A.B.Kramarenko, R.V.Pavlovich, L.V.Pavlyutin

Diagnostic value of transtelephonic ECG: approaching the standard


In spite the progress in telemedicine, wide use of digital technologies and other achievements of data transfer systems, transtelephonic ECG up till now cannot compete with standard one as to its quality. Therefore it is supposed that an ECG transmitted via phone cannot be a valid document describing the electric activity of the patient's heart. This widely spread opinion was undoubtedly correct and based on serious errors of transtelephonic electrocardiography that lover its diagnostic value.

Among the most significant drawbacks one can name the following:

  1. Analog data transmission is the most serious defect, which leads to the dependence of the quality of transmitted ECG from the quality of telephone line. Most frequently the degradation of signal-to-noise ratio occurs due to added line noise.*
  2. Acoustic coupling of the carrier emitter and handset microphone. This solution itself is acceptable, but combined with analog data transmission makes so indigestible hybrid that high quality electrocardiograms become an exception, but not a rule. The rule in this case will be highly noisy ECG, which forces the doctor to guess what happened during diastole.
  3. No indication of communication interruption. In this case, instead of the signal, you can receive anything you like, and only the operator's intuition can help to distinguish technical problems form cardiological ones.
  4. Non-synchronous transmission of the channels, which lowers the diagnostic value of the ECG and makes to remember the times when electrocardiographs were one-channel ones.
  5. Absence of indication of a poor electrode contact in the transmitter, which requires extremely high qualification of the receiving station operator. Indeed, one has only the artifact shape to guess a poor contact of the electrode and must inform at the end of transmission the sender on this. And, of cause, the investigation must be repeated.
  6. Improper application of electrodes (they are displaced in respect to required application points). This situation can lead both hyperdiagnosis and omission of pathognomonic phenomena, and to diagnostic errors.
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* Systems of this type usually use transmission of frequency-modulated pilot signal. With relatively small deviation caused by the bandwidth limitations of a telephone line and, especially, by the signal passing through systems with frequency multiplexing (still used in some regions), one can rarely obtain 'pure', i.e. noiseless ECG even with perfectly applied electrodes.
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If we imagine simultaneous action of these factors, we can only admire the enthusiasm of the people working with the transtelephonic electrocardiography and agree that this investigation has low diagnostic value, far beyond comparison with the standard 12-channel ECG recorded in a clinic.

Nevertheless the telemedicine progresses and demand in the remote ECG grows. And to make this investigation full-value one must eliminate the above mentioned factors and obtain electrocardiograms ABSOLUTELY IDENTICAL to those obtained in clinics.

Now we will try to list the requirements to a transtelephonic electrocardiograph. We exclude from consideration the requirements to ECG amplifiers (you must try hard to make a bad amplifier using modern components). Thus, a transtelephonic apparatus must be a standard 12-channel device with synchronous transmission of all channels, it must have a digital link with a central station, automatically indicate bad application of electrodes, and the central station must inform on communication interruptions and/or automatically correct malfunctions. Also, do not forget that the entire system must be adapted to Russian and Ukrainian communication lines and faultlessly operate under our conditions.

Besides, solving the problems of urgent diagnosis, the system must be survivable, that is, it must not reject the transmission, as e-mail does, but fight till the end trying to transmit at least some portion of electrocardiogram even under conditions of rural switchboard, because infarction is not a slight cold.

Let us suppose that all these requirements are satisfied and the obtained ECG does not differ from a standard one (Fig. 1). The record is made by means of a peripheral device of the system of transtelephonic electrocardiography "Тelecard GSM" with chlorine-silver disposable electrodes manufactured by Nessler Medizintechnik, located in standard pick-up points. Transmission was carried out by means of a cell phone Ericsson 1018, standard GSM-900. It is obvious that this record can be interpreted as a usual electrocardiogram and it is possible to compare records of such quality with those, which will be made later, after the patient will be admitted to a clinic. One cal also expect that such a system will trace slight changes in ECG during loading, medication, etc.

Fig.1
Fig.2

 

Record shown in Fig 2 is made when the patient drove a car in heavy city traffic. Clearly visible are not only the increase of heart rate frequency, but also changes of the shape of electrocardiogram complexes. There can be no doubt that pathological changes in ECG will be recorded similar to a standard 12-channel electrocardiograph.

