Indirect Systolic Pressures and Pulse Waves
Arterial Occlusive Disease of the Lower
Extremities
in
By STEFAN A. CARTER, M.D.
SUMMARY
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Measurements were carried out in 146 limbs with angiographically documented
arterial occlusive disease (AOD) and in 85 limbs without AOD. Ankle systolic pressure
(AP) was equal to or higher than brachial systolic pressure in limbs without AOD.
It was below 82% of the brachial in all limbs with complete occlusion, usually below 50%
in those with multiple occlusions, and above 50% in limbs with single block. AP was
below normal in 19 of 25 limbs with severe and in five of nine with mild stenosis. All
limbs with complete occlusion and 14 of 16 with stenosis had abnonnal pressures in
the thigh. The foot-to-peak time (CT) and the width of pulse waves at half amplitude
(WD) were related to heart rate in normal limbs. Considering the heart rate, the
majority of limbs with AOD had abnormally prolonged CT and WD. Normal pressures
and pulse waves were found together in only two limbs with stenosis and symptoms.
The findings indicate that pressures and pulse waves provide a sensitive method for
diagnosis and follow-up of patients with AOD.
Additional Indexing Words:
T-high systolic blood pressure
Pedal pulse waves
Ankle systolic blood pressure
Peripheral vascular disease
Crest time
Popliteal pulse waves
Intermittent claudication
Width of pulse waves
Arterial stenosis
SEVERE ARTERIAL NARROWING and
arterial occlusion both result in diminished mean pressure and in decreased amplitude of the pressure wave distal to the lesion.
Although diastolic pressure distal to arterial
stenosis does not fall until the narrowing is
severe, systolic pressure decreases with lesser
degrees of narrowing.' Systolic pressure has
been known to be diminished in the limbs of
patients with arterial occlusive disease
(AOD).2, 3 In 1956 Gaskell4 found that it
was as sensitive an index of the occlusive
process as the measurement of blood flow
during reactive hyperemia. More recently,
Strandness and co-workers`10 successfully
applied measurements of systolic pressures to
the study of various aspects of the occlusive
process. Alterations in the shape and time
components of the pulse waves recorded from
the limbs with AOD have also been reported.7, 11, 12
Although externally recorded pressures and
pulse waves may be of help in the diagnosis
of patients with AOD,3-5 7, 12 the clinical value of such studies is uncertain because detailed results in large series of angiographically documented cases are not available. For
this reason, the present study was undertaken.
From the Vascular Section, Clinical Investigation
Unit, St. Boniface General Hospital, and the Department of Physiology, University of Manitoba, Winnipeg, Canada.
Work was supported by a grant-in-aid from the
Manitoba Heart Foundation.
A "normal" group consisted of 44 limbs of
healthy volunteers or patients without clinical
evidence of cardiovascular disease. Their average age was 40 + 18 years (SD). A second control group which resembled more closely the
group with AOD consisted of 41 limbs of pa-
Methods
Groups Studied
Control Groups
624
Circulation, Volume XXXVII, April 1968
ARTERIAL OCCLUSIVE DISEASE
tients with conditions which are generally associated with a greater degree of atherosclerosis
but in which there was no evidence of the occlusive process. Patients with ischemic heart disease, cerebrovascular disease, hypertension, or
diabetes mellitus, singly or in combination, as
well as normal limbs of patients with unilateral
occlusive or stenotic process were included in
this group. In all the limbs there were strong,
easily palpable femoral, popliteal, and pedal
pulses, and no ischemic symptoms. The average
age of this group was 56 + 14 years (SD). Because aortic stenosis alters peripheral pressure
pulses in the upper limbs,13 two patients with
systolic pressure gradients of 100 and 127 mm
Hg across the aortic valve, but without regurgitation, were included in the study.
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Arterial Occlusive Disease (AOD)
This group consisted of 146 limbs of patients
with angiographic evidence of an occlusive process in the arteries supplying the lower limbs
including the abdominal aorta. The average age
of the patients was 62 + 13 years (sD). There
were 112 limbs with complete occlusion and 34
with stenosis. In 41 limbs with occlusion, the
vessels were well visualized down to the ankles
and these limbs were divided into 22 with a
single block and 19 with two or more occlusions
in series. There were 25 limbs with severe and
nine with mild stenosis. Stenosis was considered
to be mild when the encroachment on the diameter was between 25 and 40% in the vessels distal
to the bifurcation of the common femoral artery
and between 33 and 50% for the vessels proximal to this point. The stenosis was graded as
severe when the encroachment on the diameter
exceeded 40% and 50%, respectively. The different criteria for larger and smaller vessels were
used because a relatively greater encroachment
on the diameter is required in larger vessels
before a hemodynamic effect is manifested.14
For the purpose of classification of the limbs into
categories according to angiographic findings, isolated occlusions or narrowings in branch arteries
such as the internal iliac, the deep femoral, or a
tibial vessel were not considered.
