Correspondence
Single-Chamber versus Dual-Chamber Pacemakers
N Engl J Med 1998; 339:630-632August 27, 1998
- Article
To the Editor:
In their report on the Pacemaker Selection in the Elderly (PASE) trial, Lamas et al. (April 16 issue)1 compare single-chamber pacing (VVIR mode [ventricular pacing, ventricular sensing, inhibition response, rate-adaptive]) and dual-chamber pacing (DDDR mode [atrial and ventricular pacing, atrial and ventricular sensing, dual response, rate-adaptive]) in the elderly and conclude that there is no specific quality-of-life benefit for patients undergoing dual-chamber pacing as compared with those undergoing single-chamber pacing (a conclusion that the accompanying editorial notes will surprise most experts2). This conclusion is reached despite the fact that 26 percent of the patients assigned to the VVIR mode crossed over to the DDDR mode after symptoms of the pacemaker syndrome developed. The conclusion is therefore suspect, and it has implications for the selection and implantation of pacemakers that are not considered in the article.
In the PASE trial, dual-chamber pacemakers were implanted in all the study participants. The pacemakers were programmed to the VVIR or DDDR mode before implantation, and the patients were randomly assigned to single- or dual-chamber pacing. Those assigned to the VVIR mode in whom the pacemaker syndrome developed were therefore treated simply by reprogramming the pacemaker to the DDDR mode. In clinical practice, however, the development of the pacemaker syndrome in a patient with VVIR pacing requires upgrading the pacemaker, with implantation of an atrial lead and a new generator.
Experience with this procedure has not been extensively documented, but we have recently reported a retrospective assessment of patients who underwent pacemaker upgrading in our high-volume regional pacing center (where we perform 350 implantations annually).3 Forty-four patients underwent upgrading in an eight-year period. The mean duration of the procedure significantly exceeded that for implantation of a pacemaker in the VVI or DDD mode. More important, the complication rate was high. Twenty patients (45 percent) had complications, such as pneumothorax, infection, a prolonged procedure, or the need for repositioning of the atrial lead.
Lamas et al. suggest that “many patients who received dual-chamber pacemakers might fare just as well with ventricular systems.” This is no doubt true, but we cannot reliably identify these patients. If elderly patients with ongoing atrial activity are given single-chamber ventricular pacemakers, the data reported by Lamas et al. suggest that one quarter of them will need to have their pacemakers upgraded. In view of the morbidity and complication rate that we have documented, the costs of upgrading pacemakers in such a large number of patients would, we suggest, significantly outweigh any potential savings from implanting simpler pacing systems. We believe that patients with atrial activity should not be offered single-chamber ventricular pacemakers in the mistaken belief that the system can be upgraded if necessary at minimal risk.
3 ReferencesDavid J. R. Hildick-Smith, M.R.C.P.
John T. Walsh, M.D.
Papworth Hospital, Cambridge CB3 8RE, United Kingdom1
Lamas GA ,Orav EJ ,Stambler BS , et al. Quality of life and clinical outcomes in elderly patients treated with ventricular pacing as compared with dual-chamber pacing. N Engl J Med 1998;338:1097-1104
Full Text | Web of Science | Medline2
Mason JW ,Hlatky MA . Do patients prefer physiologic pacing? N Engl J Med 1998;338:1147-1148
Full Text | Web of Science | Medline3
Hildick-Smith DJR ,Lowe MD ,Newell SA , et al. Ventricular pacemaker upgrade: experience, complications and recommendations. Heart 1998;79:383-387
Web of Science | Medline
To the Editor:
Only a few days after the publication of the article by Lamas et al. and the accompanying editorial by Mason and Hlatky, newspapers carried headlines such as “Type of Pacemaker Appears Not to Matter”1 and “Pricey Pacemakers No Better: Study.”2 Although the accompanying editorial emphasized some of the important issues, it called attention to the cost of pacing in such a way as to reinforce the media's claim that dual-chamber pacemakers are overused and too expensive. This was unfortunate, and we take exception to these arguments.
Dual-chamber pacing may have been more expensive than single-chamber pacing 12 years ago, as cited by Mason and Hlatky. But advances in technology and competitive changes in the marketplace bring into question the relevancy of data from 1986. According to the last Bilitch Report,3 on 20,128 pulse generators powered by lithium cells, there was no significant difference in longevity between dual- and single-chamber devices (70.2 and 73.8 percent of the devices, respectively, were still functional at 10 years). A detailed analysis of the real long-term costs of pacing has shown, surprisingly, that single-chamber pacemakers are actually more costly than dual-chamber devices.4
Several retrospective and prospective studies have suggested that subsequent atrial fibrillation and congestive heart failure are much more common with prolonged single-chamber pacing than with dual-chamber pacing. There is also some evidence that patients with dual-chamber pacemakers live longer.4 These data refute the points about differences in cost between single- and dual-chamber pacing.
To have a full understanding of the advantage of dual-chamber pacemakers, one must also consider that with the passage of time, some patients will require various drugs that produce inappropriate bradycardia or atrioventricular block. It would be advisable to customize the device by programming it appropriately to accommodate these changes in clinical conditions. This can best be done with dual-chamber pacemakers.
As clinicians, we frequently see patients who do not tolerate VVI pacing and whose symptoms improve (or disappear) with dual-chamber pacing. It will be interesting to follow the series of patients described by Lamas et al. for a longer time, with particular attention to the late deleterious results of pacing in either mode. Until there is more convincing evidence supporting VVIR over DDDR pacing, we will continue to implant dual-chamber pacemakers in patients with underlying sinus rhythm.
4 ReferencesVictor Parsonnet, M.D.
Marc Roelke, M.D.
