WO2017064643A1

WO2017064643A1 - Method and apparatus for the continuous acquisition of an electrocardiogram

Info

Publication number: WO2017064643A1
Application number: PCT/IB2016/056133
Authority: WO
Inventors: Pietro Rossi; Giancarlo Monari
Original assignee: Miocardio S.R.L.
Priority date: 2015-10-13
Filing date: 2016-10-13
Publication date: 2017-04-20
Also published as: EP3361942A1

Abstract

The apparatus for the continuous acquisition of an electrocardiogram includes a band (1) adapted to wrap the chest of a patient and a collecting unit (2) provided in the band (1) for collecting signals corresponding to the heart electrical activity. An amplifier electronic circuit and a plurality of electrodes are provided inside said collecting unit (2), placed in the band (1) in connection with as many terminals (3, 4, 5) touching the skin, adapted to be applied to the patient's chest for detecting the heart electrical activity and connected to said unit for collecting signals (2). In the band (1), the contact terminals (3, 4, 5) include lateral terminals (3, 4) set in alignment therewith, and a central reference terminal (5), not aligned with the lateral terminals (3, 4); the central reference contact terminal (5) is connected to the amplifier electronic circuit at the last stage of the amplifier, in such a way that the difference between the signal detected by the reference electrode, set in connection with the central terminal (5) and the electrical signal detected by the other lateral electrodes set in connection with the lateral terminals (3, 4) reduces substantially the thermal shift to obtain more readable and interpretable ECG traces, thus facilitating the arrhythmologic diagnosis.

Description

METHOD AND APPARATUS FOR THE CONTINUOUS ACQUISITION OF AN ELECTROCARDIOGRAM

TECHNICAL FIELD

The present invention relates to the production of electro-medical devices, in the specific case diagnostic devices, and in particular refers to a method and apparatus for the continuous acquisition of an electrocardiogram (ECG), the latter including a detecting device, composed of a band and an amplification circuit with attenuation of the interferences caused by the thermal shift.

BACKGROUND ART As it is known, the disorders of cardiac rhythm are among the most frequent dysfunction of the cardiovascular system and represent the cardiac pathologies that require recurrent visits to emergency departments and cardiology outpatient departments.

In the prevention field, especially referring to the consequences of cardiac pathologies, it has been ascertained a long time ago that the arrhythmias (tachyarrhythmias and bradyarrhythmias) can be paroxysmal and not easy to diagnose with a short ECG performed at rest and in health care center.

For this reason, already in the fifties, instruments have been developed for the prolonged and continuous ECG acquisition with the aim of analysing the heart electrical activity for 24 hours or more.

This process using the above mentioned instruments, is called dynamic electrocardiogram or "Holter monitoring" and is performed by applying electrodes to the patient's chest and recording the data in a small portable recorder given to the patient.

The apparatus allows recording all the heartbeats during 24 hours in all various situations of everyday life. This allows recording the whole heart activity and a correlation thereof with possible symptoms reported by the patient.

The obtained recording is processed and visualized on a monitor or printed, thus allowing to study a possible alteration of the heartbeat or the presence of symptoms of ischemic heart disease, that is possible conditions which can be referred to the symptoms reported by the patient.

Over time, such instruments have been reduced in size and improved so as to make the test more comfortable and increase the patient's willingness to collaborate.

TECHNICAL PROBLEM

At present, the Holter recorders have been greatly improved, however, the present systems suffer from troubles which make the detected cardiographic signals difficult to read and interpret. Actually, the known devices, just because of their constructive configuration, involve also the risk of very probable recording of unrelated signals, generated especially during the movement.

This is caused first of all by the use of electric cables which connect the recording device to the standard adhesive electrodes, applied to patient's skin and facilitating the generation of artefact noise. As a consequence, the ECG trace is sometimes illegible, especially the parts recorded during the patient's movement. Furthermore, also the movements or rubbing of the adhesive electrodes on the skin can create interferences. The damages determined by these interferences can be significant, in view of the fact that the spoiled signals should give information that could be of vital importance for a patient. In the most limited cases, these interferences alter the quality and resolution of the ECG trace making it not only altered, but in some points even illegible.