Follow-up Studies
Measurements were carried out before and
after reconstructive arterial surgery in 25 limbs.
In 19 other limbs with clinical and hemodynamic
evidence of occlusive arterial disease in which
performed, measurements were
repeated after an interval of one or more years.
Angiographic confirmation of the occlusive process was available in six of the 19 limbs.
surgery was not
Circulation, Volume XXXV1I, April 1968
625
A
MERCURY MANOMETER
140 120 " qCUFF PRESSURE
os
E
i(
l
PULS E PICK-US
20 /___ ,
Figure
1
(A) Experimental setup for the measurement of systolic pressure at the ankles. (B) Record obtained
during measurement. The arrows point to where the
pickups signal systolic pressures by the change in
base line and, if recordable pulse is present, by the
onset of pulsation.
Techniques
Angiography
Angiography
was
carried out by injecting
through a translumbar needle
or through a catheter introduced retrogradely
from the femoral artery at the groin. Four to six
serial films, 14 by 17 inches, were taken in the
frontal projection and the run was repeated
when necessary.
contrast material
Determination of Systolic Pressures
Measurements were carried out with the suba blanket. Systolic
determined at the ankles and at
the level of the lower part of the thighs. The
blood pressure cuffs were applied with the lower
edge above the malleoli and above the patella.
The inflatable portions measured 30 by 12.5 cm
for the ankle cuff and 45 by 15 cm for the thigh
cuffs. This length of cuff encircled at least 90%
of the circumference of the limbs. Figure 1 shows
schematically the setup for measurement of pressure at the ankles and the type of record obtained. The cuffs were connected to a pressure
jects supine and covered by
pressures were
source, a mercury manometer, and a
pressure transducer.* Capacitance pulse
Statham
pickupst
were applied over the site of the dorsalis pedis
or posterior tibial arteries and were held in place
*Model PM6TC+ 5-350, Statham Instruments, Inc.,
Los Angeles, California.
t"Infraton," Model D-3, Beckman Instruments, Inc.,
Palo Alto, California.
CARTER
626
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systolic pressure at the ankle (AP), and within
13% for the systolic pressure at the lower thigh
(TP). There was no significant difference between the reproducibility of low and high pressures. In 43 lower limbs determinations of systolic pressure were repeated within 1 month.
The mean absolute difference between the measurements of pressure in the lower limbs was
6 + 5% (SD) of the brachial pressure.
In the limbs with severe impairment of blood
flow manifested by skin lesions or pain at rest, or
both, the pickups were not applied. Instead, the
systolic pressures were determined by the flush
or spectroscopic'5 techniques. The feet were
elevated to decrease the amount of blood in the
superficial vessels. The cuffs were then inflated
and the limbs returned to horizontal position.
The pressure in the cuff was lowered by decrements of 5 mm Hg at intervals of about 10 sec.
The appearance of a pink flush on the sole of the
foot signaled the systolic pressure, or, when a
hand spectroscope was used, the end-point was
signaled by the appearance of a black band of
oxyhemoglobin at 578 m,u in the light reflected
from the sole of the foot.'5 Figure 2 shows the
agreement between systolic pressures obtained
by the flush technique and by the use of pulse
pickups in 160 lower limbs. Similar results were
under tension by means of an encircling tape.
