Scientific and technical Development of transtelephone Electrocardiography in foreign Countries during the 60-80s of the twentieth Century

Vladzymyrskyy Anton Vyacheslavovich ORCID: 0000-0002-2990-7736 Doctor of Medicine Deputy Director of Research and Practical Clinical Center for Diagnostics and Telemedicine Technologies of the Moscow Health Care Department 127051, Russia, Moscow, ul. Petrovka, 24, p. 1 avv_mobile@mail.ru Other publications by this author

 The scientific and technical history of electrocardiography - a key method of examination and diagnosis of diseases of the cardiovascular system – covers a period of about 150 years and is characterized by versatility.

To date, the biographies and scientific activities of a significant number of scientists who have contributed to the emergence and evolution of this method have been studied in detail. The scientific schools that have had a significant impact both in the global perspective and at the level of individual countries are studied. The development of electrophysiology and related disciplines is described. The history of device design and the study of clinical issues is traced. At the same time, one of the aspects of the scientific and technical development of electrocardiography remains, in fact, unexplored.

The foundation of the methodology of modern electrocardiography (ECG) was laid by the Dutch physiologist Willem Einthoven (1860-1927) in the late XIX – early XX century. But even in this early period, telecommunications played a key role in the development of ECG. In the course of scientific research, V. Einthoven faced the problem of physical distance: bulky and complex equipment for recording an electrocardiosignal was designed in his home laboratory, and patients – whose signals should have been recorded – were, of course, in the clinic. V. Einthoven solved this problem by inventing a "telecardiogram" - a technology for transmitting ECG over a telephone cable ^[1]. A few decades later, this method has become extremely popular in practical healthcare. ECG has become the leading diagnostic method in cardiology, but its diagnostic interpretation required special knowledge and skills. The correct diagnosis required the participation of a qualified specialist, who was not always available. Therefore, ECG transmission technologies by means of telecommunication (telephone channel, radio, teletype) have acquired enormous clinical and social significance. After all, the data could be transmitted to any distance and get a remote expert consultation.

The set of technical and methodological aspects of remote transmission and interpretation of ECG in clinical practice in the middle of the twentieth century received the name "transtelephone electrocardiography". The scale of its application was very significant, in a number of countries new approaches to the organization of medical care were even formed on its basis ^[2]. However, a systematic study of the scientific and technical history of the formation of transtelephone electrocardiography (or tele-ECG) has not been conducted, the directions and significance of experimental design and research work have not been studied.

Research objective: to identify and systematize the patterns of development of scientific knowledge related to the creation and use of transtelephone electrocardiography technologies in foreign countries during the 1960s-1980s.

The geographical scope of the study includes the countries of Europe, Asia, North America and Australia. It should be noted that the scientific and technical history of transtelephone electrocardiography in the USSR is studied by us separately and will be presented in special publications.

The historiography on the subject of the study is sparse. The history of V. Einthoven's activity has been studied very fully and comprehensively, including the creation of the "telecardiogram" ^[3-7]. However, the events of the mid-twentieth century are, in fact, ignored. In R.Bashshur's key monograph on the development of telemedicine (that is, methods of using telecommunications to solve medical problems) in the USA, aspects of remote ECG transmission are mentioned only in passing, without the slightest systematization ^[8]. A small amount of biographical materials (Ts.Caceres, L.Larena) give only a general idea of their scientific research, but do not allow us to get an idea of the general picture of the scientific and technical evolution of the method.

The source base of the research is represented by a set of scientific works, journalistic, biographical materials, photographic materials.

Methodologically, the research is based on a systematic approach, historical-genetic, historical-comparative and general scientific methods.

Europe. In European countries, the scientific and technical development of transtelephone electrocardiography in the studied period of time can be characterized as limited. The studies were of a purely applied nature and differed mainly in their descriptive nature; 3 groups of relevant studies are quite clearly defined.

The first group of studies can be attributed, to a greater extent, to the scientific foundations of the organization of health care. The most significant was the creation of a model of remote monitoring of cardiac activity in patients who underwent cardiac surgery, most often – the installation of an artificial pacemaker (the so-called "pacemaker"). Due to the severity of the disease, such patients, quite obviously, needed long-term medical support after discharge from the hospital. In the vast majority of cases, such support consisted in the fixation and analysis of the electrocardiogram. In this situation, the use of transtelephone electrocardiography made it possible to carry out, in fact, constant monitoring; moreover, to do it quickly, comfortably and cost-effectively. Patients discharged at home received or purchased a set of equipment that allowed recording and broadcasting to a medical organization a one- or less often three-channel ECG. According to the schedule, in accordance with the doctor's appointment, or if the patient felt worse, he called the clinic by phone, transmitted an ECG to the doctor on duty, received an emergency consultation. This approach was perfectly perceived by both patients and doctors.

Several medical equipment manufacturing companies have brought relevant technical solutions to the market as part of corporate development work.

A new expression has appeared in the scientific literature, which has become quite stable: "pacemaker clinic" (from the English "pacemaker clinic") – as a designation of a model for organizing medical care for patients with an artificial rhythm driver based on technologies and methodologies of transtelephone electrocardiography. In the 1970s, such models were implemented in Germany, Denmark, Italy, the Netherlands, France, Czechoslovakia, and Sweden ^[9-14]. At the same time, there was practically no scientific analysis of the results of the activity of "pacemaker clinics"; thematic publications in scientific journals were purely descriptive in nature, contained quantitative statistics on the number of remotely monitored patients over a period of time. The structure of outcomes, economic analysis and other standard aspects of scientific evaluation in the clinical study were absent or had an episodic, non-systemic nature. It can be argued that the shortcomings of scientific analysis have adversely affected such a promising technology. The lack of evidence-based scientific information has limited its acceptance by a wide range of practitioners.

