Hemodynamic principles basics Pressure wave: Complex periodic fluctuation in force per unit area Fundamental frequency: number of times the pressure wave cycles in 1 second Harmonic: multiple of fundamental frequency Essential physiologic information is contained within the first 10 harmonics At a HR of 120, the fundamental frequency is 2Hz, and 10th harmonic is 20Hz. A pressure response system with a frequency response range that is flat to atleast 20 Hz will be required. Damped Natural frequency should be 3 times as fast as the 10thHarmonic of the pressure measured ie 60 Hz. Fidelity of the recording drops with increasing heart rate.HR. End pressure artifact Flowing blood has kinetic energy which when suddenly halted in part coverts into pressure and records a pressure which is artifactually elevated Seen with end hole catheters This added pressure may range from 2-10 mm Hg Catheter impact artifact Pressure due to impact on adjacent structure– valve, papillary muscles, moderator band. Common with the pigtail catheter in the LV, where the MV hits the catheter as they open in early diastole Normally RA diastolic pressure is equal to RV diastolic pressure except in early diastole which drives the rapid filling from atria to ventricles( E wave on ECHO) An elevated early RA-RV pressure gradient may be seen in patients with decompensated right heart failure who characteristically have elevated RA pressure that pushes blood in RV Furthermore due to the loss of RV compliance , the diastolic pressure rises rapidly to a high plateau level Wedge Pressure Pressure obtained when an end-hole catheter is positioned in a “designated” blood vessel with its open end-hole facing a capillary bed, with no connecting vessels conducting flow into or away from the “designated” blood vessel between the catheter’s tip and the capillary bed. True wedge pressure can be measured only in the absence of flow, allowing pressure to equilibrate across the capillary be

1. +
HEMODYNAMICS PRINCIPLES
-PRESSURE MEASUREMENT
-MEASUREMENT OF CARDIAC OUTPUT
BY DR UTKARSH KUMAR
SR2
LPSIC KANPUR

2. +
Topics
① Introduction
② Normal Pressure Tracings
③ Estimation of Cardiac Output

3. +
 A complex periodic fluctuation in force per unit area
 A pressure wave is the cyclical force generated by
cardiac muscle contraction
 Its amplitude and duration are influenced by various
mechanical and physiological parameters
1. Force of the contracting chamber
2. Surrounding structures - contiguous chambers of the heart
pericardium, lungs, vasculature
3. Physiological variables - heart rate, respiratory cycle
Pressure Wave

4. +
 Pressure wave: Complex periodic fluctuation in force per
unit area
 Fundamental frequency: number of times the pressure
wave cycles in 1 second
 Harmonic: multiple of fundamental frequency
Pressure Measurement
Terminology

5. +
Essential physiologic information is contained within the
first 10 harmonics
 At a HR of 120, the fundamental frequency is 2Hz, and
10th harmonic is 20Hz.
 A pressure response system with a frequency response
range that is flat to atleast 20 Hz will be required.
 Damped Natural frequency should be 3 times as fast as
the 10thHarmonic of the pressure measured ie 60 Hz.
 Fidelity of the recording drops with increasing heart
rate.HR.
Pressure Measurement
Fourier analysis

6. +
Pressure Measurement
Harmonics- Wigger’s principle

7. +
 Sensitivity
Ratio of amplitude of record signals to input
signals(The more the rigid membrane the lower the
sensitivity)
 Frequency resposnse
 Ratio of output amplitude to input amplitude over a range of
frequencies of the input pressure
 To measure pressure accurately , frequency response must be
constant over a given range of frequencies.
Pressure Measurement Devices
Terminology

8. +
NATURAL FREQUENCY AND
DAMPING
Natural frequency
Frequency at which fluid oscillates in a catheter when it is
tapped.
At Natural frequency, ratio of output/input amplitude is
maximal.
The higher the natural frequency of the system, the more
accurate the pressure measurement.
DAMPING
It is a means of dissipating the energy of the oscillations of
sensing membrane
Optimal damping dissipates the energy gradually maintaining
frequency response curve nearly flat

9. +
Pressure Measurement
Optimal Damping
0
0.5
1
1.5
2
2.5
3
0 20 40 60 80 100 120 140 160 180 200
Input Frequency as Percent of Natural Frequency
Amplitude
Ratio
(Output
/
Input)
D=0
(undamped)
D=0.20
(highly underdamped)
D=0.40
(underdamped)
D=0.64
(optimally
damped)
D=2
(over
damped)
2014
.