The outputs of the pickups and of the pressure
transducer were recorded on an optical oscillograph. The pickups signaled the systolic pressure
during deflation of the cuffs by the onset of
pulsations and by a shift in base line. The shift
in base line was due to the resumption of arterial
inflow into the foot which led to increased limb
volume and thus to increased pressure on the
pickups. This shift in base line occurred even in
the absence of a recordable pulse. Brachial
blood pressure was measured in both arms prior
to the recording of the pressure in the lower
limbs and was determined again during the recording. Three or more determinations of pressure were carried out and the values were averaged. Reproducibility of measurements within the
experiment was assessed in consecutive studies
on 160 ankles and 60 thighs. The maximal deviations of an individual determination from the
average were within 14 mm Hg of the average
in 95% of cases, at both sites. The 95% limit for
the maximal deviations of the simultaneously
measured brachial systolic pressures was 11 mm
Hg. When individual measurements in the lower
limbs were calculated as percentage of the
brachial pressure, 95% of values of the maximal
deviations were within 9% of the average for the
A/
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(% OF BRACHIAL)
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160
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PULSE PICK-UP
I
60
80
100
120
140
Figure 2
Comparison of systolic pressures at the ankles obtained by means of pickups and by visual
flush technique in mm Hg (A) and expressed as per cent of simultaneously determined brachial
systolic pressure (B). The solid line represents the line of identity; the broken lines encompass
diferences of 10 mm Hg (A) and 10% of brachial systolic pressure (B).
Circulation, Volume XXXVII, April 1968
ARTERIAL OCCLUSIVE DISEASE
obtained by use of the spectroscope and the
pickups.
Recording of Pulse Waves
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Pulse waves were recorded by the same pulse
pickups which were used in the measurements of
systolic pressure. With a little practice the pickups could be applied with appropriate degree of
tension and recordings free from obvious artifacts were obtained. Pulse waves were frequently recorded in the absence of a palpable pulse.
Waves were recorded from over the dorsalis pedis
or posterior tibial arteries and from the popliteal
fossa. For the application of the pickups in the
popliteal region the feet were elevated on a pillow. The waves were recorded on paper moving
with a speed of 100 mm/sec. Although the amplitude of the arterial pressure pulses cannot be
quantitated reliably from the records obtained
using external pulse pickups,16 the shape and the
time components of the externally recorded brachial pulse waves correspond closely to the intra-arterially recorded waves.'7 Two time components were measured as shown in figure 3.
Crest time (CT) was measured from the beginning of the systolic rise to the peak of the wave
and the width of the wave at half amplitude
(WD) was measured from the point on the upstroke when half of the amplitude was reached to
the time when half of the amplitude was reached
on the downstroke. The records were measured
using a magnifying glass with divisions of 0.1 mm
which corresponded to 0.001 sec. The measurements of three or more pulse waves were aver-
627
aged. Both time components were expressed as
per cent of the cardiac cycle. In 23 limbs recordings were repeated within 1 month. The mean
absolute difference between the repeated measurements was 2 + 2% (SD) for CT and 6 + 5%
(SD) for WD. The mean difference between the
heart rate was 7 + 6 beats/min (SD).
In seven subjects, six without evidence of AOD
and one with a proximal stenosis, pulse waves
recorded from over the dorsalis pedis artery using pulse pickups were compared with pressure pulses recorded within 45 min from the
same site using intra-arterial needles and a recording system with adequate dynamic characteristics.18 The CT and WD of the pedal waves
were expressed in per cent of the cardiac cycle.
The mean difference between the CT of the pressure pulses recorded by the pickups and
through the intra-arterial needles was 0.4 ± 0.4%
SE (P > 0.2). The WD, however, was significantly longer when the pickups were used with
the mean difference of 2.7 ± 0.9% SE (P < 0.05).
Pressure and pulse wave measurements were
not carried out in all the extremities at the proximal and distal sites. The number of measurements at different sites is given in the results.
Results
Systolic Pressures
Figure 4 shows AP expressed as per cent
of brachial systolic pressure. The higher of
COMPLE.TE
NO OCCLUSIVE
PROCESS
NORMAL
C.V.
ALL
DISEASE
140 1
STENOSI S
OCCLUSION
SINGLE
SEVERE
MULT.
MILD
I
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1 20 ...
0
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CT
Figure 3
Measurement of crest time (CT) and of the width of
the wave at half amplitude (WD). Normal dorsalis
pedis pulse wave and a wave recorded distal to an
occlusive lesion. Note abnormal prolongation of CT
and of WD in the wave recorded distal to the lesion.
Circulation, Volume XXXVII, April 1968
20
-
Figure 4
Systolic pressure at the ankle (AP) as per cent of the
brachial systolic pressure. S = limbs of patients with
severe aortic stenosis. The broken lines represent the
95% confidence limits for the limbs without evidence
of the occlusive process. Mult. = multiple. C.V. =
cardiovascular.
