Abstract:
An apparatus for measuring cardiac electric activity of a patient includes a tubular structure embodied in a lightweight, gently u-shaped form factor. The tubular structure includes: a center portion, a left handle in an upright end of the tubular structure, a right handle in a contralateral upright end; a connector positioned in the center portion; first and second receiving electrodes in the right and left handles; and an efferent cable for coupling the connector with a processor for electronically inverting signals obtained from the electrodes to produce vectors enabling a calculation of a conventional twelve-lead electrocardiogram. The processor is operatively coupled with a fourth electrode affixed to the patient&#39;s ear.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of, and claims priority from, commonly-owned, co-pending U.S. patent application Ser. No. 11/925,545 filed on Oct. 25, 2007, which is incorporated by reference as if fully set forth herein. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED-RESEARCH OR DEVELOPMENT 
       [0002]    None. 
       INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0003]    None. 
       FIELD OF THE INVENTION 
       [0004]    The invention disclosed broadly relates to the field of equipment for monitoring the electrical activity of the heart, and particularly to a three or four-lead method for monitoring cardiac electrical activity. 
       BACKGROUND OF THE INVENTION 
       [0005]    An electrocardiogram is a test that graphically records the electrical activity of the heart. The electrocardiogram or ECG (sometimes called EKG) is used worldwide as a relatively simple way of diagnosing many heart conditions. It records the small electric waves being generated during heart activity using body surface electrodes attached to a patient. The electrodes are placed in a particular pattern for clinical use because electrical signals generated by a human heart appear in a characteristic pattern throughout the body, and on its surface subject to their position. 
         [0006]    A procedure developed by Willem Einthoven in 1901 inter-related three electrodes specifically oriented on the body (right arm, left arm, and left leg). These electrodes are at the apices of a physiological triangle known as Einthoven&#39;s triangle, as shown in  FIG. 1   a.  The difference in electrical potential between the left and right arms is designated lead I; lead II is the difference in electrical potential between the left leg and right arm; and lead III is the difference in electrical potential between the left leg and left arm. Thus, the Einthoven triangle resembles a triangle standing on its tip “▾.” 
         [0007]    These electrodes provide bipolar recordings of the voltage differential between two electrodes. By convention, the positive electrode is placed on the left arm, with the negative electrode on the right arm. In the lead II configuration, the positive electrode is on the left leg and the negative electrode is on the right arm. Lead III has the positive electrode on the left leg and the negative electrode on the left arm. The limb leads can be attached to the end of the limb (wrists and ankles) or at the origin of the limb (shoulder or upper thigh). The difference in electrical potential between two of the electrodes constitutes the signal. 
         [0008]    Referring to  FIG. 1   b  there is shown a simplified illustration of a conventional electrocardiograph  100  in place on a patient. The ECG  100  requires at least three leads (therefore three electrodes are needed). These three electrodes are applied one on each of the patient&#39;s arms  110  and  112 . The third electrode  120  is applied on the patient&#39;s left leg. 
         [0009]    A fourth electrode  140  is placed on the patient&#39;s right leg as an electrical ground. The ground can be at other locations on the body but at a reasonable distance from the other electrodes to ensure a good signal. In addition, there are six precordial (chest) leads  160  designated V 1 -V 6  (not shown here), for a total of twelve leads. Their conventional placement is illustrated in  FIG. 1   c.    
         [0010]    The electrodes are easy to apply and this conventional placement of electrodes works well in a hospital setting and in a doctor&#39;s office. The problem arises, however, when it is desirable and sometimes necessary for an ECG to be used outside of a conventional medical setting. For example, a patient with chronic heart problems may want to have a portable ECG in the home or the office. Airlines may find it necessary to have a portable ECG in airplanes for in-flight emergency use. The signals produced by a portable unit can be transmitted to a doctor on the ground who can then interpret the signals and advise the airline staff as to whether to use an on-board defibrillator. 
         [0011]    Electrodes must be positioned in an anatomically correct pattern so that the readings are valid. One problem with this conventional electrode placement is that leg electrodes are not conducive to portability. 
