cardiac chamber .ppt

Study

1. Hemodynamics
Physics of Blood flow in the
circulation

2. Circulatory System
•Heart:
Has 2 collecting chambers - (Left, Right

Atria)
Has 2 Pumping chambers - (Left, Right

Ventricles)

4. Circulation Schematic
Lungs
Tissues
Left Side of Heart
Right Side of Heart
AV
VA
Pulmonary Vein
Pulmonary Artery
Aorta
Sup. & Inf. Vena Cava
Mitral Valve
Pulmonary Valve
Aortic Valve
Tricuspid Valve

5. Heart Valves
•Atrioventricular (A-V) valves - separate
Atria from Ventricles
•Bicuspid (Mitral) - Left Side
•Tricuspid - Right Side
•Semi-Lunar Valves - separate ventricles
from Arteries

6. Opening, Closing of Valves - Depends on Pressure
differences between blood
in adjacent areas

7. Heart Sounds
•‘Lubb’ (1
st
sound) - Closure of A-V valves
•‘Dupp’ (2
nd
sound) - Closure of S-L valves
Caused by Turbulence on closing.
Anything extra ’Murmur’ (swishing of blood)
Could be due to:
•Stenosis of Valves (calcification)
•Valves not closing properly
(Incompetence, Insufficiency)
Increases
Pressure on
heart

8. Blood Vessels
•Arteries
•Capillaries
•Veins
Systemic Pathway:
Left Ventricle Aorta Arteries Arterioles
of Heart
Capillaries
VenulesVeins Right Atrium
of Heart

9. Lumen of Coronary Artery

10. Blood Vessel Walls - Layers
•Arteries:
»Tunica Externa (Fibrous Connective Tissue)
»Tunica Media (Elastic Connective Tissue
and/or Smooth
Muscle)
» Tunica Intima (Endothelium)
•Capillaries:
»Endothelium
•Veins - same as Arteries except:
»Less smooth muscle in Tunica Media
»Have valves to control blood flow direction

11. Blood
•Composition:
–Approx 45% by Vol. Solid Components
»Red Blood Cells (12m x 2 m)
»White Cells
»Platelets
–Approx 55% Liquid (plasma)
»91.5% of which is water
»7% plasma proteins
»1.5% other solutes

12. Blood Functions
•Transportation
of blood gases, nutrients, wastes
•Homeostasis (regulation)
of Ph, Body Temp, water content
•Protection

13. As a Result …….
•Blood behaves as a simple Newtonian
Fluid when flowing in blood vessels
i.e. Viscous stresses  Viscosity, strain rate
dy
du

y
u(y)
No slip
at wall

14. •Viscosity of Blood = 3 3.5 times of water
•Blood acts as a non-newtonian fluid in
smaller vessels (including capillaries)

15. Cardiac Output
•Flow of blood is usually measured in l/min
•Total amount of blood flowing through the
circulation = Cardiac Output (CO)
Cardiac Ouput = Stroke Vol. x Heart Rate
= 5 l/min
Influenced by Blood Pressure & Resistance
Force of blood
against vessel wall
•Blood viscosity
•Vessel Length
•Vessel Elasticity
•Vasconstriction / Vasodilation
 with water retention
 with dehydration, hemorrage

16. Overall
•Greater Pressure  Greater Blood
Differences Flow
•Greater Resistance  Lesser Blood Flow

17. Driving force for blood flow is pressure
created by ventricular contraction
Elastic arterial walls expand and recoil
continuous blood flow
 Blood PressureBlood Pressure

18. Blood pressure is highest in the arteries (Aorta!)
and falls continuously . . .
Systolic pressure in Aorta: 120 mm Hg
Diastolic pressure in Aorta: 80 mm Hg
Diastolic pressure in ventricle: ?? mm Hg

19. Ventricular pressure difficult to measure
arterial blood pressure assumed to indicate driving pressure for
blood flow
Arterial pressure is pulsatile
useful to have single value for driving pressure: Mean Arterial
Pressure
MAP = diastolic P + 1/3 pulse pressure

20. Pulse Pressure = systolic pressure - ??
= measure of amplitude of blood pressure
wave

21. MAP influenced by
•Cardiac output
•Peripheral resistance
 MAP CO x R
arterioles
•Blood volume
–fairly constant due to homeostatic mechanisms
(kidneys!!)

22. BP too low:BP too low:
•Driving force for blood flow unable to
overcome gravity
O
2 supply to brain 
 Symptoms?

23. BP too high:BP too high:
•Weakening of arterial walls - AneurysmWeakening of arterial walls - Aneurysm
Risk of rupture & hemorrhageRisk of rupture & hemorrhage
Cerebral hemorrhage: ?Cerebral hemorrhage: ?
Rupture of major artery: Rupture of major artery:

24. Auscultation of
brachial artery
with stethoscope
Laminar flow vs.
turbulent flow
BP estimated by SphygmomanometryBP estimated by Sphygmomanometry

25. Principles ofPrinciples of SphygmomanometrySphygmomanometry
Cuff inflated until brachial artery compressed and blood
flow stopped what kind of sound?what kind of sound?