CARTER
628
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the two ann pressures was used for calculation of the percentage. In the limbs without
NO OCCLUSIVE
COMPLETE
PROCESS
OCCLUSION
evidence of occlusive process AP was equal
to or higher than the brachial in all but one
limb, in which it was 99% of the brachial. The
mean in the normal group was 115% of the
brachial and in the group with cardiovascular
disease it was 110% (P <0.05). The 95% confidence limits were 97 to 124% for the group
with cardiovascular disease and 98 to 131%
for the normal group. AP was normal in the
limbs of the two patients with aortic stenosis.
In all 112 limbs with complete occlusion, AP
was below normal. The highest value in this
group was 81% of the brachial. In 19 of 22
limbs with a single block the AP was greater
than 50%, whereas in 16 of 19 limbs with
multiple blocks it was less than 50%. In nearly
half of the limbs with severe or mild stenosis,
the pressure was less than 80% of the brachial. In five of 25 with severe and in four of
nine with mild stenosis, the pressures were
within normal limits. There was no significant
difference between the mean ankle pressure
of the limbs with severe and mild stenosis.
Figure 5 shows systolic pressures measured
at the lower thigh. In all the limbs without
occlusive process the TP exceeded the brachial pressure by 8% or more. There was no significant difference between the means of the
two control groups without occlusive process.
The TP for the combined control groups was
116% of the brachial with the 95% confidence
limits of 107 to 127%. The pressures in the
limbs of patients with aortic stenosis were
normal. The TP was below normal in all 20
limbs with complete occlusion, in nine of 11
with severe, and in all five with mild, stenosis.
There was no significant difference between
the mean pressure of the limbs with severe
and mild stenosis proximal to the knee.
NORMAL
Pulse Waves
Figures 6 and 7 show the CT of the pedal
and popliteal pulse waves, respectively, plotted against heart rate. The graphs of the WD
of the pedal and popliteal waves are shown
in figures 8 and 9. The CT of the pedal and
popliteal waves increased with increase in
140
Go
goS
S°°°
0
L_
_
X _-
MILD
DISEASE
"O*
1 20
STENOSIS
SEVERE
C.V.
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Figure
5
Systolic pressure at the lower thigh as per cent of the
brachial systolic pressure. For abbreviations and details see figure 4.
heart rate in the limbs of both control groups
without AOD (P < 0.01), and the WD of the
pedal (P <0.01) and popliteal (P <0.05)
waves of the normal control group increased.
The WD of pedal and popliteal waves recorded from the limbs of the control group
with cardiovascular disease did not change
with heart rate. Analysis of covariance* was
carried out on the relationship of CT and WD
to heart rate in the control groups. There
was a significant difference between the two
control groups in the relationship of WD of
the pedal and popliteal waves and in the
relationship of CT of the popliteal waves to
heart rate (P < 0.01), but no significant difference in the case of the CT of the pedal waves.
The 95% confidence limits were computed
separately when there was a significant difference between the two control groups,
whereas in the case of CT of the pedal waves
the two groups were combined. Where confidence limits were computed separately, the
higher value at a given heart rate was considered to be the upper limit of normal. In
*Computations were done by the University of
Manitoba computer center's IBM 360, using techniques described by Snedecor.19
Circulation, Volume XXXVII, April 1968
ARTERIAL OCCLUSIVE DISEASE
45-
629
x
40x
35x
LU
U
xx
x AX
xx x
x
330
xA
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AX
0
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10
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70
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1
100
HEART RATE
Figure 6
The relationship of crest time (CT) of the pedal pulse waves to heart rate. Symbols as in figure
4. The solid lines represent the regression of CT on heart rate for the two combined control
groups
without AOD and the 95% confidence limits.
the limbs of patients with aortic stenosis, the
CT of the pedal and popliteal waves was abnormally prolonged, but the WD of both
waves was within normal limits.
The values of CT and WD were usually
abnormally prolonged in the limbs with AOD.
The CT of the pedal waves (fig. 6) was
abnormal in 41 of 45 limbs with occlusion,
in 22 of 24 with severe and in four of nine
with mild stenosis. The CT of the popliteal
waves (fig. 7) was within normal limits in a
larger proportion of limbs with AOD. On the
other hand, the WD of the pedal waves (fig.