       SUMMARY OF THE INVENTION 
       [0012]    Briefly, according to an embodiment of the present invention, a method for measuring cardiac electrical activity of a patient includes: attaching a first electrocardiogram electrode to a patient&#39;s ear; attaching second and third electrodes to both hands of the patient, forming an inverted Einthoven triangle of electrocardiograph electrodes on the patient. A fifth electrode is attached to the patient&#39;s chest area. An electrical ground electrode is then attached to the patient&#39;s contralateral ear. The electrodes are coupled to a connector by lead wires and the connector is operatively coupled to a processor. The method further electronically inverts signals obtained from the electrodes to produce a conventional electrocardiogram recording using the processor. 
         [0013]    According to another embodiment of the present invention, an apparatus for measuring cardiac electric activity of a patient includes a tubular structure embodied in a lightweight, gently u-shaped form factor. The tubular structure includes: a center portion, a left handle in an upright end of the tubular structure, a right handle in a contralateral upright end; a connector positioned in the center portion; first and second receiving electrodes in the right and left handles; and an efferent cable for coupling the connector with a processor for electronically inverting signals obtained from the electrodes to produce vectors enabling a calculation of a conventional twelve-lead electrocardiogram. The processor is operatively coupled with a fourth electrode affixed to the patient&#39;s ear. 
         [0014]    According to another embodiment of the present invention, the apparatus is operable to transmit cardiac signals wirelessly and includes a circuit module for converting the signals from the lead wires. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    To describe the foregoing and other exemplary purposes, aspects, and advantages, we use the following detailed description of an exemplary embodiment of the invention with reference to the drawings, in which: 
           [0016]      FIG. 1   a  shows an illustration of Einthoven&#39;s inverted triangle, according to the known art; 
           [0017]      FIG. 1   b  shows an illustration of an electrocardiograph system according to the known art; 
           [0018]      FIG. 1   c  shows the placement of leads V 1 -V 6 , according to the known art; 
           [0019]      FIG. 2  shows an illustration of the placement of electrodes to form an inverted Einthoven triangle, according to an embodiment of the present invention; 
           [0020]      FIG. 3  shows an illustration with the chest electrode displaced to the left, according to an embodiment of the present invention; 
           [0021]      FIG. 4  is a flow chart of a method according to an embodiment of the present invention; 
           [0022]      FIG. 5A  shows a simplified illustration of a handlebar electrode, according to an embodiment of the present invention; 
           [0023]      FIG. 5B  shows two separate segments of the handlebar, according to an embodiment of the present invention; 
           [0024]      FIG. 6  shows a flow chart of a method for producing a 12-lead ECG without a leg electrode, according to an embodiment of the present invention; 
           [0025]      FIG. 7  shows a flow chart of a handlebar method for producing a 12-lead ECG without a leg electrode, according to an embodiment of the present invention; 
           [0026]      FIG. 8  shows the connector of the handlebar of  FIG. 7  electrically coupled with an ear electrode, according to an embodiment of the present invention; 
           [0027]      FIG. 9  shows a wireless handlebar apparatus, according to an embodiment of the present invention. 
       
    
    
       [0028]    While the invention as claimed can be modified into alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention. 
       DETAILED DESCRIPTION 
       [0029]    I describe a method for recording the electrical activity of the heart using an inverted Einthoven triangle of electrodes. The current 12 lead ECG used in modern medicine is based upon placement of electrodes on anatomical markers and calculating the 12 ECG recordings derived from these positions. However, with the advancement of computer technology it is feasible to use fewer electrode positions to synthesize the customary 12 lead ECG. This is achieved by a computer algorithm which takes readings from the available leads and calculates the readings for the missing leads. 
         [0030]    Referring to  FIG. 2  there is shown an exemplary placement of electrodes according to an embodiment of the present invention. In this example, receiving electrodes on the (R)  210  and (L)  215  hand and one receiving electrode on the (R) EAR  220  act as an inverted Einthoven triangle. The R  210  and L  215  hand electrodes produce lead  1230 . The R ear  220  and L hand  215  electrodes produces lead II  240  and the R ear  220  and R hand  210  electrodes produce lead III  250 . One electrode  225  is placed on the patient&#39;s left ear, to act as ground. 