26. turbulent flow
Slowly release pressure in cuff:

27. Pressure at which . . .
. . . sound (= blood flow) first heard:
. . . sound disappeared:

28. •Pressure can be stated in terms of column of
fluid.
Pressure Units
mm Hg cm H
2O PSI ATM
50 68 0.9 0.065
100 136 1.9 0.13
200 272 3.8 0.26
300 408 5.7 0.39
400 544 7.6 0.52

29. Pressure = Height x Density
or P = gh
If Right Atrial pressure = 1 cm H
2
O in an open
column of
blood
 Pressure in feet = 140 cm H
2
O
 Rupture
 Venous Valves
Density of blood
= 1.035 that of
water
Incompetent venous valves
 Varicosities
Actual Pressure in foot
= 4-5 cm H
2
O

30. Dynamic Fluid Mechanics
•Blood flowing through circulation follows
physical principles of pressure, flow
•Under conditions of constant flow, velocity must
increase to allow the same flow through a smaller
space
i.e. the continuity equation

31. Types of Blood Flow
•Laminar: When velocity of blood flow is below a
critical speed, the flow is orderly and streamlined
(This is the usual pattern of flow in the vascular system.)
•Turbulent: disorderly flow with eddies & vortices

32. •Turbulent flow is noisy
•In the vascular system high flow velocities cause turbulent
flow and produce sound
•The murmur heard when blood flows through a narrowed
heart valve is due to turbulent flow
•To determine whether flow is laminar or turbulent,
calculate the Reynolds Number (R) (dimensionless no.)
R = Velocity * Diameter * Density / Viscosity
•Values below 2000 define laminar flow

VD
R

33. Bernoulli Equation
•When blood flows through an artery, the total
energy of the fluid at any point is assumed to be
constant
•i.e. The sum of energy stored in pressure, energy
provided by flow and potential energy due to the
height of the blood above a reference point is
constant
Energy = [V2/2g] + [P/r] + H = Constant
•In an arterial stenosis, the increase in velocity
causes a fall in pressure in the stenosis

34. Resistance
Pressure = Flow x Resistance
Poiseulle equation:
L
Rp
Q


8
4


Pressure drop across
a length of vessel
Radius
Flow Length of Vessel

35. •For a given pressure, there is greater flow when the
blood vessel is short and wide and the blood is thin
•Since BP is constant most of the time, flow is
controlled by small changes in r--the vessel radius
•This is most effective in the arterioles
•Resistance is measured in Wood units
•Pulmonary = (PA pressure - LA pressure) / CO
resistance
e.g.R = (14 mm Hg - 7 mm Hg) / 5 l/min
= 1.4 Wood units
Pulmonary Artery

36. Pressures in the circulation
•Pressures in the arteries, veins and heart
chambers are the result of the pumping action
of the heart
•The right and left ventricles have similar
waveforms but different pressures
•The right and left atria also have similar
waveforms with pressures that are similar but
not identical

37. 1. The LV pressure begins
to rise after the QRS wave
of the ECG
2. Pressure rises until the
LV pressure exceeds the
aortic pressure
 The blood begins to
move from the ventricle
to the aorta
3. As blood enters the
aorta, the aortic pressure
begins to rise to form the
systolic pulse
4. As the LV pressure falls
in late systole the aortic
pressure falls until the LV
pressure is below the
aortic diastolic press.
5. Then the aortic valve
closes and LV pressure
falls to LA pressure

38. •The first wave of atrial pressure (the A wave) is due to atrial
contraction
•The second wave of atrial pressure (the V wave) is due to
ventricular contraction

39. Normal Pressures
•RV and pulmonary systolic pressure are 12-15
mm Hg
•Pulmonary diastolic pressure is 6-10 mm Hg
•LA pressure is difficult to measure because access
to the LA is not direct

40. •The severity of AS is determined by the pressure drop across the aortic valve
or by the aortic valve area
•The high velocity of blood flow through the narrowed valve causes turbulence
and a characteristic murmur AS can be diagnosed with a stethoscope
AS produces a
pressure gradient
between the aorta
and LV
i.e. For blood to move
rapidly through a
narrowed aortic valve
orifice, the pressure
must be higher in the
ventricle

41. AV Area
•The AV area can be calculated from pressure and
cardiac output
•The calculate the AV area, use the Gorlin equation
•In the formula, flow is calculated for the time of systole
since systolic time is the only time in the heart cycle
when blood flows across the AV
mean
p
Q
A


5.44
1
AV Area
Flow
Mean Gradient
between LV and Aorta

42. Pressure Measurement
•Accurate pressure measurements are essential to
understanding the status of the circulation
•In 1733 Steven Hales connected a long glass tube
directly to the left femoral artery of a horse and
measured the height of a column of blood (8 feet,
3 inches) to determine mean BP
•Direct pressure measurements are made frequently
in the cardiac catheterization laboratory, the ICU
and the OR

43. •A tube is inserted into an artery and connected to an
electrical strain gauge that converts pressure into
force that is sensed electrically
•The output of the transducer is an electrical signal
that is amplified and recorded on a strip chart
•For correct pressure measurements the cannula and
transducer must be free of air, the cannula should be
stiff and short

44. Cardiac Output (CO)Measurement
•The measurement of blood flow through the
circulation is usually done clinically using either
the Fick method
•The Fick method states that the cardiac output is
equal to the oxygen consumption divided by the
arterial-venous oxygen difference
CO = Oxygen consumption / A-V O
2

45. •The measurement is done by determining the
oxygen consumption using respiratory gas
measurements and the O
2 content of arterial and
mixed venous blood
•The mixed venous blood sample is obtained from
a PA with a catheter
•The arterial sample can be drawn from any artery