Portal de Periódicos da CAPES

Two Decades of Cardiac Pacing at the Mayo Clinic (1961 Through 1981)

1984; Elsevier BV; Volume: 59; Issue: 4 Linguagem: Inglês

10.1016/s0025-6196(12)61261-0

1942-5546

Peter C. Hanley, Ronald E. Vlietstra, John Merideth, David R. Holmes, James C. Broadbent, Michael J. Osborn, Dwight C. McGoon, Daniel C. Connolly,

Medical History and Innovations

Pacemaker procedures performed at the Mayo Clinic for the years 1961, 1971, and 1981 were reviewed to examine the changes that have occurred in a large pacemaker practice during the 2 decades since the advent of pacemaker therapy. Major changes in trends and practice have occurred; in addition to numerical growth, the indications for permanent pacing and the technologic alternatives available have expanded considerably. The increasing choices available today (in all areas of pacemaker practice) provide a challenging stimulus to physicians as they seek the best clinical options in patient care. Pacemaker procedures performed at the Mayo Clinic for the years 1961, 1971, and 1981 were reviewed to examine the changes that have occurred in a large pacemaker practice during the 2 decades since the advent of pacemaker therapy. Major changes in trends and practice have occurred; in addition to numerical growth, the indications for permanent pacing and the technologic alternatives available have expanded considerably. The increasing choices available today (in all areas of pacemaker practice) provide a challenging stimulus to physicians as they seek the best clinical options in patient care. The first portable pacing device was demonstrated by Lidwill in 1929 at a meeting of the Australasian Medical Congress in Sydney, Australia.1Lidwill MC: Cardiac disease in relation to anaesthesia. In Transactions of the Third Session, Australasian Medical Congress (British Medical Association), Sydney, Australia, September 2 to 7, 1929, p 160Google Scholar, 2Mond HG Sloman JG Edwards RH The first pacemaker.PACE. 1982; 5: 278-282Crossref Scopus (41) Google Scholar The prototype of this unit had been used some time before to resuscitate a stillborn infant by plunging a needle electrode into the ventricle. The separate development of a similar unit that weighed 7.2 kg by Hyman in 1932 heralded the advent of pacemaker technology in the United States.3Hyman AS Resuscitation of the stopped heart by intracardiac therapy.Arch Intern Med. 1930; 46: 553-568Crossref Scopus (34) Google Scholar, 4Hyman AS Resuscitation of the stopped heart by intracardial therapy. II. Experimental use of an artificial pacemaker.Arch Intern Med. 1932; 50: 283-305Crossref Scopus (76) Google Scholar The invention of the transistor in 1948 provided a stimulus for rapid advancement in pacemaker therapy, particularly in the areas of application of miniaturization and low-voltage power sources to pacemaker design. Zoll,5Zoll PM Resuscitation of the heart in ventricular standstill by external electric stimulation.N Engl J Med. 1952; 247: 768-771Crossref PubMed Scopus (315) Google Scholar in 1952, was the first to stimulate the heart externally by means of electrodes strapped to the chest. In the late 1950s, Elmquist and Senning6Elmquist R Senning A An implantable pacemaker for the heart.Proceedings of the Second International Conference on Medical and Electrical Engineering. Illiffe and Sons, London1959Google Scholar performed the first human pacemaker implantation, and Furman and Robinson7Furman S Robinson G The use of an intracardiac pacemaker in the correction of total heart block.Surg Forum. 1958; 9: 245-248PubMed Google Scholar reported the first use of a transvenous catheter electrode. Since that time, the rapid application of technologic advances to pacemaker design has resulted in increasing reliability and continuing extension of longevity and flexibility of pacing systems. Considerable progress occurred in the 1960s, but advances were even more impressive during the 1970s. After a brief experience with nuclear-powered pulse generators, the introduction of lithium batteries in 1972 with high power-to-weight ratios prolonged the lifetime of pacing devices. Also, beginning in the early 1970s, new technologies including complementary metal-oxide semiconductors and hybrid integrated circuitry were developed. Their application to component design greatly facilitated the increasing efficiency and sophistication of pacing systems, most apparent in the development of external radiofrequency programmability and circuitry with remarkably low power drain. Innovations in lead design, especially in the late 1970s, allowed more reliable lead function, particularly in the areas of endocardial lead fixation8Nishimura RA Vlietstra RE Maloney JD Merideth J Early follow-up of lead performance in atrioventricular sequential systems.PACE. 1982; 5: 694-699Crossref Scopus (4) Google