Elsevier

Heart Rhythm

Volume 4, Issue 7, July 2007, Pages 886-891
Heart Rhythm

Original-clinical
Eliminating right ventricular pacing may not be best for patients requiring implantable cardioverter-defibrillators

https://doi.org/10.1016/j.hrthm.2007.03.031Get rights and content

Background

Excessive right ventricular (RV) pacing has been associated with adverse clinical outcomes in patients receiving pacemakers or implantable cardioverter-defibrillators (ICDs). It remains uncertain how much RV pacing is clinically deleterious.

Objective

This retrospective analysis assessed the relationship between the amount of RV pacing and the composite of all-cause mortality and heart failure hospitalization in all patients programmed DDDR in the Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) study.

Methods

Seven hundred fifteen patients consistently programmed to DDDR mode throughout follow-up (mean 11.6 months) were examined. The relationship between RV pacing tier and death and heart failure hospitalization was determined and compared with patient characteristics.

Results

Across the six RV pacing tiers, patients differed significantly with respect to age, clinical history of ventricular tachycardia, atrial fibrillation, and atrial flutter, and amiodarone use. When controlling for these baseline differences, the best outcome was seen in the group with RV pacing between 10% and 19% (2.8% event rate; n = 106). Increasing levels of RV pacing were generally predictive of higher event rates (death or heart failure hospitalization; P = 0.003), except for the group (n = 344) with the least amount of RV pacing (0–9%). This group exhibited poorer outcomes than otherwise expected (P = 0.016), with 8.1% of these patients experiencing an event.

Conclusions

High levels of RV pacing are associated with heart failure hospitalization and mortality in a large ICD population. However, ICD patients with some RV pacing (10%–19%) exhibit lower event rates compared with those with very low levels (0–9%), possibly due to the physiologically appropriate nature of that RV pacing.

Introduction

Multicenter controlled clinical trials have shown that excessive amounts of right ventricular (RV) pacing are associated with increased risk of atrial fibrillation, heart failure hospitalization, implantable cardioverter-defibrillator (ICD) therapy, ventricular arrhythmias including ventricular fibrillation, and increased risk of cardiovascular mortality in patients who receive pacemakers or ICDs.1, 2, 3, 4 Post hoc analyses from several studies1, 4, 5, 6, 7, 8, 9 have suggested that RV pacing has negative implications. However, these studies are inconclusive with regard to how much RV pacing is deleterious. It remains uncertain how far attempts should be made to prevent RV pacing in patients with ICDs. Several device manufacturers have developed algorithms that attempt to minimize RV pacing assuming that the optimal level of RV pacing is no RV pacing at all. However, no clinical evidence currently exists to support this.

The purpose of this analysis was to assess the relationship between various tiers of RV pacing and outcomes in the Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) study.10 We questioned whether the optimal amount of RV pacing in an ICD population is no RV pacing at all. In addition, we evaluated whether there was a range of RV pacing that appeared deleterious.

Section snippets

Methods

The INTRINSIC RV study was a multicenter, randomized, controlled, clinical trial assessing total mortality and heart failure (HF) hospitalization outcomes as the primary composite endpoint in 1530 patients who met the standard criteria for ICD implant.11 Atrioventricular (AV) Search Hysteresis was chosen as a treatment feature since it has been shown to reduce RV pacing by allowing intrinsic AV conduction beyond the programmed AV delay when proper programming characteristics are applied.12 The

Results

Baseline characteristics for all 715 patients programmed to a DDDR pacing mode, reported by RV pacing tier, are presented in Table 1. These patients are typical of ICD recipients in other clinical trials but differed significantly across the six pacing groups with respect to age, clinical history of ventricular tachycardia, atrial fibrillation, and atrial flutter, and amiodarone use. Event rates (total mortality and HF hospitalization) evaluated against cumulative RV pacing are presented in

Discussion

These data show that the amount of RV pacing is associated with HF hospitalization and total mortality in a large ICD population. Remarkably, patients who were RV pacing 0–9% were more likely to experience an unfavorable event (death or HF hospitalization) than the group that demonstrated the best outcome, that is, those patients with RV pacing 10%–19%. The reasons for this are not certain but may be due to patient characteristics, a balance in the adverse effects of RV pacing, or the

Limitations

The lack of baseline electrocardiographic and echocardiographic data, not routinely mandated in the INTRINSIC RV trial, makes it difficult to correlate any findings from these parameters with the burden of ventricular pacing, susceptibility to HF hospitalization, and death. Based on the current data, it is not possible to discern the absolute benefit of RV pacing in lieu of patient-specific, physiological AV interval optimization.

Patients in different RV pacing tiers tended to differ in other

Conclusion

High and very low levels of RV pacing in ICD patients enrolled in the INTRINSIC RV trial were associated with poorer outcomes. These data suggest that reducing RV pacing to very low levels (<10%) does not necessarily improve outcomes. Furthermore, patients pacing between 10% and 19% experienced fewer events. RV pacing delivered as it was in the INTRINSIC RV trial, that is, not excessively, does not appear harmful and may benefit ICD recipients.

Acknowledgments

The authors thank the patients who participated in the INTRINSIC RV trial and the participating investigators and institutions.

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    This study was funded in full by Boston Scientific CRM (formerly Guidant Corporation).

    1

    Brian Olshansky has received support from and is a consultant for Boston Scientific CRM

    2

    Darin R. Lerew has an ownership interest in and is employed by Boston Scientific CRM

    3

    Scott Brown is an employee of the Integra Clinical Group and is employed as a consultant to Boston Scientific CRM

    4

    Kira Stolen has an ownership interest in and is employed by Boston Scientific CRM.

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