118 34 EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

disease the ballistocardiogram, through frequently abnormal, did not
often reveal a sufficiently specific pattern to permit diagnosis
whercas other available methods usually provided more specific
information for diagnostic purposes.

This opinion, though essentially valid, tells only part of the
true story and should be revised in the light of the last 10 years
of experience. Elsbach (13) later decided that, since the significance
of ballistic abnormality in older persons was uncertain, he would
focus attention on individuals under the age of 40 and his results
provided useful and stimulating information. We are in agreement
that abnormal ballistocardiograms in persons less than 40 are quite
significant; even in those in whom the ballistocardiographic «pattern»
is not distinctive enough for diagnosis, it often supplies useful infor-
mation regarding the functional state of the circulation.

I will now return to the patient with coarctation of the aorta.
In cardiovascular conditions associated with such marked structural
and functional abnormality, the diagnosis can usually be made by
methods which are more reliable and specific although an occasional
patient is seen in whom this diagnosis was not suspected until a
ballistocardiogram, with its characteristic pattern, was obtained. In
any case, even if other methods suggest this diagnosis, the ballisto-
cardiogram should supply confirmatory evidence. In addition, this
method may be useful in periodically checking the patients’ circu-
latory function and in evaluating physiologic changes after resection
of the lesion (*). In this era when right and left heart and aortic
catheterization and puncture are common place, if periodic tests of
cardiovascular function are needed, a method capable of supplying
important information which involves no pain, discomfort, or hazard
to life should be a source of considerable gratification to the
patient.

There is an urgent need to carry out systematic and extensive
investigations with the ULF ballistocardiograph on patients with
all kinds of congenital and acquired disease states, especially in
young individuals, under 40 years of age. It has been 8 years since
Elsbach published his Dutch monograph and 6 years since its
translation into English, yct no extension has been made of his
studies and no investigation, comparable in scope to his, has been
published. His work was quite productive in spite of the fact that
it was somewhat limited by the lack of a suitable multi-channel
recorder, by the fact that his transducers were not calibrated in
absolute units and by the necessity of taking records only after

(*) It is of interest that, following resection, there is usually no sudden
disappearance of the characteristic pattern, Often there is gradual change in
wave-from over a period of several months before its complete disappearance.
As with systemic blood pressure, this suggests a gradual re-adjustment of the
circulation to its new conditions of operation.


110 3d EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

the coarctation while those on the right were taken after recovery
from the operation. In each case, from above downward, they are
velocity, displacement and acceleration ballistocardiograms, respec-
tively. In the displacement record, it is to be noted that a large foot-
ward displacement of the body, corresponding to a headward displa-
cement of blood, occupies almost the whole of systole. This suggest
that the major uptake of blood during systole occurs in a direction
headward from the heart. It is evident that the lower part of the
body cannot be long deprived of a blood supply, and it is, in fact,
usually found to be reasonably adequate. The difference is that the
obstruction at the arch does not permit the blood to flow beyond
the constriction in a pulsatile fashion but allows only an almost steady
flow to the lower part of the body by devious and circuitous routes.
In this respect, the constriction of the aorta acts as a « high-cut »

Fig. 10.
Pre- and postoperative ULF ballistocardiograms from nine-year-old male with coarctation of the aorta. Left :
Preoperative records. The most striking alterations are in the displacement record which shows a deep and greatly
prolonged footward « ] occupying the whole of systole: the normal headward » M is absent. This indicates that
the displacement of blood during systole is predominantly headward. The normally large and rapid uptake of blood
by the vessels distal to the arch cannot take place because of the obstruction and these vessels fill slowly through
devious channels. This results in an unbalanced headward displacement of blood-mass during systole. The velocity
and acceleration ballistocardiograms are also altered. Right : Records taken three weeks after operation. The ballis-
focardiograms have become normal. In the displacement record the large, broad < ] has been replaced by a normal,
small « ] and this is followed by the large headward _« JM displacement. This suggest that the uptake of blood by
vessels distal to the arch now takes place normally. The velocity and acceleration records have also become normal,

(Courtesy American Journal of Cardiology.)


‘William R. SCARBOROUGH 101

at bottom, shows the frequency-response characteristics of a « high-
cut » R-C filter designed to simulate the body’s own passive charac-
teristics. Above, on the right, is a normal lead II electrocardiogram.
Immediately below it is the record of this electrocardiogram after it
had been passed through this filter; the marked distortion is obvious.