The second group of European scientific research in the field of transtelephone electrocardiography includes the design and testing of appropriate systems for the pre-hospital stage, that is, for use by emergency medical teams. The most significant scientific and practical work carried out in France under the supervision of Dr. Louis Lareng (1923-2019) is here. A portable telemetry system was developed that made it possible to remotely broadcast an electrocardiogram, pulse and respiratory rate, blood pressure readings by radio from an ambulance to a hospital. The system was successfully tested in October 1966, after that it was introduced in the ambulance service of Toulouse, where it was used in practice for a number of years. It is known that the data broadcast was supplemented by a voice consultation of a doctor, also carried out by radio ^[15]. The systematization of practical experience has not been carried out, there is no scientific analysis of the results.

It is known that transtelephone electrocardiography is used by emergency medical teams in Italy. However, the scale of this event was very modest (for example, in the period 03.1986-12.1988, only 311 remote consultations with ECG translation were carried out, thanks to which medical care was effectively provided at the patient's location, without transportation and hospitalization ^[16]).

The third group includes some experimental design work and descriptive research related to the creation and use of equipment for transtelephone electrocardiography for the purpose of remote interaction of large clinical centers and hospitals in rural areas or small private medical practices. Similar works were carried out in Germany, Italy, the Netherlands, Finland (Northern Lapland), Sweden, Yugoslavia ^{[12, 17-24]}. The scale of this activity, both from a purely scientific and practical point of view, was minimal and insignificant. For example, in Sweden, the work led by E.St?lberg was reduced to a purely experimental testing of equipment for transtelephone transmission of electrocardio and electroencephalogram from small rural hospitals to the University Clinic of Uppsala ^[25]. In the Netherlands, by 1977, experimental design work was carried out, optimal equipment configurations and technical characteristics were substantiated, a network of 10 points was deployed that carried out 1-channel ECG transmission between doctors' offices and large hospitals or between hospitals and doctors on duty at home. Experiments were conducted in the format of a "pacemaker clinic". ECG transmission by radio was also used in two emergency medical services ^[12]. This is an example of almost the largest practical application. The scientific analysis of the received experience was not carried out. It was only in 1984 that a single scientific article was published in the Netherlands with the results of comparing two methods of monitoring patients with cardiac arrhythmias on an outpatient basis: by means of periodic face-to-face examinations and by means of remote ECG transmission. The best clinical efficacy of transtelephone electrocardiography has been shown ^[26]. The most extensive descriptive study can be considered the work of Peter Bartunek (Petr Bart?wn?k) from Czechoslovakia. In the early 1980s, a group of scientists from the Faculty of Medicine of Charles University and the Czech Technical University designed their own equipment for the transtelephone transmission of a single ECG lead, which received the name "TELSAR". The equipment was successfully tested in five clinics in Prague and Bratislava, the Ministry of Health of Czechoslovakia decided to mass-produce the equipment, but political events (the coup d'etat as a result of the "velvet revolution") in 1989 prevented this from happening. In 1996, P. Bartunek gained 10 years of experience in using his own, reporting successful transtelephone transmission and remote interpretation of 3727 ECGs from 251 patients; from a clinical point of view, it was stated that tele-ECG was highly effective for detecting and controlling the treatment of cardiac arrhythmias ^[27-31].

The fourth group includes studies that combined the ideas of remote broadcasting and automated analysis of electrocardiography results.

In the mid-1970s, applied projects in the field of computational transtelephone electrocardiography were carried out in the UK, Greece, Italy, and the Netherlands. In particular, a network of 3 reception centers based on clinical institutions and at least 400 transmitters in small hospitals has been deployed in the Netherlands. Remote transmission of a 1- or 3-channel ECG was carried out for automated computer decryption using PDP-8E minicomputers and IBM-1800 computers. Diagnostic accuracy, clinical or other effectiveness have not been studied ^[12]. In Greece, the Athens National University of Technology has designed its own system of transtelephone electrocardiography and developed algorithms for computer analysis. The authors considered the fact of its use for 15 years to be the only confirmation of the quality of their development ^[32]. However, neither the volume of such use nor its results were presented again.

Most systematically, apparently under the influence of scientific trends in the USA, scientific and technical activities in the field of computational transtelephone electrocardiography were conducted in the UK.

In 1966-1970, physicist Dennis Walter Hill, with the participation of the staff of the Royal College of Surgeons in London (including Professor J. P. Payne), developed a system for remote automated ECG analysis. The first public demonstration of the telemetry component of the system took place on March 29, 1966 during the Biomedical Exhibition in Westminster. An ECG and a pneumotachogram of a 44-year-old man were broadcast over telephone channels from London to Westminster, and these studies were carried out on the patient during his bladder surgery. Further, the telemetry component was supplemented with computer analysis tools. According to subsequent descriptive scientific publications, on a certain permanent basis, single-channel ECG telemetry with computer decoding was carried out between the cities of Lincoln and London. Two experiments on cross–border remote computational diagnostics were also carried out: for automated decryption, data were transmitted to London in 1969 from France (Nancy), in 1970 from the Netherlands (Nijmegen). The researchers concluded about the possible interchangeability of computer equipment for uninterrupted diagnostics: "if one computer broke down, as for example, in Paris, then the same program can be run on the other and a call can be made to London" ^{[33, 34]}. We emphasize that these were one-time experiments that had no subsequent development.

