The Cardiac cycle & Heart sounds

Question 1

Blood flows through the heart in defined pattern

Answer 1

This pattern of flow is repeated in each cardiac cycle = with every heartbeat

Question 2

The cardiac cycle and role of valves

Answer 2

• The cardiac cycle is the period between one heartbeat
  and the next
• In each cycle, the atria and ventricles undergo separate
  phases of systole (contraction) and diastole (relaxation)

Question 3

The cardiac cycle and role of valves

- 2

Answer 3

To ensure forward blood flow and prevent backwards flow, the heart has two sets of valves: atrioventricular (AV; tricuspid & mitral) and semilunar valves (aortic and pulmonary)
A valve will open if the pressure behind it is greater than the pressure in front of it, and close if pressure behind is lower

Question 4

Heart valves come in different shapes…

Answer 4

‘Tricuspid’ valve - Right AV vale
‘Bicuspid’ or ‘mitral’ valve - left AV valve

Heart valves only open in one direction…

Question 5

Events in the cardiac cycle

Answer 5

The mechanical events occur in response to electrical activity, with phases of contraction (‘Systole’) to empty the heart, and relaxation (‘Diastole’) to allow it to fill

Question 6

Phases within the cycle

Answer 6

1. Ventricular diastole: ventricles fill with blood
2. Isovolumetric ventricular contraction: ventricles contract,
   all four valves are closed, pressure rises
3. Ventricular ejection: pressure forces blood past the semilunar valves
4. Isovolumetric ventricular relaxation: pressure falls, initially isovolumetric, but then AV valves open and filling begins again

Question 7

cardiac cycle

Answer 7

passive filling during ventriuclar and atrial diastole > actrial contraction > isovolumetric venticular contraction > ventricular ejection > isometric ventricular relaxation

Question 8

the cardiac cycle

Answer 8

passive filling- av valves open > active filling - semilunar valves close > no. change in vol. (all valves close) > emptying (venticular emptying (su valves open, av valves closed) > no change in vol (all valves close

Question 9

pressure

Answer 9

SOON AS PRESSURE LINES CROSS (LEFT VENTRICULAR AND LEFT ARTERIAL PRESSURE)- AV VALVE CLOSES
NEXT CROSS OF AORTIC AND LEFT VENTRICULAR = AORTIC VALVE CLOSES

Question 10

Left ventricular pressure-volume loop

Answer 10

1. The AV valve opens
2. Passive ventricular filling occurs Big increase in volume, but slight increase in pressure
3. Atrial contraction completes ventricular filling. End-diastolic volume is reached
4. The AV valve closes
5. Isovolumetric ventricular contraction occurs. Volume remains constant; pressure increases markedly
6. The aortic valve opens
7. Stroke volume ejected. End- systolic volume is reached
8. The aortic valve closes
9. Isovolumetric ventricular relaxation occurs. Volume constant; pressure falls sharply

Question 11

• End-diastolic volume (EDV)

Answer 11

• End-diastolic volume (EDV) is the volume of blood in the ventricle when filling is complete (aka ‘preload’)

Question 12

• End-systolic volume (ESV)

Answer 12

• End-systolic volume (ESV) is the volume of blood remaining in the ventricle when ejection is complete

Question 13

• Stroke volume (SV)

Answer 13

• Stroke volume (SV) is the volume of blood pumped out by each ventricle per beat (EDV-ESV)

Question 14

• Ejection fraction (EF

Answer 14

• Ejection fraction (EF) is the proportion of EDV pumped out in each heartbeat
calculatedas: SV/EDVx100,or70ml/135mlx100=52%

Question 15

Afterload

Answer 15

• Afterload is the pressure against which the heart

must work to eject blood during systole (also defined as the stress on the ventricular wall during systole)

Question 16

If a faster heart rate reduces filling time, how do we still get good stroke volume?

Answer 16

Passive filling occurs rapidly early in diastole, then slows, with extra boost from atrial contraction
- MX HR IS DETERMINED BY HOW THE MAX TIME IT TAKES TO
REFIL AND CONTRACT