As it is known, basically none of the electronic systems is free from interferences and almost always they have problems connected with the thermal noise and its random components. The noise is caused by the fact that the number of charged particles locally is not constant.

The most common thermal noise is produced in any real dissipating system, at a temperature different from the absolute zero. In nature, the noise moves according to the relation 1 /f, where f is the frequency, in practice indirectly proportional to the frequency.

The representation of the thermal noise is statistically composed of a Gaussian curve, having null average value, which derives, according to the central limit theorem, from the "infinite" independent basic contributions of the single particles moved by the thermal agitation. The electric thermal noise can be noticed by detecting that across a resistor, to which no voltage is applied, a noise voltage variable over time is present, depending on the temperature T: v_n ( t ) .

From experimental tests, this noise voltage, that obviously produces a direct current i_ni t \— v_n (i) /H across an open circuit resistor, can be statistically calculated as RMS value according to the following equation:

% = „ = ^kTRAf where k ~ 1 , 38 · 10^{" ~ :}\l/K is the Boltzmann constant

T is the temperature in Kelvin degrees

Δ f is the observation frequency band.

The unilateral power spectrum of the noise voltage, calculated on this experimental basis, is given by:

S_vv( ; - AkTB,

and the power spectrum of the noise current:

^!'^{' '}"^■ ' ^,N *

On the other hand, the maximum noise power that a resistor can supply (that is the power supplied in conditions of adapted load) does not depend on the resistance, but only on the temperature, as the Nyquist formula describes: In practice, the thermal noise makes the signal fluctuate as in figure 3.

Another source of interference derives from the fact that the signal to be amplified has a very low level and the transducer, in this case constituted by each of the adhesive electrodes, is not very distant from the amplifier. According to a used solution, shielded cables are used, which however are capable of filtering the radio frequency interferences, but they can do very little against the low frequency interferences. Moreover, the parasitic resistance and capacitances produced by the cables contribute to the increase of the interferences, inducing voltages that propagate with not negligible phase difference up to the terminals of the amplifier.

A method for overcoming this problem, called "shield driving" and schematized in figure 4, includes the application of an auxiliary voltage Vco_/w to the shielding sheath of the cables. In this way, since V_A ^¾ V_B, are parasitic capacitances, for example of the cable A, they are supplied with a voltage equal to =r_, ....ii...I..:....-t.;_{; :}, c and thus their influence is almost wholly cancelled. The same applies to cable B. In other words, this technique does not eliminate the interferences, but prevents the cable from displacing them out of phase.

When it is not possible to connect the transducer (detection electrode) with a shielded cable, an alternative technique is used, known as bootstrapping, which includes the amplification of the auxiliary voltage Vco_/w =(VA +VB )/2 and the application thereof, with the sign reversed, to the body of the transducer, which is considered to be the source of the interference. In practice, a counter-reaction is applied so as to minimise the interference.

This technique is used for example in the medical field in the observation of the electrocardiogram, as shown in figure 5.

A typical electrical diagram of an ECG with reference to the right leg to reduce the interferences caused by thermal shift, is shown in figure 6. The VR is buffered, inverted and sent to the reference electrode for the active drive. The object of the 100 ΚΩ final resistance is to keep the current circulating on the patient within the limits provided by the regulations, which must be less than 10 μΑ.

In addition to the interferences that affect the detected signals, another problem is caused by the discomfort of the application of the detection and recording systems, which include the application of adhesive plasters on the skin in order to keep the electrodes in contact therewith, placing of the electric cables in more points along the chest, and in general, the impossibility to take a shower.

Since the useful information is obtained in the course of the whole day, during which the test is performed, while the patient performs all his/her usual daily activities, damages to the electronic components of the apparatus should be avoided, therefore it is preferred not to sweat too much, to avoid the shower, thus, not to perform sport activities that could jeopardize the device working, even only removing the electrodes from the skin.

