1. Cardiovascular Physiology
Definition of terms
Cardiac cycle - Refers to the events of one complete heartbeat during which both atria and ventricles contract and then relax.
Systole - The time period when the heart contracting.
Diastole - The time period when the heart in the state of relaxation.
Systolic Pressure - Peak pressure in the arteries when ventricles contract.
Diastolic Pressure - Lowest pressure in the arteries when ventricles relax.
End-systolic Volume – Volume of blood in the left ventricle at the end of contraction.
End-diastolic Volume – Volume of blood in the left ventricle at the end of filling.

2. Cardiovascular Physiology

3. Cardiovascular Physiology
Stroke Volume
Volume of blood pumped by the heart in one contraction
SV = EDV – ESV
Where SV - stroke volume
EDV - end-diastolic volume
ESV - end-systolic volume
Stroke volume usually consider only volume of blood pumped from the left side of the heart because that is the amount of blood sent to all the tissues of our body.

4. Cardiovascular Physiology
Stroke Volume can increase during exercise.
Stroke volume depends on preload, afterload and contractility.
Preload
The pressure stretching the ventricular walls prior to contraction.
Depends on ventricular filling and venous return i.e. return of blood back to the heart.
Afterload
Pressure the ventricle must generate to eject blood into aorta.
Depends on arterial pressure

5. Cardiovascular Physiology
Contractility (Inotropy)
Force that muscle can create at given length.

6. Cardiovascular Physiology
Cardiac Output
Amount of blood in liter per minute pumped by the heart particularly the left ventricle.
CO = SV x HR
Where CO – cardiac output (L/min)
SV – stroke volume (L)
HR – heart beat rate (beat/min)
Normal cardiac output is 5.0 L/min.

7. Cardiovascular Physiology
Ejection Fraction
Fraction of blood ejected by ventricle relative to end-diastolic volume
EF = (SV / EDV) x 100%
Normal EF is usually greater than 60%.

8. Cardiovascular Physiology
Cardiac Cycle
Events that occur in one heart beat.

9. Cardiovascular Physiology
Atrial Contraction
Semilunar valves close, AV valves open.
Pressure within the atrial chambers increases, which forces remaining blood in the chambers flow across the open atrioventricular (AV) valves.
Isovolumetric Contraction
All valves close.
Pressure within ventricles increases.
Ventricular Ejection
Semilunar valves open, AV valves close.
Intraventricular pressure higher than pressure in large arteries.
Semilunar valves forced to open, blood rushes out from ventricle.
Isovolumetric Relaxation
Intraventricular pressure falls causes all valves to close.

10. Cardiovascular Physiology
Ventricular Filling
Semilunar valve close, AV valve open.
Intraventricular pressure falls below arterial pressure.
Blood flow through the atria into the ventricles.
Intraventricular pressure continues to briefly fall because the ventricles are still undergoing relaxation.
Once the ventricles are completely relaxed, their pressures will slowly rise as they fill with blood from the atria.

11. Cardiovascular Physiology
Pressure-Volume Relationship

12. Cardiovascular Physiology
The P-V plot shown here is for left ventricle (LV)
a, b, c and d indicate phases in cardiac cycle
- a : ventricular filling
- b : isovolumteric contraction
- c : ejection
- d : isovolumetric relaxation
Point 1 : end-diastolic pressure (EDP) and end-diastolic
volume (EDV).
Point 2 : LVP exceeds aortic diastolic pressure, the aortic valve opens, ejection phase begins.
Point 3 : aortic valve closes, ventricle relaxes isovolumetrically.
Point 4 : LVP falls below left atrial pressure mitral valve opens, ventricle begins to fill.

13. Cardiovascular Physiology
ESV – end-systolic volume.
EDV – end-diastolic volume.
ESPVR – end-systolic pressure-volume relationship
EDPVR – end-diastolic pressure-volume relationship
SV – stroke volume
Stroke Work (SW)
Work done by the ventricle to eject a volume of blood (i.e., stroke volume) into the aorta.
Basically SW is the area inside the P-V plot.
Another term is Cardiac Work which is simply product of SW and heart rate.
Cardiac Work = Stroke Work x Heart Rate

14. Cardiovascular Physiology

15. Cardiovascular Physiology
HEMODYNAMICS
The study of blood flow and blood pressure.
Hemodynamics is essential to understand cardiovascular dynamics system.
Some basic relationships :
F = ΔP/R
Where F – blood flow (unit : ml/s)
Δ P – pressure difference along vessel (unit : mmHg)
R – resistance to flow (if it is not steady and change with time we call it impedance) (unit mmHg/ml/s)

16. Cardiovascular Physiology
To apply the concept in heart, suppose we know aortic and intraventricular pressure ventricular ejection. To find flow of blood :
F = (PIv - Pao)/R
Factors that influence resistance to flow :
- length and diameter of vessel
- viscosity of blood

17. Cardiovascular Physiology
VESSEL TYPE
DIAMETER (mm)
FUNCTION
Aorta 25
Pulse dampening and distribution
Large Arteries
Distribution of arterial blood
Small Arteries
Distribution and resistance
Arterioles
Resistance (pressure & flow regulation)
Capillaries
Exchange
Venules
Exchange, collection, and capacitance
Veins
Capacitance function (blood volume)
Vena Cava 35
Collection of venous blood

18. Cardiovascular Physiology
VASCULAR COMPLIANCE
ability of a blood vessel wall to expand with changes in pressure.
C = ΔV/ΔP
C – vessel compliance
ΔV – change in blood volume
ΔP – change in pressure
Reciprocal of compliance is elastance.
What is the relationship between blood flow and volume?

19. Frank-Starling Mechanism
The change of heart’s force of contraction in response to change in venous return.
During exercise, venous return i.e. blood that returns to the heart increased which then causes increase to stroke volume.
Frank-Starling mechanism tells how change in venous return will alters the stroke volume.
Increased venous return increases the ventricular filling (end-diastolic volume) and therefore preload, which is the initial stretching of the cardiac myocytes prior to contraction. Myocyte stretching causes an increase in force generation. This mechanism enables the heart to eject the additional venous return, thereby increasing stroke volume.

20. Frank-Starling Mechanism

21. Frank-Starling Mechanism