Cardiac cycle

Question 1

What are the 2 main phases of the cardiac cycle

Answer 1

diastole and systole

Question 2

how long does each phase last

Answer 2

diastole - about 2/3

systole - about 1/3

Question 3

what is diastole

Answer 3

ventricular relaxation - ventricles fill up with blood

Question 4

what is systole

Answer 4

ventricular contraction - ventricles generate pressure and eject blood into the arterie

Question 5

how many distinct phases are there in systole

Answer 5

3

Question 6

how many distinct phases are there in diasystole

Answer 6

4

Question 7

what is the end diastolic volume

Answer 7

the maximum volume of blood in the heart just before the ventricle start to contract, just before the systolic period starts

Question 8

what is the end systolic volume

Answer 8

amount of blood in the heart after contraction has been completed

Question 9

How do you measure stroke volume

Answer 9

end diastolic volume - end systolic volume

Question 10

What is an ejection fraction and why is it clinically relevant

Answer 10

a percentage and a clinical indicator of how well the heart is functioning

(stroke volume/ end diastolic volume)*100 = ejection fraction

Question 11

what is a normal healthy range for an ejection fraction

Answer 11

52 to 72%

Question 12

describe what the p wave on ECG is for

Answer 12

atrial contraction

Question 13

What is the atrial contraction responsible for

Answer 13

topping up the volume of the blood in the atrium

The atria are almost full due to passively filling up from pressure gradient

Question 14

In what conditions does atrial contraction contribute more to the volume of blood in the ventricle

Answer 14

• 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

Question 15

what does 4th heart sound suggest

Answer 15

abnormality (congestive heart failure, pulmonary embolism or tricuspid incompetence)

Question 16

describe the isovolumetric contraction

Answer 16

• 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

Question 17

when does rapid ejection begin

Answer 17

• when intraventricular pressure exceeds that of the aorta and pulmonary artery
• opening of semi lunar valves

Question 18

what does reduced ejection suggest and describe it

Answer 18

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

Question 19

Describe isovolumetric relaxation

Answer 19

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)

Question 20

Describe rapid passive filling

Answer 20

• isoelectric ECG
• AV valves open as higher pressure in atria so rapid increase in ventricular volume (and a slight increase in ventricular pressure)

Question 21

At what stage could 3rd heart sound occur and what does it suggest

Answer 21

rapid passive filling
abnormal
severe hypertension or mitral incompetence

Question 22

Describe reduced passive filling

Answer 22

ventricular volume fills more slowly than it used to

ventricles can fill at least 60% without atrial systole

Question 23

What are the difference between the cardiac cycles on the RHS and LHS of the heart

Answer 23

• same pattern

- just much lower pressure in RHS (25mm/Hg peak in systole in right pulmonary artery

Question 24

what does pulmonary capillary wedge pressure sugges

Answer 24

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