Pulse analysis:
stroke volume, vascular stiffening
and cardiovascular disease
Tom Archer, MD, MBA
UCSD Anesthesia
Pulse analysis is an ancient practice, now
making a comeback.
http://www.itmonline.org/image/pulse2.jpg
Pablo Picasso, “Science and Charity”, 1897
Traditional pulse “analysis”:
subjective and hard to quantify
• “Waterhammer pulse”-- AI
• “Slow upstroke”-- AS
• “Pulsus paradoxus”– cardiac tamponade
• Is this silly and obsolete stuff?
Pulse analysis was serious
business in the 19th century
• Sphygmographs in common use.
• Insurance companies relied on their
results.
Etienne-Jules Marey (1830-1904) invented the
sphygmograph to record the arterial pulse on
smoked paper. It was used by Engelmann,
Mackenzie and Wenckebach.
Sphygmograph 1876
http://www.mamweb.org/modules.php?name=Content&pa=showpage&pid=32000
Life insurance
examination
manual from
1891 discussed
pulse analysis by
sphygmography.
Tom Archer, 58 y.o., good general health. Takes
Crestor for high cholesterol.
Radial and predicted ascending aortic pressure
waveform when subject is cold.
Scipione RivaRocci introduced
the mercury
sphygmomanometer in
1896.
Measured
systolic BP only.
Harvey Cushing used it.
Korotkoff introduced
auscultation for diastolic
pressure in 1905.
history.library.ucsf.edu/.../chapter2_03.html
In the 20th century, Riva-Rocci and
Korotkoff’s sphygmomanometer
eclipsed pulse analysis
• Two simple numbers: systolic / diastolic.
• Easy to use.
• Pulse analysis fell into disuse.
• 20th century saw tremendous gains from simple
sphygmomanometry: dangers of high BP.
Increased
diastolic
is associated
with CAD– with
High
diastolic
bloodBPpressure
is associated
multiple large
increased
risk studies.
of coronary disease.
K Hirata (Circ J 2006; 70: 1231–1239)
High systolic
Both
pressure and
increased
pulse pressure
brachial
are also SBP
associated
with
and
increased
coronary
brachial
disease. pulse
pressure
are
For any given
associated
systolic
pressure,
with
cardiac risk
increased
increases with
coronary
decreasing
diastolic BP!
disease.
K Hirata (Circ J 2006; 70: 1231–1239)
But simple sphygmomanometry
ignores valuable information within
the pulse trace.
• Extra information can be extracted from the pulse
using transducers and computers.
• Pulse analysis is becoming reproducible and
objective.
• Pulse analysis is JUST SOFTWARE analyzing the BP
signal.
Pulse analysis gives
two types of information
• “Central blood pressure”
– Ascending aortic blood pressure from
radial waveform.
– Specifically, we get “Augmentation
Index” (AIx)– a measure of extra heart
work.
• Stroke volume (CO, SVR)
Central blood pressure (CBP)
• Systolic pressure in the ascending aorta
is NOT the same as brachial or radial
systolic BP.
• Diastolic and mean pressures are very
similar at radial / brachial and central
sites.
LV “sees” the
SBP in the
ascending aorta.
With normal aortic
valve, LV wall
tension depends
on pressure in
ascending aorta
(and diameter of
LV chamber).
health.yahoo.com/topic/heart/overview/article...
Heart “sees” central aortic
systolic pressure, not brachial
artery pressure.
• Obviously, it’s hard to measure
ascending aorta pressure directly.
• Ascending aortic (“central”) BP can
be extrapolated from the radial pulse.
SphygmoCor system for measuring central blood
pressures
What creates central BP?
• Stroke volume
• Aortic stiffness (compliance / Windkessel)
• Systemic vascular resistance (“runoff”)
• Reflected pressure wave
What creates
central BP?
#2 Stiffness of
AIR
aorta (“windkessel”)
BLOOD
heart
#1 SV
Central BP
veins
arteries
#4 Wave
reflection–
#3 Systemic vascular
resistance (resistance
arterioles)
Muscular arteries
timing and
amount
Augmentation
index– extra
cardiac work
due to wave
reflection
AIx =
Augmentation
Pressure /
Pulse Pressure
Kozo Hirata, MD; Masanobu Kawakami, MD; Michael F O’Rourke, MD, DSc*Circ J 2006; 70: 1231–1239
Augmentation
index is a
deadly
backdraft of
pressure
which
exhausts the
heart over
time.
Run animation
• Wave reflection animation can be
found at:
• http://atcormedical.com/wave_ref
lection.html
Augmentation Index (AIx)
• AIx = unnecessary heart work.
• High AIx leads to LVH and
cardiomyopathy.
• Lower AIx is better.
• Treatments that lower AIx help the patient.
Hypertensive patients
treated to identical
brachial BP
endpoints with
amlodipine
and
atenolol
show lower
central BPs and AIx
with amlodipine
CAFE / ASCOT study, M. O’Rourke
(Circulation. 2006;113:12131225.)
A given brachial BP measurement
does not say what central BP the heart
is actually generating.