         [0031]    The above electrodes make contact with the patient&#39;s skin and pick up trans-cutaneous electrical signals from the patient&#39;s heart. Thus, electrical potential differences between the right arm, left arm, and ear can be measured. The ear electrode  220  forms the apex of the inverted Einthoven triangle, with the hand electrodes  210  and  215  forming the base of the triangle. Another electrode  225  used for ground potential may optionally be placed in the patient&#39;s contralateral ear as shown in  FIG. 2 . 
         [0032]    The ear electrodes  220  and  225  may be embodied in an earphone form factor, or they may simply be clipped to the earlobes. The electrodes can be rectangular or some other shape. They may be suction, button, or plate electrodes. Each electrode has a substantially flat surface for secure attachment to a patient&#39;s skin. Modern electrodes are self-adhesive; but to aid in electrical conduction, a conductive gel is sometimes applied to the flat surface of each electrode before attachment. If necessary, tape can be used to secure the electrode. The non-contact surface of the electrode is a conductor attached to an electrode lead wire which in turn may be attached to a multiplex cable. The cable is preferably coupled with a connector. The connector includes ports for coupling with a reader and other input/output devices. 
         [0033]    With electrode placement on the right arm, left arm, and right ear, the combination of left arm-right arm is equivalent to a standard lead I  230  ECG configuration. The right arm-right ear combination acts as an inverted lead II  240  and the left arm-right ear combination produces an inverted lead III  250 . Readings from these two latter leads are transformed back to the conventional Einthoven configuration mathematically by taking into account: 1) the angular variation of the cardiac dipole measured by a right ear electrode as opposed to a left leg electrode; and 2) the magnitude variation of the cardiac dipole measured by a right ear electrode as opposed to a left leg electrode. 
         [0034]    An electronic circuit, as used in conventional ECG devices, additionally inverts the electrical signals received from the electrodes to produce a conventional cardiac signal, which can be displayed on a monitor or transmitted to a remote location by landline or wireless means. 
         [0035]    To facilitate use by non-medical personnel, standardized color coding of the electrodes and/or lead wires can be used, and the color codes can be made available to the patient. 
         [0036]    In one embodiment, without precordial recordings, the minimum number of electrodes that can be advantageously used for cardiac monitoring is four: one receiving electrode in the patient&#39;s ear  220 , two electrodes on each hand  210  and  215 , and one electrode to be used as ground. This ground electrode  225  may be placed in the patient&#39;s contralateral ear. 
         [0037]    The apex of the inverted Einthoven triangle is formed by a receiving electrode preferably located in or on the patient&#39;s ear. The system as described can be self-applied by a patient and is devoid of leg electrodes. 
         [0038]    Up to this point, the embodiment presented herein has been described in commonly-owned, co-pending application Ser. No. 11/925,545. Now is presented a novel embodiment enabling the calculation of a 12-lead ECG. Referring to  FIG. 3 , there is shown an embodiment which differs from the previously described embodiment by the addition of a fifth electrode. The contact of a fifth electrode  310  in the chest area plus the other electrodes described above provide information which is input into the algorithm to produce vectors enabling the calculation of the customary  12  lead ECG. 
         [0039]    Referring now to  FIG. 3 , there is shown an illustration depicting another embodiment of the present invention, wherein the chest electrode  310  is displaced to the left of the sternum (breast bone) taking into consideration that a person&#39;s cardiac silhouette is predominantly in the left side of the chest. 
         [0040]    Referring now to  FIG. 5A  there is shown an embodiment wherein a “handlebar” is used to receive the cardiac signals. As shown in  FIG. 5 , a chest electrode  510  is disposed on the handlebar  550 . This chest electrode  510  is able to “slide” along the center portion of the “handlebar”  550  a few inches in each direction to give some versatility to the chest and hand positions. A patient grasps the upright ends  552  and  556  of the handlebar  550 . The handlebar  550  is aligned over the patient along the plane of the nipples. The center chest electrode  510  is positioned slightly to the left of the sternum. The patient grasps the ends of the handlebar  550  and places the handlebar  550  on his/her chest, making contact with the skin at the point of the chest electrode  510 . When properly positioned, the ends of the handlebar  550  flare up and away from the patient, thus avoiding any contact with the patient&#39;s skin. 