It has been rather clearly demonstrated that ultra-low frequency
ballistocardiographic systems largely circumvent the errors
inherent in the older methods. The ULF systems may be characterized
by the following attributes : 1) low natural frequency or « soft »
coupling to earth; 2) low platform mass; 3) minimal damping. To
this should be added a fourth at least; 4) a support structure for
the body so designed that parasitic oscillations of an extraneous
nature do not interfere.

|, MERCURY BED 2, DOUBLE PENDULUM (2-D) BED
i Bt Hh na
Hi e it
: :

a aaa
ae

es

i

i
CEE

a

Fig. 3.

Ballistocardiograms from same subject using different types of highly-compliant suspensions. Note simi-

larities. Lower two tracings, 3 and +t, were ovtained with temporary experimental suspensions in which accel-

erometers were not well mounted; this probably accounts for most of the differences between them and
tracings 1 and 2.



‘William R, SCARBOROUGH 119

the suspension of respiration. The current availability of more equip-
ment of improved types and designs should now permit more exten-
sive and definitive clinical investigations to be carried out. Even
though records in axes other than the longitudinal are imperfect
from the physical point of view, this does not mean that they may
not provide important information in clinical studies, Thusfar such
records have received almost no attention by investigators and this
would seem virgin territory.

Summary and Conclusions :

I will conclude by saying that much has been accomplished by
research efforts but more must be done in the biophysical, physio-
logic, and clinical area before the true potential of ballistocardio-
graphy can be measured. The enigma which must stimulate the
imagination of any curious investigator is the reason for the
changes which occur in the human ballistocardiogram with age;
what causes the definite decrease in amplitude with increasing age
and why the deterioration in waveform in individuals above the
age of 40? If some of the foregoing questions could be answered,
then a very large step will have been made in determining the true
significance of the ballistocardiogram in the human.

BIBLIOGRAPHY

1. GORDON, J.W. : On certain molar movements of the human body produced
by the circulation of the blood. J. Anat. & Physiol. 11 : 533, 1877.

2. HENDERSON, Y. : The mags-movements of the circulation as shown by a
recoil curve. Am, J. Physiol. 14: 277, 1905.

3. BURGER, H.C. NOORDERGRAAF, A. and VERHAGEN, A.M.W. :
Physical basis of the low-frequency ballistocardiograph. Amer. Heart J. 46:11,
1953.

4. BURGER, H.C. and NOORDERGRAAF, A. : Physical basis of ballistocar-
diography. II. The quantities that can be measured with different types of
ballistocardiographs and their mutual relations. Am. Heart J. 51: 127, January
1956.

5. BURGER, H.C. and NOORDERGRAAF, A. : Physical basis of ballistocardio-
graphy. II]. Am. Heart J. 51:179 Feb. 1956.

6. von WITTERN, W. : Ballistocardiography with elimination of the influence
of the vibration properties of the body. Amer. Heart J. 46 : 705, Nov. 1953.

7. TALBOT, S.A. and HARRISON, W.K., Jr. : Dynamic comparison of current
ballistocardiographic methods. Part I. Artefacts in the dynamically simple ballis-
tocardiographic methods. Part II. Effect of a platform in BCG dynamics.
Part III. Derivation of cardiovascular force from body motions. Circulation
Vol. XII, Nos. 4, 5 and 6, Oct., Nov. & Dec. 1955.

8. STARR, IL, RAWSON, A,J., SCHROEDER, H.A. and JOSEPH, N.K. :
Studies on the estimation of cardiac output in man; of abnormalities in cardiac
function from the heart's recoil and the blood’s impact. Am. J. of Physiol.
127: 1, 1939.



116 3¢ EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

shown rather better correlation between ballistocardiographic measu-
rements and records of the force of cardiac ejection. Of the more
recent investigators, Professor Klensch recognized that the ultralow
frequency displacement record was the one most closely related to
stroke volume and he remains the most experienced in this approach.
(OF historical interest is the fact that this was Henderson's goal,
more than 50 years ago.) The difficulties inherent in deriving a
method for computing stroke volume from the displacement record
are not to be minimized. These include the differential uptake by,
and relative sizes of, the arterial tree above and below the heart level,
the unknown values for elastic modulus of all vessels, and the lack
of a method for determining cardiac ejection velocity. In spite of
these and other difficulties, these investigations are of very real
importance because there is no method available now for recording
beat-to-beat stroke volume in large numbers of subjets without
significant risk.