In the late 1970s, a scientific group of doctors and physicists, under the general supervision of Dr. Peter MacFarlane (Peter W.MacFarlane), developed an algorithm for computer decoding of ECG. The corresponding system was deployed in the cardiology department of the University of Glasgow, and the transmitting equipment was placed in the Karluk Hospital. A 3-channel ECG was broadcast over two telephone channels and "digital information" (passport, anthropological and other patient data) was transmitted for subsequent machine analysis. The accompanying data was entered via a separate computer terminal, data transmission was carried out via a modem. The results of the computer decryption were sent in the opposite direction along the same line, which were then printed out. The authors claimed that the system could work with a clinically complete 12-channel ECG, but "there is no need for this for machine processing" ^[35]. It was extremely important that Dr. MacFarlane's scientific group, almost the only one, conducted a scientific analysis of the diagnostic accuracy of remote automated ECG analysis. To do this, the materials of transcripts of the results of 100 electrocardiographs were analyzed. This sample was first broadcast over telephone communication channels for machine analysis; then, the same ECGs were recorded on magnetic media and sent to the University of Glasgow by regular mail for re-analysis. The results of two consecutive transcripts were compared and found that the computer algorithm made mistakes in 4% of cases. According to the results of the evaluation of diagnostic accuracy, the system was improved, the authors stated the possibility of remote automated interpretation of about 65 thousand ECGs per year ^[35]. We emphasize that against the background of a purely practical approach to transtelephone electrocardiography in European countries, the work of Dr. MacFarlane's scientific group is distinguished by a more thorough scientific analysis at the stage of creating and scientifically substantiating a new diagnostic method.

Thus, during the time period under study, experimental and minor scientific research in the field of transtelephone electrocardiography was conducted in European countries. From a practical point of view, the corresponding systems were used to control patients with artificial pacemakers and arrhythmias ("pacemaker clinics"), to help emergency medical teams with emergency diagnostics, in separate centers for automated (computer) ECG decoding. The idea of creating a pan-European system of telemetric transmission of biomedical information was declared ^[12]. It should be noted that in the vast majority of European developments, the equipment created allowed remote ECG transmission only in 1 lead, the diagnostic value of which is minimal (the standard is to conduct this study in 12 leads). Due to the almost complete absence of a scientific approach to the study of transtelephone electrocardiography, no systemic changes have occurred in the healthcare of European countries. While in the USSR, the study and use of tele-ECG was of a large-scale nature. At the end of the 1970s, a nationwide scientific experiment was conducted on a comprehensive technical and clinical study of this method. On the basis of scientific results, regulatory documents have been adopted, a branch of production of appropriate equipment has been formed, a nationwide network of 354 remote diagnostic centers has been deployed. From a practical point of view, the number of remote tele-ECG consultations was measured in tens of thousands per year; the performance of the health system improved. From a scientific point of view, methodological recommendations, scientific articles, monographs have been published ^[2]. In the USA, the scientific and technical development of transtelephone electrocardiography was also very active. Based on the stage-by-stage development and research work, a new model of medical care organization based on remote automated interpretation of electrocardiography results was developed and implemented. This process will be studied in more detail later.

Asia and Australia. In the late 1960s and early 1980s, scientific and technical work in the field of transtelephone electrocardiography was carried out in Japan. The earliest experimental design work in this area was conducted at the Medical School of the University of Shova (Tokyo) in 1969. Later, in 1973, the scientific and technical implementation of the "pacemaker clinics" model began. In particular, a scientific group led by doctors D. Hattori (Jun-ichi Hattori, Kanto-Teishin Hospital, Tokyo) and Yu. Sakurai (Y. Sakurai, Niigata Hospital) in September 1973 conducted an experimental study of the possibility of transtelephone transmission of data on the work of an artificial rhythm driver. A year later, in October 1974, after technical improvements, the corresponding equipment was put into practice. Initially, data transmission was carried out through two channels, but this design of the transmitting part was too difficult for patients – 60% of them failed for technical reasons. Then the equipment was once again refined, simplified. After that, the "pacemaker clinic" functioned in a routine manner. It should be noted that this organizational model of medical care was implemented in Japan by analogy with European countries. However, unlike their colleagues, the group of D. Hattori and Yu. Sakurai performed a scientific evaluation of its effectiveness. In total, over 2 years, about 60 people have become patients of the "pacemaker clinic". In 1978, scientists analyzed the results of remote monitoring of 15 of them, who carried out a long-term transtelephone transmission of a single-channel ECG, the pulse frequency of the pacemaker and the frequency of cardiovascular contractions. Scientists compared the accuracy of diagnostic solutions for remote observation and face-to-face visits of patients and found them to be the same. An analysis of transport and time costs was also carried out; again, the remote monitoring format turned out to be more economical and convenient for patients ^[36-38].

From 1975 to 1980, the issue of creating regional medical networks for transtelephone transmission of ECG at the outpatient stage of treatment was discussed in the Japanese scientific literature. The study of the technical suitability of public telephone communication channels for the transmission of medical data was carried out (data transmission was carried out between Tokyo and Fukuoka at a distance of about 1000 km) ^[39]. In the first half of the 1980s, the most significant activity here was the scientific group of Professor Yoshiaki Nose (Medical Faculty of Kuishu University). Technical testing was carried out by this team, and the communication channels were found to be quite suitable. Next, equipment imported from the USA was deployed: an IBM computer and software for automated ECG analysis developed by Bonner et al, 1972. During the first month of operation, 1236 electrocardiograms were remotely transmitted. The technical quality in 98.6% of cases was completely satisfactory. Nevertheless, the participants of the scientific group modified the software, adding a remarkable functionality for its time – automated analysis of the quality of data received by phone and informing the subscriber about the need to resend ECG results if this quality was low. That is, the actual decoding of the ECG was preceded by technical control of incoming data. The Center for Remote Automated ECG Analysis has been actively functioning on the basis of the Medical Faculty of Kuishu University for 5 years, during which time about 35,000 remote computer transcripts have been carried out ^[40-42].

