Cardiac Cycle Flashcards
List the 7 phases of the cardiac cycle?
Atrial systole Isovolumetric contraction Rapid ejection Reduced ejection Isovolumetric relaxation Rapid ventricular filling Reduced ventricular filling (diastasis)
What parts of the EKG overlap atrial systole?
end of P wave (atrial depolarization) through R peak (ventricular depolarization)
During atrial systole, what are the pressures in the atria and ventricles?
both are increased due to increased ventricular volume
What occurs after atrial systole?
mitral and tricuspid valves close as pressure in ventricles exceeds the atria
What parts of the EKG overlap isovolumetric contraction?
end of R wave through S wave (ventricular depolarization)
During isovolumetric contraction, what is the pressure like in the ventricle?
very high, because both mitral valve and aortic valve are closed
What occurs after isovolumetric contraction?
aortic valve opens when pressure in the ventricle exceeds the aorta
When do aortic pressures peak? What does this cause?
during rapid ejection–leading to closure of the aortic valve
What occurs after rapid ejection?
reduced ejection–ventricular peak pressures decline and atria are in diastole getting filled up with venous return
What part of the EKG overlaps reduced ejection?
T wave (ventricular repolarization)
When the aortic valve closes, what does this due to blood flow?
there is a slight retrograde flow for a fraction of a second
What are the pressures in the atria and ventricles during isovolumetric relaxation?
rapid decline in ventricular pressure, increase in atrial pressure
What occurs just before rapid ventricular filling?
pressure in atria is greater than ventricle, so the mitral valve opens
When do you hear S1 heart sound?
systole
What is the S1 heart sound caused by?
vibrations from closure of AV valves (NO splitting)
When do you hear the S2 heart sound?
start of diastole
What is the S2 heart sound caused by?
vibrations from the closure of the aortic and pulmonary valves
When do you hear S2 split?
inspiration, pulls more blood into right heart and this will lead to a slight delay in the closure of the pulmonic valve
When would you hear an S3?
early diastole
What causes the S3 heart sound?
filling of ventricles (ventricular overload or mitral valve problems)
In what patients is it normal to hear S3?
children and pregnant women
When would you hear S4?
late diastole
What causes the S4 heart sound?
vibrations induced by stiffened ventricle during atrial contraction
What does the surface area of the pressure volume loop tell you?
work
What is the equation for work?
work= pressure X volume
What is occurring during “a” - bottom horizontal line- of the pressure volume loop?
ventricular filling (diastole)
What is point 1 - bottom right corner- of the pressure volume loop? What occurs at this time?
EDV (preload)
mitral valve closes
What is occurring during “b” - right vertical line- of the pressure volume loop?
isovolumetric contraction (diastole)
What is point 2 - top right corner- of the pressure volume loop?
afterload (pressure in aorta that the ventricle must push up against)
What is occurring during “c” - top horizontal line- of the pressure volume loop?
ventricular ejection (systole)
What is point 3 - top left corner- of the pressure volume loop? What occurs at this time?
ESPVR (maximum pressure the the ventricle can generate)
aortic valve closes
What is occurring during “d” - left vertical line- of the pressure volume loop?
isovolumetric relaxation
What is point 4 - bottom left corner- of the pressure volume loop? What occurs at this time?
ESV
mitral valve opens
According to Frank Starling, what regulates ventricular contractility (ESPVR)?
EDPVR, or the left ventricular volume at the end of diastole
When you simply say systolic or diastolic pressure, what are you referring to?
maximum/minimum pressure int he AORTA
What is the ejection fraction?
fraction of the EDV ejected by the ventricle during systole
What is the equation for EF? What is normal?
EF= SV/EDV normal= 55-75%
What is CO?
volume of blood ejected by the ventricle in one minute
What is the equation for CO?
CO = SV * HR
What is preload?
ventricular pressure at the end of diastole (determined by the ventricular end diastolic volume)
What happens to the pressure-volume loop if you increase preload only?
it just gets stretched out to the right
- Increase SV (so increase BP)
- Increase peak systolic pressure
What compensatory changes occur if you increase preload?
increase in SV increases cardiac output which will increase afterload (slightly increase ESV)
What is afterload?
ventricular pressure during contraction (diastolic aortic pressure that the ventricular muscle must pump against)
What happens to the pressure-volume loop if you increase afterload only?
curve gets taller and skinnier and pulls in to the right
- you get decreased ventricular contraction velocity and reduced SV since the heart will pump slower
- ESV increased
What compensatory changes occur if you increase afterload?
increase in ESV will increase EDV (preload) because blood will be added into the venous return
What is contractility?
inotropy- strength of ventricular contraction independent of preload or afterload
What does an increase in contractility do to the pressure-volume loop?
it stretches it out to the left and makes it taller
- also makes slope of ESPVR greater
- decreases ESV
- increases SV (and blood pressure)
What compensatory changes occur if you increase contractility?
-increase SV will increase CO and increase afterload
What is aortic stenosis?
left ventricle is having to push extra hard (increase pressure) to get through the turbulent flow (resistance) in the aorta.
What type of murmur is caused by aortic stenosis?
Leads to a crescendo-decrescendo murmur between S1 and S2 (when velocity of blood is increased due to narrow valve, you get more turbulence, so this is NOISY)
What does aortic stenosis do to the pressure volume loop?
- increase EDV
- lowers SV
- lowers EF
What is aortic regurgitation?
aortic valve is leaking—get aortic run off (rapidly decreasing aortic diastolic pressure—flowing forward and backward back into ventricle)
What type of murmur is caused by aortic regurgitation?
decrescendo diastolic murmur (after S2)
What is mitral stenosis?
left atrium is having to push extra hard (increase pressure) to get through the bad valve into the left ventricle.
What type of murmur is caused by mitral stenosis?
High velocity of blood flow and turbulence leads to a diastolic murmur (after S2)
What is mitral regurgitation?
mitral valve allows backflow into atria (increasing pressure in atria) during ventricular contraction
What type of murmur is caused by mitral regurgiation?
• Systolic murmur (after S1) due to the turbulent back-flow
