series, programming was "mechanical" insofar as a stationary or .... o The heart of the programmer could be a ... forbidden to use a code for which protective.
PROGRAMMING OF PACEMAKERS POSSIBILITIES OF STANDARDIZATION
M. Abignoli, B. Dodinot, J. P. Thomesse, E. Yvroud
Institut National Polytechnique de Lorraine Nancy, France The first true programmable pacemaker made its appearance in 1970. Chardack, who--together with his friend Greatbatch--was unquestionably the first to develop a reliable pacemaker containing a potentiometer which could be activated from the outside by a rotating magnetic field at the Mcpaco Symposium. By actuating a sort of magnetic whirligig, it was possible to vary pulse widths from 0.05 to 2 ms, measure the stimulating threshold and select a value compatible with a suitable safety margin. Through this procedure, it was demonstrsted that 0.1 ms was adequate for pacing in the majority of cases; under these conditions, amplitudes of 1.5 to 2 ms--the ones frequently selected at the time--were unnecessary: 0.5 ms (or even 0.3 ms) proved sufficient.
Introduction Europe is the battlefield of all pacemaker companies. In 1981, a European pacemaker center should possess nearly two dozen different pacemaker programming devices, or "programmers". In the absence of consensus between pacemaker companies to jointly design a universal circuit and "programmer", a compromise could be to build a multiprogramming device. This unit could be made of a minicomputer with two or three different output modules for signal transmission. A "pacemaker center" should be defined as a unit capable of caring for the needs of all pacemaker patients, regardless of the type of device implanted.
The presumable world record for longetivity held by a mercury pacemaker was beaten by a 5931 pacemaker programmed for a pulse duration of 0.3 ms, explanted for prophylactic reasons after 7 years and 7 months of implantation. Connected to a 500 ohm load, the parameters of this device have not changed over a period of 9 months. This purely mechanical programming procedure (the potentiometer was fabricated by a small Swiss watchmaking firm) was also adopted to modify the pacing frequency of demand pacemakers.
In 1981, the term "pacemaker center" is inapplicable to any European hospital department which does not have a full set of programming devices (to be supplemented from month to month); without this panoply of equipment, no pacing specialist--regardless of his ability--can trouble shoot or adjust the full range of programmable pacemakers sold in Europe.
Such a system would greatly simplify the life of the stimulists and increase patient safety, since programming could be performed by all clinics possessing the multiprogrammer.
1974: Electronic
Until the appearance of Cordis' Omnicor series, programming was "mechanical" insofar as a stationary or rotating magnetic field was used to activate a switch or potentiometer. The system designed by Cordis' engineers is a much more sophisticated one, and marks the starting point for all modern programming procedures. It makes use of the transcutaneous transmission of a coded message which is decoded by the pacemaker.
A Bit of History
The ability to modify one or more parameters of an implanted pacemaker non-invasively is a feature whose usefulness was recognized from the very first days of this therapy. At the beginning of the 60's, Vitraton and General Electric developed asynchronous 2-speed pacemakers: one standard (70), the other high-speed, which the physician (or pacemaker recipient) could select by means of a plain magnet. The approach failed to meet widespread acceptance.
The system is simple and has proved to be extremely reliable. In spite of the theoretical technical superiority of this sytem, then unique in the world, the Cordis programmable series (mercury models at the time) did not meet with the success anticipated by its designer. This rela-
In about 1965, Medtronic manufactured pacemakers containing systems for pacing frequency and amplitude adjustment. These were not true programmable models, as these parameters could be changed only by percutaneous insertion of a needle into the potentiometer. The procedure was uncomfortable, if not dangerous, and it failed to
tive failure was due to three factors: o lack of genuine necessity for frequency
programming; o small effect of
amplitude programming
pacemaker longevity;
arouse enthusiasm.
0195-4210/81/0000/0027$00.75 @ 1981 IEEE
Programming
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on
o price of these devices, substantially higher than that of competing pacemakers with preset parameters.
1980: Anarchy The manufacturers have made no effort to agree on a shared, common programming mode. Each pacemaker manufacturer has developed his own circuit, transmission mode, code and, of course, programming device. In Europe--more so than in the United States, where a discreet but effective protectionism limits the number of brands available--the state of anarchy has become alarming. It is important that we review the numerous disadvantages arising from this situation.
Lithium The resurgence of interest in programmable pacemakers was undoubtedly due to the marketing of devices fitted with long-life cells. Insofar as a pacemaker had an anticipated lifetime of only 2 or 3 years, it was possible to stick to standard units, if necessary selecting models having nonstandard frequency, amplitude or sensitivity characteristics. With pacemakers with lifetimes of up to 10 years, it proved preferable to have the ability to modify one or more parameters with passing time, in order to account for changes in both the myocardium and in conduction and the pacemaker proper (wire, cell, electronic circuit).