Antihypertensive drugs may exert
their beneficial effects via effects on
central blood pressure.
These effects may not be appreciated
by just measuring brachial BP
Central BPs–
ASCOT / CAFE study
• Lower central BPs are associated with
better CV outcomes.
• Amlodipine achieved lower central
BPs and had better CV outcomes
than atenolol, despite achieving the
same brachial artery BPs.
CAFE / ASCOT study, M. O’Rourke (Circulation. 2006;113:1213-1225.)
When is AIx high-- chronically?
•
•
•
•
•
•
•
Normal aging
Obesity
Atherosclerosis
Diabetes
Pre-eclampsia
Inflammatory arthritis
Renal failure
As healthy individuals
age, reflected wave
arrives at ascending
aorta earlier and
increases
augmentation index
and central pulse
pressure.
WW Nichols Curr Opin Cardiol
2002, 17:543–551
Tom Archer, 58 yo, after work, seated
comfortably. Aix = 11%.
67 y.o. obese female-- AIx 24%
77 y.o. man. Never smoked.
Aix = 29%.
42 y.o. obese female, smoker.
Aix = 36%
77 yo male, ESRD, AV fistula, CAD, HBP
Takes atenolol, lisinopril, terazosin,
finasteride. Aix = 39%
When is Aix high– acutely?
• Arterial compression in legs (squatting)
• Cold body temperature.
• Nicotine ingestion
Tom Archer, 58 y.o., while squatting.
Aix = 21%
Tom Archer, seated, very cold from being
outside in winter.
Aix = 27%
Exposure of
healthy young
adults to cold
air for 30 min
increases
augmentation
index.
David G. Edwards,1 Amie
L. Gauthier,2 Melissa A.
Hayman,2 Jesse T. Lang,2
and Robert W. Kenefick2J
Appl Physiol 100: 1210–
1214, 2006.
Does cold weather increase
MI rate due to increased AIx?
Perioperative hypothermia
increases cardiac event rate.
Is this due to increased AIx
with hypothermia?
What makes AIx go down-chronically?
•
•
•
•
•
Exercise
Weight loss
Red wine
Statins
Control of blood pressure (ACEI and
CCB)
• NTG
Ted A, 30 yo, at rest, seated. Subject runs
marathons. Aix = -14%.
64 yo obese male. HBP on lisinopril.
Moderate ETOH consumption.
Aix = 14%.
What makes Aix go down-acutely?
• Exercise
• Red wine
• Lowering blood pressure
• NTG
Tom Archer, 58 yo, after exercise and
wine.
AIx = 1%
NTG reduces wave reflection and AIx by
dilating muscular arteries.
Is this its primary mechanism of action?
S. C. MILLASSEAU, R. P. KELLY, J. M. RITTER and P. J. CHOWIENCZYK
Clinical Science (2002) 103, 371–377
What determines
augmentation index?
• Timing of wave reflection– pulse wave
velocity. Faster wave return is bad.
• Amount of wave reflection– muscular
artery tone.
–NTG reduces muscular artery tone and
wave reflection
–Does NTG work by decreasing AIx?
Yes, at least in part.
PWV (aortic stiffness)
increases with age.
AR Khoshdel Journal of Hypertension 2006, 24:1231–1237
AIx increases in
“inflammatory” states:
•
•
•
•
•
•
•
Obesity
OSA
Hyperglycemia
Sepsis
Pre-eclampsia
Lupus
Cocaine
Hypercholesterolemia
MT, 22 yo, healthy, in labor, epidural in
place and she is comfortable.
Aix = -1%.
JM, 21 yo, in labor, recent onset lupus, on
prednisone and plaquenil
Aix = 6%
Statins and ACE inhibitors
can lower central BPs
and AIx
6 months Rx
with
atorvastatin
decreased
central aortic
pulse pressure
and
augmentation
index.
WW Nichols Curr Opin Cardiol
2002, 17:543–551
Four months
Rx with
lisinopril
decreased
central aortic
pulse pressure
and
augmentation
index.
WW Nichols Curr Opin Cardiol
2002, 17:543–551
DO, 56 yo female, hypertensive, diabetic
May 31, 2007. Aix = 41%
DO, 56 yo female, hypertensive, diabetic
January 3, 2008. After weight loss and 3
weeks Lipitor. AIx = 26%
ACE inhibitors and
aldosterone antagonists
can reverse
LV hypertrophy—
is this due to decreased AIx
and strain on the heart?
ACE inhibitors and aldosterone antagonists
reverse LV hypertrophy– via central BP effects?.
Adams KF, Am J Health-Syst Pharm—Vol 61 May 1, 2004 Suppl 2
Radial Pulse Analysis II:
Pulse analysis to determine
stroke volume and cardiac
output from the arterial
pressure trace.
Pulse contour analysis
• We’ll skip the math and validation studies.
• Intuitively– the bigger the waveform and the
longer it lasts, the bigger the stroke volume.
• Calibration (e.g. with lithium dilution) vs. age /
weight / height algorithm to predict probable
aortic compliance and then follow trends.