         [0041]    To secure accurate readings, a fourth electrode  220  (not shown here) is affixed to the patient&#39;s ear, forming the apex of the inverted Einthoven triangle. Lead wires from the fourth electrode  220  feed into a computer. As shown in  FIG. 8 , in an alternate embodiment, the lead wires  840  from the fourth electrode  220  are fed into the connector  560 . 
         [0042]    In another embodiment, the electrodes on the extremities of the handlebar  550  can also be fitted over the handlebar  550 . In this embodiment, the electrodes are hollow cylindrical bars that fit over the upright ends of the handlebar  550 . 
         [0043]    The handlebar  550  can be formed of a thermoplastic, self-insulating material. Preferably, it should be amenable to molding. Alternately, a metal could also be used. In such an embodiment the internal wires would need to be covered by insulating sheaths and the hand electrodes would also need to be insulated. 
         [0044]    The circumference of the handlebar  550  is preferably approximately four inches. The length of the handlebar  550  can be anywhere from 20-26 inches. The handlebar  550  form factor shown here embodies a gentle u-shape in order to avoid contact with the chest at any point other than the chest electrode  510 . The gentle u-shape is shown here for exemplary purposes, not for limitation. It will be appreciated that other shapes may be advantageously used, such as, for example, a wide v-shaped form factor with the chest electrode at the apex of the “V.” 
         [0045]    In one embodiment, the right  556  and left  552  ends of the handlebar  550  are fixed contact surfaces which function as electrodes  554  and  558  and encircle the handlebar  550 . The handles  552  and  556  are circumferential. This is similar to the grasp bars found on treadmills and exercise bikes which record a person&#39;s heart rate. 
         [0046]    The electrodes  554  and  558  make contact with the patient&#39;s hands and are connected by internal wires to a connector  560  near the center of the handlebar  550  which is connected via an efferent cable  562  to a computer (not shown). 
         [0047]    Referring to  FIG. 5B , in an alternate embodiment, the handlebar  550  can be formed in two separate pieces, making it easier for storage (as on a plane).  FIG. 5B  shows one embodiment wherein the two separate sections of the handlebar  550  fit together with an end piece of one section fitting into the slightly wider end piece of the other section, similar to the extension tubes of a vacuum cleaner hose. This allows the handlebar  550  to be assembled by hand or disassembled for easy storage when the handlebar  550  is not in use. Since the left portion of the handlebar would contain wiring from the left hand electrode and the chest electrode, an internal connector would be required to connect these wires to the wiring from the right hand electrode, should disassembly be desired. 
         [0048]    In another embodiment a small central section could be added to facilitate elongation so that different sizes of individuals can be easily accommodated. In yet another embodiment, the connector  560  could act as the joining piece. In such an embodiment, the connector  560  would include apertures at opposite ends wherein each handlebar section can be attached. Other variations can be envisioned within the spirit and scope of the invention. 
         [0049]    Referring to  FIG. 6 , there is shown a flow chart  600  of a method according to an embodiment of the present invention. First, in step  610 , the patient is placed into position. In a hospital setting, the patient generally is placed supine on a table. For this method, it is not necessary to have the patient recumbent. The patient may stand or sit while the procedure takes place. 
         [0050]    Next in step  620 , electrode  220  is placed on the patient, in or on one of the patient&#39;s ears. It is also possible to place one electrode in or on each ear. In step  630  two electrodes  210  and  215  are placed in each of the patient&#39;s hands. Now the inverted Einthoven triangle is complete. 
         [0051]    In step  640  an electrode  310  is placed in the chest area of the patient. Next, an electrode acting as ground is attached to the patient&#39;s contralateral ear  225  in step  650 . Lastly, in step  660 , the signals from the receiving electrodes are inverted to produce a conventional 12-lead electrocardiogram recording. 