OBJECTS OF THE INVENTION

The object of the present invention is to overcome the above mentioned undesirable problems in order to record a signal of better quality, reducing noises, interferences and electrical shifts. Another object of the invention is to propose an apparatus so configured as to obtain a substantial improvement of the quality of the detected signal, without illegible pieces referred to conditions and situations in which the check of the cardiac activity is of vital importance for the correct diagnosis and an effective prevention.

A further object of the invention is to propose a recording apparatus which is comfortable for the person who wears it and is easy to install.

A further object of the invention is to propose an apparatus which adapts perfectly and stably to the user's anatomy.

A still further object of the invention is to propose the above mentioned system obtained by means of a solution which is as simple as possible and whose production and subsequent implementation do not require high costs. SUMMARY OF THE INVENTION

These and other objects which become evident from the following description, are all obtained by means of a method and apparatus for the continuous acquisition of an electrocardiogram, the latter including a band adapted to wrap the chest of a patient and a unit for collecting the signals corresponding to the heart electric activity, provided in the band. An amplifier electronic circuit and a plurality of electrodes are provided inside the collecting unit, placed in the band at as many terminals touching the skin, adapted to be applied to the patient's chest for detecting the heart electrical activity and connected to the unit for collecting signals.

In the band, the contact terminals include aligned lateral terminals and a central reference terminal, which is not aligned with the lateral terminals; the central reference contact terminal is connected to the amplifier electronic circuit at the last stage of the amplifier, in such a way that the difference between the signal detected by the reference electrode, situated on the central terminal and the electrical signal detected by the other lateral electrodes situated on the lateral terminals reduces substantially the thermal shift to obtain more readable and interpretable ECG traces, thus facilitating the arrhythmologic diagnosis.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics of the invention not appearing from what has been said above, will become evident from the following description, to be considered with reference to the enclosed drawings, in which:

figure 1 and figure 2 illustrate a band type apparatus for the continuous acquisition of an electrocardiogram, which integrates the present invention, seen from the side and from the opposite side, respectively; figure 3 illustrates a representation of the detected electrical signal disturbed by the thermal noise;

figure 4 and figure 5 illustrate simplified representations for the correction of the disturbed signal according to the prior art;

figure 6 shows a typical electrical diagram of the ECG recorder, with the configuration adapted to reduce the interferences caused by the thermal shift according to the prior art;

figure 7 shows the simplified diagram of the additional configuration of the electronic circuit according to the invention which allows to limit the interference caused by thermal shift, when applied in an apparatus for

ECG recording;

figure 8 illustrates the simplified diagram of the electronic circuit which implements the method proposed by the present invention and comprises the additional layout of figure 6;

figure 9 is a perspective view of a different and preferred embodiment of the apparatus for the continuous acquisition of an electrocardiogram, proposed by the invention;

figure 10 is a top view of the apparatus of figure 9;

figure 10 is a front view of the apparatus of figure 9, which shows the inner part of the band.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

With reference to the above mentioned figures, reference numeral 1 indicates a band of an apparatus for continuous and prolonged acquisition of an electrocardiogram (ECG) developed by the Applicant and proposed by the present invention.

The band 1 is adapted to wrap the patient's chest and is kept close by connecting means consisting of a portion of Velcro 10 (figure 2) adapted to adhere to the opposite end of the band 1 . In order to be kept tight around the chest, the band 1 includes a first portion A of an inelastic material and a second portion E of an elastic material. As far as the used material is concerned, the band 1 can be made of fabric or in a single structure of a synthetic or rubber plastic material, without excluding the use of other suitable materials. Besides the above mentioned Velcro, other known ways can be used to make the connecting means, for example, strips or buckles, or snap or hook fastening means, according to different needs, which can occur case by case.

As a pure not limiting example, the band 1 can have an average width of 3.5 cm, a thickness included in the range of 3 to 6 mm and a length of about 100 cm, or in any case as necessary to wrap a chest.

A wave-shaped projection 7, whose function will be set forth later, is provided along the upper edge 1 1 of the band 1 , that is the one intended to remain turned upwards, when the band is worn.