8) was abnormal in all limbs with complete
occlusion and the WD of the popliteal waves
(fig. 9) in all but two. The WD of the pedal
waves was also abnormal in 19 of 24 limbs
with severe and in four of nine with mild
Circulation, Volume XXXVII, April 1968
stenosis. Abnormalities of the WD of the
popliteal waves were found in 14 of 18 limbs
with severe and in three of seven with mild
stenosis.
Table 1 shows further analysis of the results in the limbs with arterial narrowing.
The limbs with mild and severe stenosis were
combined for this purpose. Among 20 limbs
in which there was history of intermittent
claudication, the AP and the WD of the pedal
pulse waves were abnormal in 16 and the CT
was abnormal in 18. In 14 of the 20 limbs all
three parameters were abnormal, in four limbs
two parameters were abnormal, and in two,
both with mild stenosis, all three parameters
were normal. In the latter two cases, there
was complete arterial occlusion and more severe symptoms in the contralateral limb.
630
CARTER
Each parameter showed abnormality in
eight or nine of the 13 limbs without intermittent claudication. The absence of symptoms in many of these limbs was probably
due to the existence of a more severe occlu-
sive process in the contralateral limb or to a
cardiac condition which may have limited the
amount of walking by the patient. All three
parameters were within normal limits in only
three of the 13 limbs in this group.
x
45
-
40
x
35
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HEART RATE
Figure 7
The relationship of CT of the popliteal pulse waves to heart rate. Symbols as in figure 4. The
solid lines represent the regression of CT on heart rate and the lower 95% confidence limit for
the normal control group; the broken lines represent the regression and the upper 95% confidence limit for the control group with cardiovascular disease. There was a significant difference
between the regressions of the two control groups.
Table 1
Abnormalities of Systolic Pressure at the Ankles and of Pedal Pulse Waves in the Limbs
with Proximal Arterial Stenosis
Intermittent
claudication
Total
no.
limbs
Present
Absent
20
13
No. of limbs with abnormal measurements
No. of abnormal parameters
per limb
3
2
1
0
Individual parameters
AP
CT
WD
16
8
18
9
16
9
14
7
4
2
1
2
3
Circulation, Volume XXXVII, April 1968
ARTERIAL OCCLUSIVE DISEASE
70
631
-
X
X X
X
X
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Iu
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50
70
60
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1
00
HEART RATE
Figure 8
The relationship of the width of the pedal pulse waves at half amplitude (WD) to heart rate.
Symbols as in figure 4. The solid lines represent the regression of WD on heart rate and the
95% confidence limits for the normal control group; the broken lines represent the 95% confidence limits of the control group with cardiovascular disease in which the relationship of
WD to heart rate was not significant.
Follow-up Studies
Figure 10 shows ankle systolic pressures
measured during the initial and follow-up
studies. Among 15 limbs with essentially normal vessels distal to the occlusive or stenotic
lesion, there was a substantial increase in the
pressure after arterial reconstruction in 14
(fig. IOA). In 11, the postoperative pressure
was
just
within normal limits, and in one it was
below normal. There was no change in
of an early graft failure.
marked improvement in the
case in which the pressure rose from 42 to
70%, but 6 months later the graft occluded.
Figure lOB shows the results before and after
arterial reconstruction in 10 limbs in which a
residual distal occlusive or stenotic lesion was
present in addition to the lesion which was
corrected by surgery. In four limbs the change
in AP was less than 10% of the brachial, whereas in six the AP increased by 10 to 35% of the
pressure
There
in
was
a case
a
Circulation, Volume XXXVI, April 1968
brachial pressure. However, all the postoperative pressures were below normal. Figure lOC
shows AP measured at intervals of 1 to 2',2
in 19 limbs in which arterial reconstruction was not undertaken. In five limbs, the
years
changed by less than 5%. In 10, the
decreased by 10% or more of the
brachial. In many of these, larger decreases
in pressure were associated with development
or increase in symptoms. In four limbs increases of 18 to 27% of the brachial pressure
were found. In two of the four the pressure
increased but to a level still well below normal. In one of them, the initial measurement
was carried out shortly after an acute occlusive
episode. In the other two limbs, an initially
abnormal pressure of 80 and 85% of the
brachial pressure increased to values within
normal limits. In one of the two, this was associated with disappearance of symptoms.
Angiograms were not carried out in these two
pressure
pressure
cases.