Another correlation on which there has been progress is that
relating the ballistocardiogram to « cardiac force ». Reference has
already been made to Starr's cadaver ejection work in which a
high degree of correlation was found between « cardiac force »
and the high-frequency ballistocardiogram, the latter being a close
relative to the ultra-low frequency acceleration ballistocardiogram.
Correlations of this sort have also been obtained by Darby and the
South Carolina group in dogs and humans (18). Another type of
investigation should be referred to because, as yet, nothing has been
published about it (19). This was carried out through collaboration
between Drs Samuel Fox, Donald Fry and their associates at the
National Institutes of Health, and my colleagues and me now
working in the medical research facilities of the Aviation Medical
Service, Federal Aviation Agency. In this study Dr Fry's method
(20) of measuring differential pressure in the ascending aorta was
used and this measurement permitted the instantaneous computation
of the velocity and acceleration of blood flow in the ascending
aorta; the latter quantities were recorded simultaneously with an
ultra-low frequency acceleration ballistocardiogram, Although the
number of human subjects involved was small the number of experi-
mental observations was considerably larger, inasmuch as various
procedures were used to produce changes in stroke volume and
blood flow. The results yielded a surprisingly high degree of corre-
lation between the maximum acceleration of blood in the ascending
aorta and the H-I segment of the acceleration ballistocardiogram.
This work has been suspended through factors beyond our control
but it is hoped that it can be pursued in the future because it is
thought that this is an extremely fertile area for investigation. Ideally,
we would like, in the living intact man, to be able to measure instan-
taneous pulsatile blood flow at many points in the circulatory system.


106 3d EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

changes in the center of gravity are recorded. However, there are
a number of complicating factors which makes a biophysical evalua-
tion of this kind of system extremely difficult.

To sumarize my views about instrumentation, I would say the
following : rugged, reliable ultra-low frequency systems are available
for head-foot or longitudinal recording but the lack of commercial
instruments which can be obtained by competent research groups
has hindered progress; simplier, more practical, 3-D beds for clinical
work are in development but are not yet available.

Physiologic Significance of the Ballistocardiogram :

A few comments seem in order about the physiologic significance
of the ballistocardiogram. My own view is that the principal aim of
research in this area is to provide ballistocardiography with a sound
physiologic basis. Those of you who have worked in this field are
clearly aware of the difficulties which exist in quantitating, in any
exact fashion, the various determinants of the ballistocardiogram.
These determinants are multiple and are often mutually dependent;
they are often inaccessible in the human subject. Some of the
quantities which are needed cannot be obtained because no adequate
method of measurement exists, either in man or animal. Nevertheless,
the determinants which are known, or believed, to be important can
be listed. These include : 1) motion of the heart’s mass; 2) stroke
volume; 3) acceleration of blood from the heart during systole;
4) velocity of blood flow through the major arteries; and 5) size, spa-
tial orientation, and elasticity of the larger vessels. Fig. 7 shows nor-
mal ULF ballistocardiograms aligned in time with various events in
the cardiac cycle in man. Although there is a certain amount of over-
lap and mixing, three series of events in the acceleration ballistocar-
diogram are distinguishable. These are motions asociated with
1) atrial contraction and ventricular presystole (wave-tips preceding
the H wave); 2) ventricular ejection (H and successive waves to
but not including the L tip); and 3) early ventricular filling (wave
tips L, M & N). Fig. 8 shows what is considered to be a reasonably
representative normal acceleration ballistocardiogram from a dog
plotted along with measurements of the phases of the cardiac cycle,
the latter published by Moskovitz and Wilder (9). Our own
results (10), in which simultaneous ballistocardiograms and specific
events during the cardiac cycle were obtained, are similar to these.
You will note the similarity, both in general waveform and in rela-
tion to events in the cardiac cycle, of the acceleration ULF ballisto-
cardiograms in man and dog, even though in the latter the duration
of systole, and of ejection, is considerably shorter than in man. In
this record from a dog, the duration of systole is 0.22 sec. while
the interval between the H and L ware is 0.26 sec. In the previous
figure the duration of systole was 0.34 while the H-L interval was



‘William R, SCARBOROUGH 103

obtained on the same subject with four different systems, The simi-
larity among them is apparent and such differences as do exist pro-
bably relate more to the manner in which the accelerometer was
coupled to the supporting system than to the characteristics of the
system itself. Fig. 4 shows a differential-pendulum bed design which
permits the recording of head-foot and lateral (side-to-side) motions-
displacement, velocity, and acceleration. This bed has been proven
rugged and reliable through five or six years of routine work. Fig. 5
shows displacement, velocity, and acceleration records obtained with
it from three normal subjects; this illustrates some of the individual

Fig. 5.
Normal ULF ballistocardiograms from three young females. Baselines ae drawn in to indicate the manner in which
they are placed. (Courtesy American Journal of Cardiology.)

variation normally observed. Fig. 6 shows the simultaneously recorded
displacement and acceleration ballistocardiograms in the head-foot
and lateral axes in one subject. There is ample reason to believe that
the records in the longitudinal axis are relatively free of distortion but
this probably is not the case for the lateral records from beds which
do not permit « roll » (rotation about the longitudinal or y axis).
The evidence indicates that the records in the lateral mode represent
a mixture of rotations and translations.

