Seymour Furman

Implantable Cardioverter Defibrillator Infection

This issue of PACE contains three articles concerning infection of implantable cardioverter defibrillators (ICD). It seems that infection is the constant accompaniment and the bane (when it occurs) of any implantable device therapy whether orthopedic, vascular, or, in this instance, cardiovascular. Wunderly demonstrates that ICD implantation is associated with an incidence of infection that is both troublesome and much more frequent than we have grown to expect in other devices. Implantable devices, such as cardiac pacemakers, seem to be implantable with a far lower infection rate, indeed a rate near zero for initial implants seems to be usual. There have been reports of ICD infection in the 3%-7% range from other centers, and as in this report, infection is much more common following ICD pulse generator replacement than during primary implantation. The reason for either occurrence are not always clear, though poor vascularity of the ICD site has been considered as etiologic for a higher infection rate following pulse generator replacement. Early secondary procedures are commonly associated with higher infection rates for all foreign bodies and one of the penalties of the need to revise a previous intervention is infection. Whatever the reasons for infection and the means of prevention, it seems that occasional infection may always be with us. As that is the case, all who implant foreign materials, i.e., devices, must continually be ready with a plan for consistent, rational, and reliable management of infection when it occurs. We should not have to relearn what we already know.

AV Synchrony and Cardiac Rate

The past year has, for the first time in the 25-year history of direct cardiac pacing, seen a large number of paced patients returned to the normal AV sequence by the implant of a pacemaker. It is estimated that 15% of all pacemakers initially implanted in the U.S.A. are now in the DDD mode. The concept of pacemaker restoration of the AV sequence is an old one. It was initially proposed in 1958 and an AV synchronous (VAT) pacemaker was implanted in 1962. It depended, for effectiveness, on normal, flexible atrial function, the existence of complete heai-t block and the absence of ventricular premature contractions to avoid competition with spontaneous ventricular activity. Because of the need then to implant by thoracotomy and the inflexibility described, the approach never reached widespread utilization. An area of investigation, undertaken during those early years, was the effect of AV synchrony on cardiac function. Two conclusions were drawn by a number of investigators: the first that cardiac output increased substantially with increasing ventricular rate and second, that the restoration of AV synchrony, at any selected ventricular rate, added another 15-20%.

External defibrillation and implanted cardiac pacemakers.

The articles by Das and Gould in this issue of PACE reinforce sporadic reports over the past few years of recurrent perception that the implanted cardiac pacemaker and external defibrillation are substantially incompatible. Reports have appeared sporadically over the years, and with greater and greater frequency more recently. The present report adds to this growing literature and a recent event in the experience of the present editorial writer adds still another case. Pacemakers are totally destroyed, the surge of power may destroy the pacemaker and the lead or the myocardial electrode interface, or it may cause the deterioration of pacemaker function such as the near, but not total, destruction of the sensing circuit. It is impossible to know what the total number of defibrillations with an implanted cardiac pacemaker in place has been. It is equally difficult to know how many of these defibrillations have destroyed the pacemaker and because the defibrillation itself was unsuccessful the patient died, the pacemaker was not retrieved, and in any event, the state of its function was never ascertained. It is equally difficult to ascertain how many patients, having undergone defibrillation with an implanted cardiace pacemaker would have survived had the pacemaker continued to function normally after the cardioversion shock. For example, one would hardly blame an emergency room physician who after defibrillating a patient found that the patient had an implanted cardiac pacemaker, that stimuli continued but capture did not occur and the patient died. It is hardly likely that were the pacemaker buried with the patient that any manuscript concerning the pacemaker function would have been submitted. It would have been impossible to know whether the episode of fibrillation was a result of pacemaker malfunction, or pacemaker malfunction a result of the defibrillation. Thats exactly what makes this variety of report all the more important. It indicates to the medical and to the manufacturing community the fact that the destruction of the pulse generator is a distinct possibility and further that this variety of occurrence may be more frequent than any of us think. Dr. Gould suggests that the use of two anterior paddles be avoided if possible and that if they are used that they be kept away from the site of the pulse generator and the lead in the apex of the ventricle, especially with a unipolar pacemaker. Placement of the two paddles in that position would direct a larger portion of the defibrillatory vector directly into the pulse generator. He suggests as well that the anterior paddles, if they are used, be placed as far as possible from generator and lead tip and that if the option exists the anterior-posterior paddles be used to direct the output vector of the defibrillator at right angles to the sensing vector of the generator. This is all well and good and it is no criticism of the suggestion or of the report to state that it is most unlikely that that will almost certainly not be accomplished. It is hardly likely that a patient admitted in extremis to an emergency room with ventricular tachycardia or fibrillation will be known to have an implanted cardiac pacemaker or that the emergency room personnel will feel that the time is available to review the patients entire medical history. What is far more likely is that such a patient will have an electrocardiogram performed, and if the pacemaker is inhibited as it may very well be in the presence of ventricular tachycardia