The Disadvantages
a)
High cost of development
The development and implementation of a complex circuit intended for limited distribution (pacemakers have not become a consumer good) is an expensive formula reflected in the sales price of pacemakers.
1980: Programmable Pacemakers: 30 to 80% of the Market In the United States, practically all firstimplants pacemakers are programmable models. These devices are meeting with increasingly widespread use in France, but we have not yet arrived at this extreme position. It is probable that programmable pacemakers will represent no more than half of all models implanted in France in 1980. This difference is basically due to the fact that physicians hesitate to make use of devices which are clearly more expensive than their less-sophisticated competitors when there is no overwhelming reason to do so. It should also be noted--although this argument is a more questionable one--that French manufacturers offered only standard versions up to 1980.
b)
High cost of equipment
A pacemaker center which intends to be able to handle any pacemaker patient who walks through the door must be equipped with all programming devices capable of acting on all available pacemakers: for the time being, this amounts to 15 units, each costing about 10,000 French francs. In practice, programming devices are given free of charge to implant centers which implant a given number of pacemakers. This is not a convincing argument, however, as there are not always enough patients available for implanting all pacemaker brands. Should a center agree to implant a given number of pacemakers of a given brand simply in order to receive a free programming device?
Nonetheless, there is no doubt that physicians will be led to make more frequent use of programmable pacemakers in the future, for a variety
c)
of reasons:
Patient dependency
A few years ago, the International Pacemaker Society defined a pacemaker center as a hospital
o The extension of indications justifying the use of pacemakers with non-standard parameters: atrial pacing, for example
in which more than fifty implants are performed annually, and one equipped with an emergency ward for efficient handling of pacemaker patients.
(high sensitivity, long refractory period, adjustable frequency); o Decrease in frequency of replacements, thanks to programming; o There is a long list of cases in which programming may prove useful. It is quite difficult to make an advance selection of patients likely to benefit from programming: given this situation, the physician tends to adopt the easy way out, leading to the replacement of asynchronous pacemakers by demand versions. Programming has also been supplemented by telemetry, which makes it possible to query the pacemaker, receive information concerning the state of parameters, wire and cell. This possibility opens new horizons to programmable pacing, and helps encourage the physician--often delighted with "gadgets"--to turn to this type of device even though few patients actually benefit from it.
In 1980, patients fitted with programmable models have become dependent on those centers having a compatible programming device.
d)
Increased complexity of the physician's task
The physician must maintain a number of devices in stock, the majority of which must be kept in a state of charge. A risk of programming errors exists. Two solutions might be proposed to eliminate this chaotic situation: o Taking existing equipment into account, develop a multiprogrammer capable of modifying the parameters of all pacemakers available on the market. o Start from zero and design a circuit, a code and a programmer adopted by some or
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all manufacturers: this is the true universal programming device.
istics.
Purpose
o The physician will be able to program all existing pacemakers without the need for purchasing and storing different programming devices.
The purpose of this device is to replace all existing programming device by a single unit capable of handling all past, present and future pacemakers. This multiprogrammer will also permit:
o The patient will not longer be dependent on any particular center as this multiprogrammer should be available in all true implant centers.
o display of the characteristics of each pacemaker handled: not only the characteristics of the program, but also the
o The cost of this device, which makes use of a mass-manufactured computer, will certainly not be prohibitive, particularly since it will eliminate the need to manufacture special programmers for each pacemaker brand in small production runs.
Solution No. 1 - The Multiprogranmmer
pacemaker's technical characteristics (e.g., end-of-life signs). o interrogation of the pacemaker, if it includes a telemetry system.
Disadvantages
Implementation
o One reason why the manufacturers have not been motivated to arrive at a common standard is that the personalization of the programming system makes the physician artificially dependent on the manufacturer. A physician with a limited volume of activity will hesitate to change his brand of pacemaker, and consequently his programming device, even if a system designed by a competitor seems to offer superior features.
Only a general description is offered here for pacing physicians, a practical implementation falling within the realm of the engineer. o The heart of the programmer could be a minicomputer, with a display console indicating the characteristics of the pacemaker and the program, enabling the physician to monitor the programming process and check the pacemaker's charac-
o Manufacturers will find false pretexts to hinder the development of a device which will enable physicians to switch from one brand to another without having to acquire additional equipment. We are dealing here with spurious arguments, but ones which can still lead to a number of objections that stall progress toward a standard.
teristics. o A magnetic card or cassette containing all data for each pacemaker handled by the programmer will be stored independently, and entered in the computer by the physician. A duplicate of the magnetic card stored at the implant center could be issued to the patient and entered in his medical record. In this case, the card could contain other items of personalized information concerning the patient and pacemaker settings.
