U.S. patent number 3,908,639 [Application Number 05/403,202] was granted by the patent office on 1975-09-30 for detecting impaired heart mechanical performance.
Invention is credited to Kevin M. McIntyre.
United States Patent |
3,908,639 |
McIntyre |
* September 30, 1975 |
Detecting impaired heart mechanical performance
Abstract
A pressure-sensitive device contacts the skin of a patient near
an artery noninvasively to provide a signal representative of
systemic arterial blood pressure both before and after a Valsalva
Manoeuvre. This blood pressure signal is differentiated, and the
changes in amplitude before and during the Valsalva Manoeuvre
detected to indicate potential left ventricle failure when the
change is to less than a predetermined value. Signals
representative of pulse pressure, the mean systemic arterial blood
pressure, heart rate and left ventricular ejection time are also
provided to facilitate detection of impaired mechanical performance
of the heart.
Inventors: |
McIntyre; Kevin M. (Jamaica
Plain, MA) |
[*] Notice: |
The portion of the term of this patent
subsequent to December 4, 1990 has been disclaimed. |
Family
ID: |
26828601 |
Appl.
No.: |
05/403,202 |
Filed: |
October 3, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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130572 |
Apr 2, 1971 |
3776221 |
Dec 4, 1973 |
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Current U.S.
Class: |
600/485;
600/508 |
Current CPC
Class: |
A61B
5/7239 (20130101); A61B 5/022 (20130101); A61B
5/0205 (20130101) |
Current International
Class: |
A61B
5/0205 (20060101); A61B 5/022 (20060101); A61b
005/02 () |
Field of
Search: |
;128/2.5A,2.5D,2.5E,2.5F,2.5G,2.5M,2.5N,2.5P,2.5Q,2.5R |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
George et al., "Medical Research Engineering," 4th Qtr., 1967, pp.
21-24..
|
Primary Examiner: Kamm; William E.
Attorney, Agent or Firm: Hieken; Charles Cohen; Jerry
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation in part of my copending
application, Ser. No. 130,572 filed Apr. 2, 1971, and now U.S. Pat.
No. 3,776,221, dated Dec. 4, 1973.
Claims
What is claimed is:
1. A method of detecting mechanical heart impairment which method
includes the steps of,
noninvasively providing a blood pressure signal representative of
blood pressure by placing pressure sensitive means in contact with
the skin of a patient near an artery,
differentiating said blood pressure signal,
subjecting said patient whose blood pressure is characterized by
said pressure signal to a heart straining manoeuvre,
detecting the change in the amplitude of the differentiated
pressure signal after initiating said straining manoeuvre from its
amplitude before said manoeuvre,
and determining a probable mechanical impairment of the heart when
the amplitude is not changed to a predetermined extent.
2. A method of detecting mechanical heart impairment in accordance
with claim 1 wherein said detection of change in amplitude of the
differentiated pressure signal after initiation of said manoeuvre
is made with respect to a diminution, if any, of said amplitude
before completion of said manoeuvre.
3. A method of detecting mechanical heart impairment in accordance
with claim 2 wherein said heart straining manoeuvre is a Valsalva
manoeuvre.
4. A method of detecting mechanical heart impairment in accordance
with claim 3 wherein said Valsalva manoeuvre is involuntarily
induced in said patient.
5. A method of detecting mechanical heart impairment in accordance
with claim 2 and further including the steps of providing signals
representative of systemic peak pressure, systemic mean pressure,
heart rate, and left ventrical ejection time both before and after
said manoeuvre and sensing the differences between respective
signals before and during said manoeuvre.
6. A method of detecting mechanical heart impairment in accordance
with claim 2 which method includes the steps of,
recording the differentiated blood pressure signal so that its peak
amplitude before said manoeuvre is related to a predetermined
control line,
and observing the amplitude of said differentiated blood pressure
signal during said manoeuvre relative to a predetermined normal
limit line spaced below said control line to determine potential
mechanical impairment when the peak amplitude during said manoeuvre
is above the normal limit line and no mechanical impairment when
below said normal limit line.
Description
BACKGROUND OF THE INVENTION
The present invention relates in general to detecting impaired
mechanical performance of the heart and/or cardiac failure, and
more particularly concerns novel apparatus and techniques for
detecting such potential impairment in a reliable manner through
external measurements.