Thus, geographically, the scientific and technical development of transtelephone electrocardiography in Asian countries during the time period under study is limited to the territory of Japan. The relevant studies carried out did not differ in scale and originality. Structurally, most often equipment was created for the transmission of ECG in one lead, which has minimal clinical value. Organizationally, the model of a "pacemaker clinic" was reproduced for remote monitoring of patients with cardiac arrhythmias. In terms of automated remote ECG analysis, foreign developments were used. Although it is necessary to emphasize a certain innovativeness of local improvements of the corresponding software. The ideas of scaling transtelephone electrocardiography to the national level, in the studied period of time, remained unfulfilled.

In the world, the following situation was quite typical during the time period under study: a scientific group of doctors and engineers was formed on the basis of a clinical medical organization; experimental design work was carried out with a great deal of enthusiasm, as a result of which their own technical solution for transtelephone electrocardiography appeared; 1-2 descriptive articles or theses were usually published after initial testing. Quite often, research stopped there, the authors themselves usually did not give explicit reasons for this, but indirectly we assume that in most cases the level of technical implementation did not allow for high-quality data transmission. With the positive development of the situation (sufficient technical level), the tele-ECG system functioned on the basis of a medical organization for several years. Commercial services were provided or other forms of cooperation were established with remote medical organizations that needed advisory support. After some time, 1-2 scientific articles reappeared, most often of a descriptive nature, with minimal scientific value.

A classic example of such a typical situation is the activity of a scientific group from the Royal Melbourne Hospital (Australia). In the early 1970s, an initiative scientific group was formed in this medical organization under the leadership of the head of the cardiology laboratory, doctor John Graeme Sloman and the head of the Department of Electronic Engineering Raymond D. McDonald. At the first stage, a proprietary design of equipment for transtelephone electrocardiography was developed ^[43]. At the second stage, the system was tested and the experience of remote consultations was analyzed. Despite the extremely small sample size (only 22 patients), the authors argued that the tele-ECG made it possible to improve the quality of diagnosis of various cardiac arrhythmias, as well as to manage "self-medication" by patients under remote control.  Finally, at the third stage, the system was implemented at the Royal Melbourne Hospital to solve two practical tasks on a routine basis: consultations of nursing staff by specialist doctors outside of working hours (ECG receivers were installed in the homes of six cardiologists - employees of the Royal Hospital); remote consultation of regional hospitals (about 10 medical organizations, including, Royal Perth Hospital, Sutherland Hospital) and individual private offices of general practitioners ^[44]. According to the results of all activities, only 2 scientific articles were published.

Thus, both in Asia and in Australia, scientific and technical activity in the field of transtelephone electrocardiography was limited in the period under study. Experimental design work prevailed, while clinical scientific research was descriptive or very superficial. Such an imbalance in favor of technological aspects (as opposed to medical and organizational ones) has become a deterrent. The development of such an important methodology for healthcare turned out to be minimal. A fundamentally different situation was observed in North America.

North America. During the 1950s, the problems of transtelephone ECG transmission in the USA were studied in parallel by a research laboratory at a large corporation and by individual scientific groups of enthusiastic scientists.

The latter include two associations.

In 1952, a group of specialists from the University of Nebraska College of Medicine (W.E. Rahm, John Lucian Barmore and Lowell Dunn) a device was designed for signal modulation/demodulation and ECG translation. The equipment was tested in 1953. approbation by remote transmission of more than 50 individual ECGs between the settlements of the states of Nebraska and South Dakota at a distance of 500 to 1200 km. The authors reported on the high diagnostic quality of the data obtained and the reliability of the technical design ^{[45, 46]}.

In 1952, a group of enthusiasts was formed consisting of a doctor and an employee of the University of Kansas Medical Center Edmund Dimond (Edmunds Grey Dimond), engineers Fred Berry (Fred M. Berry) and John Walker (John L.Walker) ^{[47, 48]}. For 6 months, the group conducted experimental design work, as a result of which an original transistor device for transmitting heart tones and ECG over telephone communication channels appeared. In the first samples of the device, 9 vacuum tubes were used, later they were replaced with 15 transistors; the power supply was organized from batteries; the receiving device included a modified recorder. An interesting feature of the technical solution was the possibility of temporarily interrupting the transmission of the electrocardiogram "for questions and comments", followed by the resumption of data transmission without loss of their diagnostic quality and integrity.

On October 13, 1952, the system was first tested by broadcasting an ECG from Watkins Memorial Hospital (Lawrence) to the laboratory (Kansas City), where the device was being developed. It should be noted that, in general, the American scientific school in the field of biotelemetry and telemedicine is characterized by a mandatory emphasis on the dimension of the distance at which the exchange of biomedical data is carried out. The authors of the described system also did the same: for the first time, the ECG was successfully transmitted over a distance of about 70 km ^[49].

Further technical improvements continued. On March 13, 1953, the test data exchanges were repeated many times, now the researchers were exchanging ECGs between the cities of Kansas City, Wichita, Hayes and Joplin (Massachusetts). The results of the testing were encouraging. Financial resources for the development of the equipment were provided by John Walker, who also founded the company "Johnnie Walker Cardiovascular Engineering", engaged in the serial production of original equipment for tele-ECG. In April 1954, a public advertising campaign ("the first commercial broadcast") took place, followed by the first introduction. The tele-ECG system is installed in the tuberculosis sanatorium of Norton and the private office of Dr. J. J.L. Morgan in Emporia, who supervised the patients of this institution on internal medicine and cardiology. The technology was a success. By 1958, about 70 implementations were implemented on a commercial basis in different states, mainly to solve diagnostic problems in rural areas (for information, the cost of the system was 450-500 US dollars) ^[50]. The technical solution was presented to military specialists ^[47-49]. By 1961, researchers had designed a modification of the device for transmitting ECG by radio, assuming the ability to record the electrical activity of the heart during the performance of a particular physical activity by the person being examined. However, this version of the device did not leave the walls of the laboratory ^[51]. The authors did not admit the true reasons for this. However, taking into account the situation with other similar development work ^[2], it can be assumed that the task of transmitting a signal with the required level of diagnostic quality by radio remained technically unresolved.

