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European Heart Journal Advance Access originally published online on October 5, 2005
European Heart Journal 2006 27(2):132-135; doi:10.1093/eurheartj/ehi591
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© The European Society of Cardiology 2005. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Pacemaker selection: time for a rethinking of complex pacing systems?

Nicola Musilli and Luigi Padeletti*

Internal Medicine and Cardiology Institute, University of Florence, V.le Morgagni 85, 50134 Florence, Italy

Received 25 March 2005; revised 22 August 2005; accepted 22 September 2005; online publish-ahead-of-print 5 October 2005.

* Corresponding author. Tel: +39 055 4277634/+39 329 4204310. E-mail address: elettrofisiologia{at}dac.unifi.it or lpadeletti{at}interfree.it

Abstract

Evidence from randomized trials indicates that the clinical benefits of dual-chamber (DDD) pacing are modest: (i) no significant differences exist between physiological pacing and single-chamber pacing in mortality and stroke; (ii) ventricular desynchronization resulting from chronic right-ventricular pacing in DDD mode, induces a significantly increased incidence of atrial fibrillation (AF) and heart failure hospitalizations; (iii) AF pacing prevention and therapy algorithms have shown a modest to minimal or absent efficacy; (iv) the widespread use of physiological pacemakers is not an economically attractive strategy. Thus, these data provide a reliable body of evidence on which to make more rationale clinical decisions for individual patients and policy decisions for health costs saving. The cheaper single-chamber AAI(R) or VVI(R) has been shown to satisfy both conditions in most cases of sinus node disease and AV block.

Key Words: Pacemakers • Trials • Atrial fibrillation • Mortality

Introduction

Health care expenditures on the elderly are a challenge to the financial compatibility of health system because they tend to grow very rapidly than the US gross domestic product.1,2 This is attributable to (i) demographic change, with a number of elderly growing ~10% per year faster than the rest of population and (ii) advances and diffusion of medical technology which result in large increase of expenditures. One of the routes of slowing the growth of health care spending is to reduce the rate of growth of the prices of the resources used in health care.1

The therapeutic clinical pacing can be divided into three main categories: (i) ‘brady therapy’ (conventional pacing), (ii) ‘tachy therapy’ [implantable cardioverter defibrillators (ICDs)], and (iii) ‘resynchronization therapy’ (biventricular pacing).3 Increased elderly population size will see a steady growth in brady therapy. In contrast, the industry continuously delivers high technology products whose diffusion results in large increase of spending over the time. Thus, for the brady population, sophisticated devices with Holter monitoring capabilities and algorithms for prevention and termination of atrial fibrillation (AF) are available. Moreover, physicians are increasingly encouraged to employ the most cost-effective treatment for a given condition. Given the limited proportion of national income devoted to social programs, and of the consequence the limited budgeting for future health care spending, it is necessary to avoid that spending in ‘brady therapy’ crowd out available spending for other purposes, as ‘tachy therapy’ and ‘resynchronization therapy’. Thus, is it time to be aware that we can give up the idea that implanting a sophisticated dual-chamber device furnishes a clinical benefit to this population anyway?

Several randomized parallel studies4–10 comparing ‘physiological’ pacing to ventricular pacing have shown that even if for all-cause mortalities, stroke, and heart failure, there was a trend towards a benefit from physiological pacing, none of these differences were statistically significant. In these studies, dual-chamber (DDD) pacing was the most employed form of physiological pacing. The MOST trial was the only one to report cardiovascular mortality:8 no statistically significant difference between ventricular (8.9%) and DDD mode (9.2%) was reported after a median follow-up of 33.1 months. The composite outcome of stroke or death due to cardiovascular cause in sinus node disease (SND) or atrioventricular block (AVB) patients was investigated in the Canadian trial:7 no significant differences were observed between the two patient populations after a 5-year follow-up. For stroke, heart failure, and mortality, the PASE trial6 found no significant differences betweeen SND and AVB patients according to the pacing mode.

Health-related quality of life (QoL) has become a useful and validated tool in the assessment of symptoms-related outcomes. Seven crossover comparative studies used validated instruments in small patients groups (the largest being 33 patients) and have had contradictory findings, two favouring11,12 and five showing no differences between DDD and ventricular pacing.13–17 The available data from the PASE,6,18 MOST,8 and CTOPP19 trials, which shared at least two health-related QoL instruments, showed that pacing-induced restoration of chronotropic competence has a significant effect on QoL on both SND and AVB patients. However, no significant differences were observed between single-chamber ventricular and dual-chamber randomly assigned pacing modes. Only in the PASE trial, the Specific Activity Scale detected differences favouring DDD that increased over time and were significant in longitudinal analysis.10,18

The incidence of AF is significantly higher in single-chamber ventricular than in physiological pacing users, both in SND and AVB patients.4–10,20 AAI and DDD pacing modes preserve AV synchrony, but ventricular desynchronization resulting from right-ventricular pacing in DDD mode, induces in patients with SND, a significantly increased incidence of AF and heart failure hospitalizations.21–23 In the DAVID study,24 the primary combined endpoint of hospitalization for congestive heart failure or death was significantly increased in patients paced in the DDD (DDDR, 70 b.p.m.) when compared with patients randomized to backup pacing (VVI, 40 b.p.m.). The same mechanism probably explains the higher incidence of new or worsened congestive heart failure in the ICD group than that in conventionally treated group in the MADIT II trial.25