Since the introduction of aortic valvotomy, the assessment of
aortic valve disease has become increasingly important. One
approach to such an assessment involves studying recorded arterial
pressure pulse tracings. Stenosis is the narrowing of a blood
passage, such as the pulmonary artery or aortic valve. One approach
to studying stenosis is the so-called Valsalva Manoeuvre. The
patient's blood pressure is recorded prior to holding his breath.
Then the patient holds his breath and releases it while recording
continues.
Reference is made to an article in 19 BRITISH HEART JOURNAL
525-31(1957) entitled THE VALSALVA MANOEUVRE IN AORTIC VALVE
DISEASE by Doyle and Neilson, a copy of which is in the file
history of the application. The article states that neither
systolic upstroke time nor pulse pressure alone correlates well
with the severity of stenosis and that the shape of the pulse
derived during Valsalva Manoeuvre is an unreliable guide to the
relative dominance of stenosis or incompetence. That article
concludes that variations in pulse pressure during the Valsalva
Manoeuvre or in atrial fibrillation and variations of upstroke time
in the same pulses do have a linear relationship to the severity of
stenosis when stenosis is present alone.
It is an important object of this invention to provide improved
techniques for detecting left ventricular impairment.
It is a further object of the invention to achieve the preceding
object with techniques that permit detection by relatively
unskilled personnel.
SUMMARY OF THE INVENTION
According to the invention, the time derivative of the systemic
arterial pulse pressure is established at a control level in the
subject patient. Then the patient performs a straining manoeuvre,
such as a Valsalva manoeuvre, while recording the time derivative
of the systemic arterial pulse pressure signal. Preferably, the
systemic arterial pulse pressure, mean pressure, heart rate and
left ventricular ejection time are also established and may be
interpreted so that the presence or absence of impairment in the
performance of the left ventricle may be detected. Specifically,
the time derivative of systemic arterial pressure responds in a
characteristic fashion in the presence of heart impairment; the
other parameters are useful in defining the expected normal
response of the time derivative of this pressure. Diminution of
said time derivative relative to a control during the manoeuvre
and/or increase of said time derivative relative to a control after
said manoeuvre are detected and evaluated in light of the other
parameters as determinants of probable mechanical impairment.
Numerous other features, objects and advantages of the invention
will become apparent from the following specification when read in
connection with the accompanying drawing in which:
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a graphical representation of stroke volume as a function
of end-diastolic pressure of the left ventricle during a Valsalva
manoeuvre helpful in understanding the phenomena with which the
invention is associated;
FIG. 2 is a block diagram illustrating the logical arrangement of a
system according to the invention which includes means for
detecting left ventricle mechanical impairment;
FIGS. 3 and 5 are graphical representations of time derivative of
pressure waveforms helpful in understanding the operation of the
invention; and
FIGS. 4A and 4C are graphical representations of typical peripheral
arterial pulse waveforms generated during Valsalva Manoeuvre in the
presence and absence, respectively, of heart impairment and
FIGS. 4B and 4D are graphical representations of time derivatives
of the 4A and 4C waveforms, respectively.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
With reference now to the drawing, and more particularly FIG. 1
thereof, there is shown a graphical representation of stroke volume
as a function of end-diastolic pressure in the left ventricle
during a Valsalva manoeuvre. Curve 11 illustrates this relationship
for a normal left ventricle. Point 1 represents the normal stroke
volume and end-diastolic pressure immediately prior to the patient
holding his breath. As the patient holds his breath and makes a
forceful expiratory effort without allowing air to escape from his
lungs (equivalent to straining at stool), both pressure and stroke
volume decrease along curve 11 to point 2 when the patient releases
his breath. Stroke volume and end-diastolic pressure then begin to
increase rapidly until point 3 is reached. This analysis indicates
that the time derivative of the pressure signal of a healthy
patient will increase significantly when he releases his breath.
Since other changes occur during the Valsalva manoeuvre which may
on occasion independently influence the response of stroke volume
and the time derivative of pressure, the influence of such changes
as heart rate and left ventricular ejection time are also
measured.