10. +
Baim DS and Grossman W. Cardiac Catheterization, Angiography, and Intervention. 8h Edition. Baltimore: Williams and
Wilkins, 2014
Pressure Measurement
optimal damping
Natural
frequency
catheter
radius
𝑓𝑙𝑢𝑖𝑑 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 𝑥 𝑐𝑎𝑡ℎ𝑒𝑡𝑒𝑟 𝑐𝑜𝑚𝑝𝑙𝑖𝑎𝑛𝑐𝑒
= x
SHORTER catheter
LARGER catheter lumen
LIGHTER fluid
HIGHER natural frequency
Catheter
length
√
1
1

11. +
Transforming pressure wave to electrical
signals
Strain gauge pressure transducer Strain gauge connection of Wheatstone
bridge

12. +
Balancing and Zeroing
 Balancing a transducer
Add variable resistance into the circuit so that at an arbitrary baseline
pressure the output can be reduced to zero
 Zeroing
Zero reference level at mid chest

13. +
Pressure Measurement Systems
 Fluid-filled Systems
 Micromanometer Catheters

14. + Fluid Filled Catheter
 Fluid-filled catheter attached to a pressure transducer
 Pressure wave is transmitted by the fluid column within
the catheter
 Data should be collected ,with the patient in steady state
and before introduction of radiographic contrast.

15. +
Deterioration of frequency response
 Introduction of air permits damping and reduces natural frequency by
serving as added compliance.
 When natural frequency of pressure system falls, high frequency
components of the pressure waveform (intraventricular pressure rise
and fall) may set the system into oscillation, producing “pressure
overshoots” ( early systole & diastole of ventricular pressure curve).
 Flushing-restores the frequency response of system.
Artifacts

16. +
Movement artifact (WHIP Artifact)
 May produce superimposed waves of ±10 mm Hg
 Motion of tip of the catheter within the measured chamber
→ Enhance the fluid oscillations of the transducer system
 Render systolic and to a lesser extent diastolic pressures unreliable.
 No way to fix it internally.
 Stabilize externally.
Artifacts

17. +
End pressure artifact
 Flowing blood has kinetic energy which when suddenly halted in part
coverts into pressure and records a pressure which is artifactually elevated
 Seen with end hole catheters
 This added pressure may range from 2-10 mm Hg
Catheter impact artifact
 Pressure due to impact on adjacent structure– valve, papillary muscles,
moderator band.
 Common with the pigtail catheter in the LV, where the MV hits the catheter
as they open in early diastole

18. +
Systolic Pressure amplification in the periphery
 Reflected wave (tidal wave)
 Peak SBP in radial, brachial, femoral > peak SBP in central Aorta by
up to 20 mmHg
 Largely as a consequence of reflected wave from Aortic bifurcation,
arterial branching, small peripheral vessels.
 Use of a double lumen catheter(double lumen pigtail) allows
measurement of LV and central aorta measurements simultaneously ,
thus avoiding this problem

19. + Micromanometer –Tipped Catheters
 Fluid filled system- distortion of wave forms- artifacts, amplification of
systolic pressure in periphery, damping or augmentation of frequency
response system.
 For precise, undistorted ,high fidelity pressure recordings
 Micromamometer chips at the end of catheters
 Interposing fluid column is eliminated
 Have higher natural frequencies and more optimal damping
characteristics
a. To assess pressure waveform contours in a tachycardia
situation, rate of ventricular pressure rise(dp/dt) etc
b. Limitation- additional cost, fragility , time needed for properly
calibrating and using the system