Despite the successes of individual groups, the emergence of a universal technical solution for data conversion and translation contributed to the really active scientific and practical development of transtelephone electrocardiography in the USA.

Since the early 1950s, the AT&T Group of telecommunications companies (also known as the Bell System monopoly) has been developing modulating/demodulating devices (modems) for exchanging various types of data over public telephone communication channels. In 1953, this technology was applied in the field of medical science: together with the Medical College of the University of Nebraska, an experiment was carried out to broadcast the results of electrocardiography and electroencephalography. The diagnostic quality of the information received was clinically significant, the technology of transtelephone ECG was considered potentially important for connecting doctors from hospitals in rural areas with specialized medical centers. Later, a commercially available solution appeared: in the early 1960s, AT&T Bell Laboratories launched a modem called Dataphone, which allows data exchange over telephone communication channels at a speed of about 1200 bits per second ^[52]. It was a reliable device, easily integrated with various digital devices, including medical devices. The modem was used on a very large scale, in various fields of activity, including medicine. Its name has even become a household name, the term "dataphone" in the corresponding meaning is also found in the Russian-language scientific medical literature ^[53]. Now scientists-enthusiasts of tele-ECG have no need for complex experimental design work, it was only enough to solve the quite trivial task of connecting this model of an electrocardiograph and a dataphone. During the 60s of the twentieth century, a number of networks emerged throughout the United States connecting the offices of private practitioners, small, more often rural hospitals with large medical organizations. At the same time, each time a group was formed of engineers – representatives of the regional monopoly company "Bell System" and enthusiastic doctors, more often from local university clinics. Such a group performed a small experimental design work on the integration of a typical electrocardiograph with a dataphone. After that, a center was opened on the basis of the corresponding clinic, which provided remote consultations with transcription of the transmitted ECGs. In many cases, the medical representatives of the group analyzed their own experience, formed methodologies for organizing and providing medical care using transtelephone electrocardiography, and published relevant scientific articles. Next, we list the activities of such scientific and practical groups.

1961, Birmingham, Alabama – a scientific group led by doctor True W. Robinson, including engineers from Southern Bell Telephone and Telegraph, integrated an electrocardiograph with a dataphone; on December 20, the system was successfully tested, after which a decision was made on its serial production ^[54].

1963, Creighton, Nebraska - a scientific group led by physician Richard W. Booth, including engineers from Northwestern Bell, deployed an advisory center at the university clinic and created a "dataphone network" for remote ECG diagnostics. In the early years, the network consisted of only 2 transmitting stations, by 1970 the number of connected hospitals had increased to 178 (and the network already covered not one, but 10 states); by 1980, the total number of remote consultations was about 84,000. Dr. R. Booth himself described the work of the network as follows: "Even on weekends we could get 50 ECGs for analysis at home… In our best years, we processed 100,000 [ECGs] each... We have expanded [the telemedicine network – author's note] from Wyoming to Illinois and from the Canadian border to Kansas" ^[54].

By 1964, AT&T Bell Laboratories had developed its own complete system, which included both a portable electrocardiograph and a dataphone. For promotional purposes, a public demonstration of an ECG was held between two hospitals in New York and Long Island (Prospect High Hospital and Long Island College Clinic) ^[55].

1966 – Miami, Florida. A comprehensive solution for tele-ECG from Southern Bell was tested by doctors Louis Lemberg and Paul D. Unger, after which an advisory center was opened on its basis at Jackson Memorial Hospital ^[56].

1968, Appleton, Wisconsin. An advisory center has been opened on the basis of St. Elizabeth's Hospital, to which 5 local hospitals are connected, physically remote at a distance of 16 to 80 km (in 1973 another medical organization was connected to the network). Scheduled ECG transcriptions by cardiologists were carried out on an ongoing basis, the total number of remote consultations was measured in thousands ^[57].

1970, Arizona, on a regular basis, remote consultations based on transtelephone electrocardiography were conducted between the Medical College of the University of Arizona (Tucson) and St. John's Hospital. Joseph, located at a distance of 130 km ^[58].

In the context of the scientific and technical development of tele-ECG in the USA, it is necessary to note the development work on the creation of equipment for the pre-hospital stage, that is, for use by emergency medical teams during visits to patients. In such situations, the ECG had to be broadcast not by phone, but by radio; however, this did not change the methodological essence of the developments ^[59-61]. You should specify the activity:

1.      A scientific group consisting of assistant Professor Eugene L.Nagel, physician James Hirschman and radio engineer Ben Denby, who designed radio telemetry equipment for the Miami rescue services in 1965. In the future, this development was used by similar structures in Washington, Seattle, New York, Los Angeles, Nassau, etc. ^[62-67]. 

2. Dr. Herman N. Uhley and the Electra-Biometrics of Lancaster company, who designed radio telemetry equipment for the rescue services of San Francisco in 1970 ^{[68, 69]}.

3.      Companies "Biophone Company" and "Motorola", which launched two tele-ECG systems on the market in the early 1970s, which provided remote transmission of ECG in 12 leads and voice communication for consulting via radio (devices "Biophone" and "APCOR (Advanced Portable Coronal Observation Radio)", respectively).

The medical, psychological and social significance of prehospital systems for remote ECG consultations is aptly reflected in a quote from 1974: "In those early years of the development of the system, telemetry was like a handshake, indicating boundless trust between paramedics on the streets and consulting doctors in the hospital" ^[67].