In an attempt to eliminate distortion of the type referred to
above, efforts have been made to develop ULF-BCG systems with
multiple degrees of freedom, each independent of the other. Talbot's
3-D (three directional) bed is an experimental one and is quite
complicated, but it does permit the recording of three translations



102 8d EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

A variety of methods for attaining suitable performance charac-
teristics has been used. These include very long simple pendular
systems, shorter simple pendular systems with lateral offsets (similar
to Henderson’s original design), differential-pendulum systems with
balancing legs, horizontal-pendulum systems of the « swinging door »
variety, floatation in mercury or other liquids (these have been
experimental only), « airbearing » systems (*), and others of mixed
mechanical design. Fig. 3 illustrates acceleration ballistocardiograms

nese coo Are view oo
TENS 7 SSS SS SATS TT i / 7
// MeL LO) A
—— |___Plettorm
CO =a
= ALAS _ tee
L//. T/L /\s [fe
LSI TT RTT ITT TT TA i *
rane | Sp ae wew ge Opt ;
Ase. wire —
min Ho
KP roses,
Bolt ToT ]h}
daha?
TIT
oe
} EM Frome
3
io 7/11)
/] D DETAIL OF LEG
Ces SIDE VIEW
Fig. 4.

Diagrams of the constcuction of the differential-pendulum ULF bed. Portions of the wooden

frame are indicated in A, C, and D but are not included in B for reasons of clarity. Symbols :

L : differential-pendulum leg; Lb : legs used for balancing platform; R : restraint rod to

prevent lateral motion; FB : footboard; Acc : accelerometers; P : platform; EM : electro-

magnetic transducer; SP : suspension point for platform; D : dampers; CC : rubber pads with

grooves for seating the postero-lateral chest constraints. (Courtesy American Journal of Car-
diology.)

(*) A bed based on this principle is now commercialy available in the
United States from the Cordis Corporation, 241 N.E. 36th St., Miami 37, Fla.
In Europe, two types of beds based on different principles are being produced
commercially.


‘William R, SCARBOROUGH 117

While a great deal of progress has been made in the last two years
in the development of electronic flow meters, work with them has
been, for the most part, limited to use in animals. There is as yet
only Fry's method for use with intact humans, Further technical
advances in the future may make it possible to more nearly approach
the ideal requirements in the human.

One final short comment is in order pertaining to animal work.
Physiologic studies in animals have been undertaken by several
groups in an effort to provide a sound physiologic basis for ballisto-
cardiography because it is possible in animals to make measurements
of a sort not generally possible in humans. It is unfortunate, but true,
that work in this important area has thusfar been so limited that
no really sizable contribution has been made. My associates and I
at the Johns Hopkins Hospital carried out work on animals for
several years about which very little has been published. Early in
this work we were forced to the conclusion that ballistocardiograms
from dogs under general anaesthesia and on artificial respiration
were inconsistent in wave-form and showed marked variations from
time to time. This forced us to turn attention to the origin of the
« abnormality » of the dog ballistocardiogram. The results of these
studies, which have been reported (12), suggest that these altera~
tions are a consequence of anaesthesia and artificial respiration, both
of which appear to conspire to produce rather marked circulatory
derangement. Candid appraisal of the contribution made by our
group in animal investigation is, that if any contribution were made
at all, it was most modest. However, three groups in Europe that
have impressed us with the quality of their work; these include
Professor Hoitink and Drs Knoop and Pretorius, in Amsterdam
and Professor Klensch, in Bonn. The third is Dr Manuel Moreira
at the University of Porto, Portugal; Dr Moreira’s work is not
known to many but an Englisch translation of his original Portu-
guese monograph is now available.

To summarize these few comments concerning physiologic work
in the animal, I would like to reiterate that I feel this work is quite
important and it needs greater emphasis in the future.