Curve 12 is the curve illustrating the relationship between stroke
volume and end-diastolic pressure of the left ventricle of a person
having left ventricle mechanical impairment. Point 1' is just
before the patient holds his breath. He then makes a forceful
expiratory effort without allowing air to escape. This initial
pressure (EDP) is somewhat higher and the initial stroke volume
(SV) usually somewhat lower than for a normal person, then
decreases to point 2' shortly before the breath is released. When
breath is released, the blood which was prevented from returning to
the heart does so at an increased rate, causing an increase in
end-diastolic pressure. During the positive pressure phase,
pressure generated in the chest exceeds the pressure of returning
blood.
In a patient with mechanical impairment of the heart, no increase
in stroke volume occurs with a rise in end-diastolic pressure
(position 3'), and this is detectable by a failure of the time
derivative of the systemic arterial pulse pressure to increase. The
range of changes which occur are acceptable in the individual
patient depending to some extent on changes in other parameters,
such as heart rate and left ventricular ejection time.
Referring to FIG. 2, there is shown a block diagram illustrating
the logical arrangement of a system according to the invention.
Basically the invention senses a recovery derivative signal to
indicate left ventricular impairment when this amplitude is equal
to or less than a predetermined value. To this end the invention
may include a number of different sources of a pressure signal. One
such source may be a piezoelectric pulse pick-up 11, an impedance
plethysmograph 12 or a sphygmomanometer 13 whose pressure signal is
converted by transducer 14 into an electrical signal that is
delivered to amplifier means 15. Each of these sources is a
pressure sensitive means noninvasive of the human body and derives
a signal from contact with the skin surface near an artery.
Amplifier means 15 includes means for amplifying one of the
selected pressure signals and providing the amplified pressure
signal to differentiator 16 that provides a differentiated pressure
signal for analysis.
The apparatus also may include computer analysis control recovery
means 21, which may receive a pressure signal from amplifier means
15 and a computer analysis control recovery means 22 for responding
to the time derivative pressure signal provided by differentiator
16. Computer analysis control recovery means 21 preferably responds
to heart rate, systemic arterial pulse pressure, peak systemic
pressure, systemic mean pressure and left ventricular ejection time
so that changes in these latter parameters may be used to more
accurately define the predicted normal range for the time
derivative of systemic arterial pulse and to provide a 1 signal to
indicate a condition consistent with left ventricular mechanical
impairment and a 2 signal to indicate a signal inconsistent with
left ventricular mechanical impairment. Similarly computer analysis
control recovery means 22 provides a 1 signal consistent with left
ventricular failure and a 2 signal consistent with no failure.
These 1 signals are applied to an AND gate 23 which provides an
output to indicate left ventricular mechanical impairment, and the
2 outputs are applied to the legs of a second AND gate 24 that
provides an output to indicate no ventricular failure.
The invention may also comprise write-out means 25, which may be a
graphical recorder whose output may be manually analyzed or appear
on calibrated paper that automatically displays the presence or
absence of mechanical impairment.
Referring to FIG. 3, there is shown three pairs of pulses that
might be recorded during the course of a Valsalva manoeuvre. The
first pair of pulses 31 occurs prior to holding the breath. The
gain of amplifier means 15 is then adjusted so that the peak of the
time derivative pressure waveform just reaches the control line 32
with its baseline adjusted to 31A. After the breath is released, if
the pulses have a height, such as that of pair 33, that is less
than level 34, left ventricular mechanical impairment is probable.
If they have a height greater than level 34, such as that of pulse
pair 35, there is no left ventricular impairment.
If the height is less than level 34, such as that of pulse pair 33,
then the heart rate signals, systemic pulse pressure signals, peak
systemic pressure signals, mean systemic pressure signals and left
ventricular ejection time signals are subjected to further computer
analysis to determine the extent to which certain of these
parameters may independently alter the time derivative signal. For
example, if changes in heart rate, the systemic arterial pulse
pressure, mean pressure, systolic peak pressure and left
ventricular ejection time are greater than a predetermined level, a
second independent reanalysis of the pressure derivative signal is
provided which takes into account the possible influence of changes
in the latter parameters on the time derivative of pressure. Such
an analysis is unlikely to be required in routine use but will
improve the accuracy of the instrument.
Details of the various elements of the system represented by the
boxes have not been described to avoid obscuring the principles of
this invention and because such elements are known to those having
ordinary skill in the signal analysis art.