The proposed apparatus includes a unit for collecting the signals corresponding to the heart electrical activity, consisting of an electronic circuit 2 situated along the inelastic portion A of the band 1 , approximately in a longitudinally central position and near the lower border 6 of the band. The electronic circuit 2 can be, for example, introduced between two layers of the fabric that forms the band 1 , or embedded therein, if composed of a synthetic plastic material or rubber. Consequently, the area of the band 1 with the electronic circuit 2 has a bigger thickness, for example of 6 mm. An opening for the access to a USB port associated to the circuit 2 is provided on the rear face of the band 1 or along the lower border 6 thereof.

The heart electrical activity is detected by the collecting unit (electronic circuit 2) using a plurality of electrodes applied to the patient's chest (not shown) connected to the collecting unit by connecting means 3, 4, 5, in this case constituted by connection buttons 3, 4, 5, called also terminal snaps, connected to said electronic circuit 2 by corresponding conductors 13, 14, 15.

The connection buttons 3, 4, 5, called also terminal snaps, are fastened to the fabric of the band or are embedded in the synthetic or rubber plastic material thereof. In any case, the buttons or snaps are fastened to the band by means of elastic supports 23, 24, 25 that support resiliently the buttons, almost as a damper, so as to prevent the adhesive electrodes from being pulled away.

This support system of the buttons or snaps allows to avoid, or at least substantially reduce the production of artefacts caused by the movement of the buttons or snaps, due to the mechanical traction of the band, which can provoke the partial or total detachment of the electrodes during the patient's movement.

Two lateral connection buttons or snaps 3, 4 are arranged at or in proximity of the lower border 6, with respect to the width of the band 1 , being spaced by such a distance as to remain situated at the sides of the patient's chest, while a third central connection button or snap 5 is situated in an intermediate portion between the two lateral connection buttons or snaps 3, 4 and vertically spaced from the horizontal plane passing therebetween, for example by about 3 cm.

In a more detailed way, the central connection button or snap 5 is situated at the upper pole of the area of the band 1 defined by a wave- shaped projection 7.

It will be appreciated that, in addition to the two lateral buttons or snaps 3, 4, other buttons or snaps (not shown) can be provided in order to detect other electrical signals, so as to have more electrocardiographic sources at the same time. For example, other buttons or snaps can be advantageously arranged on the same line of the lateral buttons or snaps 3,4, in order to obtain more precise readings.

Advantageously, the central connection button or snap 5 can be provided at an extroversion 7a made in the band 1 and more precisely in the above mentioned projection 7 (see figures 9 and 10). In this way, the central snap 5, which during the operations is positioned at the top of the patient's breastbone, generally having a concave morphology, and even more marked in subjects with "pectus escavatum", provides more stable and precise contact with the patient's skin. The central connection button or snap 5 is used as reference electrode, while the two lateral connection buttons or snaps 3, 4 are used as recording electrodes.

According to an advantageous version, instead of the buttons or snaps and the respective adhesive electrodes, the recording mode of the heart electrical activity uses strips of highly conductive material, for example graphite, applied to the band and intended to be positioned directly in contact with the patient's skin, when the belt is worn. In order to assure the optimal contact, the width of the strips is equal to the width of the band and they are 5-8 cm long. This solution practically eliminates very annoying operations of the electrodes application, requiring only a particular attention, when the band is put on, as regards a correct placing of the strips.

Moreover, power means 8 are provided, in this case composed of one or more batteries applied in suitable positions to the band 1 and connected to the electronic circuit 2 by relative cable 18 with a suitable connector.

The battery 8, or the battery pack, since in fact there are more batteries connected together, is joined removably to the band 1 , for example, it can be introduced in a bag of a waterproofed fabric (not shown) made adhere to the band 1 by means of a portion of fabric like Velcro, or by other suitable adhesion systems. This system allows to replace the battery pack, when it is discharged, or to introduce a pack with batteries having different characteristics, for example more or less powerful, as needed.

Non removable batteries can also be used, for example, of the dedicated type having a very reduced thickness (2-3 mm), and the width slightly smaller than the width of the band (about 3 cm) and the length equal to about 5-6 cm or as required, for constructive technique reasons. Such batteries can be introduced or embedded into the material that composes the thickness of the band (fabric, plastic, rubber or other suitable materials, as well seen in figures 9 and 1 1 ). In this case, also in order to compensate for the smaller capacity of each of them, the batteries can be placed in different areas along the inelastic part of the band (on one side or on both sides), as illustrated by way of a not limiting example in the above mentioned figures 9 and 1 1 .