20. +
Micromanometer

21. +
Topics
① Introduction
② Normal Pressure Tracings
③ Estimation of Cardiac Output

22. +
Hemodynamic Parameters
Reference Values
Davidson CJ, et al. Cardiac Catheterization. In: Heart Disease: A Textbook of Cardiovascular Medicine,
Edited by E. Braunwald
Average Range Average Range
a wave
v wave
mean
Right ventricle
peak systolic
end diastolic
Pulmonary artery
peak systolic
Right atrium
end diastolic
mean
6
5
25
9
15
25
4
3
2 - 7
2 - 7
15 - 30
4-12
9-19
15-30
1 - 7
1 - 5
mean
Left atrium
a wave
v wave
mean
Left ventricle
peak systolic
end diastolic
PCWP
Central aorta
peak systolic
9
12
8
130
8
10
4 - 12
6 - 21
2 - 12
90 - 140
5 - 12
4 - 16
130 90 - 140
70 60 - 90
end diastolic
mean 85 70 -105

23. +
Right Heart Catheterization
Right Atrial Pressure
• “a” wave
– Atrial systole
• “c” wave
– Protrusion of TV into RA
• “a” wave
– Atrial systole
• “c” wave
– Protrusion of TV into RA
• “x” descent
– Relaxation of RA
– Downward pulling of tricuspid
annulus by RV contraction
• “v” wave
– RV contraction
– Height related to atrial compliance & amount of blood return
– Smaller than a wave
• “a” wave
– Atrial systole
• “c” wave
– Protrusion of TV into RA
• “x” descent
– Relaxation of RA
– Downward pulling of tricuspid
annulus by RV contraction
• “v” wave
– RV contraction
– Height --- atrial compliance & amount of blood return
• “y” descent
– opening and RA emptying into RV
• “a” wave
– Atrial systole
• “c” wave
– Protrusion of TV into RA
• “x” descent
– Relaxation of RA
– Downward pulling of tricuspid
annulus by RV contraction

24. +
CORRELATION WITH ECG

25. +
Kern MJ. Right Heart Catheterization. CATHSAP II CD-ROM. Bethesda, American College of Cardiology, 2001.
Right Heart Catheterization
Inspiratory Effect on Right Atrial Pressure
 Normal physiology
 Inhalation: Intrathoracic pressure falls  RA pressure falls
 Exhalation: Intrathoracic pressure increases  RA pressure
increases
 Pressures are best measured at end expiration at which the
pressure is maximum
Exp

26. +
 Elevated a wave
 Tricuspid stenosis,
 Decreased RV compliance ; PS, PAH
 Cannon a wave
 A-V asynchrony(3rd degree AVB, V-paced)
 Absent a wave
 Atrial fibrillation
 Elevated v wave
 SEVERE TR
 RV failure
 Reduced atrial compliance(restrictive myopathy)
 Equal a and v waves
 ASD
Abnormalities in RA tracing

27. +
 Prominent x descent
 – Tamponade
 – CP/RCMP
 Prominent y descent
 – TR
 – Constrictive pericarditis
 – Restrictive myopathy
Abnormalities in RA tracing

28. +
Right Ventricular Pressure
 Systole
 Isovolumetric contraction
 From TV closure to PV opening
 Ejection
 From PV opening to PV closure
 Diastole
 Isovolumetric relaxation
 From PV closure to TV opening
 Filling
 From TV opening to TV closure
 Early Rapid Phase
 Slow Phase
 Atrial Contraction (“a”wave”)

29. +
 Normally RA diastolic pressure is equal to RV diastolic
pressure except in early diastole which drives the rapid filling
from atria to ventricles( E wave on ECHO)
 An elevated early RA-RV pressure gradient may be seen in
patients with decompensated right heart failure who
characteristically have elevated RA pressure that pushes blood
in RV
 Furthermore due to the loss of RV compliance , the diastolic
pressure rises rapidly to a high plateau level