Scholar (by means of tined passive fixation and, more recently, screw-in active fixation) and reduction of late failure of leads (by means of multifilament helical construction). The recent use of large-scale integrated circuitry and microcomputers in modern “software-organized” pacemakers also allows functional redesign after implantation. Pacemakers of the 1980s are complex: they include multiprogrammable dual-chamber devices with provision for physiologic adaptability and transcutaneous interrogation, telemetry, and antitachycardia capability. The greater complexity of modern units has naturally raised questions of utility, applicability, and cost-effectiveness.9Liu P Chisholm AW Froggatt GM Harrison AW Cameron JR Cost effectiveness in cardiac pacing (abstract).PACE. 1981; 4: 241Google Scholar, 10Parsonnet V The proliferation of cardiac pacing: medical, technical, and socioeconomic dilemmas.Circulation. 1982; 65: 841-845Crossref PubMed Scopus (27) Google Scholar The purpose of the current study was to examine the changes that have occurred in a large pacemaker practice with time. To this end, we compared our practice in the years 1961, 1971, and 1981—the first 2 decades of our pacing experience. The subgroup of patients which most closely represented our pacing system decision-making practices during those study years was the subgroup that had insertion of a first pacing system during those years (no previous pacemaker group). These patients were least likely to have procedural decisions influenced by prior practices because none had pacing procedures performed during previous years. Consequently, most of the data comparisons presented in this report relate primarily to that subgroup. The data for this study were collected retrospectively by examination of the medical records and pacemaker files of patients who had undergone pacemaker procedures at the Mayo Clinic during the years 1961, 1971, and 1981. Each procedure was coded separately. The data coded included patient identification, indication for pacing, pacemaker and lead model, manufacturer, pacing mode, physician implanter (surgeon or cardiologist), duration of procedure, and requirement for other surgical procedures (for example, valve replacement). The total data set (of procedures) was analyzed as a group and by subgroups. Subgroups (Table 1) included those patients who had not had a pacing system implanted previously (no previous pacemaker), those who had had one or more previous pacemaker implants either at our institution or elsewhere (previous pacemaker[s]), and those who had one or more pacemakers implanted during a study year irrespective of the number of previous pacemaker implants (pacemaker placement). Certain subgroups that required pacing under special circumstances were identified (postinfarction, surgical bradycardia, pacemaker syndrome); also identified was a subgroup of patients who had had pacemaker implantation in previous years and required operative troubleshooting of their pacing system without generator replacement in a study year (no pacemaker implant).Table 1Summary of Data and Analysis by Patient and Procedure Subgroups196119711981Absolute change (%), 1971 to 1981Patient groups All patients*Excludes 6 in 1971 and 18 in 1981 in whom epicardial leads only were inserted during a cardiac operation (that is, prophylactic lead placement). All patients in 1961 had epicardial leads inserted at thoracotomy (three during a cardiac operation).12138262Increased 90 No previous pacemaker1072210Increased 192 Previous pacemaker(s)26652Decreased 21 Pacemaker placement10134253Increased 89 Postinfarction007… Surgical bradycardia1411Increased 175 Pacemaker syndromet†Not recognized in 1961 or 1971.005… Procedures: 1 only11116234Increased 102 212228Increased 27 3095Decreased 44 4030Decreased 100Procedure groups All procedures*Excludes 6 in 1971 and 18 in 1981 in whom epicardial leads only were inserted during a cardiac operation (that is, prophylactic lead placement). All patients in 1961 had epicardial leads inserted at thoracotomy (three during a cardiac operation).13172295Increased 72 No previous pacemaker1192236Increased 157 Previous pacemaker(s)28059Decreased 26 No pacemaker implant‡See text for explanation.049Increased 125 Pacemaker placement11141258Increased 83Operator Surgeon1317213Decreased 92 Cardiologist00282…Procedure duration (min)…9278Decreased 15Male patients (%)676366Increased 5Mean age (yr)49.866.766.2Decreased 0.7* Excludes 6 in 1971 and 18 in 1981 in whom epicardial leads only were inserted during a cardiac operation (that is, prophylactic lead placement). All patients in 1961 had epicardial leads inserted at thoracotomy (three during a cardiac operation).† Not recognized in 1961 or 1971.