In the mid-1970s, several US medical centers implemented the "pacemaker clinic" model ^[13], which we described in detail above. However, unlike in Europe, scientists from the USA conducted a scientific analysis of the effectiveness of remote outpatient monitoring of patients with artificial pacemakers and arrhythmias ^[70]. For example, a scientific group from San Joaquin Hospital (Bakersfield, California) has scientifically proven a reduction in the number of complications, emergency hospitalizations and other negative outcomes in the case of regular ECG autotranslation by the patient by phone to the supervising medical organization. These results played a significant role for clinical science ^[71-74].

It should be noted that there have been single attempts to use an alternative approach: instead of modulation/demodulation of the electrocardiog signal, use the transmission of still images (i.e. ECG on film) via teletype ^[75]. However, the poor quality of the data obtained and the overall complexity of the process stopped the development in this direction.

The listed stages and directions of scientific and technical development of transtelephone electrocardiography were of a pronounced applied nature. However, at the same time, extensive practical experience was accumulated and, most importantly, scientifically studied. The results of such an analysis were significant for clinical medicine (clarification and development of the methodology of remote interaction through telecommunications and data telemetry) and were the scientific basis for the development of the healthcare system.

The leading scientific direction in the field of transtelephone data transmission and remote cardiological diagnostics in the USA, during the time period under study, can undoubtedly be considered computational diagnostics – research work in the field of automated analysis of electrocardiography results.

The basis for effective automation is the system of standardization of ECG decoding created in 1960 – the so-called "Minnesota Code" ^[76]. This is a unified system of terms and codes for a unified description of the results of electrocardiography, almost ideally suited for algorithmization.

The leading North American scientific group in the field of computational diagnostics is the association led by Professor Cesar Augusto Caceres (1927-2020).

The corresponding research work has been carried out since 1961 in Washington at the Medical Systems Development Laboratory (MSDL) of the US Department of Health and Education ^[77-79].

The key achievement was the creation of original algorithms and software based on them for decoding the results of electrocardiography in accordance with the Minnesota Code. Both direct and telemetric data entry was provided. Accordingly, in the first case, the electrocardiograph was connected to a computer, in the second – the data was received via telephone or radio communication channels. It is important to note that the analysis of the most clinically significant ECG was performed in 12 leads. Initially, the software was deployed on a CDC-1700 computer, later it was improved many times, adaptation for different computer platforms was carried out. Let's quote the original description of the system: "...A telephone system is used to send signals in analog form to a computer. The signal is received by a dataphone, entered into an analog-to-digital converter and sent to a digital computing system for analysis. The signals are processed, interpreted and prepared to be transmitted back to the doctor within a few seconds after they are received in the processing center. Measurement and interpretation data are output to a teletype or to a remote printing device" ^[77-79].

The first regular user of the remote ECG transcription service was a private practitioner (Dr. John Stauffer, Hagerstone, Maryland), others began to follow his example. By 1963, the volume of remotely decoded ECG computers reached 5,000, the number of users increased by leaps and bounds; hospitals from the cities of Washington, San Francisco and Columbia, surrounding rural settlements became users of the system ^[77]. Such a rapid accumulation of data allowed the scientific group of Professor Caceres to continuously improve their algorithms, increasing the accuracy of ECG decoding. In 1966, the "United Archive of Electrocardiographic Data of the Federal Department of Health" was organized on the basis of the Laboratory for the Development of Medical Systems ^[77]. Thus, the service of automated ECG decoding was centralized, and at the national level. The centralization of diagnostics met the specific needs of the US national health system. Let's explain this statement. A significant amount of medical care, especially outside of large cities, was provided by general practitioners. The corresponding private offices or small outpatient clinics could be equipped with rather complex diagnostic equipment at that time. However, the interpretation of the data received had to be carried out by a specialist doctor. The competence of a general practitioner in such situations was usually not enough. The outsourcing model of professional expertise is very typical for US healthcare. Accordingly, the presence of centralized diagnostic centers was in demand and justified. This is confirmed by the above number of annual appeals to the "United Archive".

Professor Caceres' group continued scientific work, in particular, additional algorithms were developed for decoding the spirogram (recording the results of a diagnostic examination of the function of external respiration).

A significant number of medical organizations began to use the capabilities of the "United Archive", the average annual number of analyzed diagnostic results reached 50 thousand. ECGs in this array occupied 70%, only spirograms – 10%, and the remaining 20% - sequentially recorded ECGs and spirograms. The demand for technologies for automated analysis of medical diagnostic data was obvious. At the same time, it is important to point out that indeed remote decoding of ECGs transmitted by telecommunication means was carried out only in 40% of cases. In other situations, the recorded ECGs were transmitted to the decryption center physically, by messengers or by mail on magnetic media.

Regardless of the method of obtaining the initial data, the duration of the automated consultation was no more than 24 hours. It is obvious that the diagnosis was carried out only for planned situations (a patient with acute cardiological pathology could not wait for a diagnosis for such a long time).

At the end of the 1960s, ECGs were transmitted from 14 localities on a permanent basis by transtelephone means. Only 8 medical organizations were particularly active, providing a total of 25% of requests for remote transcripts. It is noteworthy to note that geographical remoteness did not affect such activity in any way: the physical distance from hospitals to the "United Archive" varied from several hundred meters (the neighboring block) to 5000 km.

Electrocardiographs integrated with standard telecommunication means (teletypes and dataphones) or special telemetry devices for broadcasting an electrocardiogram signal by telephone or cable channel directly into a computer were used for data transmission. A notable development was mobile electrocardiographs (so-called "trolleys") with built-in modems for data transmission over telephone communication channels. During the time period under study, such technical solutions were almost simultaneously released to the market by several manufacturers of medical equipment. Thanks to this, it became possible to transmit an ECG for remote automated decoding directly from the patient's bedside. The exchange of additional clinical information and the results of decoding took place via teletypes, less often in the format of telephone calls ^{[78, 79]}.

