Exam 1 - Lecture 4 Flashcards
Mixed vasodilators examples
sodium nitroprusside, which are nitric oxide donors.
They fall apart when exposed to sunlight
Venous dilators will do what 2 things?
Reduce preload (dilate veins) and Reduce metabolic demands of the heart
2 examples of arterial vasodilators and what do they do for the heart? Onset of action?
ACE-I and Hydralazine; reduce afterload
20-30 minutes
Phenylephrine is an arterial, venous, or mixed pressor?
Mixed, but has a greater effect on constricting veins for increased venous return.
How much right atrial pressure is needed in order to return cardiac output to normal with a failing heart and normal sympathetic activity?
8mmHg (would need increased PSF too)
With a failing heart, catecholamines will act on both ______
heart and circulatory system to help
Talk about the bodies compensation to a failing heart acutely vs chronically
Acutely, catecholamines constrict the veins to increase blood return to heart.
Chronically, the catecholamines tell the kidney to retain more fluid, to keep the pressure in the veins elevated and the catecholamines will reduce.
If our sympathetic nervous system is maxed out with an acute failing heart, what is the issue with standing up?
Our nervous system prevents us from passing out when we stand up by increasing catecholamine release, and if its already maxxed out, it cant help us.
What is a risk of an overly sympathetic nervous system for the heart?
Increased catecholamines in the heart puts extra risk of an arrythmia due to the phosphorylation in the cardiac muscle cells
3 compensations by the body for cardiac failure
Increased volume retention, Decreased venous compliance, increased SVR (which will reduce slope of venous return curve)
Definition for Preload
Pressures available to fill the heart with blood, measured in mmHg
The pressures determine volume of blood that will fill in the heart.
Afterload definition
Pressure right outside the aortic valve
When its high, puts more stress on heart to pump blood out.
Contractility definition
A change in stroke volume when preload and afterload are held constant.
If you increase preload, what are the changes on the graph?
Increase filling, increase stroke volume, increased EDV
What is the measure of after load?
80mmHg, pressure right outside ventricle in aorta BEFORE the valve opens
Does afterload change with increased preload?
Not really. Maybe a little bit but not on the chart
How is contractility measured on the graph?
Where it intersects on the top of the graph. Higher contractility moves to the left; lower to the right
If preload and after load are held constant, and contractility increases, what happens to the ESV?
Decreased
A higher ESV with no changes to preload and afterload could indicate
Lower contractility
What happens with decreased preload?
Less filling, lower EDV, lower SV
What changes with increased afterload?
Takes a longer time to open up aortic valve, gives less time for contraction, so lower stroke volume, and higher ESV
What phase is increased with afterload? Decreased?
Phase 2 increased; phase 1 and 3 decreased
What about phase 4? Idk…
What pressure does aortic valve usually CLOSE?
100mmHg
Why is stroke volume reduced with increased afterload?
Less time for contraction since phase 2 is longer, but also extra pressure slams aortic valve shut
What changes happen with decreased afterload?
Phase 2 and 4 is shorter, and aortic valve shuts later than normal… phase 1 and 3 longer, and decreased ESV since there was more time and less resistance. Increases stroke volume. Preload doesn’t change
If contractility increases, what are the changes?
Phase 1 and 3 longer, phase 2 and 4 are the SAME, lower ESV, same EDV. Overall larger stroke volume
Decreased contractility causes what effects?
Shortens every phase except phase 2
Increase ESV, decreased CO.
Decrease BP
Does contractility changes change the BP?
Yes. More contractility raises BP and vice versa
How does cardiac failure change the cardiac curves?
Depressed contractility, higher ESV, increased EDV, lower SV, shorter phase 1 and 3
What changes with filling pressure with cardiac failure?
Higher filling pressure cause heart can’t beat it out and increased volume retention
Aortic valve stenosis will occur by the time you are
50-60 years old
how many leaflets does the aortic valve have
3
Aortic valve stenosis is what kind of load issue
afterload
Does aortic stenosis require more or less pressure to eject blood
more
What are the changes on the chart seen with aortic valve stenosis?
Reduced SV, longer phase 2 and 4 (?)
Higher EDV/filling pressure
Heart rate has to elevate with decreased SV
How does the aortic valve stenosis affect blood pressure? pulse pressure?
High pressure in the ventricle with resistance from the valve means its going to lower the pressure in the aorta, so that means blood pressure will actually be lower with a narrow pulse pressure.
Mitral valve stenosis changes on curve graph shit
shortened phase 1 because it cant fill as well, so less EDV
Decreased stroke volume
Increased LA pressure
Increased pulmonary venous pressures
If no other compensations, HR will have to pick up.
Compensations for mitral valve stenosis
increase Psf, increased atrial pressure, increased blood volume
What’s a systemic effect of mitral valve stenosis?
The extra Psf and increased blood volume can cause pulmonary edema cause the pressure backflows into the lungs/pulmonary hypertension
Aortic regurgitation looks like what on a graph?
sideways A, like a fat blob
Aortic regurgitation happens with which pressures and phases?
High in aorta, low in ventricle.
During diastole, So the ventricle starts filling during phase 4, and continues through phase 1 and into phase 2.
If we have a chronic leaky aortic valve, the EDV can end up being
much much higher from ventricle walls being overstretched (almost 200mL on graph)
At the beginning of phase 4 with aortic regurgitation, explain the backwards blood flow?
Not as much at first cause the ventricle hasnt relaxed yet, but towards the end of phase 4, it fills alot more as the ventricle relaxes.
As the ventricle gets fuller and fuller, with aortic regurgitation, their is more or less backflow from the aorta?
less, since the pressure in the ventricle is building.
With aortic regurgitation, how does this affect EDV? And what does that do to stroke volume?
Increases both, which is good that it has increased stroke volume to make up for some of the blood coming back in.
How do you know what the net forward stroke volume is?
You dont, at least not from the pressure volume loop chart.
How do you know whether its a mitral valve regurgitation or aortic regurgitation looking at the pressure volume loop?
If interventricular volume is increasing during phase 4, then its aortic regurgitation.
What pressure does the aortic valve open with aortic regurgitation?
Lower than normal since its backflowing anyway ( 80mmHg)
Where is the diastolic pressure measured on the pressure volume loop with aortic regurgitation? Systolic peak pressure?
The further right side. The tallest side.
When does a mitral valve regurgitation leak?
when the pressure is higher in the ventricle than atria (no shit..?)
With mitral valve regurgitation, how does phase 2 act?
It curves down in volume because blood is moving out of the ventricle back into the atria. (should be isovolumetric contraction)
with mitral valve regurgitation, how does phase 4 act?
Should be losing volume back into the atria during early phase 4, then less volume change at end of phase 4.