Advantageously, the batteries 8 can have a curved conformation (the embodiment illustrated in figures 9 and 10), so as to better adapt to anatomy of the patient's chest, when the band 1 is applied. This allows to minimize the nuisance experienced by the patient when the electrocardiogram is carried out, especially at night.

It is to be noted that the embodiment of the band 1 illustrated in figures 9, 10 and 1 1 includes a front part 1 a of the band, illustrated in the figures, which houses the above described devices, and a belt, not shown since readily understood, adapted to connect the two ends of the front part of the band 1 a by means of slots 30a, 30b made therein.

An opening for a switch 17 and a window for a LED 16, provided on the front face of the band 1 at the electronic circuit, are adapted to operate the system and to signal its correct operation, respectively.

A further feature, illustrated in figures 9 and 1 1 , provides a pair of bends 31 a, 31 b on the upper side of the band 1 , substantially symmetrical with respect to the band center and thus to the projection 7 thereof. This allows to obtain better comfort for the user of the band 1 , especially if the user is a woman, since these areas of the band 1 adapt to the conformation of the lower part of the user's breasts.

According to another feature, not shown in figures, since it can be easily understood, the inner face of the band, at the terminal snap, is provided with a portion of Velcro material, and a corresponding portion of Velcro material, of complementary type, is fixed to the non conductive surface of the electrodes. In this way, the mechanical stresses, which merge in three points of the metallic snaps, are distributed on the whole surface of the adhesive electrode. The obtained advantage derives from the fact that the mechanical stresses of the snaps, especially during the movement of the user, are reduced and thus the band is prevented from sliding on the skin and the generation of reading artefacts is avoided.

According to the invention, in addition to the particular circuital configuration, some devices have been provided aimed at reducing as much as possible the problems deriving from the low frequency interferences and those produced by thermal effects.

According to a first feature, the electrodes are placed very close to the differential amplifier, so as to reduce the difference of the path and reduce the effects of the low frequency interferences.

According to the proposed method, a surface electrical signal detected by the reference electrode is measured. Such surface electrical signal contains the level of human body potential as well as known interferences, like those caused by the electromagnetic, thermal fields and others, coming from the surrounding environment. The signal of the reference electrode is introduced in the final stage of the amplifier, in a central point between the two gain resistors (see figure 7) so as to dynamically adjust the amplifier gain of the final stage. The modulation section of the final stage is connected in the circuit to the differential amplifier in order to calculate the difference with respect to the signal detected by the other two electrodes placed beside the circuit. This method produces a reduction of all the effects deriving from the low frequency interference and also from those caused by the thermal noise. The so obtained final electrical signal will have a significant reduction of the thermal shift.

Such methodology assures the above described result only if the reference electrode is placed exactly in the middle between the two lateral electrodes and not on the same conduction line of the two lateral electrodes. In fact, the reference electrode is situated at the level of the band wave (about 3-4 cm above the line that connects the two lateral electrodes).

According to the invention, in the used electronic circuit, a terminal contacting the skin, of the "Patch" type (plaster), picks up a signal of thermal interference, which is differentiated in the last stage of the amplification, so that the difference between the interference signal and the detected signal corresponding to the heart electrical activity applied in the last stage of amplification substantially reduces the thermal shift, to obtain more readable and interpretable ECG traces, thus facilitating the arrhythmologic diagnosis.

The electrode used to detect the signal of thermal interference can be, for example, the one connected to the third central connection button or snap 5, used also as reference electrode, while the other two electrodes act as real detectors of the cardiographic signal.

In detail, with reference to the circuit configuration of the inlet illustrated in figure 7, the technique has been adopted, proposed by the theory that reduces the current consumption in the two input terminals, and the voltage gain is that given by the relation:

The common mode voltage « i±Zl is also available, which will be used to minimize the effect of thermal interferences, as will be shown in the following.