The idea of computational remote diagnostics was scaled up very quickly. Firstly, the volume of services provided by the United Archives increased, secondly, copies of the Caceres group's software began to be purchased by individual hospitals for installation on their own computer facilities, and thirdly, other scientific groups began to conduct their own, often quite successful, developments to create machine analysis algorithms.

In a number of cases, ECG remote interpretation centers (where doctors worked) expanded their capabilities by outsourcing automated transcription. An example is the "dataphone network" and the advisory center in Creighton, described above. By 1966, this network already included about 30 hospitals and offices of general practitioners in rural areas. ECGs were sent both for remote interpretation by cardiologists and for machine analysis in Washington.

The scientific analysis of the quality and effectiveness of remote automated ECG diagnostics was carried out on the material of three networks - in Hartford (Connecticut), Knoxville (Tennessee) and Columbia (Missouri) ^[77].

The City Hospital of Hartford joined the "United Archive" as an active user – up to 20,000 ECGs were sent annually for remote automated analysis. The data was transmitted via dataphones, the decryption results were received back via teletype. When studying the accuracy, the coincidence of remote automated and face-to-face medical diagnostic solutions was found in 85% of cases ^[77].

In Knoxville, in 1966, an independent automated analysis center based on the software of the C. Caceres Group was deployed on the basis of the St. Mary's Clinic. Data transmission points were organized first in three, then in nine hospitals in the surrounding areas; a mobile ECG removal point for preventive examinations of the population was also organized. The ECG results were sent to Knoxville via telephone communication channels, the conclusions were "returned" by teletype. For the transtelephone transmission of ECG, a special device "Tel-EK" was used, which ensures the integration of an electrocardiograph and a communication channel. The total number of remote automated ECG transcriptions was 4000-6000 per year. In 1967 and 1968, two scientific studies were conducted to assess the diagnostic accuracy of this diagnostic method. According to the first study, based on the material of 200 remote transcripts, complete coincidence of diagnostic solutions was noted in 72.5% of cases, minor discrepancies were detected in 18%, significant discrepancies – in 9.5%. Next year, the sample size was increased to 300 cases, the corresponding accuracy values were 81%, 12.7% and 6,3% ^{[77, 80, 81]}.

In Columbia, an independent center for automated analysis based on the software of the C. Caceres group and the CDC809 computer was established in 1968 on the basis of the University of Missouri Clinic. Initially, ECG transmission over telephone lines was carried out from the offices of six general practitioners from Columbia itself and from the cities of Bonneville, Kansas City, Cordwell, Springfield, Trenton. By 1976, the network already included 25 transmitting points within a radius of 500 km from the advisory center. In 1968, the initiators of the creation of the network - assistant Professor Donald A.B. Lindberg (Donald A.B. Lindberg) and doctor Philip Amlinger (Phillip Rudolph Amlinger) - conducted a scientific analysis of the experience of the first year of remote automated ECG transcripts, identified and described a number of technical features of this process (including increased noise immunity and reliability), evaluated diagnostic accuracy, scientifically substantiated further development of both the remote computer diagnostics method itself and specific hardware and software complexes ^[82-85].Additionally, it should be noted that the creation of all the above-mentioned networks and the corresponding scientific and practical activities were carried out under the auspices of the development of rural health and were funded by grants from various government agencies.

Here it is necessary to draw a certain boundary. The development of computer (automated) analysis of biomedical data is a very special, separate issue in the history of science and technology. Our research is devoted to the application of telecommunications in medical science and technology. Therefore, we limit ourselves to studying and describing the scientific and practical aspects of the use of machine analysis only as a component of remote medical care, without considering it as an independent subject of research. At the same time, we would like to note the undoubted relevance and importance of a separate study of the history of scientific and technical formation of automated analysis of biomedical data - the forerunner and basis of modern, so–called "artificial intelligence technologies".

A characteristic element of Professor Caceres' activity was active advertising. In modern terms, he combined "scientific PR" and commercial promotion of automated ECG decoding services. The main method of such advertising was a variety of public events of a popular scientific nature, including those covered in the media. These include [77-79, 86]:

- "competitions" between expert doctors and computers on the accuracy and speed of ECG decoding (doctors most often won on accuracy, due to the identification of important clinical nuances, the computer, quite predictably, invariably turned out to be faster);

- experiments on the transmission of ECG over long distances with the rapid return of the result of machine decoding (1965, 1500 ECGs were simultaneously transmitted along the Las Vegas - Washington line; in the same year, the fastest cycle of transmission, decoding and response transmission of results was recorded less than 1 minutes; 1968 transmission via Lima (Peru) - Washington (USA); 1967 intercontinental transmission via Tours (France) - Washington (USA) during the first meeting of the Congress on Medical Electronics and Bioengineering).

  The result of the scientific and technical activities of Professor Caceres' group was the creation of an automated ECG decoding technology, a methodology for the clinical application of this technology and an appropriate way of organizing medical care. Such a comprehensive scientific result has had a significant impact on practical healthcare. The results of the experimental design and research work of Ts. Caceres were scaled and taken as a basis for further research ^[87-92]. For example, in 1965, during a research and experimental project at the Massachusetts Institute of Technology, Lawrence Stark and James F. Dickson developed original algorithms and a computer program for analyzing biomedical data, including ECG results. Transcripts were carried out remotely, the data came from the Massachusetts Memorial Hospital ^[93].

