Method And Apparatus For Obtaining And Displaying Cardiovascular Data

Abstract

Method and apparatus for obtaining and displaying cardiovascular data by simultaneously sensing the performance of both the heart and an artery during a succession of cardiac cycles. A microphone adjacent the heart and a sensor adjacent an artery are coupled to the input of a cathode ray tube for intensity and/or amplitude modulation of its output. The horizontal sweep of the cathode ray tube is initated at the beginning of each cardiac cycle as by ECG electrodes. Variable pressure applied externally to the artery is also used to establish the quiescent vertical output of the cathode ray tube. In one embodiment, a memory tube temporarily stores the output of the cathode ray tube for visual examination, after which facsimiles can be made if desired.

Description

This invention relates generally to the field of cardiovascular medicine, and more particularly to a system of obtaining and displaying cardiovascular data derived from a succession of cardiac cycles.

In the course of detecting, diagnosing and treating cardiovascular problems, it is desirable and often necessary to be able to evaluate the performance and condition of the heart and arteries without having to resort to intra-arterial puncture, exploratory surgery, or the like. One such prior art technique provides for recording a succession of arterial sounds (Korotkoff sounds) during blood pressure measurement, simultaneously with a reference tracing by an electrocardiograph, as more fully described in the following: "Device for Indirect Registration of the Calibrated Arterial Upstroke in Man," by Simon Rodbard and Roderick Mohrherr, published in The Review of Scientific Instruments, Vol. 32, No. 9, pp. 1022-1023, September 1961; and "A Device for Objective Indirect Recording of the Arterial Pressure and Related Data," by Simon Rodbard and Thomas C. MacArthur, published in Medical Research Engineering, Vol. 8, No. 4, 1969. Another prior art technique provides for the recording and analysis of heart sounds and murmurs by displaying such acoustics in an aligned consecutive series of discrete impulses, as more fully set forth in the following: "A New Technique for the Recording and Analysis of Heart Sounds and Murmurs," by S. Rodbard and M. Keller, published in Cardiologia, 52: 145-153, 1969.

Another prior art technique provides for the generation of a contourgraph of successive electrocardiogram waves such that each wave is displayed in adjacent aligned relationship.

However, nothing has been developed to obtain and display in simple composite form cardiovascular data for up to one hundred or more successive cardiac cycles, including electrocardiogram (ECG) waveforms, heart sounds, arterial (or Korotkoff) sounds, arterial pressure waves, the systolic propagation time QKs, the diastolic propagation time QKd, the systolic and diastolic arterial pressures, the time consistency and patterns of the sequential succession of such parameters, and therefore such obtaining and displaying of cardiovascular data in the aforementioned manner are a primary object of the invention.

Another object of the invention is to provide for automatic recording of the aforementioned cardiovascular data, including visual monitoring of the actual display of such data before making a facsimile thereof for evaluation and storage.

A further object of the invention is to provide for intensity and/or amplitude modulation of the ECG waves, heart sounds and arterial sounds in order to accurately reflect the existence, position and magnitude of such data.

A more specific object of the invention is to provide monitoring of the performance of the heart and arteries by providing a microphone for detecting the Korotkoff sounds resulting from applying a variable external pressure to a specific artery, and a cathode ray tube coupled to the microphones to produce a modulated output. A related object is to couple the variable external pressure to the cathode ray tube to establish the vertical quiescent position of the output.

Another specific object is to provide a method and apparatus having the aforementioned characteristics wherein ECG electrodes are coupled to the cathode ray tube to initiate the horizontal sweep at the onset of each successive cardiac cycle.

Another object is to provide an invention having the aforementioned characteristics which allows time-sharing of the inputs of the cathode ray tube in order for identification and calibration indicia to be generated as part of the output.

Further purposes, objects, features, and advantages of the invention will be evident to those skilled in the art from the following description of the preferred and alternate embodiments of the invention.

In the drawings:

FIG. 1 is a block diagram showing a system for obtaining and displaying cardiovascular data which incorporates a presently preferred embodiment of the invention;

FIG. 2 shows an alternative embodiment of the portion of FIG. 1 enclosed by broken lines;

FIG. 3 shows an exemplary form of data display for the embodiments of FIGS. 1 and 2; and

FIG. 4 is a timing diagram showing how the system shown in the embodiments of FIGS. 1 and 2 produces the exemplary form of data display of FIG. 3.

Referring to the block diagram of the preferred embodiment of FIG. 1, a scan converter 10 includes a cathode ray tube having x-axis, y-axis, and z-axis inputs at 11, 12, and 13, respectively. The usual fluorescent screen is replaced by a memory tube for temporarily storing the output of the cathode ray tube for such time as is necessary for viewing on a connected television monitor 14 and also for "hard copy" reproduction by a connected facsimile generator 15. A typical high resolution scan converter usable here is made by Princeton Electron Products and incorporates a Lithocon Storage tube, although high resolution storage scopes and the like could also be used. Exemplary facsimile generators are made by Tektronix and also by Alden.