The Benefits of Regulation

Some time ago, during a dual chamber pacemaker implantation, in a patient thought to be pacemaker dependent, we were presented with an interesting dilemma. As readers of this editorial series are aware, implants in my institution are preferentially performed via cephalic vein cutdown. Subclavian vein puncture is reserved for those implants in which the cephalic vein is too small or in which it is tortuous, or somehow does not lead to the axillary-subclavian system sufficiently directly to be useful for implant. Several issues have been clarified over the years of widespread use of subclavian puncture. One is that there is a complication rate associated with subclavian puncture, as may be expected, lower in experienced hands and higher for the inexperienced and infrequent operator. The operative complications are not inconsequential as they result from the (relatively large) needle striking and injuring a structure close to the subclavian vein, the pleural space, the subclavian artery, a branch of the brachial plexus, or any of less frequently injured structures. An arterial hematoma, a pneumothorax, or a hemopneumothorax may result. A long-term complication that has been well described^ and is now in the process of being explained^ is that of crush injury to a pair of bipolar leads trapped between the first rib and the clavicle, seemingly occurring only following subclavian puncture. It also seems that the more medial the subclavian puncture, the more likely is this late complication.

Sensors in Implantable Cardiac Devices

Implantable cardiac devices, i.e., pacemakers and implantable defibrillators have been created by the same burst of technology and invention that has created the modern electronic world. Specifically, progress has been derived from improvements in efficiency of electronic circuits, battery chemistry and capacity, hermeticity, lead durability, and a whole host of other factors. Probably the most important of these improvements is the understanding that greater input of data allows a device a greater sensitivity to body needs and correspondingly more flexibility in its response. Despite all of the other technological improvements, probably that which is most descriptive of change in the fields of pacing and defibrillation is the increase in the ability of devices to sense a multiplicity of inputs.

Regulation of Pacemaker Industry and Practice

The present issue of PACE contains a group of articles (by Parker, Welti and MacGregor) and a panel discussion which address the problem of regulation of the pacemaker industry, the qualifications of physicians and surgeons who perform pacemaker work and the requirements of institutions in which pacemakers are implanted and managed. The trend of medical care and delivery in the United States has been toward regulation of drugs and progressively more regulation of those who deliver medical care. This degree of control has not been matched in other developed countries; though Welti feels that the lesser control which now exists in France should be supplemented by more government intervention, while Parker in his evaluation of the present state of device legislation in the U.S.A. argues that, perhaps, too much already exists. It almost seems that where little regulation exists more is perceived as necessary, and where more regulation exists less is desirable. There is little doubt, as well, that such regulation that does exist in the United States affects other nations as well. Food and Drug Administration personnel inspect manufacturing facilities in other countries if those manufacturers intend to sell pacemakers in the U.S.A. Reports of pulse generator recalls are distributed by the Department of State, and a recall in the U.S.A. soon affects patients over the entire world.

Industrial Authorship of Manuscripts

In the past few months several manuscripts have crossed this desk which have described some interesting or unusual pulse generator function. Surely that is no surprise; such articles are commonly published in PACE and other journals. What was different ahout these articles is that in each instance one of the authors was an employee of a competitor. (PACE has never had an article submitted by an industry employee which was favorable to a competitive product.) In each instance I insisted that the employee remove himself as an author if the manuscript were to be considered for publication. That position was hased on resistance to the possibility that a scientific, peer-reviewed journal could, or would, be viewed as a place to publish articles which could be construed as essentially commercially competitive. I believe the authors involved acted in what they believed to be good faith and with good and dispassionate intention.

Pacemaker Lead Extraction

The article by Schwartz and his colleagues describing a technique for the extraction of intravascularized leads is of importance both for the technique described and for the emphasis that it gives to a persistent and vexing problem. From the earliest days of implantable pacing, lead systems and pacemakers have required removal after their utility had passed and especially if the lead system or the implanted pulse generator had become infected. Pulse generators have always been easy to remove; lead systems have been very difficuU to remove. Virtually all pulse generators have been placed subcutaneously or in a submuscular pocket from which they are readily removed. Lead systems, implanted by thoracotomy or transvenously, extend away from the accessible site of attachment to the pulse generator and penetrate to the myocardium br to an intracardiac position. They are, therefore, far less accessible and are far less eksy to remove.