30. +
 HENCE RV FAILIURE IS CHARACTERISED BY EARLY
DIASTOLIC DIP AND PLATEAUED HIGH DIASTOLIC
PRESSURE

31. +
 Systolic pressure overload
 Pulmonary HTN
 Pulmonary valve stenosis
 Right ventricular outflow obstruction
 Systolic pressure reduced
 Hypovolemia
 Cardiogenic shock
 Tamponade
Abnormalities in RV Tracing
}outflow obstruction

32. +
Abnormalities in RV Tracing
 End-diastolic pressure overload
 CHF
 Diminished compliance
 Tamponade/Pericardial constriction
 End-diastolic pressure reduced
 Hypovolemia
 Tricuspid stenosis

33. +
PA Pressure Tracing
 Biphasic tracing
 – Systole
 – Diastole
 Pulmonary HTN
 – Mild: PAP>20mmHg
 – Moderate: PAP>35mmHg
 – Severe: PAP>50mmHg

34. +
Abnormalities in PA tracing
 Elevated systolic pressure
 – Primary pulmonary HTN
 – MS / MR
 – CHF
 – Restrictive myopathy
 – Left-to-right shunt
 Reduced systolic pressure
 – Pulmonic stenosis
 – Supra or subvalvular stenosis
 – Ebstein’s anomaly
 – Tricuspid stenosis / atresia

35. +

36. + How to differentiate atrial,
ventricular and arterial tracings
Atrial Presuure Ventricular
Pressure
Arterial Pressure
No of dominanat
waves for every
QRS
2 (A and V) 1 1
Timing of pressure
peak in relation to
ECG
V wave peaks at or
after the end of T
Peaks during ST/T Peaks during ST/T
Shape in diastole Upsloping or
horizontal
Upsloping Downsloping
Presence of A wave Yes Yes No
Dicrotic Notch No No Yes

37. +
Pulmonary Capillary Wedge
Pressure
 “a” wave- occurs 240 msec after p wave
on ecg
– Atrial systole
 “c” wave
– Protrusion of MV into LA
 “x” descent
– Relaxation of LA
– Downward pulling of mitral annulus by LV
contraction
 “v” wave
– LV contraction
– Height related to atrial compliance & amount
of blood return – Higher than ‘a’ wave
 “y” descent
– MV opening and LA emptying into LV

38. +
Baim DS and Grossman W. Cardiac Catheterization, Angiography, and Intervention. 8th Edition. Baltimore: Williams and
Wilkins, 2014
Physiologic characteristics
Wedge Pressure
 Wedge Pressure
 Pressure obtained when an end-hole catheter is positioned in
a “designated” blood vessel with its open end-hole facing a
capillary bed, with no connecting vessels conducting flow into
or away from the “designated” blood vessel between the
catheter’s tip and the capillary bed.
 True wedge pressure can be measured only in the absence
of flow, allowing pressure to equilibrate across the capillary
bed

39. +
CHARACTERISTICS OF HIGH
QUALITY PCWP
 Presence of well defined a and v waves
 Appropriate fluoroscopic confirmation of the catheter tip in
distal pulmonary artery and no apparent motion of the catheter
with balloon inflated
 Oxygen saturation obtained from the PCWP position greater
than 90%

40. +
Baim DS and Grossman W. Cardiac Catheterization, Angiography, and Intervention. 5th Edition. Baltimore: Williams and
Wilkins, 1996.
Right Heart Catheterization
Left Atrial and PCW Pressure
 PCW tracing “approximates” actual LA tracing but is
slightly delayed since pressure wave is transmitted
retrograde through pulmonary veins
 PCWP is delayed approximately 50-150 milli sec in
comparison to LA pressure

41. +
 PCWP has a smoother contour with less deep X and Y
descents than LA pressure, as the pressure gets damped while
being transmitted from LA through pulmonary capillaries