A conventional sweep generator circuit 16 connects to the x-axis input 11 and is activated by a Q-wave trigger device 17 which initiates the horizontal sweep at a predetermined time in each cardiac cycle, such as at time 18 when the Q deflection of a QRS wave complex 19 occurs (see FIG. 4). ECG electrodes 20 connect through an amplifier to the Q-wave trigger 17. A heart microphone 21 and an arterial vibration sensor 22 are provided to monitor the performance of the heart and arteries during a succession of cardiac cycles. A pressure cuff 23 applies variable pressure to a specified artery being monitored by the arterial vibration sensor 22. The invention is not limited to any specific arterial vibration sensor, so long as the sensor detects the existence and magnitude of the vibrating "flitter" action of the artery walls resulting from the combination of external cuff pressure and the internal pressure wave generated from the heart. In this regard, ultrasonic sensors are available which monitor the motion of the arterial wall. However, in the preferred embodiment, a microphone is employed to sense the arterial Korotkoff sounds generated by the arterial vibrations.

These three voltage waveforms produced by ECG electrodes 20, heart microphone 21, and arterial vibration sensor 22 are amplified, and then transmitted through an analog adder and intensity modulator 24 to the z-axis input 13 and also through an analog adder and vertical amplifier 25 to the y-axis input 12 of the cathode ray tube. Both modulators 24, 25 include conventional analog adding circuits to assure proper mixing of the incoming waveforms. The pressure existing in the pressure cuff 23 is converted by a conventional transducer to electrical form for passage through the analog adder and vertical amplifier 25 to the y-axis input 12 to vary the quiescent vertical position of the cathode ray tube output in accordance with the variation of the cuff pressure. Typical waveforms coming from the ECG electrodes 20, the heart microphone 21, the arterial vibration sensor 22, and the pressure cuff 23 are displayed in the timing diagram of FIG. 4, along with the concurrent voltage wave of the sweep generator 16 and a typical arterial pressure wave passing through the artery being monitored.

Referring now to FIGS. 3 and 4, the actual accumulation of cardiovascular data occurs as follows. The patient to be examined is placed in the desired position, such as reclining, and ECG electrodes 20, heart microphone 21, arterial sensor 22, and pressure cuff 23 are appropriately placed on the patient's body. Typically, the arterial vibration sensor 22 is placed over the antecubital fossa (opposite the elbow) and the pressure cuff 23 is positioned around the upper arm. The cuff pressure is increased to a pressure of 200 mm of Hg and then slowly decreased, as at the rate of about 2 mm of Hg per second. At the same time a horizontal sweep is initiated in the cathode ray tube at the Q-wave or onset of each cardiac cycle, thus producing a succession of horizontal plots in vertically aligned adjacent relationship (see FIG. 3).

In order to facilitate comparison and analysis of the cardiovascular data waveforms of each successive csrdiac cycle, the illustrated embodiment provides for suppression of the base line output of the cathode ray tube by adjusting z-axis bias (intensity) such that the base line is just suppressed, with zero amplitude present at the y-axis input. Voltage input from any one of the elements 20, 21, 22 produces a signal which varies both in amplitude and intensity at the cathode ray tube output. Of course, the invention contemplates either amplitude modulation or intensity modulation alone where the need requires.

When the cuff pressure decreases to a point slightly less than the systolic arterial pressure, the blood begins passing through the artery and produces the first arterial sounds as at 26. During each successive cycle, as the external cuff pressure is continually decreasing, the arterial sounds are heard sooner, thereby making the QK2 time less than the QK1 time for the preceeding arterial pressure wave (see FIG. 4). Thus, the left side of the envelope of arterial sound waveforms constitutes a reproduction of the leading edge of the arterial pressure wave. The diastolic arterial pressure is indicated by the cessation of the arterial sound waveforms, as at 26a. The arterial sounds usually occur at both the onset of the arterial pressure wave, as at time 27, and also at time 28 on the decreasing portion of the pressure wave. The actual waveforms shown in FIG. 3 are exemplary only both as to shape, specific positioning, and number of cardiac cycles shown, but the general representation of a sequence of heart sound waveforms and arterial sound waveforms positioned in exact adjacent relationship relative to a predetermined reference time in successive cardiac cycles as a result of decreasing external arterial pressure has been found useful in examining and studying more than 500 cardiovascular patients. The inclusion in the display of an aligned sequence in electrocardiogram waves has also been found useful, although in some instances such display is not necessary, so long as ECG electrodes or the like are used to generate the necessary synchronizing pulse.

