The cardiac cycle

Question 1

Essentials for normal cardiac function

Answer 1

intact myocardium + myocytes
substrate to pump around (blood)
own fuel supply
electrical activity

Question 2

Cardiac output equation

Answer 2

heart rate x stroke volume

Question 3

6 stages of the cardiac cycle

Answer 3

atrial contraction
isovolumic contraction
rapid ejection
isovolumic relaxation
rapid ventricular filling
diastasis

Question 4

Describe atrial contraction

Answer 4

ventricles already filled passively
contraction causes increase in atrial pressure + blood is pushed into the ventricles
P-wave on ECG

Question 5

Describe isovolumic contraction

Answer 5

no change in volume
pressure starts to increase
aortic + pulmonary semi lunar valves open
QRS complex on ECG
S1 heart sound = mitral + tricuspid valves closing

Question 6

What causes S1 heart sound?

Answer 6

mitral + tricuspid valves closing

Question 7

Describe rapid ejection

Answer 7

pulmonary + aortic valves open
blood pushed from ventricles to aorta + pulmonary artery
ECG = repolarisation of ventricles, ST segment + T wave
S2 heart sound = pulmonary + aortic valves closing

Question 8

What causes S2 heart sound?

Answer 8

pulmonary + aortic valves closing

Question 9

Describe isovolumic relaxation

Answer 9

heart is relaxed
valves close
S3 = rapid filling sound + ?heart failure

Question 10

Describe rapid ventricular filling

Answer 10

beginning of diastole
pressure in ventricles low
blood flows passively from atria to ventricles

Question 11

What causes S3 heart sound?

Answer 11

rapid filling sound
?heart failure
?stiff ventricle

Question 12

Describe diastasis

Answer 12

reduced ventricular filling

Question 13

If HR increases, what happens to the length of diastole and systole?

Answer 13

diastole shortens, length of systole cannot change

Question 14

What is the S4 heart sound?

Answer 14

atrial gallop

Question 15

What order do mitral and tricuspid valves close?

Answer 15

mitral closes first then tricuspid

Question 16

What can cause a split between aortic and pulmonary valves closing?

Answer 16

deep breathing
heart conditions eg. atrial septal defect

Question 17

Equation for flow

Answer 17

flow = pressure difference/resistance

the current (flow, cardiac output) through a conductor is directly proportional to the voltage (pressure difference) across the conductor and inversely proportional to the resistance

Question 18

Cardiac output equation (in relation to pressure and resistance)

Answer 18

Cardiac output = mean arterial pressure (MAP)/systemic vascular resistance (SVR)

Question 19

Cardiac power equation

Answer 19

CPO = MAP x CO

[MAP = mean arterial pressure]

Question 20

How can you image the cardiac cycle?

Answer 20

echocardiography