
Because the pressure in the Atrium MUST be higher than the ventricle for blood to flow from the atria to the ventricle! (Blood flow must be from high pressure to low pressure)
Why throughout diastole
do we get a gradual drop in aortic pressure (AP below)?
due to the windkessel effect, the recoiling of the aorta! remember this leads to a continuous flow of blood!
Rapid Ventricular Filling and Slow Ventricular filling are passive or active filling steps?
Passive filling steps!
Which phase is the only active filling phase?
- Phase 3, atrial contraction phase
- leads to a small rise in both A/V pressure, leading to the "a wave" highlighted bump below
What is the "a wave"
- It is part of the atrial contraction phase (phase 3) towards the end of diastole in which the atria contracts (increasing LA pressure, producing a little "bump in the pressure diagram for LA)
- Also increases LV volume by +10 mL (total LV volume about 70 mL now due to Rapid Ventricular Filling Phase and Slow Ventricular Filling Phase)
What sounds triggers the begining of systole (contraction)?
- S1 heart sound, which is the mitral valve closing to prevent blood from flowing back into the left atrium
- (also involves the tricuspid valve closing also)
What occurs in the isovolumetric contraction phase?
- Begining of systole!
- BIG increase in ventricular pressure, but no change in the venticular volume because the mitral and aortic valves are closed.
- The aortic valve remains closed until the LV pressure exceeds the pressure in the aorta
- EDV: also important to remember, the volume in the heart during the isovolumetric contraction phase is called the EDV, or end diastolic volume.
- c-wave: we get a little wave called the c-wave in this phase which is a rise in LA pressure due to mitral valve bulging into the atrium when the LV contracts.NO CHANGE IN VOLUME, COMON! it's called the isovolumetric contraction phase for a reason.
What is the EDV?
- End Diastolic Volume,
- which is the volume in the left ventricle during the isovolumetric contraction phase, where mitral/aortic valves are closed and you have a BIG increase in the ventricular pressure
- *remember there is NO change in ventricular volume during this phase
When does the aortic valve open?
- When the left ventricle pressure, LVP = AP (aortic pressure)
- You push the aortic valve open at the end of the isovolumetric contraction phase when the pressure in the left ventricle is raising very very high, very quickly (because mitral and aortic valves are both closed, no volume change, just increases in pressure)
What is the c-wave? What causes it?
we get a little wave called the c-wave in the isovolumetric contraction phase which is a little rise in LA pressure due to mitral valve bulging
into the atrium when the LV contracts.
What occurs during the rapid ejection phase?
What happens to the volume in the LV?
Pressure in the LV/Aorta during this phase?
- The pressure of the left ventricle exceeds the pressure in the aorta ( = 80mmHg) , thus causing the opening of the aortic valve
- The pressure in the LV must continue to rise in order to provide a pressure gradient for the blood to flow from the LV into the aorta.
- Ventricle volume decreases (lose 1/2 volume of the ventricle)
What occurs in the slow ejection phase?
What's happening to the LV pressure and rate of blood flow into the aorta?
- Less cardiomyocytes contracting
- This reduces ventricular pressure and rate of blood flow into the aorta
- When LV pressure falls below the pressure in the aorta, the aortic valve shuts.
- Volume of the LV reaches a low
What occurs during the isovolumetric relaxtion phase?
- DIASTOLE BEGINS (relaxation)
- Aortic Valve Closes
- S2 Heart Sound due to this closure!
- Mitral and Aortic valve both shut
- LA pressure increases, producing a v wave
- Rapid LV pressure decrease, when it drops to below the LA pressure, the mitral valve will open again and we get another ventricular filling phase
- Dicrotic notch due to windkessel effect, continuous flow of blood from aorta even when the aortic valve is closed due to the recoil of the aortic wall
What is the v-wave?
When is the peak of the v-wave?
- corresponds to increase in LA pressure due to LA fillingDuring most of systole the LA is filling with blood when the mitral valve is closed.
- LA always filling with blood from the lung, so this appears as a gradual increase in LA pressure until diastole again when we fill the ventricles.
- Peak of v wave occurs when the mitral valve opens.
What does the S2 heart sound correspond to?
the closure of the aortic valve during the isovolumetric relaxation phase
What is the dicrotic notch correspond to?
- A little increase in Aortic pressure during the isovolumetric contraction phase when the aortic valve is shut and the recoling of the aorta allows a continuous blood flow (some of the recoiling blood flows backward against the aortic valve which causes the little increase in pressure)
- Due to the "windkessel effect"
When you exercise what phase of the cardiac cycle is eliminated?
the slow ventricular filling phase, or diastasis
it's shortened or eliminated!
What 4 changes occur in the cardiac cycle during contraction?
- 1.) Shortening of the period (shortened by 200 ms to 400 ms) make diastole shorter.
- 2.) Reduction or Loss of Diastasis
- 3.) Stoke Volume is Increased (due to atrial contraction volume increase or atrial contraction phase)---ADD MORE BLOOD VOLUME!!--can x4 the volume added during the atrial contraction phase.
- 4.)Ventricular/Aortic Pressures are Increased.
What node is very important during exercise?
- SA node!
- Important for raising the heart rate & stroke volume
During exercise what major contribution does the atrium make?
It increases its volume! It can add more blood (x4 as much) and increase the stroke volume simply by increasing the atrial contraction.
When your heart rate is above 200BPM what happens?
- There isn't enough time to have all of the events of the cardiac cycle to take place
- Not enough time to fill the ventricles and eject blood so you have inadequate pumping
- Major Reduction in stroke volume due to decreased ventricular filling time.
What are venous pressure waves used to diagnose?
- Pressure waves in the jugular vein mainly produced by events in the right heart
- Used to diagnose right heart failure
Our jugular vein is very superficial, and if the pressure in the vein is very high, we can physically see the pulse at this location. This is a physical diagnosis we can make regarding something involving the right side side of the heart (right heart failure) why?
- If your right heart is failing then that means that blood is going to back up into your venous system, increasing pressure in the jugular vein and we will be able to physically see the pulse.
- Depicted visually in the venous pressure wave
What events take place that are depicted on the Jugular venous pressure graph?
What events correspond to the a, c, and v waves?
What is the importance of the jugular venous pressure graph?
- When a PT is unhealthy or has some sort of right heart failure, we get an increase in venous jugular pressure and this graphs line can be greatly elevated
- Very Important DIAGNOSTIC TOOL.
All events that occur in the RA are reflected where?
- Back into the jugular vein, because there is no valve between the venous system and the RA...causes pressure changes in the jugular vein!
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