‡ See text for explanation. Open table in a new tab The early Mayo Clinic experience with cardiac pacing has been described elsewhere.11Ellis Jr, FH Manning Jr, PC Connolly DC Treatment of Stokes-Adams disease.Mayo Clin Proc. 1964; 39: 945-953PubMed Google Scholar, 12Burchell HB Connolly DC Ellis Jr, FH Indications for and results of implanting cardiac pacemakers.Am J Med. 1964; 37: 764-777Abstract Full Text PDF PubMed Scopus (18) Google Scholar Our 1961 patients have not previously been described as a distinct group; however, they are of considerable historical interest because they represent our entire experience with transcutaneous epicardial pacing systems (a method of pacing first used at our institution in late 1960). Both of our first two pacemaker patients (who had pacemakers inserted in 1960) underwent procedures in 1961 to remove their pacing systems when 1:1 atrioventricular conduction returned; consequently, they are included in the 1961 group of 12 patients (Table 1) who underwent pacemaker procedures. The remaining 10 patients (who are described in detail in the subsequent material) had pacing instituted in 1961 by means of a bipolar epicardial lead inserted at thoracotomy. This lead was plunged into and sutured to the right or left ventricular myocardium and tunneled through the chest wall, where it was connected to an external pulse generator (Medtronic) carried by the patient. These transcutaneous leads, however, invariably became infected, and when implantable pulse generators (Medtronic, Electrodyne) became available in early 1962, this method of cardiac pacing was discontinued. The mean age of the 10 patients (6 men and 4 women) who initially received pacemakers in 1961 was 49.8 years. The indication for pacing was complete heart block in all cases. The decision to insert a pacemaker was often difficult because the risks of chronic lead infection and thoracotomy had to be weighed against the anticipated benefits of fixed-rate pacing of the ventricle. Medical therapy at that time was limited to sublingual or intravenous administration of isoproterenol and administration of thiazide diuretics to induce hypokalemia and thereby enhance ventricular pacemaker activity. Failure of such medical therapy to control recurrent Adams-Stokes syncope was usually a prerequisite to the institution of pacemaker therapy. Three patients had pacemakers implanted during a cardiac surgical procedure. These patients included a 1-year-old girl (who underwent repair of a ventricular septal defect), the only patient who received a pacemaker during a cardiac surgical procedure because of surgically induced heart block; 6 days after insertion of the pacing system, fatal asystole developed. A woman (who received a pacemaker at the time of repair of an atrial septal defect) had her myocardial electrode removed 10 days postoperatively because 1:1 atrioventricular conduction had returned. The third patient was a man who had aortic valvulotomy performed at the time of pacing. Only one patient had undergone a cardiac operation before institution of pacemaker therapy: a man in whom aortic valvulotomy had been done 2 years previously. Five patients died within 1 year after insertion of a pacemaker: three of Adams-Stokes syncope, one of presumed Adams-Stokes syncope, and one of staphylococcal endocarditis on an aortic valve that had previously been subjected to valvulotomy. Five patients survived beyond 1 year after pacemaker implantation. Myocardial stimulation ultimately failed in all cases, and the last transcutaneous epicardial lead was removed in early 1964. Three patients had implantable generators and transvenous leads inserted after discontinuation of transthoracic pacing. The remaining two patients did well without pacing; one died in 1972 from noncardiac causes, and the other was lost to follow-up in 1967, both patients without recurrence of Adams-Stokes syncope. The age distribution and the breakdown by sex in our 1971 and 1981 patient groups were similar (Table 1). The percentage of patients younger than 30 years of age and older than 80 years of age, however, was twice as high in 1981 as in 1971. In 1971, 4.5% of all pacemakers were implanted in patients younger than 20 years of age; in 1981, the corresponding figure was 5.1% A summary of patient and procedure data is presented in Table 1. The total number of procedures increased by 72% from 1971 to 1981, and the total number of patients increased by 90%. In the latter year, considerably fewer patients required generator replacement only (20% of our patients in 1981 versus 48% in 1971). Similarly, the need for subsequent procedures to correct pacing system malfunction after initial implantation decreased considerably with time. The percentage of patients who received pacemakers because of perioperative or postoperative bradycardia increased slightly from 2.9% in 1971 to 4.2% in 1981. Corresponding figures for pacing after myocardial infarction are shown in