Cardiac cycle Flashcards
What are the 2 main phases of the cardiac cycle
diastole and systole
how long does each phase last
diastole - about 2/3
systole - about 1/3
what is diastole
ventricular relaxation - ventricles fill up with blood
what is systole
ventricular contraction - ventricles generate pressure and eject blood into the arterie
how many distinct phases are there in systole
3
how many distinct phases are there in diasystole
4
what is the end diastolic volume
the maximum volume of blood in the heart just before the ventricle start to contract, just before the systolic period starts
what is the end systolic volume
amount of blood in the heart after contraction has been completed
How do you measure stroke volume
end diastolic volume - end systolic volume
What is an ejection fraction and why is it clinically relevant
a percentage and a clinical indicator of how well the heart is functioning
(stroke volume/ end diastolic volume)*100 = ejection fraction
what is a normal healthy range for an ejection fraction
52 to 72%
describe what the p wave on ECG is for
atrial contraction
What is the atrial contraction responsible for
topping up the volume of the blood in the atrium
The atria are almost full due to passively filling up from pressure gradient
In what conditions does atrial contraction contribute more to the volume of blood in the ventricle
- when there is a short diastole (if the heart is beating fast, there is less time for the ventricle to passively fill up, so atrial systole fills it up)
- in a high heart rate, atrial contraction may account for up o 40% of ventricular filling
what does 4th heart sound suggest
abnormality (congestive heart failure, pulmonary embolism or tricuspid incompetence)
describe the isovolumetric contraction
- isometric contraction
- contraction of ventricles but there is NO change in volume of ventricles so there is an increased pressure
- 1st lub sound happen (closure of TC and MV )
- interval between AV valves closing and semi lunar valves opening
when does rapid ejection begin
- when intraventricular pressure exceeds that of the aorta and pulmonary artery
- opening of semi lunar valves
what does reduced ejection suggest and describe it
end of systole
reduced pressure gradient so the semi lunar valves being to close so less ventricular blood flows out of the ventricles so the ventricular volume decreases more slowly
- when the pressure in the ventricles is less than that in the aorta, there is blood flow into the ventricles from the aorta, causing the semi lunar valves to close
- T repolarisation
Describe isovolumetric relaxation
All the valves are closed
ventricular volume stays the same but ventricular pressure decreases as there is NO contraction
Aortic pressure rises a bit as distended aortic wall relaxes (dichrotic notch)
Describe rapid passive filling
- isoelectric ECG
- AV valves open as higher pressure in atria so rapid increase in ventricular volume (and a slight increase in ventricular pressure)
At what stage could 3rd heart sound occur and what does it suggest
rapid passive filling
abnormal
severe hypertension or mitral incompetence
Describe reduced passive filling
ventricular volume fills more slowly than it used to
ventricles can fill at least 60% without atrial systole
What are the difference between the cardiac cycles on the RHS and LHS of the heart
- same pattern
- just much lower pressure in RHS (25mm/Hg peak in systole in right pulmonary artery
what does pulmonary capillary wedge pressure sugges
indication of left atrium pressure and measure severity of mitral valve stenosis and left ventricular failure (both of which are caused by an increase in left atrial pressure) = also associted ith increase in pulmonary oedema