Nevertheless, irreproachable digital quality of transmission does not guarantee correct diagnosis when the electrodes are applied improperly or when simplified, i.e. ersatz electrodes are used. This apparently trivial notion far from always is taken into account in practical work. The reasons must be looked for in the field of psychology rather than technology.

Let us take into account that transtelephonic ECG always was an investigation of not a first grade and it is quite clear that there is no use to waist good electrodes on ECG which will in any case become 'dirty' and of small diagnostic value. Besides, mass production of toy electrocardiographs with built-in metal electrodes (apply it to the chest and see ECG on the screen) has substantially reduced the exactingness to the quality of recording. And if we consider the number of half-operable 'Malysh' (Midget) (model of electrocardiograph) with ink recording which are used, it is not surprising that a doctor makes statement without any hesitation from an ECG with noise, trend, interference and 50 Hz hum. He can be understood - anyway, there will be no better recording.

Now we try to simulate a typical situation with ersatz electrodes. The record shown in Fig.3 was made with stainless steel electrodes 20 mm in diameter.

Fig.3
Fig.4

Standard gel was used, the places of electrode application were usual. The result can be called expected, as it is hard to imagine that respectful companies manufacturing disposable electrodes and respectful clinics all over the world, which use them, did not hit upon pieces of stainless steel in stead of electrodes. That is, there is no need to prove that a good ECG requires good electrodes, just see the result. But fact that electrodes must be applied to proper places must be proved, and best of all experimentally but not theoretically.

Let us carry out such an experiment: record a standard ECG (Fig. 4), reapply disposable electrodes to the position usual for cycle ergometry (Fig. 5) and then make one more recording, placing the electrodes in a single belt, as it is done in some system of transtelephonic ECG (Fig. 6). Records 3 through 6 are made with a standard 12-channel electrocardiograph "Decard-3m".

Of course, in the latter case (Fig 6) the differences are so large that the ECG BECOMES NONSTANDARD, and correct diagnosis is possible only by a specially trained investigator deprived from the possibility to use the generally accepted ECG semantics. It would be better to free the reader from contemplation of the record made with the combination of ersatz electrodes with the belt locating them in non-standard places. For the reason of humaneness.

Commercial companies, which consult on the basis of wide implementation of transtelephonic electrocardiographs, have made their business rather lucrative. The greatest achievements are in Israel, where locally manufactured equipment is widely used. In Russia systems of remote ECG diagnosis are already working in Moscow, Saint-Petersburg and some other large cities. There is no doubt that soon the companies offering their clients similar services will appear in the Ukraine as well. This is really extremely necessary aid to the patients from the risk group of corresponding groups of diseases. The transtelephonic electrocardiography has an excellent future in the market of advanced medical technologies and their applications in the interest of the patient.

Fig. 5
Fig.6

However, thoughtless transfer of foreign designs to local conditions is fraught with rather serious complications. In particular, completely different diagnoses can be established from one and the same ECG by two specialists, one of which is guided by the generally accepted international ECG standards, and the second uses the standards specially adapted to non-standard application of electrodes. In the case of diagnostic error, which has lead to substantial aggravation of the patient's health or his or her death, this contradiction immediately jumps from the narrowly medical field to the legal or even criminal one.

It would be better to avoid such collisions already at the stage of studying the experience of others. For this it will be sufficient either to use the systems of transtelephonic ECG working with the standard leads, or carry out additional standardization oriented to the electrode application technique distorted in respect to the generally accepted one. Besides, it is necessary also to additionally retrain the cardiologists who begin to work with non-standard transtelephonic diagnostic equipment. Nevertheless, the patient's electrocardiograms obtained with such "non-standard" service will have a diagnostic value only within this service itself and cannot be used by other cardiologists not completed the course of retraining without the risk of making an error.

Which version is more expedient - it is up to the reader to judge, as well as up to those state officials, who is responsible for certifying and legalizing foreign medical diagnostic equipment in Ukraine and Russia. However, we are sure that the digital 12-channel transtelephonic ECG, which does not differ from the standard one, will substitute the ersatz cardiographs, which the telemedical market offers today.


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