Clinical Investigations :

Time and space do not permit more than a mere mention of
clinical investigations in this field. In a review of ballistocardiography
published 10 years ago (21), I expressed the opinion that ballisto-
cardiography would probably prove most useful as a clinical tool
for the diagnosis and prognosis of non-valvular heart disease. This
opinion was based on the facts : 1) that patients with this kind of
disease frequently demonstrated ballistocardiographic abnormalities
while the results obtained with other methods were often normal or
non-specific and 2) that in patients with congenital or valvular heart



William R. SCARBOROUGH

'
J
5
A A f /
KT He H
6
e I
1 y j
Myo
\
Pa
ry |
'F |
v /\ 5
6 LA
1 ammpes.
|
|
4 i
\
|
N | MN
" "rT i
D Go nm i
Y lt
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. ppt
if !
1 Low
‘sec.
Phono / }
Sq 3s
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1
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Lt. Heart T
[Atrial jast ole|
Rt Heart H

Fig. 7.
Normal human displacement (D), velocity (V) and acceleration (A)
ballistocardiograms from an ultra-low frequency (ULF) system and
their temporal relation to events in the cardiac cycle. The BCG, heart
sounds (phono), and ECG tracings were based on the measurements
form 25 males, 20-29 years of age. The block diagrams at the bottom
represent the timing of cardiac events on the two sides of the heart
and are based on data supplied by Braunwald and by Wiggers (see
text). IC = isometric contraction (Crossed-hatched), E = ejection
phase (solid black), RF = rapid filling, and D = diastasis. Cali-
brations for the three ballistocardiograms are shown on the right.
mG represents milli-G; 1.0 mG (0.001G) is approximately equal to
1.0 cm/sec2; , represents micron; 20 y, is equal to 0.02 mm. (Courtesy
American Journal Cardiology.)



AM 64-12

COMMENTS ON
PROGRESS IN BALLISTOCARDIOGRAPHIC RESEARCH

AND THE CURRENT STATE OF THE ART

by William R. Scarborough, M.D.

Reprinted from Proceedings of the
3rd EUROPEAN SYMPOSIUM FOR

BALLISTOCARDIOGRAPHY
Belgium, 1962



108 3a EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

balistocardiogram which is « normal » resembles a normal human
record and that when the dog’s acceleration ballistocardiogram no
longer resembles that in young normal humans, it is likely that some
derangement in circulatory function has occurred, possibly as a
consequence of the anaesthetic used, the nature of respiration, and
the duration of the experiment (12). During a given experiment in
a dog, it was found that while the initial records may be large and
resemble the human ballistocardiogram in wave-form, yet as the
experiment progressed but with no change whatsoever in the condi-
tions of the experiment, there was often marked deterioration in
wave form. In many of these cases the application of abdominal
contpression resulted in restoration of the normal wave-form. It
seems apparent that the changes described represent acute and very
real circulatory changes and it seems unlikely under these conditions
that the alterations could be accounted for by the position of the
dog on the BCG bed itself. I understand that Drs. Knoop and
Pretorius will have another explanation to account for the diffe-
rences between ballistocardiograms obtained on men and dogs.
Fig. 9 shows a simplified schematic outline of the circulation in
the human. This simply shows the circulatory system divided into
three lumped regional beds, the cerebral, the abdominal and the
lower extremity. The sizes of the round or oval « beds » in this
diagram were drawn to be roughly proportional to the relative
quantity of total cardiac output going to these three regions. The
displacement ballistocardiogram is a reflection of the mass-motions of
the body and its support and this in turn is proportional in magnitude,
but opposite in direction, to the mass-motions occurring internally,
within the cardiovascular system. The internal mass-motions are
obviously an algebraic sum of all of the internal motions of blood,
so there is a certain degree of mutual cancellation by the uptake of
blood in footward and in headward vascular beds. What this implies
is that the size and shape of the normal ULF ballistocardiogram is
determined by the spatial and temporal distribution, during the
whole cardiac cycle, of the mass of blood ejected during each systole.
(Spatial distribution, in this connection, is confined to the longitudinal
axis since the validity of records taken along the other two axes is
still questionable). Although there is the usual individual variability
as in all biologic measurements, the consistency in magnitude and
wave-from of the ULF ballistocardiograms from young, healthy
individuals suggests that systolic stroke volume is distributed through
the circulatory system in space and time in a similar fashion among
these persons, When the ballistocardiogram from a single individual
is abnormal, presumably reflecting abnormal changes in the «pattern»
of distribution of blood mass, to what factor or factors may this be
attributed ? Here, we are groping in the dark on uncertain terrain.
It is known that such abnormal alterations in distribution do
occur as a result of certain marked structural and functional changes


William R, SCARBOROUGH 107

0.33 sec. Systole is shorter in the dog but so is the duration of the
systolic ballistic complex; thus the relationship between specific
ballistic waves and the events which mark the onset and termination
of ventricular contraction is retained. In the humans there is a highly
significant correlation between the H-L interval and the duration of
systole; there are, however, systematic differences when men and
women are considered separately (11). With respect to the dog
ballistocardiogram, our impression remains that, in general, a dog

a
UF-BCG
DOG
N
FA
Ejection
iastole
on A
k-0.1 Sec}
V ees V

Fig. 8.