Table 1. The availability of dual-chamber devices in 1981 allowed treatment of the newly recognized pacemaker syndrome13Nishimura RA Gersh BJ Holmes Jr, DR Vlietstra RE Broadbent JC Outcome of dual-chamber pacing for the pacemaker syndrome.Mayo Clin Proc. 1983; 58: 452-456PubMed Google Scholar (hypotension that develops or worsens during or after ventricular pacing). The indications for pacing have substantially changed during the 2 decades encompassed in our study, as shown in Table 2 for patients who received their first pacemaker in a study year. In 1971, relatively few patients underwent pacing procedures for sinus node disease, whereas in 1981 this indication applied to 41% of patients. The indication for pacing in all patients in 1961 was complete heart block. Eighty-five percent of patients in 1971 and 60% of patients in 1981 had atrioventricular nodal disease with high-grade heart block as an indication; 11% of patients in 1981 also had diffuse conduction system disease as an indication.Table 2Indications for Pacing (No Previous Pacemaker Group)Indication1961 (%)1971 (%)1981*Figures for 1981 total more than 100% because more than one indication for pacing was identified in certain patients. (%)Relative change (%), 1971 to 1981Sinus node disease01141Increased 30High-grade heart block1008560Decreased 25Conduction system disease0011Increased 11Carotid sinus hypersensitivity005Increased 5Vasovagal syncope014Increased 3Supraventricular tachycardia001Increased 1Ventricular tachycardia0110Cardiogenic (unspecified)†Patients thought to have a cardiogenic cause for syncope (mechanism not defined).022Increased 0* Figures for 1981 total more than 100% because more than one indication for pacing was identified in certain patients.† Patients thought to have a cardiogenic cause for syncope (mechanism not defined). Open table in a new tab The pacing modes used in the group of patients who received their first pacemaker are shown in Table 3. All pacing systems in 1961 operated in the VOO mode (ventricular fixed-rate pacing). Subsequently, the dominant pacing mode has been VVI (ventricular demand pacing; 100% in 1971, 75% in 1981), although in 1981 dual-chamber pacemakers constituted 25% of all systems implanted. The DVI pacing mode (atrioventricular sequential pacing) was the usual approach used in dual-chamber systems. Only one pacemaker manufacturer was used for the first pacemaker patients in 1961 and 1971; in 1981, four manufacturers were used, and their percentage share of pacemakers supplied was 74, 16, 9, and 1%. The early model pacemakers were either fixed-rate nonprogrammable or rate programmable by means of a transcutaneous needle; very few had an additional output programmability function. In 1981, virtually all pacemakers were multi-programmable by means of external radiofrequency transmission (only two fixed-rate nonprogrammable units were implanted). Only one antitachycardia pacemaker was implanted in 1981.Table 3Pacing Mode Used (No Previous Pacemaker Group)Mode *Three-letter code established by the Inter-Society Commission for Heart Disease Resources. The first letter designates the chamber paced (A = atrium, V = ventricle, D = dual); the second, the chamber sensed (A = atrium, V = ventricle, D = dual, O = none); and the third, the response to sensing (I = inhibited, T = triggered, D = dual [atrial triggered and ventricular inhibited], 0 = none). VOO = ventricular fixed-rate pacing; VVI = ventricular demand pacing; AAI = atrial demand pacing; DVI = atrioventricular sequential pacing; DDD = atrioventricular sequential, atrioventricular sensing pacing; and VDD = atrial synchronous, ventricular inhibited pacing.1961 (%)1971 (%)1981 (%)VOO10000VVI010075AAI001DVI0021DDD002VDD001* Three-letter code established by the Inter-Society Commission for Heart Disease Resources. The first letter designates the chamber paced (A = atrium, V = ventricle, D = dual); the second, the chamber sensed (A = atrium, V = ventricle, D = dual, O = none); and the third, the response to sensing (I = inhibited, T = triggered, D = dual [atrial triggered and ventricular inhibited], 0 = none). VOO = ventricular fixed-rate pacing; VVI = ventricular demand pacing; AAI = atrial demand pacing; DVI = atrioventricular sequential pacing; DDD = atrioventricular sequential, atrioventricular sensing pacing; and VDD = atrial synchronous, ventricular inhibited pacing. Open table in a new tab Lead data in the group of patients who had their first pacemaker procedure in 1971 and 1981 are summarized in Table 4. Twenty-five percent of patients in 1981 received dual-chamber pacemakers with both atrial and ventricular leads. Two patients in this group received coronary sinus leads. Lead polarity changed considerably, a reflection of the ability to counter myopotential inhibition by sensing-threshold reprogramming and the current