CARTER
632
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_~~~~~
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x
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=
20 -
Iu
I
50
60
70
80
90
HEART RATE,
Figure 9
The relationship of the width of the popliteal pulse waves at half amplitude (WD) to heart
as in figure 4. The solid lines represent the regression of WD on heart rate
and the 95% confidence limits for the normal control group; the broken lines represent the 95%
confidence limits of the control group with cardiovascular disease in which the relationship
of WD to heart rate was not significant.
rate. Symbols
Discussion
Systolic Pressures
Clinical Applications
The techniques presented in this report
lend themselves well to the study of patients
with peripheral vascular disease. About 600
studies were performed in this laboratory over
4 years without the patients having any ill
effects. Estimation of the local systolic pressure is easy to perform and its reproducibility
is comparable to that of the auscultatory
estimation of the brachial systolic pressure.
Although electronic equipment was used in
the majority of the reported measurements,
it was found that the flush technique, which
does not require any special equipment, gives
results which are equally reliable for clinical
application. Therefore, measurement of sys-
tolic pressure in the lower limbs may be performed at bedside by any interested physician.
Results of the study indicate that measurement
of systolic pressure provides a valuable and
sensitive objective method for the evaluation
of patients with occlusive arterial disease of
the extremities, a conclusion which is in agreement with previous reports based on smaller
series of cases.3-5 7 The use of this technique
may eliminate the need for angiography in
a number of cases, whereas in others it may
enhance the diagnostic precision by complementing the angiographic findings.
In subjects without occlusive arterial disease, AP exceeded the brachial systolic pressure, which is in keeping with the peripheral
amplification of the arterial pressure pulse
found using intra-arterial recording.20 AP was
Circulation, Volume XXXVII, April 1968
ARTERIAL OCCLUSIVE DISEASE
ARTERIAL
A
633
SURGERY
AF TE R
FOLLOW - UP
STU D I E S
B
C
F IR ST
SECOND
1 00
AFTER
LU
-
80
-
oc
D
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4A
tn
:L U
co
0
1*6 0
40
20
-
Figure 10
Systolic pressures at the ankle. (A) Before and after arterial surgery in limbs with a single
occlusion or stenosis. (B) Before and after arterial surgery in limbs with a residual lesion in
addition to the lesion corrected by surgery. (C) Repeated studies at intervals of 1 to 232 years
in limbs in which arterial
surgery was
not
undertaken.
slightly but significantly higher in the normal
control group than in the controls with cardiovascular disease who did not have occlusive
disease in the arteries of the extremities.
Since the mean age was 16 years higher in
the latter group (P < 0.01), the lower systolic
pressure may be due to a greater degree of
damping of the pulse wave associated with
gradual decrease in the diameter of the vessels to the lower limbs with increasing age.2'
There was complete separation of the values
of the AP between the control limbs and the
limbs with complete arterial occlusion, and
there were only four limbs with stenosis and
Circulation, Volume XXXVII, April 1968
symptoms in which the pressures were within normal limits. Therefore, in patients with
questionable or borderline physical signs and
atypical history, a normal AP might
help to rule out the presence of a hemodynamically significant occlusive arterial process and
thus to eliminate the need for angiography, a
procedure which is associated with a small
but definite incidence of serious complications.22 Measurements of systolic pressure
often complement angiography. They are of
value in assessing the hemodynamic significance of the arterial narrowing and may be
helpful in determining the adequacy of the
poor or
CARTER
634
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"<runoff" distal to an occlusive lesion. Abnormal AP was recorded in five of nine limbs with
mild arterial narrowing, as judged by the
degree of encroachment of the lesion on the
diameter of the lumen in the frontal projection. In four of these five limbs intermittent
claudication was present. Also, there was no
significant difference in the mean AP between the limbs with mild and severe stenosis. This finding, which is in agreement with
similar results on the pressures across the
stenoses of the renal arteries,23 confirms the
observation that estimation of the severity of
the stenotic lesion by the encroachment on
the diameter in a single projection is not
reliable. Demonstration of an abnormal AP in
a limb with stenosis establishes the physiological significance of the lesion. On the other
hand, it is hazardous to assume the clinical
importance of a mild or moderate narrowing
if a physiological abnormality cannot be demonstrated. Measurement of AP is valuable,
not only in the demonstration of the presence
or absence of the occlusive process, but also
in the evaluation of its severity. This was
shown by the good, although not complete,
separation of the limbs with a single block
from those with multiple occlusions on the
basis of the AP. AP should be useful as an
index of the runoff distal to the lesion with
the pressure of over 50% of the brachial indicating at least a reasonably good runoff.