In order to provide initial information on the cathode ray tube output for display adjacent the succession of waveforms, a calculator 38 is connected through a character generator 29 to the inputs of the scan converter 10. A grid line generator 30 is also connected to the inputs. The calculator 38 is connected to the arterial sensor 22 and the measures the systolic propagation time QKs and the diastolic propagation time QKd, and can also be used to sense the actual systolic and diastolic pressure magnitudes, as well as make any other calculations deemed pertinent. This data can be processed by a data logger and/or digital readout 31 to make it independently accessible to the doctor, as well as being transmitted to the character generator 29 for display purposes. The character generator is a conventional type, and can also be used in connection with a thumb-wheel switch or magnetically encoded card to generate the patient's identification number for display purposes. The grid line generator can be used for varying the calibration of the output of the cathode ray tube. The output of the character generator 29 and the grid line generator 30 as well as the outputs of the intensity modulator 24 and the amplitude modulator 25 all pass through control circuitry (not shown) to allow the inputs of the cathode ray tube to be time-shared without interfering with the display of data.

The combination of the scan converter 10 and the television monitor 14 enables the physician or operator to visually examine the output display of the cathode ray tube to assure that the data is reasonable, and that no malfunction has occurred in the system. If desired, the facsimile generator 15 can then be actuated to produce a hard copy for further examination and storage. In this regard, it is possible to replace elements 10, 14, and 15 of FIG. 1 with an oscilloscope 32 and camera 33 as shown in FIG. 2. However, the alternative embodiment in FIG. 2 requires that the camera shutter be kept open during the entire examination in order to store on the camera negative each output of the cathode ray tube, thereby requiring development of the film before being able to view the display of cardiovascular data obtained. Of course, a camera would be unnecessary if a storage scope were used. However, most storage scopes currently on the market do not have sufficiently high resolution for use here.

It will be appreciated from the foregoing that the invention provides a unique method and apparatus for obtaining and displaying cardiovascular data which greatly facilitates the analysis and retention of such data in a way not heretofore possble.

Although exemplary embodiments of the invention have been disclosed herein for purposes of illustration, it will be understood that various changes, modifications, and substitutions may be incorporated in such embodiments without departing from the spirit of the invention as defined by the claims which follow.

Claims

We claim as our invention:

1. Apparatus for obtaining cardiovascular data, including in combination:

Ecg electrodes;

microphone means for detecting heart sounds;

sensing means for monitoring the pulse waveform of a specified artery;

a cathode ray tube having x-axis, y-axis and z-axis inputs, said ECG electrodes connected to said x-axis inputs for initiating a horizontal sweep at the beginning of each cardiac cycle, and said microphone means and said sensing means each connected to at least one of said y-axis and z-axis inputs;

pressure means for applying variable external pressure to said artery, said pressure means connected with said y-axis input to control the quiescent vertical position of said output of said cathode ray tube and to display the waveforms generated by said microphone means and said sensing means during each of a succession of cardiac cycles with the waveforms of each of said succession of cardiac cycles vertically aligned; and

readout means coupled to said ECG electrodes and said sensing means for continuously monitoring, measuring, and displaying the magnitude of the time interval between the beginning of each cardiac cycle and the onset of the pulse waveform in the artery.

2. The apparatus of claim 1 including means for connecting said ECG electrodes with at least one of said y-axis and z-axis inputs of said cathode ray tube.

3. Apparatus for obtaining and displaying cardiovascular data including in combination:

1. a cathode ray tube having x-axis, y-axis and z-axis inputs;

2. ECG electrodes connected to said x-axis input for initiating the horizontal sweep at the beginning of each cardiac cycle;

3. first microphone means for detecting heart sounds;

4.

4. second microphone means for detecting arterial sounds;

5. said first and second microphone means connected with said y-axis input to provide amplitude modulation of the output of said cathode ray tube and also connected with said z-axis input to provide intensity modulation of the output of said cathode ray tube;

6. pressure means for applying variable external pressure to an artery, said pressure means connected with said y-axis input to change the quiescent vertical position of the output of said cathode ray tube at a rate proportional to the variable external pressure applied to the artery to generate a series of vertically aligned waveforms of both heart sounds and arterial sounds; and

7. means coupled to said cathode ray tube for temporarily preserving the output of said cathode ray tube during a succession of cardiac cycles and

for producing a facsimile of said output of said cathode ray tube. 4. A method of obtaining cardiovascular data during a succession of cardiac cycles, including:

detecting an onset reference for each cardiac cycle;

applying a varying external pressure to an artery;

sensing the existence and magnitude of heart sounds and arterial vibrations relative to said onset reference;

initiating a horizontal sweep of a cathode ray tube at the same predetermined time during each cardiac cycle;

modulating the output of the cathode ray tube to generate a waveform reflecting the existence and magnitude of the heart sounds and the arterial vibrations obtained by said sensing; and

changing the quiescent vertical output of the cathode ray tube at a rate proportional to said varying to display the modulated output for one cardiac cycle in vertical alignment with the modulated output for the other cardiac cycles.

5. The method of claim 4 including measuring and displaying the magnitude of the time interval between the onset reference for each cardiac cycle and the leading edge of the waveform reflecting the magnitude of the arterial vibrations.