Representative normal ULF Acceleration Ballistocardiogram from a Dog

and associated events of the Cardiac Cycle. Timing of right and left
sided cardiac events from data by Moscovitz and Wilder.



104 8d EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

and three rotations independently (14). Such a bed has been dupli-
cated in no other laboratory with which I am familiar and a rugged
tri-directional design which is relatively simple to operate is yet to
emerge. This is a long-sought-for hope for the future, as is a
design which permits upright, sitting or standing recordings which
allow a study of circulatory function under normal gravitational
forces.

Finally, one other specific design should be referred to and this
is the system described by Babskii and his Russian colleagues (15).
This is a chest support device which behaves as though there were
a small bathroom scale under each of four corners. The pressures
applied to these scales are recorded in such a way that longitudinal

Fig. 6.
Simultaneous head-foot displacement (HF-D) and acceleration (HF-A) records and
lateral displacement (LAT-D) and acceleration (LAT-A) records. From a young normal
female. Polarity of the tracings is indicated by the arrows. (Courtesy American Journal of
Cardiology.)


120

10.
MW.

19.

20.

21.

8d EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

. MOSCOVITZ, H.L. and WILDER, R.J. : Pressure events of the cardiac

cycle in the dog : Normal right and left heart. Circulation 4: 574, 1956.
SCARBOROUGH, Wm. R. : Unpublished observations.

SCARBOROUGH, Wm. R., SMITH, P.M. and FOLK, E.E. III : Unpublished
observations.

. SCARBOROUGH, Wn. R. : Some circulatory effects of morphine-barbiturate

anaesthesia, artificial respiration, and abdominal compression based on ballisto-
cardiographic observations on dogs. With a review of pertinent literature.
Am. Heart J. 54: 651 Nov., 1957.

. ELSBACH, H. : Klinische Onderzoekingen met de laag-frequente ballisto-

cardiograph volgens Burger (Clinical Investigations with the low-frequency
ballistocardiograph according to the method of Burger). Monograph in Dutch
with English summary. Uitgeverij Excelsior - s’ Gravenhage (1954). English
Translation by Roger D. Freeman re-edited by Wm. R. Scarborough, 1956.

. TALBOT, S.A. : Physical principles of vector ballistocardiographic measure-

ment. ARDC Technical Report TR 58-72, ASTIA Document No. 158301,
June 1958,

. BABSKII, E.B. : The technique and some results of the investigation of the

mechanical manifestations of heart action in man in the normal and pathological
states. Biophysics 2:20, 1957.

. BABSKII, E.B. and KARPMAN, V.L. : The differences of principle between

ballistocardiography and dynamocardiography. Biophysics 3: 563, 1958. (Ori-
ginal Russian Reference : Biofizika 3 : 596, 1958.)

BABSKII, EB, VENEDIKTOV, A.B.. KARPMAN, V.L. and TISH-
CHENKO, MI. : The dynamiocardiograph. Biophysics 5:703, 1960. (This
journal is cover-to-coover translation from the Russian original reference :
Biofizika 5 : 620, 1960.)

. DARBY, T.D,, WALTON, R.P. and GAZES, P.C. : Effects of drugs on

ballistocardiographic recordings. Amer. J. Cardiol. 3 : 668, 1959.

FOX, S.M., III, WARBASSE, J.R., CRAWFORD, R.B., GREENFIELD, J.
and SCARBOROUGH, Wn. R. : Studies in instantaneous ascending aortic
blood velocity in intact man relative to the acceleration ballistocardiogram.
Presented before the Ballistocardiographic Research Society, April 29, 1961,
Atlantic City, New Jersey.

FRY, Donald L. : The measurement of pulsatile blood flow by the computed
pressure gradient technique. I.R.E. Transactions on Med. Electronics ME-6:
259, 1959. (Presented at a Blood Flowmeters Symposium, June 17-19, 1959,
Univ. of Nebraska, Coll. of Med., Omaha, Neb.)

SCARBOROUGH, Wn. R., DAVIS, F.W.., Jr. BAKER, B.M., Jr, MASON,
RE. and SINGEWALD, MLL. : A review of ballistocardiography. Amer.
Heart J. 44:910, 1952.