P
Big stroke volume
R
E
S
S
U
R
E
Small stroke volume
PiCCO system of pulse contour analysis
Aortic
compliance
(low
compliance
and stiff
aorta means
high pulse
pressure)
Systemic
vascular
resistance
(low
resistance
means rapid
fall in diastolic
pressure)
Godje O Crit Care Med 2002 Vol. 30, No. 1
Stroke volume from arterial
pressure trace--- PulseCO from
LiDCO Ltd. (UK)
Stroke volume from arterial pressure
trace--- Edwards Life Sciences, Irvine
California
Stroke Volume Estimation by
Pulse Contour Analysis
•
•
•
•
•
•
Complicated
Lots of physics and math
Computerized
Real time
Needs a good waveform
Has limitations, but it usually
works
Stroke volume estimation by
pulse contour analysis
• Just software for analyzing pulse
contour.
• No additional patient risk or
invasion over that of arterial line
alone.
PulseCO:
Hemodynamic
examples
Dramatic drop in SV, CO and BP with small dose
of propofol (40 mg) after loading with fentanyl,
lidocaine and esmolol.
CO
SVR
BP
SV
HR
Continuous spinal in morbidly obese
parturient at C/S causes fall in SVR, rise in
CO. Phenylephrine increases SVR and
decreases CO.
GA induction with etomidate and sux associated with
extreme hypertension in patient with pre-eclampsia and
lupus. Hypertension due to both inc CO and inc SVR.
Repeat CS. Epidural anesthesia. Delivery with
inc in HR and CO, oxytocin bolus with decrease
SVR and BP, increase in CO and SV.
Septic woman for CS. SVR does not rise
with intubation (A) and incision (B).
Nominal cardiac output L/min
20
10
0
Nominal systemic vascular resistance dyn.sec.cm-5
1000
500
0
Blood pressure mm Hg
200
100
0
Heart rate beats/min and nominal stroke volume mL
150
100
SV
50
0
0
A5
10
minutes
B
15
C/D 20
Tourniquet inflation on leg increases SVR
and MAP and decreases CO. Deflation
reverses these changes.
Phenylephrine and vasopressin both
increase SVR and decrease CO (in this
patient).
Repeat CS, CSE. Severe pre-eclampsia.
Multiple nicardipine boluses cause decreases
in SVR and MAP, increases in SV and CO.
CS patient with severe pre-eclampsia superimposed on CRF: Antihypertensive therapy with labetalol 25 mg and
hydralazine 5 mg (A) and nicardipine 250 µ total (B). Behind almost “stable” BP is drop in SVR, rise in CO.
Nominal cardiac output L/min
8
4
0
Nominal systemic vascular resistance dyn.sec.cm-5
3000
2000
1000
0
Blood pressure mm Hg
200
100
0
150
Heart rate beats/min and nominal stroke volume mL
100
50
0
0
10
A
20
minutes
30
B
40
V
Methylene blue x 2 and indigo carmine x 1
scavenge NO and increase SVR. Cystoscopy
after C-hysterectomy, GA, placenta percreta.
In conclusion
• Radial pulse wave analysis can give
us two types of information:
–Central BPs and augmentation index, a
measure of unnecessary heart work
–Stroke volume (and CO and SVR)
In conclusion
• Pulse wave analysis has two distinct
techniques:
– Radial pulse tonometry (CBP and AIx)
• AtCor Medical (SphygmoCor)
– Pulse contour analysis (SV, CO and SVR)
• LiDCO
• Vigileo (Edwards)
• PiCCO
• Others
In conclusion
• Radial pulse tonometry gives us
central blood pressures and a
measure of unnecessary heart work
during systole– augmentation index
(AIx).
• Central BPs and AIx may be the
“smoking gun” for CV damage.
In conclusion
• Helpful therapeutic interventions such
as ACE inhibitors, statins, calcium
channel blockers and NTG may exert
some of their therapeutic effects via
their effects on central BP and AIx.
• Hence, measurement of these
parameters may become part of the
routine Dx and Rx of CV disorders.
In conclusion
• Measurement of CBP and AIx may
become useful in acute CV care. This
is speculative at this point.
• It behooves us to put this technology
on our “radar screen”.
In conclusion
• Pulse contour analysis: several
companies are working hard in this
field.
• I am most familiar with LiDCO, but
Edwards is pushing hard with Vigileo.
In conclusion
• Pulse contour analysis to estimate stroke
volume, CO and SVR works well enough to be
clinically useful.
• I find it fascinating and a great teaching and
learning tool.
• Even if the numerical estimates are incorrect,
the trends are correct.
• Both LiDCO and Edwards have “calibrationfree” products.
Questions for the future
• Will radial pulse tonometry (and AIx)
become a routine office evaluation of
patients at risk for CV disease?
• Will it provide an “early warning system”
for the development of CV disease?
• Will it guide drug therapy of CV disease?
Questions for the future
• Will measurement and
pharmacological manipulation of AIx
in critical care improve patient
outcomes?
Questions for the future
• Will pulse contour analysis for CO and
SVR be incorporated into standard
arterial line monitoring as a routine?
The End
Questions?