For example, heart rate is readily determined by a digital counter
whose count is compared by known techniques with a predetermined
reference count equal to a control heart rate. The other two
pressures may be readily determined by analog comparison techniques
or by first converting these signals to digital values and making
the comparison digitally.
While the above embodiment of the invention contemplates utilizing
both derivatives and other signals in sensing for mechanical
impairment of the heart, the derivative signal itself provided by
differentiator 16 is most significant. Those skilled in the art
might also determine the derivative by analyzing the pressure
signal.
An advantage of differentiating before analyzing is that shifts in
d-c pressure levels are essentially removed so that the resultant
output signal waveform clearly represents a manifestation of the
change in rate of pressure as a function of time to facilitate
diagnosing left ventricular impairment.
Referring to FIGS. 4A-4D, phenomena involved according to another
important aspect of the invention may be explained. The single
curves of each of these figures have a common time x-axis taken
over a period encompassing the initiation and release of strain
pursuant to a Valsalva manoeuvre, recovery therefrom and periods
just prior to initiation of strain and following the beginning of
recovery. FIGS. 4A and 4C have curves 111 and 112, respectively,
which exemplify typical peripheral arterial pulse measurements for
patients with normal and impaired hearts, respectively. During the
time period A, the normal and impaired hearts produce similar pulse
measurements. During the following period B, which includes at
least the latter half of the manoeuvre, the normal heart produces
progressively and markedly reduced pulse amplitudes relative to the
amplitude initially induced during period A by the onset of strain.
In the next subsequent period C, the normal heart produces at least
some pulse peaks higher than the peaks measured before strain onset
in period A. The impaired heart produces and maintains the new
higher amplitude throughout the strain time with little or no
diminution in period B. The recovery transition of the impaired
heart in period C is unaccompanied by significant higher peaks
compared to those preceding strain in period A.
Waveforms 121 in FIG. 4B and 122 in FIG. 4D are time derivatives of
curves 111 in FIG. 4A and 112 in FIG. 4C, respectively. Diminution
of peak height of 121 in period B for the normal heart and the
essential absence of such diminution of peak height of curve 122
for the impaired heart provides a highly sensitive determinant of
impairment, usable in addition to or in lieu of comparative
behavior in periods A and C as described above in connection with
FIGS. 1, 2 and 3.
The apparatus cited above in connection with FIG. 2 may be
employed. The same patient preparation, apparatus manipulation and
data acquisition techniques may be used. The data evaluation taught
above in connection with FIG. 3 is however substituted or
supplemented as follows.
Referring to FIG. 5, there is shown three pairs of time derivative
pulses that might be recorded during the course of a Valsalva
manoeuvre. The first pair of pulses 131 occurs prior to holding the
breath. The gain of amplifier means 15 (FIG. 2) is then adjusted so
that the peak of the time derivative pressure waveform just reaches
or slightly exceeds control line 132 with its baseline adjusted to
131A. During the manoeuvre if the pulses have a height such as that
of pair 133, that is about the same as pulses 131, left ventricular
mechanical impairment is probable. If they have a substantially
lower height such as that of pulse pair 135, there is no left
ventricular impairment. A control level 134 may be established. If
the peak height is greater than level 134, such as that of pulse
pair 133, then the heart rate signals, systemic pulse pressure
signals, peak systemic pressure signals, mean systemic pressure
signals and left ventricular ejection time signals are subjected to
further computer analysis to determine the extent to which certain
of these parameters may independently alter the time derivative
signal. For example, if changes in heart rate, the systemic
arterial pulse pressure, mean pressure, systolic peak pressure and
left ventricular ejection time are greater than a predetermined
level, a second independent reanalysis of the pressure derivative
signal is provided which takes into account the possible influence
of changes in the latter parameters on the time derivative of
pressure. Such an analysis is unlikely to be required in routine
use but will improve the accuracy of the instrument.
There has been described novel apparatus and techniques for
facilitating the detection of mechanical heart impairment by
relatively unskilled personnel. It is evident that those skilled in
the art may now make numerous uses and modifications of and
departures from the specific embodiments disclosed herein without
departing from the inventive concepts. Consequently, the invention
is to be construed as embracing each and every novel feature and
novel combination of features present in or possessed by the
apparatus and techniques herein disclosed and limited solely by the
spirit and scope of the appended claims.
* * * * *