100 3d EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

damping and shows the frequency-response characteristics of a Starr
high-frequency bed, a Nickerson low-frequency bed, and a « direct-
body » (shin pick-up type) system. With the « direct-body » and
Starr systems there is a large resonance peak in the vicinity of 5
cycles/second, with marked attenuation thereafter. For the Nickerson
method there is a loss of most of the high-frequency components.
The effects of the distortion introduced by these systems is
illustrated by the next diagram which simply shows what would
happen if the electrocardiogram were distorted in a way similar to
that in which the internal cardiovascular forces are distorted by the
older classical methods of ballistocardiographic recording. Fig. 2,

Peer re re

Thru. Filter
Network.

Fig. 2.

Simulation by R-C-L- filter of distortion introduced by body's « Dorsal Spring ». This

filter was designed to demonstrate the appearance of an ECG if it were distorted in the same

way as internal cardiovascular forces are distorted if body's support is too stiff and/or

heavy. At bottom : F.R.C. curve of the filter: note similiarity to D.B. in Fig. 1. At top, right :

At the extreme top is a standard ECG lead and immediately below it is the same lead after
it is run through the R-C-L filter; the marked distortion of the latter is evident.


‘William R, SCARBOROUGH M1

filter, as Elsbach pointed out earlier (13). The records on the right
in Fig. 10 show the return to a normal ballistocardiographic confi-
guration with re-establishment of normal aortic filling and distri-
bution after the obstruction had been eliminated. This kind of alte-
ration as been produced in our laboratory on dogs and Professor
Klensch has simulated it in hydraulic models.

Fig. 11.
ULF ballistocardiograms (D. V and A) from a normal subject (A) and a patient (B) who
sustained a myocardial infarction in the past. The men were comparable in age, weight and
habitus, Calibration is the same for both. All three headfoot records in B are abnormal and
are quite different from the normal records in A, both in amplitude and waveform. (Courtesy,
Progress in Cardiovascular Diseases.)

Mention has already been made of the multiple variables which
play a part in the genesis of the ballistocardiogram. One of the
difficulties in the clinical interpretation of the ULF ballistocardiogram
lies in determining which of the variables is responsible for observed
alterations. In Fig. 11 are shown the ULF ballistocardiograms from



William R, SCARBOROUGH NS

and Michael Taylor. These have permitted correction for the
« sleeve effect » at the vessel wall and for the effect of anomalous
viscosity. Limited time does not permit a further digression into
this new and fascinating work. However, it may be said that this

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Fig. 13.

Noordergraaf’s computed ULF Ballistocardiograms (left) compared with ULF Records

from normal Subjects (rights). No calibration shown for records on right; for compa-
rison of amplitude values see Fig. 7.

new analog is one of almost incredible sophistication by curreat
standards but it will require further development to more closely
simulate the human circulatory system. In order to improve it further,
a considerable body of data, anatomic and physiologic, must be
accumulated of a kind not now available. It is expected that this
type of work will be quite productive in the future.

A few other research results must be touched on and these
relate to correlations between the ballistocardiogram and various
aspects of cardiovascular physiology. Dr Starr's early work dealing
with the calculation of cardiac output with measurements made on the
ballistocardiogram is well known (8). His more recent work has



William R, SCARBOROUGH 99

many years later as a consequence.of the rigorous physical analyses
by Burger and his group (3-5), by von Wittern (6) and by Talbot
and Harrison (7). As is known to all of you here, the efforts by
the early investigators were not sustained and it remained for
Starr (8) with his development of the rugged, reliable high-frequency
bed to excite the continued interest of investigators in this field.
Dr Starr recognized at the outset that the records from this bed
were distorted but, and I think rightly, he chose to use it, for it per-
mitted him to study a large number of subjects with many different
kinds of disease states. The results of the several physical analyses
referred to already can be rather briefly summarized. and illustrated
in fig. 1, This demonstrates the distortion which is due to the stiff
coupling to « ground », heavy platform mass and/or excessive

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5 = fe He He
fri i
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Fig. 1.

Frequency Response Characteristics (F.R.C.) for 3 Ballistocardiographic Systems. N :

Nickerson low-frenquency. S : Starr high-frequency. D.B. : « Direct-body » (with stiff

footboards). Displacement amplitude values when applied force is held constant but varies
in frequency.



Comments on progress in ballistocardiographic
research and the current state of the art (*)

by William R. SCARBOROUGH, M.D. (**)

Introduction :

I would like to express my pleasure at being able to attend,
for the first time, your society and to discuss with you the type of
cardiovascular research which is of interest to us all. During the
last few years, I have been impressed and greatly gratified at the
volume and quality of work relating to ballistocardiography which
has been carried out in Europe. My remarks during this discourse
will be of a general nature and will concern what I feel to have been
significant advances in the field. I propose to indicate those areas in
which it seems to me more research effort is needed. I cannot, of
course, include the more recent work you have been doing in Europe
but by the end of this meeting I hope to be better informed about it.