Sophisticated pacing algorithms have been developed and delivered for the purpose of prevention and therapy of AF. Some important clinical data need to be considered: (i) at present, AF pacing prevention and therapy algorithms have shown a modest to minimal or absent incremental benefit,26–32 and more studies are required to determine whether they provide significant long-term benefits and which patients might benefit; (ii) development of AF in the PASE trial33 was not associated with a significant impact on QoL, functional status, and the pre-specified clinical endpoints (death, stroke, or heart failure hospitalization); (iii) after the AFFIRM and PIAF trials,34,35 the clinical need to prevent AF is less clear: the two therapeutic strategies of rate and rhythm control in AF are both associated with improvement in QoL with no significant differences between them.

Clarke et al.36 calculated that if their 290 patients with SND received a single-chamber atrial pacemaker (PM), with revision for symptomatic AVB (17 upgradings at the same cost of a DDD implant), saving in excess of £103 000 (149 587 EUROs in July 2005) a year would have been made in the biennium 1995–96. The results of the recently published Canadian Health Economic Assessment of Physiologic Pacing (CHEAPP), a prospective economic study conducted as a part of the CTOPP, showed how a strategy of routine implantation of physiological PM is not cost effective by currently accepted standards.37 Among all substudy patients in January 2004, the incremental cost effectiveness of dual-chamber devices was C$297 600 per life-year gained and C$74 400 per AF avoided over a follow-up period of 5.2 years (182 800 and 45 700 EUROs, respectively). Moreover, dual-chamber PMs are not only more expensive to implant (including also the cost of the additional lead) and to replace, but also must be replaced more often and sooner than ventricular devices.38 Ventricular dysfunction may be caused or at least worsened by continuous right-ventricular pacing8,24 in both VVI and DDD pacing modes. The need of upgrading some patients to cardiac resynchronization therapy may increase the overall costs of individual treatment and should be considered while designing future cost-effectiveness studies.

Changing from single-chamber to a DDD system may be determined by the occurrence of complete AVB in AAI(R) mode or a pacemaker syndrome (PMS) in VVI(R) and, less frequently, AAI(R) modes. Previous studies have shown that symptomatic high degree AVB develops in a range between 0.6 and 8.4% of patients with atrial PM.20,21,36,39 The subsequent implantation of a ventricular lead was reported to occur more often in those patients with a pre-existing prolonged PR interval, low Wenckebach rate, or bundle branch block.21,36,39,40 The impact of the assessment of the Wenckebach rate by the atrial lead on the duration and the costs of the implantation procedure may be considered irrelevant.

The classical PMS includes a constellation of symptoms associated with ventricular pacing. In the study of Horenstein and Karpawich,41 PMS appeared in 19 of 89 growing children after the first decade from PM implantation. The authors concluded that VVIR pacing mode may be an adequate and cost-effective initial therapy for complete AVB in those patients. In older adult patients, PMS has been reported to range from 1.720 to 83%.42 In 30 months PASE6 and in 33 months MOST8 trials, the incidence of PMS has been reported in 26 and 18.3% of the patients, respectively. Nevertheless, in the PASE trial,6 >70% of patients, who were assigned to ventricular pacing and were alive at the end of the study, were still in their assigned mode. In the 5 years CTOPP study,7 the percentage of patients initially assigned to ventricular pacing who had their devices programmed to a physiological mode at 5 years was 4.3%. In contrast, the percentage of patients initially assigned to physiological pacing who had their devices programmed to a ventricular mode at 5 years was 17.1%. This suggests that some of the earlier reports have greatly exaggerated the true incidence and prevalence of this syndrome.19 A decrease in systolic blood pressure during ventricular pacing at the time of PM implantation, the use of beta-blockers and the presence of non-ischaemic cardiomyopathy43 have been identified as predictors of crossover to DDD pacing. None of these factors need to spend additional time in investigations designed in order to choose a dual-chamber instead of a single-chamber device.

Thus at present time, SSI(R) pacing mode at the right atrium or ventricle seems to be the optimal treatment for SND and AVB, DDD being restricted to SND patients with impaired AV conduction44 at implantation or who will develop AV block after implantation36,40 and to AVB patients who will develop or in whom the development of a PMS may be predicted at implantation.43

Conclusions

The history of cardiac pacing is rich of significant advances in PM technology, providing even more miniaturized, long lasting, and sophisticated pacing systems. Very small pulse generators are already available and new or improved battery sources will be developed to support a further miniaturization. The industry by continuous evolution in programmability, rate adaptive pacing, telemetry, and autoprogrammability has furnished high-technology products extending and improving the lives of the patients around the world. In contrast, dual-chamber pacing has not shown a significant greater effectiveness when compared with single-chamber atrial or ventricular pacing. Moreover, sophisticated algorithms of AF prevention and therapy do not provide significant benefit. These data provide a reliable body of evidence on which to make more rationale clinical decisions for individual patients and policy decisions for health costs saving. The cheaper single-chamber AAI(R) or VVI(R) has been shown to satisfy both conditions in most cases of SND and AVB.

Conflict of interest: none declared.

Footnotes

The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology.

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