Divulging Transmission Codes Transmission codes are often patented, thereby possibly preventing independent companies from developing competing programming devices. Of course, it is an extremely easy matter to learn the codes employed by individual manufacturers: a pacemaker and a programmer need merely be turned over to an engineer, who can figure out the "secret" using the most rudimentary equipment. It remains to be determined whether it is legally forbidden to use a code for which protective patents have been taken out!
o The only modification iquired by this computer is its being equipped with output heads for transmission of the message to the pacemaker and--in the case of a telemetry system--to collect information
issued by the device. In view of the transmission modes employed, at least two output heads will probably be required: one intended for the programming device and making use of magnetic transmission, the other handling radio frequency systems. Switching between heads should be automatic, with the physician informed of this fact by the computer.
The Manufacturer's Responsibility A manufacturer might be considered liable for erroneous design or incorrect use of a multiprogrammer which he has not approved. This, too, is a specious argument. A patient having suffered the effects of the impossible programming of a little-used pacemaker might justly be entitled to criticize his physician for having fitted him with a device which, rightly or wrongly, might be termed experimental. The manufacturer's responsibility might be invoked in case of refusal to participate in a system aimed at eliminating this handicap, which is bound up with non-standardization.
Advantages of the system o This procedure places no limitations on manufacturers; it accounts for all existing and future pacemaker types, and the manufacturer need only provide the pacemaker designer with device and program character-
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in comparison with existing models. Not a single manufacturer wanted to join forces with another to pool their energy and resources for the design of a programming mode which, if not universal, would at least be free of the domination of a single manufacturer.
Complexity of Manipulation There is no doubt that the manipulation of a multiprogrammer will be more complex than that of a device designed to handle a single pacemaker type. This complexity will be offset by the performance of the multiprogrammer, which will not only program, but also inform the physician concerning the chracteristics and performances of each pacemaker. It would also be surprising if a physician engaging in implants and in the monitoring of expensive, complex pacemakers could not manage to handle a minicomputer.
It must be acknowledged that it is hard to propose a standardization which, if excessively rigorous, might hinder the development of the technology. Some two years ago, it was possible to imagine the universal programmer as a device with three or four adjustable parameters. Today, telemetry appears to be a necessary feature; we are promised the Holter in a few years . . . extreme standardization would thus seem utopian. Nonetheless, the medium-term adoption of a certain standardization by means of multiprogramming is a feasible prospect. It is also probable that, in a few years, a sizeable number of manufacturers will stop fighting one another over a limited and increasingly controlled market. The joint development of a uniform circuit, the potential of which can be exploited in a variety of ways, would appear to be the logical and unavoidable solution. This trend is already taking shape insofar as some small manufacturers are closing their doors or merging with others.
System Cost On an individual basis, the multiprogrammer will be an expensive device. In any case, it would not be installed in all implants sites, but only in true centers whose activity is sufficient to warrant full equipment.
The future of the multiprogrammer No matter how objective, all physicians consider the current multiplication of programs and programmers as more of a hindrance than a help. The multiprogrammer is the ideal of the majority of heart specialists throughout the world, and particularly in Europe, which is a veritable battlefield where all of the world's manufacturers are struggling to win ground. The multiprogrammer can thus be manufactured on a large scale, with a European--and worldwide--market.
Conclusion In view of the proliferation of programming systems, priority should be placed on development of a multiprogrammer capable of handling all present and future systems. Such a device should be rapidly designed by an independent firm, financed by a body fully independent of manufacturer pressure. The necessary investment would be rapidly amortized, given the large potential market for this type of device, which could quite easily be implemented in France if a team of researchers and manufacturers were to receive the necessary resources without delay.
The manufacturers would soon cease to drag their feet if the multiprogrammer seemed reliable and easily manipulated. Major manufacturers will have the financial resources to provide their good customers with these devices, which will facilitate maintenance of their pacemakers. It might be more advantageous for the smaller manufacturers to rally round the multiprogrammer than to implement their personalized systems in small
production runs. If financing by the manufacturers themselves fails to appear desirable, it is conceivable that such devices could be financed by government agencies, laying the groundwork for a decrease in the sale price of programmable models. If this system is to operate without excessive friction between the various parties involved, the multiprogrammer should be rapidly designed and developed by an independent firm, but not by a pacemaker manufacturer, who might be accused of trying to muscle out his competitors in this manner.
Solution No. 2
-
The Universal Programmer
A year ago, we organized a meeting between European manufacturers in order to propose the development of a common circuit and program capable of replacing all existing systems. The only result of the idea was the development of a new circuit which offered absolutely no new features
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