Pacemaker Programmability: NASPE Recommendations

The recent North American Society of Pacing and Electrophysiology (NASPE) policy conference concerned with programmability was held in response to a series of questions posed in the Federal Register by the Office of Health Technology Assessment concerning the two topics of pacemaker programmability and pacemaker follow-up. This Federal agency had, apparently, felt that inadequate information existed concerning both programmability and follow-up techniques. Pacemaker programmability, which has existed since 1972, has generated a rich literature, and is the basis of cardiac pacing today. Despite both circumstances, further evaluation seemed to be required. NASPE responded promptly despite the Seventh World Symposium on Cardiac Pacing held in Vienna, only 3 weeks before the end of the 90 day deadline for a response. That Symposium had consumed the time and energy of most of the physician participants in the policy conference. A visit to the Symposium might have been more educational, as the entire modern technology and range of therapeutic of cardiac pacing was available for review; but, it was clear that the requirement for a response was not so much educational as a formal response for governmental purposes.

The Seventh World Symposium

The Seventh World Symposium on Cardiac Pacing was held during the first week of May 1983, in Vienna, Austria. Attended by almost 3000 physicians, scientists, and commercial exhibitors it provided, as has each of the preceding symposia, the state of the art and science of cardiac pacing and electrophysiology. The presentations covered the entire range of electrophysiology and pacing. The oral presentations and poster sessions covered material which was new and that which had previously been presented but perhaps not to world audience. The commercial exhibitors provided an insight into the pacing technology of the immediate future. That insight provided a broad range of therapeutic intervention into management of bradyarrhythmias and tachyarrhythmias and a dazzling array of new equipment, much of it computer based, all of it highly varied. Unlike earlier symposia when the differences between equipment was little and, in retrospect, the distinction between many pacemakers was more artifice than science, there were real differences between pacemakers and programming systems. These differences will affect the pacer management of our patients over the four years until the next symposium. There were four prominent areas dealt with in both the scientific and technical presentations. One was the progressive development of dualchamber (DDD) systems and their widespread availability, from a variety of manufacturers, both in the U.S.A. and Europe. From the number of presentations and the informal talk at the symposium, there is intense and worldwide interest in dual-chamber pacing at a level of interest which extends far beyond that exhibited for dualchamber pacing in the past. Neither atrial synchronous (VAT) nor AV sequential (DVI) pacing had ever stimulated the kind of enthusiasm which AV universal (DDD) now generates. The turning point which this symposium marks will be much like an earlier one in which the momentum of ventricular inhibited pacing swept away earlier ventricular asynchronous pacing. While single chamber pacing will be used for many years, the dominant thrust will be the restoration of the AV sequence and increase in cardiac rate activity. The second major area was that of the development and utilization of sensors and pacemakers for single chamber pacing which will provide rate responsiveness when needed by body activity. A battle is developing over whether the restoration of the AV sequence, or single chamber rate response, or a combination of both is the best approach to the maintenance of optimal cardiac function. The third area of greater exposition at the symposium was the management of tachyarrhythmias. Manufacturers showed implantable pacing systems capable of far greater variety of stimulation algorithms than had previously been available. It may be that multiprogrammability of the stimulation pattern for tachycardia termination has now become a practical reality. If so, then tachycardia management by pacing may begin as a therapeutic reality rather than a curiosity. Some devices could be programmed to begin one stimulation pattern and then continue with another if the first were unsuccessful. Such complex devices, as well as others which will be developed, are necessary for tachycardia management. Almost all of the new pacemakers have telemetry of some sort. Most have telemetry for both physiologic and hardware functions. Many have telemetry for a memory of a variety of functions such as the number of paced and sensed beats and for episodes of tachyarrhythmias. While telemetry exists widely, there is little agreement concerning coding systems and what it is that should go into the pacemaker memory. This area will probably be fruitful for joint physician and manufacturer input. If much of the capability of memory and data transmission is to be used fruitfully, some basic agreement on print-outs, transmission, and memory contents will be required. There was one thread which ran through the entire conference. That was the increasing use of computer technology throughout all of pacing. Programmers and data recording systems are more and more computer-based and pulse generators themselves are microprocessor-based. This evolution to computer-based programming of computer-based pacemakers is likely to produce the most profound changes of all and will make the next four years dazzling and even bewildering. Amidst the charm of lost empires this new world of computer-based medical technology was presented in all its enticing brilliance.