1. Cardiac Cycle- 1
Mechanical events, Volume & Pressure changes in cardiac chambers & the great vessels during the cardiac cycle.

2. Cardiac cycle- Definition
Events occurring between the beginning of one heart beat i.e a period of contraction (systole) followed by a period of relaxation (diastole) to the beginning of the next beat.

3. Cardiac Cycle

4. Duration of Systole & Diastole.
For a HR of 75/min
Systole = 0.27S, Diastole=0.62S
HR of 200/min:
Systole = 0.16S, Diastole =0.14S
Effect of increased HR & its significance?

5. Events during cardiac cycle

6. Atrial Systole Duration – About 0.1Sec
Causes additional 20% of ventricular filling
Lt atrial pressure ↑ by 7-8 mmHg
Rt atrial pressure ↑ by 4-6mmHg
‘a’ wave appears in the atrial pr curve

7. Ventricular Systole

8. Ventricular Systole
Mechanically- Ventricular systole is defined as the interval between the closing of the AV valves and the Closure of the semilunar valves (aortic and pulmonary valves).

9. Phases of Ventricular Systole-
Period of isovolumetric (isovolumic, isometric) ventricular contraction
Ventricular contraction→ ↑Ventricular Press,
Closure of A-V valves-
Pressure/tension builds up, no emptying
lasts for sec

10. Ventricular Systole (Cont.)
Ejection Phase- lasts for about 0.22Secs
Rise in left ventricular press above 80mmHg (above aortic press) & rt ventricular above 10mmHg (above pulmon artery press) → opening of semilunar valves → Rapid ejection (70%) & slow ejection (30%)

11. Phases of ventricular Diastole
Protodiastole / Isovolumetric relaxation
Ventricular Filling Phase:
1st third of diastole - Period of rapid filling
Middle third- diastasis
Last third- Atrial systole 20% of filling
Duration of Ventricular diastole- 0.53Sec--

12. Isovolumic (isometric relaxation) phase
Starts with closure of aortic & pulmonary valves
Fall in ventricular pressure
Lasts Secs till the pressure in the ventricles drop below that in the atria
Followed by:
Opening of A-V Valves→ Ventricular filling

13. Phases of Cardiac Cycle
Isovolumetric Contraction
Ejection
Isovolumetric Relaxation
Rapid inflow
Diastasis
Atrial Systole

14. Pressure changes in cardiac chambers & big vessels
Lt & Rt Atria
Lt & Rt ventricles
Aorta
Pulmonary arteries & veins

15. Right Ventricular Pressure
Normal 20-30/2-8 mmHg
Pressure has a systolic and diastolic reading.

16. Aortic Pressure
↑ (120mmHg) of blood pressure in the arteries during systole with the entry of blood
At the end of systole the elastic walls of the arteries maintain high pressure.
‘incisura’ due to brief backward flow just before closure of aortic valve.

17. Pulmonary Artery Pressure
Normal 20-30/8-15 mmHg
The pulmonary artery systolic pressure (PAS) approximates the systolic pressure in the RV, but the pulmonary diastolic pressure (PAD) is higher, and the waveform less steep. The PA waveform includes a diastolic notch which represents closure of the pulmonic valve.

18. Pulmonary Capillary Wedge Pressure
PCWP is measured by inserting balloon-tipped, multi-lumen catheter (Swan-Ganz catheter) into a peripheral vein
Normal 2-15 mmHg
PAWP- the most accurate reflection of left atrial pressure, / left ventricular end-diastolic pressure (LVEDP), or preload.

19. Normal Pressure ranges (mmHg)
Central Venous pressure- 3–8
Rt Ventricular Pressure- systolic 15–30 diastolic 3–8
Pulmonary artery pressure- systolic 15–30 diastolic 4–12
Pulmonary vein/ Pulmonary capillary wedge pressure 2–15
Lt Ventricular pressure-systolic100–140 diastolic3-12

20. Arterial Pulse
Due to the ejection of blood into the aorta there occurs transmission of pressure pulse /wave in the arteries.
Velocity of transmission depends on the compliance (distensibility) of the vessel wall.
The other factor that affects the strength of the pulse is pulse pressure/ the stroke volume
‘Dicrotic notch’/ an oscillation on the falling phase (recorded not felt) due to snapping shut of the aortic valve.

21. Arterial Pulse

22. Terms End Diastolic Volume Stroke volume End Systolic Volume
Ejection Fraction

23. Relate ECG Waves to mechanical events during the cardiac cycle

24. Events during cardiac cycle

25. Learning Outcomes -Cardiac Cycle-1
1.Define cardiac cycle and state its normal duration.
2. Describe mechanical events occurring within the chambers of the heart during the cardiac cycle.
3. State different phases of cardiac cycle and with the help of appropriate diagram/s, describe the pressure volume changes in the ventricles, aorta and pulmonary arteries during various phases of cardiac cycle.
4. State the normal length of systole & diastole at a HR of 75/min.
5. Describe the determinants of arterial pulse and describe it with a labelled diagram.
6. Explain the relationship & functional importance of ECG waves to the mechanical events during different phases of cardiac cycle.
7. Define, explain and give the normal values of: End diastolic ventricular volume, End systolic ventricular volume and ejection fraction.