The difference between the prior art and the circuit of the invention and the method implemented thereby is that the signal of thermal interference, taken by the reference electrode, is connected to the final stage of the amplifier in a central point between the two gain resistors, to dynamically adjust the amplifier gain and so as to substantially reduce the thermal shift.

Once the band 1 is worn and the electrodes are connected, the electronic circuit begins immediately to collect the detected signals corresponding to the surface electrocardiographic signal and to record them. They can be sent automatically to a cardiology data center every hour or with a programmable frequency, wireless interacting with a dedicated software downloadable on the mobile electronic devices (Telephone, PC, Tablet or yet other electronic systems of graphic visualization) or directly by a data SIM introduced into the system circuitry.

Furthermore, in case of arrhythmia symptoms, besides storing the data in the device memory, the patient who wears the band 1 will be able to visualize the ECG trace on his/her mobile phone or tablet, and send it directly to his/her cardiologist and reporting medical center.

It appears obvious, from what has been set forth above, that all the proposed objects have been obtained due to the device of the invention. A compact apparatus of reduced dimensions has been obtained. The band allows recordal of one or more branches (three branches) without using electrical cables coming out from the system, and its thickness includes therein the whole circuitry aimed at recording the electrical signal, as well as the power supply, by means of 'thin' batteries.

The quality of the signal is improved because the used devices reduce the artefacts caused by the electrodes traction and the configuration of the adhesive electrodes under the band which allows a constant compression thereof, prevent the electrodes from detaching. These devices, together with the circuital measures mentioned above, allow to use the system also for recording a good quality of the signal also during the sport activity.

The possibility to replace the battery pack provides functional flexibility which allows to apply the batteries with different power and which can allow variable recording time depending on clinical needs, for example, for short, medium and long term recording, that is hours, days or weeks.

Furthermore, the apparatus assures the functional interactivity, to make the arrhythmias detection rapid, with the possibility to send automatically the recorded data to a cardiology data center every hour or with a programmable frequency, interacting wireless or directly by a data SIM.

Furthermore, if the patient who wears the recording band recognizes symptoms of arrhythmia, besides storing the data, he/she will be able to visualize the ECG trace on his/her mobile phone or tablet and send it directly to his/her cardiologist and reporting medical center.

Finally, since the apparatus allows the patient to wear in an independent way the band and all the components associated thereto, he/she can temporarily remove it, for example, to take a shower.

It is understood that what above has been described as a pure not limiting example. Therefore, possible changes and variants of the invention are considered within the protective scope granted to the present technical solution, as described above and claimed below.

Claims

A method for the continuous electrocardiogram acquisition, by means of an apparatus including a band (1 ) provided with a unit for collecting signals (2) corresponding to heart electrical activity and a plurality of electrodes, placed in connection with as many terminals (3,4,5) set in contact with the skin, applied to the patient's chest for recording heart electrical activity and connected to said unit for collecting signals (2), from which said signals are then transferred to a center for processing and analyzing said signals, said system being characterized by dampening interferences caused by thermal shift by taking a surface reference electric signal by means of a "Patch" type terminal (5) forming a reference electrode that is set in contact with the skin and placed in a central part of said band (1 ), not in alignment with the other contact terminals (3, 4), the reference signal including a human body potential level together with other interference signals caused by electromagnetic and thermal phenomena of the surrounding environment, which signal is input in the amplification final stage of said electronic circuit in a central point between two gain resistors, so as to dynamically modulate the amplifier gain in the final stage, the modulation section of the final stage being connected to the differential amplifier in the circuit, in order to calculate the difference with respect to the signal detected by the other two electrodes placed beside said electronic circuit (2), so as to reduce all the effects resulting from the low-frequency interference and also the thermal noise, and to obtain more readable and interpretable ECG traces thus facilitating arrhythmologic diagnosis.