technical preference for unipolar leads in dual-chamber pacing. The composition of sheath material substantially shifted from silicone to urethane, especially in dual-chamber systems in which concomitant manipulation of two leads is frequently necessary. There has also been a recent proliferation of lead models: 28 different models were used in 1981, whereas that corresponding figure for 1971 was 7. In 1971, the dominant lead model was used in 80% of all cases, whereas in 1981, the corresponding figure was only 30%.Table 4Information About Leads Used (No Previous Pacemaker Group)*Total number of leads used was 75 in 1971 and 269 in 1981.1961 (%)1971 (%)1981 (%)Lead location Endocardial09294 Epicardial10086Site of pacemaker Ventricle10010077 Atrium0022 Coronary sinus001Lead polarity Unipolar01840 Bipolar1008260Sheath material Silicone10010056 Urethane0044* Total number of leads used was 75 in 1971 and 269 in 1981. Open table in a new tab An analysis of procedures performed because of lead malfunction is shown in Table 5. We have classified our patients into three groups: those in whom lead repositioning only was performed, those in whom a new lead was inserted and the old malfunctioning lead was removed, and those in whom a new lead was inserted but removal of the old malfunctioning lead was not achieved (retained lead). The incidence of lead malfunction (expressed relative to the total patient number) decreased from 26.7% in 1971 to 14.5% in 1981; this trend was also observed in the group with no previous pacemaker. The need for repositioning of leads decreased from 17.4% in 1971 to 5.3% in 1981. During that same period, the percentage of patients who required new lead insertion remained essentially unchanged; however, the percentage of patients in whom it proved possible to remove malfunctioning leads increased.Table 5Procedures Performed Because of Lead Malfunction19711981ProcedureNo.Malfunction rate per patient (%)No.Malfunction rate per patient (%)All patients*See Table 1 for total numbers of patients and procedures. Lead repositioning2417.4145.3 New lead insertion Old lead removed85.7186.9 Old lead retained53.662.3 Total procedures3726.73814.5 Total patients3336No previous pacemaker group*See Table 1 for total numbers of patients and procedures. Lead repositioning1419.4104.8 New lead insertion Old lead removed11.494.3 Old lead retained11.40… Total procedures1622.2199.1 Total patients1319 Leads involved Atrial0…915.5 Ventricular Ventricular systems1622.274.85.8†Overall ventricular lead malfunction rate per patient was 5.8% in 1981. Dual-chamber systems0…510.0* See Table 1 for total numbers of patients and procedures.† Overall ventricular lead malfunction rate per patient was 5.8% in 1981. Open table in a new tab Dual-chamber systems were the most frequently involved in the procedures performed because of lead malfunction in 1981; 15 of the 38 procedures involved these units, in which nine atrial leads (four repositioned, five replaced) and nine ventricular leads (five repositioned, four replaced) had malfunctioned. In 1981 in the group of patients with no previous pacemaker, the ventricular lead malfunction rate was higher for dual-chamber systems (10.0%) than for ventricular systems (4.8%). The overall ventricular lead malfunction rate was 5.8%. The overall atrial lead malfunction rate (including atrial systems and dual-chamber systems) in that same group was 15.5%. Overall, in 19.7% of all dual-chamber systems inserted in 1981, subsequent lead procedures were necessary during that year. This outcome probably reflects relative operative inexperience with two-lead systems (first used in 1981) and unsatisfactory performance of the unipolar tined atrial and ventricular leads in use in 1981. Procedures other than pacemaker implants and lead malfunction procedures are shown in Table 6. The rate of explantation because of infection was essentially unchanged (3.5% in 1971 and 4.1% in 1981). All epicardial to endocardial conversions (three in 1971 and three in 1981) were performed because chronic epicardial pacing thresholds were found to be inadequate. Less frequent procedure indications included repositioning of a generator pack and evacuation of a hematoma of the generator pocket. These “surgical indications” for revision of the generator pocket were no more common during 1981, despite a change to cardiologist implanters.Table 6Other Procedures (All Patients)Procedure196119711981Explantation (infection)2612Epicardial to endocardial conversion033Other operation*This group includes explantations (no infection), conversion from endocardial to epicardial location, generator repositioning, and surgical evacuation of hematoma of the generator pocket.169 Total patients31422* This group includes explantations (no infection), conversion from endocardial to epicardial location, generator