Instrumental Considerations :

First, I would like to turn to instrumental considerations. In an
earlier paper, Dr Starr discussed the history and development of
ballistocardiography and therefore I need not repeat the evolution
of the method. However, I would like to emphasize the fact that the
two earliest « adventurers » in this field, Gordon (1) in 1877 and
Henderson (2) in 1905, intuitively selected methods for supporting
the human body which were the proper ones, a fact which emerged

(*) Presented before the Society for Ballistocardiographic Research in Brussels,
Belgium, on April 16, 1962 (Third Symposium).

From the Georgetown Clinical Research Institute, AM-12, Aviation Medical
Service, Federal Aviation Agency, Wash. 25, D.C. and the Georgetown University
Medical Center, 3800 Reservoir Rd., Wash. 7, D.C.

Supported in part by a research grant (H-327) from the National Heart
Institute, National Institutes of Health, U.S. Public Health Service.

(**) Medical Officer (Cardiovascular Disease-Research) Georgetown Clinical
Research Institute, Aviation Medical Service. Clinical Asst. Prof. of Med., George-
town Univ. Sch. of Med., Wash. D.C.


‘William R. SCARBOROUGH 109

Fig. 9.
Diagram of the circulation to represent direction and
distribution of blood flow. The systemic arterial system
is in black, the venous and pulmonary arterial system
in white. The size and shape of the cardiac chambers
and intra-thoracic vessels were based on angiocardio-
graphic measurements. Estimated distribution of blood
flow to various parts of the body is represented by round
or ovoid « lumped » vascular beds. (Courtesy American
Journal Cardiology.)

in the circulatory tree. In coarctation of the aorta, nature has
designed an experiment to demonstrate this point. Fig. 10 shows
the pre- and post-operative records on a young man who had this
condition. The records on the left were taken prior to resection of



112 3d EUROPEAN SYMPOSIUM FOR BALLISTOCARDIOGRAPHY

two subjects similar in age, body size, and weight; the only diffe-
rence between the two is that the records in «A» were from a
normal individual while those in «B» were from a patient who
had sustained a myocardial infarction at an earlier date. The cali-
bration in the two sets of records is the same so that they are directly
comparable in amplitude. The differences between these two sets of
records are obvious, even to anyone not familiar with tracings of
this kind. Knowing that this man had sustained a myocardial infarc-
tion in the past, can one assume that the abnormalitites manifested
by the ballistocardiogram are necessarily a result of altered cardiac
ejection consequent to impaired coronary circulation? While this
may, in fact, be true, it seems an unjustified assumption. If there is
atherosclerosis of sufficient degree to produce severe coronary arte-
rial disease, one might also expect a considerable degree of athero-
sclerosis throughout the remainder of the arterial tree. This being
the case, it is likely that changes in the elastic properties of the
vessel walls have taken place. Therefore, in this case, it is not
clear which of the factors, cardiac ejection force or arterial elasticity,
is responsible for the observed changes, although the former seems
more likely. In dogs, if the main left coronary artery is suddenly
ligated, the dog ballistocardiogram very promptly deteriorates and
disappears within a short period of time (10). This could be used
as an argument that the abnormal ballistocardiograms in the 37 year
old man with an old myocardial infarct is due, in fact, to deficient
coronary blood supply. However, the two cases are not comparable.
The human patient had fully recovered from his infarction; acute
occlusion of a major coronary artery in the dog causes a very
prompt drop in systemic arterial pressure to shock levels, diminution
of cardiac contraction and ultimate cardiac standstill. This is such
an acute and severe derangement of the circulation that it cannot
be compared with the case of the man with an old infarct. Therefore,
some doubt remains as to the basic cause of the abnormal ballisto-
cardiogram in this man.

The solution to some of these perplexing problems regarding the
factors responsible for normal and abnormal ballistocardiograms in
man has been sought by attempts to simulate the circulatory system
in various ways. One method which has been used is that of hydraulic
models. Professor Klensch’s group has had considerable experience
with them but they have been used by other groups, as well. These
studies have unquestionably contributed important information to
our basic knowledge. However, there are a number of difficulties,
some quite large, in simulating the human circulatory system. One
of the most difficult problems is to find a tubing-material with the
proper elastic properties which may be used to make a model with
proper junctions, branchings, and changes in taper. Such models are
rather difficult to work with since it is necessary to change its
characteristics at will; without instruments of proven precision for