This information may be helpful in deciding
whether or not surgery for intermittent
claudication should be done on an individual
patient, particularly since angiography is frequently unreliable in the demonstration of the
vessels distal to an occlusive lesion.24 25 Since
estimation of systolic pressure is easy, reliable,
and without ill effects, it can be carried out
repeatedly to follow the patient's condition
and to evaluate the result of arterial surgery,
thereby eliminating the need for repeated
angiography.
Systolic pressures measured at the level of
the lower thigh appear to be clinically as
reliable as those measured at the ankle. It is
important to use a cuff with a long inflatable
bag which encircles all or most of the cir-
cumference of the limb. Otherwise the pressure in the cuff may not be transmitted fully
into the tissues and too high values will be
obtained. As was the case with AP, abnormal
TP was recorded in the large majority of
limbs with proximal stenosis (14 of 16) and
in all the limbs with complete proximal occlusion.
Limitations
No appreciable discomfort is associated
with the inflation of the ankle cuffs; however,
the sensation of pressure is much more intense
when the thigh cuffs are inflated, and many
patients complain of considerable discomfort.
In an occasional limb with heavy calcification
of the arterial media, measurement of the systolic pressure may be impossible because of
the incompressibility of the wall of the vessel.7
This occurred in one of 146 limbs with angiographic documentation of the occlusive vascular disease in the present series and in a
total of six limbs among over 600 studied
during the past 4 years, an incidence of about
1%. Although measurement of local systolic
pressure is a sensitive method for the evaluation of an occlusive or stenotic lesion located
proximally in the main arterial pathway to
the limb, it provides no information about
the presence or absence of lesions in the
branch vessels such as the internal iliac, the
deep femoral, or the individual branches of
the popliteal artery. Normal AP will be recorded in the presence of only one patent
artery in the leg. Normal pressure was obtained in a limb with the occlusion of both
anterior and posterior tibial vessels, but with
a patent peroneal artery. This limitation of
the method is probably of minor importance,
because isolated lesions of the internal iliac and
deep femoral arteries are relatively rare26' 27
and reconstructive surgery on the vessels below the popliteal artery is not as yet in general
use.
In some cases in which the occlusion is at
the same site as the blood pressure cuff, the
systolic pressures show an abnormality, but
they may underestimate the hemodynamic
significance of the lesion. In two cases of
Circulation, Volume XXXVII, April 1968
ARTERIAL OCCLUSIVE DISEASE
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complete occlusion of the superficial femoral
artery in the adductor canal, the TP was only
slightly below normal limits. This was probably due to the large collateral branches from
the deep femoral artery which transmitted
near normal pressure to a level distal to the
site of the block before connecting with
smaller collateral vessels in the region of the
knee. Normal AP was recorded in four of 20
and normal TP in one of 14 limbs with
proximal stenosis and symptoms consistent
with intermittent claudication. Abnormal
pulse waves were found in two of the four
limbs with normal AP and in the one with
normal TP, thus decreasing to two the total
number of limbs in this study in which "false
negative" results were obtained. It appears,
therefore, that pulse waves and systolic pressures recorded at rest will be abnormal in a
large majority of patients with symptoms due
to occlusive arterial disease. However, in a
small percentage of cases with arterial narrowing, exercise studies may be necessary to
demonstrate the hemodynamic abnormality by
showing an abnormal fall in the AP6 or an
abnormal change in pulse wave'2 or blood
flow.28
Pulse Waves
Clinical Applications
Indirect recording of pulse waves from
over the arterial sites in the human extremities provides a useful adjunct to the measurement of systolic pressures. Good agreement
of the CT and WD was found between the
pedal waves recorded by the pickups and by
the intra-arterial route, although the pickups
overestimated the WD by about 10%. These
findings are similar to the comparison of the
brachial pressure waves recorded through
intra-arterial needles and from externally applied cuffs.17 Pulse waves can often be recorded in the absence of a palpable pulse.
The same externally applied pulse pickups
can be used both to record the waves and to
signal the systolic pressure during deflation of
the pneumatic cuffs. Therefore, recording of
the pulse waves can be obtained rapidly
and without ill effects, together with the
Circulation, Volume XXXVII, April 1968
635
measurement of systolic pressure. However,
since the pickups have to be applied with a
certain degree of tension, application to severely ischemic parts of the limbs should be
avoided.