repositioning, and surgical evacuation of hematoma of the generator pocket. Open table in a new tab In 1971, all pacing systems at the Mayo Clinic were inserted by surgeons as compared with only 4.4% in 1981. This change was a consequence of an alteration in policy in 1978 which led to most pacemaker implantations at our institution being performed by cardiologists. Therefore, 1981 was the third complete year that cardiologists had been performing pacemaker surgical procedures. Approximately the same percentage of pacemakers (2% in 1971 and 3% in 1981) were inserted during cardiac operations by surgeons, who also implanted all epicardial systems. The average duration for the procedure of pacing system insertion has decreased from 92 minutes in 1971 to 78 minutes in 1981. These changes have occurred despite the increased complexity of intraoperative testing and the devices themselves and reflect refinements in insertion techniques during this period. The growth and development of pacemaker therapy have been reported by Parsonnet and others.14Parsonnet V The status of permanent pacing of the heart in the United States and Canada.Ann Cardiol Angeiol (Paris). 1971; 20: 287-291PubMed Google Scholar, 15Irnich W Parsonnet V Myers GH Compendium of pacemaker technology: introduction and historical review.PACE. 1978; 1: 371-374Crossref Scopus (2) Google Scholar, 16Parsonnet V Bernstein AD Cardiac pacing in the 1980s: treatment and techniques in transition.J Am Coll Cardiol. 1983; 1: 339-354Abstract Full Text PDF PubMed Scopus (45) Google Scholar Apparently, early estimates of the projected growth of pacemaker therapy were too conservative. The “growth curve” of pacemaker implantation16Parsonnet V Bernstein AD Cardiac pacing in the 1980s: treatment and techniques in transition.J Am Coll Cardiol. 1983; 1: 339-354Abstract Full Text PDF PubMed Scopus (45) Google Scholar shows no sign of leveling off and is currently still increasing at a rapid rate. In our own practice, we have also seen a similar growth rate of implants despite a decrease in replacement implants. The data reported herein describe the Mayo Clinic experience for three discrete yearly periods and, as such, they cannot be appropriately compared with the results of other collected series. In that they are also the experience from a single institution, they may be considerably influenced by referral factors and local practice habits. The availability of newly developed pacemaker systems also may have an impact on our practice before trends are reflected nationally. Improved lead insertion techniques (for example, the peel-away introducer)17Miller Jr, FA Holmes Jr, DR Gersh BJ Maloney JD Permanent transvenous pacemaker implantation via the subclavian vein.Mayo Clin Proc. 1980; 55: 309-314PubMed Google Scholar have facilitated the shift from surgeon to cardiologist implanter. Currently, transvenous pacing systems at the Mayo Clinic are usually implanted by cardiologists, and the surgical service is involved for insertion of epicardial systems or systems inserted during a cardiac surgical procedure. The transthoracic approach to pacing used in 1961 was short-lived, primarily because of the requirement for thoracotomy but also because of the major problem of electrode malfunction due to infection introduced along the pacing catheter. The transvenous approach to electrode placement avoided these problems but raised other possibilities for lead malfunction—namely, lead fracture and electrode displacement. The former mechanism has been essentially eliminated with improvements in the construction of conductors; however, the latter mechanism was a substantial clinical problem in 1981, especially when unipolar tined atrial and ventricular electrodes were involved. The relatively poor performance of these leads in our experience may reflect both sub-optimal lead construction and relative operator inexperience. Changes in the pattern of procedures performed for lead malfunction have been observed. Lead malfunction in pacing systems inserted in 1961 was usually caused by infection or a high threshold for myocardial stimulation and necessitated transvenous pacing and removal of the transthoracic catheter. In 1971 and 1981, however, troubleshooting of malfunctioning transvenous leads involved checks of lead and connector integrity and measurements of stimulation and sensing thresholds, together with resultant repositioning or removal (if possible) of the malfunctioning lead. The lead repositioning rate decreased considerably between 1971 and 1981 despite the increased use of atrial leads. This change reflects the decreased micro-displacement and macrodisplacement rates related to improved techniques for electrode fixation. The lead replacement rate during the same period, however, remained essentially unchanged. One possible explanation could be an unchanged