New Jersey Pacemaker and Defibrillator Evaluation Center, Newark, NJ 071121
Type of pacemaker appears not to matter. USA Today. April 16, 1998.
2
Pricey pacemakers no better: study. Daily News. April 16, 1998.
3
Song SL . Performance of implantable rhythm management devices. Pacing Clin Electrophysiol 1994;17:692-708
CrossRef | Web of Science | Medline4
Brown Mahoney C ,Sharma A ,O'Neill PG . Costs of follow-up cardiovascular care in pacemaker patients -- correction for mortality. Pacing Clin Electrophysiol 1996;19:622-622 abstract.
To the Editor:
We have reservations about the use of the 36-item Medical Outcomes Study Short-Form General Health Survey (SF-36) in the age group studied by Lamas et al. Its use as a generic quality-of-life measure is well established in culturally and demographically diverse populations, but its usefulness in elderly persons, particularly those with serious disorders, has been questioned.1 The assessment of quality of life in elderly patients may be improved by the use of instruments that allow patients to select and rate the areas of life that are important to them (e.g., the Schedule for Evaluation of Individual Quality of Life).2 In addition, cognitive function, which is important both because it is a determinant of quality of life and because of its potential confounding effects on the reliability and validity of the SF-36, was not assessed.
2 ReferencesGuy M. Gribbin, B.M., B.Ch.
Steve W. Parry, M.B., B.S.
Freeman Hospital, Newcastle upon Tyne NE7 7DN, United Kingdom1
Hill S ,Harries U ,Popay J . Is the short form 36 (SF-36) suitable for routine health outcomes assessment in health care for older people? Evidence from preliminary work in community based health services in England. J Epidemiol Community Health 1996;50:94-98
CrossRef | Web of Science | Medline2
Browne JP ,O'Boyle C ,McGee HM , et al. Individual quality of life in the healthy elderly. Qual Life Res 1994;3:235-244
CrossRef | Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: Drs. Hildick-Smith and Walsh point out that if the pacemaker syndrome develops in 26 percent of patients receiving ventricular pacemakers and an upgrade to dual-chamber pacing is required, then ventricular pacemakers should never be used in patients with sinus rhythm. However, the crossover rate in the PASE trial1 probably overestimates the incidence of the pacemaker syndrome. In the PASE trial, a crossover from single-chamber ventricular pacing to dual-chamber pacing required only reprogramming, not surgery. The one other published randomized trial of pacemakers2 found that only 1.7 percent of patients with ventricular pacing had severe pacemaker syndrome. The true incidence of severe pacemaker syndrome is probably considerably lower than the crossover rate in the PASE trial.
Drs. Gribbin and Parry discuss possible problems in accurately measuring quality of life in elderly patients. We used an interviewer-administered SF-36 questionnaire to avoid the problem of a low completion rate among elderly patients. Although the Schedule for Evaluation of Individual Quality of Life is conceptually interesting, there is no compelling evidence that it would provide a better assessment of quality of life than the SF-36 among elderly patients.3 Indeed, the importance ratings that respondents must provide on the Schedule for Evaluation of Individual Quality of Life are cognitively more demanding than the simple rating scales used in the SF-36. All patients in the PASE trial had to have sufficient cognitive function to provide informed consent, complete the base-line interview, and pass a simple cognitive screening with the Telephone Interview for Cognitive Status. Furthermore, we expect that randomization balanced the confounding influence of mild, undetected cognitive impairment in the two treatment groups.
Drs. Parsonnet and Roelke comment on the cost and longevity of pacemakers and on the clinical outcomes. Dual-chamber pacemakers require two leads instead of one, and the prices for dual-chamber systems are higher than those for ventricular pacemakers of similar sophistication. The battery drain is greater with dual-chamber pacemakers than with ventricular pacemakers. However, individual variations in pacemaker programming have made these differences more difficult to demonstrate.
The comments on clinical outcomes and cost effectiveness are based on retrospective data, which are confounded by profound biases with regard to the selection of the pacemaker mode. Patients with dual-chamber pacing are younger and healthier, are more likely to be men, and have higher socioeconomic status than patients with ventricular pacing.4 Therefore, it is not surprising that retrospective studies report that patients with dual-chamber pacing have a better prognosis. The results of prospective studies, such as the study by Andersen et al.,2 the PASE trial,1 and the large ongoing trials (the Canadian Trial of Physiologic Pacing, Mode Selection Trial, and United Kingdom Pacing and Clinical Events Trial), will establish the clinical benefits and cost effectiveness of atrial-based pacing.
4 ReferencesGervasio A. Lamas, M.D.
Mount Sinai Medical Center, Miami Beach, FL 33140Lee Goldman, M.D.
University of California, San Francisco, San Francisco, CA 94143Carol Mangione, M.D.
University of California, Los Angeles, Los Angeles, CA 900241
Lamas GA ,Orav EJ ,Stambler BS , et al. Quality of life and clinical outcomes in elderly patients treated with ventricular pacing as compared with dual-chamber pacing. N Engl J Med 1998;338:1097-1104
Full Text | Web of Science | Medline2
Andersen HR ,Nielsen JC ,Thomsen PEB , et al. Long-term follow-up of patients from a randomised trial of atrial versus ventricular pacing for sick-sinus syndrome. Lancet 1997;350:1210-1216
CrossRef | Web of Science | Medline3
Brazier JE ,Walters SJ ,Nicholl JP ,Kohler B . Using the SF-36 and Euroqol on an elderly population. Qual Life Res 1996;5:195-204
CrossRef | Web of Science | Medline4
Lamas GA ,Pashos CL ,Normand SL ,McNeil B . Permanent pacemaker selection and subsequent survival in elderly Medicare pacemaker recipients. Circulation 1995;91:1063-1069
Web of Science | Medline