42. +
1. LARGE V WAVE:
- Acute severe/decompensated MR (not in chronic
compensated MR)
- VSD
- MS
- AF( as only one wave)
Abnormalities of PCWP Tracing

43. +

44. +
 LARGE A WAVE
Seen with impaired LV compliance

45. +
LV Pressure
 Systole
 Isovolumetric contraction
 From MV closure to AoV opening –
 Ejection
 From AoV opening to AoV closure
 Diastole
 Isovolumetric relaxation
 From AoV closure to MV opening
 Filling
 From MV opening to MV closure
 Early Rapid Phase
 Slow Phase
 Atrial Contraction(“a”wave”)

46. +
PCWP AND LV PRESSURE

47. +

48. +
Right vs Left Ventricular Pressure
 Diastolic amplitude similar between RV and LV tracings
 Systolic amplitude higher for LV than RV
 Duration of systole, isovolumetric contraction, and
isovolumetric relaxation are longer for LV compared to RV
 Duration of ejection is shorter for LV than RV.

49. +
Arterial Pressure Monitoring
 Aortic waveform varies along length of
the aorta
 Systolic wave increases in amplitude
while diastolic wave decreases
 Dicrotic notch less apparent in peripheral
tracing
 Mean aortic pressure is somewhat
constant

50. +
Pulsus Bisferiens
 Hypertrophic obstructive cardiomyopathy –
 Aortic insufficiency
Abnormalities in Central Aortic
Tracing

51. +
 PULSUS PARVUS ET TARDUS

52. +
Pulsus Alterans
 Pericardial effusion
 Cardiomyopathy
 CHF
Abnormalities in Central Aortic
Tracing

53. +
Pulsus Paradoxus
 Tamponade
 COPD
 Pulmonary embolism
Abnormalities in Central Aortic
Tracing

54. +
Spike and dome pattern
 Hypertrophic obstructive cardiomyopathy
Abnormalities in Central Aortic
Tracing

55. +
Abnormalities in Central Aortic
Tracing
Dicrotic Pulse
 Low stroke volume
 Severe LV failure
 Hypovolemia

56. +
Topics
① Introduction
② Normal Pressure Tracings
③ Estimation of Cardiac Output
④ Estimation of Valve Area
⑤ Estimation of shunt

57. +Techniques for determination of cardiac output
Fick Oxygen technique
Thermodilution technique
Indicator dilution technique
Angiographic technique

58. +
 Technique described by Adolph Fick in 1870
 The total uptake or release of any substance by an organ is the product of
blood flow to the organ and arterio-venous oxygen difference of the
substance
 If no intracardiac shunt, ie PBF=SBF
 Pulmonary blood flow = oxygen consumption/ arteriovenous oxygen
content difference across the lungs
FICKS OXYGEN TECHNIQUE

59. +
 AV O2 difference is defined as arterial oxygen content – mixed
venous oxygen content
 CO = O2 consumption (ml/min)
-------------------------------------------------------------
arterial O2 content - mixed venous (PA) O2
content

60. +
 At low cardiac output states ,greater extraction of oxygen is
present from the tissues and MVO2 is low, resulting in high
AVO2 difference and vice versa
 MVO2 alone is a crude estimation of cardiac output states, with
low saturation indicating a low output state and vice versa
 The AVO2 content difference is accurately measured by
simultaneously obtaining systemic arterial and mixed venous
saturations.
 Ideally arterial sample to be taken from pulmonary veins and
venous from pulmonary artery

61. +
 To determine oxygen content , the AVO2 difference is multiplied
by Hb content and oxygen carrying capacity(1.36ml O2/g of
Hb). This is then multiplied by 10 to convert the vaule from g/dl
to g/L
 Oxygen Consumption: At a steady state, oxygen consumption
is the rate at which oxygen is taken by the blood from the
lungs.