As a result, in the mid-1970s, at least 20 large centers for automated ECG analysis operated in the USA, conducting up to 5 million transcripts (both remote and magnetic media) per year ^[77]. For example, the commercial service "CEIS" (Colorado) served 35 medical institutions within a radius of several hundred kilometers, the service "TELEMED Corporation" (Illinois) - 480 hospitals that sent up to 4,500 ECGs per day for automated remote transcriptions ^{[12, 94]}.

Later, at the end of the twentieth century, the implementation of automated ECG analysis changed: the corresponding function began to be implemented on the technical basis of electrocardiographs. Actually, to this day, each such diagnostic device performs an automatic preliminary decoding of the recorded electrocardiogram.

Thus, in the USA, the scientific and technical development of transtelephone electrocardiography - as a set of technologies and methodologies for remote diagnostics using telecommunication means – was active, multilateral. Thanks to a number of parallel development works, the domestic market was saturated with financially accessible and technically reliable means for transmitting ECG both between medical organizations (by phone) and from the pre-hospital stage by ambulance crews (by radio). An important difference from the European developments of this time was that in the USA, remote transmission of ECG in 12 leads was mainly provided. The situation developed similarly in the USSR: a nationwide network of remote diagnostic centers provided work with this most clinically significant type of electrocardiogram.

The key direction of scientific and technical development of the transtelephone ECG in the USA was the creation of algorithms and means of automated (computer) decoding of ECG results. The undoubted theoretical and applied success in this field has become the key to the emergence of a new model of the organization of medical care – the centralization of diagnostics, which has had a significant clinical and social impact.

At the same time, it should be noted the limited capabilities of purely machine analysis. After all, it was reduced exclusively to processing the ECG curve, the anthropological and clinical data of the patient were not taken into account; the result was the output of several standard digital codes. Against this background, remote consultation by a cardiologist had undeniable clinical advantages. That is why it was quickly concluded that the purpose of using automated remote diagnostics is "not to replace a person with a machine or a doctor with a computer", but to quickly sort the ECG into "normal" and "pathological", while the latter were carefully studied by a specialist doctor ^[95]. Thus, by the end of the study period, an understanding of automated analysis as a means of supporting medical decision-making began to form. Regarding the "United Archive", it should be noted that the idea of creating a similar, but not a state, but an international center for the accumulation and interpretation of electrocardiography data was proposed in the USSR by academician Z.I. Yanushkevich in the 1970s ^[96], however, it was not fully implemented.

In Canada, during the time period under study, experimental design and research work was also carried out in the field of transtelephone electrocardiography.

In the early 1960s, proactive development work was carried out to create equipment for transmitting ECG results via telephone communication channels. For example, a scientific group consisting of the staff of the University of Western Ontario, Professor George W. Manning, doctor Konstantin T. Cerkez and Director of Technology of the Cardiology Center Gordon C. Steward ^{[97, 98]} designed a 12-channel electrocardiograph connected to a standard dataphone.  During the first four months of 1964, clinical trials were conducted: 102 remote ECG consultations were carried out between the hospital in London (Ontario) and the cardiology center in Wingham. The authors focused their attention on the clinical and organizational significance of this technology, in particular, the proportion of situations where timely ECG diagnosis was critical for determining treatment tactics was established. Also, thanks to the tele-ECG, the duration of the diagnosis was reduced from 3 days to several minutes, since before the introduction of the technology, the ECG results had to be physically transported to the Wingem. According to the test results, the authors carried out technical improvements of the equipment. The remote transtelephone electrocardiography system has been in operation for about 20 years; by 1986, about 350,000 remote ECG consultations were carried out. This scientific group also carried out developments in the field of radioelectrocardiography, having proposed an original design of a device for transmitting an ECG recorded by radio in conditions of normal life ^{[97, 98]}. However, this question is beyond the scope of this study.

In the mid-1970s, the well-known model of the "pacemaker clinic" was introduced in Toronto. In medical organizations, ECGs were received, independently transmitted by patients from home. At the Western Hospital, this process was led by Dr. Neil D. Berman, at the General Hospital by Dr. Kenneth W. Taylor. In both cases, a scientific analysis of this activity was carried out, positive clinical results were revealed ^{[99, 100]}.

Computational ECG diagnostics was developed at Dolhouse University (Halifax), where original algorithms and software for IBM 1800 computers were created. The ECG was received and analyzed both physically from hospital electrocardiographs and remotely via telephone channels. The system performance was low, about 30 ECGs could be processed within an hour ^[77].

Thus, in Canada, the scientific and technical development of transtelephone electrocardiography, in general, followed in the wake of medical science in the USA, not differing in either scale or novelty.

Conclusions. Summing up the above, we state that in the period of 1960-1980s scientific and technical development of transtelephone electrocardiography took place in many countries of the world, however, the activity and significance of these processes seriously differed. From the point of view of technical sciences, there were two main trends in scientific research: a) the design of hardware solutions for broadcasting and receiving ECG via cable or radio channels; b) the development of algorithms for computer analysis of ECG; from the point of view of medical sciences: a) clinical trials, including an assessment of the technical reliability of equipment; b) evaluation of diagnostic accuracy remote (both "human" and machine) interpretation of ECG; c) study of the clinical significance of tele-ECG.

The listed research directions were "intertwined", mutually complementing each other. The overall result was the emergence of clinically significant remote diagnostics techniques and new models of medical care organization based on them.

When comparing the trends of scientific and technological development of transtelephone electrocardiography in foreign countries, it is obvious that the countries of Europe and Asia follow in the wake of medical science in the USA. In the studies of scientists from Eastern Europe, the influence of medical science of the USSR in the form of the use of tele-ECG in occupational medicine is noted. Expanding the geographical scope of this study, it is necessary to note the following. The scale of scientific development and the importance for healthcare of transtelephone electrocardiography in the USSR and in the USA in the studied period of time were identical. However, methodologically, the development went in different directions. We will study this issue in more detail in the future.