overall failure rate of conductor(s), insulation sheath, and connector apparatus, but this explanation seems unlikely. Alternatively, physician and clinical practice factors seemed to allow for less frequent in situ lead repair (such as lead splicing and insulator repair) in 1981 than in 1971. Thus, this apparent unwillingness to attempt to repair potentially damaged leads in 1981 despite increasing lead reliability resulted in essentially unchanged lead replacement rates. In 1981, leads were retained approximately a third less frequently than in 1971, and malfunctioning leads were removed slightly more frequently. The observed relative decrease in retained leads is of interest because with the change from passive to active fixation techniques that occurred in the late 1970s, removal of the malfunctioning leads might have been expected to be more difficult. The indications for cardiac pacing have broadened considerably in recent years.18Mond HG The bradyarrhythmias: current indications for permanent pacing (part 1).PACE. 1981; 4: 432-442Crossref Scopus (7) Google Scholar, 19Kastor JA Preventive pacemaking (editorial).N Engl J Med. 1982; 307: 180-181Crossref PubMed Scopus (6) Google Scholar This trend is primarily the result of the increased flexibility of function of modern pacemakers, the enhanced sophistication of arrhythmia detection, and the recognition that certain conditions, such as carotid sinus hypersensitivity, hypervagotonia, and the pacemaker syndrome, are amenable to pacemaker therapy. The diversity and specialization of function that have become increasingly available in pacemaker therapy in recent years are reflected in the proliferation of various models of both pacemakers and leads used in our patients and in the changing patterns of pacing modes. The relative advantages of multiprogrammability are still debated.20Parsonnet V Rodgers T The present status of programmable pacemakers.Prog Cardiovasc Dis. 1981; 23: 401-420Abstract Full Text PDF PubMed Scopus (13) Google Scholar Multiprogrammable units are more costly and complex. In our experience, some programmable functions have substantially enhanced our practice because the ability to reprogram allows adjustment of pacemaker function during serious illness or at the end of pacemaker life, facilitates the diagnosis of pacing system problems, and avoids reoperations.21Hayes DL Maloney JD Merideth J Holmes Jr, DR Gersh B Broadbent JC Osborn MJ Fetter J Initial and early follow-up assessment of the clinical efficacy of a multiparameter-program-mable pulse generator.PACE. 1981; 4: 417-431Crossref Scopus (7) Google Scholar Furthermore, prudent programming during service may prolong pacemaker life. Pacemaker practice is evolving at an increasingly rapid rate, mainly in response to the prompt incorporation of technologic developments into the design of pacing system components.22Barold SS Mugica J The Third Decade of Cardiac Pacing: Advances in Technology and Clinical Applications. Futura Publishing Company, Mount Kisco, New York1982Google Scholar, 23Dreifus LS Pacemaker therapy.Cardiovasc Clin. 1983; 14: 1-287PubMed Google Scholar We expect that this trend will persist and that, increasingly, the clinical practice of pacemaker therapy will become the province of pacemaker specialists. Finding and maintaining a rational balance among technologic sophistication, clinical utility, and cost are necessary. To attain these goals, clinicians must define those developments or functions that are most needed. Indeed, many of the programmable functions that clinicians might need for their patients are currently routinely available except for good antitachycardia systems, the features of which are yet to be clearly defined by electrophysiologic research. Already some new devices have incorporated extensive telemetric capability and thereby have facilitated follow-up and data acquisition, particularly at the cardiac interface (for example, frequency and type of arrhythmias and sensing-pacing ratios). Where we are lacking is in the analysis of cost versus benefit for many of these new developments. The ultimate goal of pacemaker technology research is the development of a truly universal but still affordable pacemaker. In addition to multichamber operation and extensive programmability, such pacemaker systems would be reliable and long-lasting. They would possess the capacities to respond to the body's physiologic needs and to recognize arrhythmias and treat some of them. They would also recognize their own malfunctions and allow noninvasive troubleshooting and updating of software. When the remarkable advances that have already been made in pacemaker development are considered, and reflected in the experience reported herein, it is not unreasonable to expect that these goals will be affordably met within the next 2 decades of cardiac pacing.