The Cardiac Cycle

Question 1

What are the phases of the cardiac cycle?

Answer 1

1. atrial contraction
2. systolic isovolumetric contraction
3. systolic rapid ejection
4. reduced ejection phase
5. diastolic isovolumetric relaxation
6. diastolic ventricular rapid filling
7. diastolic ventricular reduced filling

Question 2

What is the electrical event of atrial contraction?

Answer 2

firing of the SA node (P wave)

Question 3

What is the mechanical event of atrial contraction?

Answer 3

contraction of atria

Question 4

What is happening anatomically during atrial contraction?

Answer 4

• av valves open, semilunar valves closed
• 20-40% of ventricular filling
• atrial systole produces “A” wave

Question 5

What is the electrical event of systolic isovolumetric contraction?

Answer 5

peak of the “R” wave

Question 6

What is the mechanical event of systolic isovolumetric contraction?

Answer 6

ventricles contract and atria relax

Question 7

What is happening anatomically during systolic isovolumetric contraction?

Answer 7

• all valves are closed (produces S1 sound)
• no change in volume
• amount of blood in left vent at end of diastole is called EDV (end diastolic volume)

Question 8

What is the electrical event of systolic rapid ejection?

Answer 8

none

Question 9

What is the mechanical event of systolic rapid ejection?

Answer 9

• ventricular pressure > arterial pressure

- rapid ejection of blood into arteries occurs

Question 10

What is happening anatomically during systolic rapid ejection?

Answer 10

• semilunar valves open

- as ventricles contact, av valves bulge back into atria to produce “C” wave

Question 11

What is the electrical event of reduced ejection?

Answer 11

“T” wave on the ECG

Question 12

What is the mechanical event of reduced ejection?

Answer 12

ventricular volume decreases then ventricle pressure plateaus and decreases

Question 13

What is happening anatomically during reduced ejection?

Answer 13

• atrial pressure continues to rise during ejection period because of continued flow of blood into the atria
• produces the “V” in the arterial pressure waveform

Question 14

What is the electrical event of diastolic isovolumetric relaxation?

Answer 14

as blood impacts the semilunar valves, they snap shut. closure produces the S2 sound

Question 15

What is the mechanical event of diastolic isovolumetric relaxation?

Answer 15

ventricles relax

Question 16

What is happening anatomically during diastolic isovolumetric relaxation?

Answer 16

• all valves are closed
• no change in volume
• abrupt shift in aortic pressure and produces the dicrotic notch

Question 17

What is the electrical event of diastolic ventricular filling?

Answer 17

none

Question 18

What is the mechanical event of diastolic ventricular filling?

Answer 18

atria have continued to fill and atria pressure exceed ventricular pressure

Question 19

What is happening anatomically during diastolic ventricular filling?

Answer 19

• av valves open, semilunar valves closed

- lasts 0.1 second and accounts for 60-80% of filling

Question 20

What must precede mechanical events?

Answer 20

electrical events

Question 21

What are the keys to the direction of blood flow?

Answer 21

• pressure events

- pressure gradients

Question 22

What does blood volume rely on?

Answer 22

• chamber filling
• filling pressures
• chamber emptying

Question 23

What are heart sounds normally associated with?

Answer 23

valve closure

Question 24

How do you calculate stroke volume?

Answer 24

EDV - ESV = SV

Question 25

How do you calculate ejection fraction?

Answer 25

EF = (SV/EDV) x 100%