The Heart Pump Flashcards
THe diastolic phase of the cardiac cycle begins with what?
opening of the atroventricular AV valves (mitral and tricuspid)
What happens to ventricular pressure and atrial pressure when the AV valves open?
blood flows rapidly into the ventricles, causing an increase in ventricular pressure and an initial drop in atrial pressure
Why does overall pressure gradually rise in both the ventricle and atrium during passive ventricular filling?
because blood is returning to the atrium from the veins as well
Near the end of ventricular diastole, contraction is initiated where?
in the atrium
What is the EKG equivalent of this atrial contraction?
P wave
WHen atrial pressure rises during atrial contraction an additional pulse of blood is pushed into the ventricles. This isn’t essentialf or adequate ventricular filling at rest, but it is important in times of increased heart rate. why?
because the passive filling time is shortened with elevated heart rate, so you need this extra push of blood to reach a necessary ventricular volume to maintain adequate stroke volume.
What maintins the arterial pressure during diastole?
the elastic recoil of the walls of the aorta and other large arteries.
Despite this, aortic pressure gradually falls during diastole. why?
during diastole the aorta continues to supply blood to the systemic vascular beds
What is the lowest aortic pressure called? When is it reached?
Diastolic pressure - reached at the end of diastole
What are the three things that proper ventricular filling depends on?
- filling pressure of blood returning to the heart
- ability of the AV valves to open fully
- Ability of the ventricular wall to expand passively with little resistance - high compliance
What triggers the beginning of systole/
the action potential passing thorugh the AV node to the ventricles
What EKG point corresponds with the depolarization and ventricular contraction?
the QRS complex
What happens when contraction of the ventricular muscle causes intraventricular pressure to rise above that in the atrium?
the AV valve slams shut
What heart sound corresponds to the AV valve closure?
S1 - this is the “lub”
What do you call the period between mitral valve closure and aortic valve opening?
isovolumetric contraction phase
What causes the aortic valve to passively open?
Contraction intensifies which means left ventricular pressure will exceed the pressure in the aorta - opening the aortic valve
What period starts when the aortic valve opens?
ventricular ejection
Do ventricular pressure and aortic pressure differ much during ventricular ejection? Why?
Not really…
ventricular pressure increases because contraction continues
aortic pressure increases because the blood is being pushed into it
they don’t differ much because the aortic valve orifice is large and presents very little resistance to flow
What is peak systolic pressure?
the maximum of aortic pressure that occurs during mid-systole
Ventricular relaxation and repolarization is represented by which peak on an EKG?
the T wave
After the strength of contraction wanes, aortic pressure falls because of what?
the blood is leaving the aorta and large arteries faster than is entering from the left ventricle
What happens when intraventricular pressure falls below aortic pressure when contraction is done?
the aortic valve leaflets close
What is the incisura or dicrotic notch in aortic pressure?
You get a slight bump back up in aortic pressure because the aortic valve leaflets close and the elastic recoil of the valve and the aorta cause a temporary rise in aortic pressure. it’s basically just a temporary rebound.
THe period between the aortic vavle closure and mitral valve opening is called what?
isovolumetric relaxation
What happens when intraventricular pressure falls below atrial pressure?
the AV valve opens - new cardiac cycle begins
Why does the atrial pressure progressively rise during ventricular systole?
Because while the ventricles contract, blood is still returning to the heart and filling the atrium, which is good because it promotes rapid ventricular filling once the AV valve opens to begin the next heart cycle
What is the arterial pulse pressure?
It’s systolic pressure - diastolic pressure
peak aortic pressure - lowest aortic pressure
What is stroke volume?
the amount of blood ejected from the ventricle during a single beat.
end diastolic volume minus end systolic volume
The right heart wigger’s graph is very similar to the left heart except for what important difference?
the magnitude of peak systolic pressure is lower on the right than the left because there is less resistance to flow form the lungs vs. systemic organs, less resistance, less pressure
What are the average left heart systolic and diastolic pressures?
How about the right?
left: 120 mmHg systolic and 80 mmHg diastolic - look familiar?! This is normal blood pressure!!!!!
right; 24 mmHg systolic and 8 mmHg diastolic
How do you calculate ejection fraction?
it’s stroke volume (EDV-ESV) divided by peak volume
What is the easiest way to alter cardiac output?
increasing or decreasing heart rate through changing the characteristics of depolarization of pacemakers cells via sympathetic or parasympathetic nerves
For the heart, what is “preload”?
the preload is the initial stretching (tension) of the cardiomyocytes PRIOR to contraction
related to the sarcomere length at the end of diastole
What do we use as surrogate measures of ventricular preload?
end diastolic volume or atrial pressure
A DECREASE in which of the following will result in an increase in ventricular filling (hence an increase in preload)? atrial contractility heart rate aortic pressure central venous pressure ventricular compliance
heart rate - a decrease in heart rate leads to a longer passive filling time, thus high ventricular filling
an increase in all the others will result in an increase in ventricular filling
If you increase preload, what happens to stroke volume?
You increase stroke volume
goes back to sarcomere length - if you stretch the sarcomeres a little more (higher preload), there will be more myosin and actin filaments to interact with each other and you increase potential shortening during contraction= higher stroke volume
What is ventricular afterload?
it’s the pressure that the heart must generate in order to eject the blood (the tension develops in the cardiomyocytes of the left ventricle during ejection/contraction)
As afterload increases, what happens to cardiac output?
CO decreases
the harder the heart needs to pump to get the blood out, the less likely it will succeed
What does NE from the sympathetic nervous system do for contractility
It increases contractility by giving the cardiomyocytes more shortening potential
What does NE do for stroke volume?
increases it - higher contractility leads to higher stroke volume and thus a higher ejection fraction
What is the primary source of fueld for the heart?
ATP from oxidative phosphorylation - fatty acids are the main source in adults
How do fetal and newborn metabolism for the heart differ from that of adults?
they use glucose and lactate to make ATP for the heart while we primarily use fatty acids
What is most of the ATP used by the heart used for?
muscle contraction - 75%
basal metabolism = 25%
Which is more efficient toachieve CO, high HR low SV or low HR, high SV?
low HR and high SV - heart rate is a very costly determinant because it takes a lot more O2 to ocntract rapidly than to do so slowly
Thus, what is the best way to reduce O2 consumption by the heart?
reduce heart rate (reduce sympathetic drive)