A method according to claim 1 , wherein said electrodes are applied to the chest of the patient in a position close to the differential amplifier of said amplifier electronic circuit, so as to reduce low frequency interference, and the reference electrode is positioned exactly at half the distance between two lateral electrodes,

3-4 cm above the line joining the two lateral electrodes and clear of the same conduction line of the two lateral electrodes. An apparatus for continuous acquisition of an electrocardiogram, of the type including a band (1 ) adapted to wrap the chest of a patient, a collecting unit (2) for collecting signals corresponding to the heart electrical activity, provided in said band (1 ), with said collecting unit (2) having therein an amplifier electronic circuit, and a plurality of electrodes, placed in the band (1 ) in connection with as many terminals (3,4,5) touching the skin, adapted to be applied to the patient's chest for detecting the heart electrical activity and connected to said unit for collecting signals (2), from which said signals are transferred to a processing and analysing center, said apparatus being characterized in that in said band (1 ), said contact terminals (3,4,5) include lateral terminals (3,4) aligned therewith, and a central reference terminal (5), not aligned with said lateral terminals (3,4), said central reference contact terminal (5) being connected to said amplifier electronic circuit at the last stage of the amplifier, in such a way that the difference between the signal detected by the reference electrode, in connection with the central terminal (5), and the electrical signal detected by the other lateral electrodes in connection with the lateral terminals (3,4) reduces substantially the thermal shift to obtain more readable and interpretable ECG traces, thus facilitating the arrhythmologic diagnosis. An apparatus according to claim 3, wherein said band (1 ) consists of fabric and/or plastic or rubber material to wrap the chest of a patient and is provided with detection means for detecting cardiographic signals of the patient, with connecting means (10) for joining the extreme ends of said band (1 ), and with power means (8) connected to said electronic circuit (2).

An apparatus according to claim 4, wherein said detection means for detecting the cardiographic signals of the patient include connection buttons (3,

4,

5), also known as terminal snaps, for the connection of said electronic circuit (2) to said electrodes, joined to the band by means of elastic supports (23, 24, 25) suited to provide a resilient support of the buttons or snaps and connected to said electronic circuit (2) via corresponding leads (13, 14, 15), wherein a central connection button or snap (5) is situated at the upper pole of the area of the band (1 ) defined by a wave-shaped projection (7), in an intermediate portion between the two lateral connection buttons or snaps (3, 4) and vertically spaced from a horizontal plane passing between the latter, with the central connection button or snap (5) connected with said reference and detection of the thermal interference signal electrode, while the two lateral connection buttons or snaps (3, 4) are connected to electrodes for detecting the cardiographic signals.

6. An apparatus according to claim 5, wherein in addition to the two lateral buttons or snaps (3, 4) other buttons or snaps are arranged along said band (1 ) for the detection of other electrical signals, so as to have more electrocardiographic sources at the same time.

7. An apparatus according to one of the claims 3 to 6, wherein said detection means are formed by strips of highly conductive material, such as graphite, applied to the band and intended to be positioned directly in contact with the patient's skin, when the belt is worn.

8. An apparatus according to one of the claims 3 to 7, wherein said band is formed by a first portion (A) made from an inelastic material, inside which said electronic circuit (2) is positioned, and a second portion (E) made from a resilient material.

9. An apparatus according to one of the claims 3 to 8, wherein said power means consist of a battery (8) joined removably to said band (1 ) and connected to said electronic circuit by means of a corresponding cable (18), or having very limited thickness and embedded into the material constituting the thickness of said band, or even by a battery pack (8) or two individual batteries placed symmetrically at the sides of said electronic circuit (2) and joined removably or irremovably to the band (1 ).

10. An apparatus according to claim 9, wherein a pair of batteries (8) is provided on the opposite sides of said band (1 ).

1 1 . An apparatus according to claim 9 or claim 10, wherein each of said batteries (8) has a curved conformation.

12. An apparatus according to claim 3, wherein said central reference terminal (5) is provided at an extroversion (7a) made in said band (1 ).

13. An apparatus according to claim 3, wherein said contact terminals (3,4,5) are fastened to said band (1 ) by strips of Velcro material, complementary one to another, placed respectively on the band and the respective terminal (3,4,5) which acts as electrode.

14. An apparatus according to claim 3, wherein said band (1 ) is provided, at its upper side, with a pair of bends (31 a, 31 b), arranged substantially symmetrical with respect to its center.