62. +Methods of measuring oxygen consumption
• Douglas bag method
• Polarographic method
• Paramagnetic method
Assumed Fick method – 125ml/min/m2 for average
indivisuals and 110ml/min/m2 for elderly (Lafarge &
Meittinem)

63. +

64. +SOURCES OF ERROR
 Use of assumed rather than directly measured oxygen
consumption
 Assumes prevalance of steady state
 Improper collection of the mixed venous sample
 O2 con- error-6%. A-V O2 diff -error -5%
 The total error Fick CO– about 10 %

65. +
 Merely a specific application of fick’s general principle
“An indicator mixed into a unit volume of constantly flowing blood can
be used to identify that volume of blood in time, provided the
indicator remains in the system between injection and
measurement and mixes completely in the blood”
 Indocyanine green is the indicator usually used
 Continous infusion & single injection method
 It is injected as a bolus into the pulmonary artery and samples
are taken from the peripheral systemic artery
 Severe allergic reactions can occur
Indicator dilution methods

66.  Amount of dye added = 5 mg
 Average dye concentration = 2 mg/L
 Therefore the volume that diluted the dye =
5mg/2mg per L = 2.5 L
 Time it took to go past = 0.5 min
 ie flow rate = 2.5 L /0.5 min = 5 L/min
Concentration
(g/L)
Time (min)
0 0.5
average conc (X) = 2 mg/L
time of passage (t) = 0.5 min
~

67. Flow rate = mass of dye (Q g)
____________________
average dye conc (X g/L) x time of passage (t min)

68. +
THERMODILUTION TECHNIQUE
 Fegler described the thermodilution method in 1954.
 This method is the easiest to perform and the most widely used
 . The thermodilution technique is a variation of the indicator-
dilution technique, using blood temperature as the indicator.
 Saline at a known temperature is injected into the right atrium
from the proximal port of a Swan–Ganz catheter.
 The saline mixes with blood and lowers its temperature.
.

69. +
 The temperature of blood is measured in the pulmonary artery
by a thermistor mounted on the distal tip of the catheter which
is a variable resistor in which the resistance is proportional to
the temperature
 As the resistance changes, a change in voltage occurs.
 The measured change in voltage over time generates a
temperature curve that is related to the cardiac output.
 Similar to the indicator-dilution method, cardiac output is
inversely related to the area under the time–temperature curve.

70. +
 If the area under the curve is small, this means the temperature
equilibrates rapidly with the ambient body temperature,
indicating a high cardiac output. Conversely, if the area under
the curve is large, it takes longer for the blood temperature to
reach ambient body temperature, implying low cardiac output.
 The thermodilution method is preferable to the indicator-dilution
method because right-sided injection and right-sided sampling
of the cold saline yields a curve that is less subject to
recirculation-induced distortion than right-sided injection and
left-sided sampling of indocyanine dye.

71. +
normal curve
 sharp upstroke
 smooth curve
 mildly prolonged
downslope until baseline
Thermodilution

72. +
 area under the curve is inversely
proportional to the flow rate in the
pulmonary artery which equals the
cardiac output in absence of
intracardiac shunt

73. + Advantages
 Easy widely available
 No withdrawal of blood
 No arterial puncture
 Inert and inexpensive indicator
 No recirculation –analysis simple
 Less measurement variability and
correlation with Fick.
Sources of error
 Unreliable- TR,PR, INTRA
CARDIAC SHUNTS
 Inaccurate in low flow- low output
states (overestimation upto 35%)

74. +
ANGIOGRAPHIC CO
 Calculated by tracing end diastolic and end systolic images
 SV= EDV-ESV
 CO= ( EDV-ESV ) × HR
 AF- not accurate
 But preferred over fick to measure co in calculation of valve areas in
combined stenotic and regurgitant lesions
 Erroneous in RWMA or structurally abnormal ventricles

75. +
METHOD MOST RELIABLE LEAST RELIABLE
FICK METHOD LOW CO HIGH CO
THERMODILUTION HIGH CO PR, TR
INTRACARDIAC
SHUNTS
ANGIORAPHIC Mixed stenotic and
regurgitant lesions
EXTENSIVE RWMA
DILATED VENTRICLE