         [0052]    Referring to  FIG. 7  there is shown a flow chart  700  of a method according to another embodiment of the present invention. First, in step  710 , the patient is placed into position. Again, for this method, it is not necessary to have the patient recumbent. The patient may stand or sit while the procedure takes place. 
         [0053]    Next in step  720 , electrode  220  is placed on the patient, in or on the patient&#39;s ears. In step  730  the patient grasps the ends of the handlebar  550  with both hands, thus making contact with the end electrodes of the handlebar  550 . The patient does not need to squeeze the handlebar; it is sufficient to grasp firmly so that the palm of the hand and the fingers are in substantial contact with the handlebar end. When the patient grasps the handlebar and makes contact with the end electrodes the inverted Einthoven triangle is complete. 
         [0054]    Next in step  740  the chest electrode  510  on the handlebar  550  is positioned to the desired location over the patient&#39;s chest. The patient next pulls down the handlebar  550  so that the center chest electrode  510  is in contact with the patient&#39;s chest in step  750 . Note that is preferable to position the chest electrode  510  slightly to the left of the sternum. The position of the chest electrode  510  may need to be adjusted after the handlebar  550  is placed on the chest. 
         [0055]    Next, an electrode acting as ground is attached to the patient&#39;s contralateral ear  225  in step  760 . Lastly, in step  770 , the signals from the receiving electrodes are inverted to produce a conventional 12-lead electrocardiogram recording. 
         [0056]    With reference now to  FIG. 9  there is shown a wireless handlebar apparatus  950  according to another embodiment of the present invention. The wireless handlebar  950  is substantially similar to the handlebar apparatus  550  of  FIG. 5A , except that the wireless embodiment includes a circuit module  920  for transmitting signals to a computer or display device. A further difference is that the wireless embodiment  950  does not require the efferent cable  562  as shown in  FIG. 5A . 
         [0057]    The wireless handlebar apparatus  950  can be embodied in the same form factors as the wired embodiment  550 . The example shown here in  FIG. 9  is a gentle u-shaped form factor. The patient grasps the upright ends  952  and  956  of the handlebar  950 . The handlebar  950  is aligned over the patient along the plane of the nipples. The center chest electrode  910  is positioned slightly to the left of the sternum. This chest electrode  910  is able to “slide” along the center portion of the handlebar  950  a few inches in each direction to give some versatility to the chest and hand positions. Just like with the wired version, the patient grasps the ends of the handlebar  950  and places the handlebar  950  on his/her chest, making contact with the skin at the point of the chest electrode  910 . 
         [0058]    To secure accurate readings, a fourth electrode  220  (not shown here) is affixed to the patient&#39;s ear, forming the apex of the inverted Einthoven triangle. Lead wire  914  from this ear electrode  220  is input into the circuit module  920 . An additional lead wire  912  from ground is also input into the circuit module  920 . 
         [0059]    In one possible embodiment, the right  956  and left  952  ends of the handlebar  950  are fixed contact surfaces which function as electrodes  954  and  958  and encircle the handlebar  950 . The handles  952  and  956  are circumferential. The electrodes  954  and  958  make contact with the patient&#39;s hands and are connected by internal wires to the connector  960  near the center of the handlebar  950 . The connector  960  is in turn electronically coupled with the circuit module  920  by a cable  940 . 
         [0060]    The circuit module  920  receives the lead wire signals, converts them, and then transmits the converted signals wirelessly to a computer (not shown) or display screen. The components of the circuit module  920  are: 
         [0061]    a filter  922  for receiving the lead wires  912  and  914  as input; 
         [0062]    a bioamplifier  924  for amplifying the signals from the filter  922 ; 
         [0063]    an analog-to-digital converter  926  for converting the signals from the bioamplifier  924 ; 
         [0064]    a wireless transmitter  928  for transmitting the signals to the computer or other device; and 
         [0065]    a battery  925  operatively coupled with the above components for providing power to the components. 
         [0066]    Therefore, while there have been described what are presently considered to be the preferred embodiments, it will be understood by those skilled in the art that other modifications can be made within the spirit of the invention.