There was complete separation of the WD
of the pedal pulse waves between the control
limbs and those with complete proximal occlusion and, with the exception of two limbs
with occlusion, complete separation of the
WD of the popliteal waves. Therefore, the
WD was essentially as good as the systolic
pressure in separating the limbs with complete occlusion from the normal. The incidence of normal WD of the pedal pulse
waves among the limbs with proximal stenosis was the same as the incidence of normal
systolic pressures, but it was greater in the
case of the popliteal waves. Information derived from pulse waves complements the
study of systolic pressures and it may increase
the diagnostic sensitivity of the procedure.
As indicated above, abnormal pulse waves
recorded in three of five symptomatic limbs
with stenosis and normal systolic pressures
reduced the number of symptomatic limbs
with "false negative" results to two in the
present series. Recording of pulse waves provides other advantages. There is no discomfort to the patient, so that the information
derived from the popliteal waves may eliminate the need for measurement of systolic
pressure in the thigh which is frequently
associated with considerable discomfort. When
systolic pressure cannot be determined because of incompressibility of the calcified
arterial walls, the pulse waves may provide
valuable information about the presence or
absence of a proximal occlusive lesion. Since
the pickups are applied distal to the pneumatic cuffs, they may provide additional information about the arterial segment between
the cuff and the pickup. For example, in the
two cases of complete occlusion of the femoral artery in the adductor canal, in which TP
was only slightly below normal limits, the
popliteal waves were grossly abnormal in
keeping with proximal occlusion. Similarly,
in the case of occlusion of the anterior and
636
posterior tibial vessels, in which normal pressure was recorded at the ankle because of the
patent peroneal artery, the pedal wave was
grossly abnormal because of damping in the
small collaterals which connected the peroneal
artery to the vessels in the foot.
Limitations
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A certain amount of distortion may be
associated with external recording of the
arterial pressure pulses. Although there was
a good agreement of the time components
of the externally and directly recorded pulse
waves from the dorsalis pedis artery, more
distortion may be present in the records from
the popliteal fossa, because of the greater
volume of soft tissues between the popliteal
artery and the skin. It is likely that the peak
of the wave may be particularly sensitive to
such distortion. This might explain the relatively large overlap between the CT of the
popliteal waves recorded from the limbs with
and without arterial occlusive disease. The
reproducibility of the time components of
the pulse waves was not as good as that of the
systolic pressures. This may be due to the
different amount of distortion associated with
the application of pickups on different days
and to the differences in heart rate and in
the vasomotor state of the subjects. The lesser
degree of overlap of the values of WD between the control limbs and those with AOD
suggests that this part of the wave is less
affected by distortions than CT. Also, WD
(as well as systolic pressure) was normal in
the limbs of patients with aortic stenosis,
while the CT was abnormal. None of the
patients in this series was in overt heart
failure. It is possible, however, that abnormal
peripheral pulse waves may be recorded in
patients with gross abnormalities of the
cardiac function which are associated with
marked alterations of the central pressure
wave.
Since the results of this study indicate that
abnormal systolic pressures, or pulse waves,
or both, are found at rest in the large majority
of limbs with AOD, it appears that, for clinical
purpose, the more cumbersome exercise stud-
CARTER
ies will be needed
only in a small percentage
of patients referred to vascular laboratories.
In addition to their value in the management
of the individual patients, recording of systolic pressures and pulse waves may be conveniently applied to the study of the effect
of treatment, natural history, and physiology
of the occlusive arterial disease.5-10 Also,
since the absence of a palpable ankle pulse
by itself may be a risk-factor variable of
prognostic significance in coronary and cerebral arterial disease,29 recording of systolic
pressures and of arterial pulse waves might
be successfully applied to the epidemiological population studies of arterial disease.
Acknowledgment
The author would like to acknowledge the assistance of Dr. F. Chebib in statistical computations,
helpful discussions with Dr. J. P. Maclean, and technical assistance of Mr. E. Hamel and Miss H. Harvey.
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Indirect Systolic Pressures and Pulse Waves in Arterial Occlusive Disease of the
Lower Extremities
STEFAN A. CARTER
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Circulation. 1968;37:624-637
doi: 10.1161/01.CIR.37.4.624
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1968 American Heart Association, Inc. All rights reserved.
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