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A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation
Published on: February 28, 2012
Heart rate, pacing, and outcome in the Dual Chamber and VVI Implantable Defibrillator (DAVID) trials
Peter J Kudenchuk1, Alfred P Hallstrom, John M Herre
1University of Washington, Seattle, Washginton 98195-6422, USA.
Insights
Patients with isolated bradycardia (slow heart rate) show a lower risk of heart failure (HF) hospitalization and death. This protective effect persists even with faster heart rates from atrial pacing, challenging traditional therapeutic targets.
Area of Science:
- Cardiology
- Electrophysiology
- Heart Failure Research
Background:
- Slower heart rates are associated with better prognosis in heart disease.
- The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial noted reduced heart failure (HF) hospitalization and mortality in patients with ventricular dysfunction and isolated sinus bradycardia when paced infrequently.
- Isolated sinus bradycardia is defined as a heart rate below 60 beats per minute with a normal PR interval.
Purpose of the Study:
- To prospectively evaluate if bradycardia confers a similar benefit in the DAVID II trial as observed in the DAVID trial.
- To determine if faster heart rates achieved during atrial pacing in DAVID II negate the potential benefits of bradycardia.
- To test the hypothesis that atrial pacing might nullify the protective association of bradycardia with heart failure outcomes.
Main Methods:
- Prospective evaluation of outcomes in defibrillator recipients with isolated bradycardia in the DAVID II trial.
- Comparison of outcomes between patients with and without isolated bradycardia.
- Assessment of the effects of atrial versus minimal ventricular pacing on outcomes.
Main Results:
- Patients with isolated bradycardia (n=98) had less baseline heart failure (HF) compared to those without (n=502).
- Overall, patients with isolated bradycardia were less likely to die or be hospitalized for HF (12.2% vs. 26%; P = .01).
- Atrial pacing did not diminish the association between isolated bradycardia and reduced HF/mortality risk (adjusted relative risks of 0.47 with and 0.71 without atrial pacing).
Conclusions:
- Isolated bradycardia identifies patients at lower risk for heart failure (HF) and mortality.
- The association between bradycardia and lower HF risk is not necessarily negated by accelerating heart rate with atrial pacing.
- This finding challenges the established use of heart rate as a sole therapeutic target in patients with ventricular dysfunction.
Background:
Slower heart rates are believed to confer a better prognosis in heart disease. The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial found that patients with ventricular dysfunction and isolated sinus bradycardia (rate <60 with normal PR interval) had an unusually low incidence of heart failure (HF) hospitalization and mortality when paced infrequently.
Objectives:
The purpose of this study was to prospectively test our hypotheses that a similar benefit from bradycardia would be conferred in DAVID II as in DAVID but that this would be nullified by the faster heart rate achieved during atrial pacing in DAVID II.
Methods:
Effects of atrial versus minimal ventricular pacing on outcome in defibrillator recipients with isolated bradycardia in DAVID II were prospectively evaluated.
Results:
Ninety-eight DAVID II patients with isolated bradycardia were similar to 502 patients without it but had less baseline HF. HF medications were used comparably in both groups at baseline and throughout the study. Overall, patients with isolated bradycardia were less likely to die or be hospitalized for HF than others (12.2% vs. 26%; P = .01). There was no evidence that atrial pacing diminished this association. Adjusted for covariates, particularly baseline HF and its treatment, isolated bradycardia patients had substantially reduced risk for HF/death (P = .018) with or without atrial pacing (relative risk 0.47 and 0.71, respectively).
Conclusions:
Isolated bradycardia identifies patients at lower risk for HF and mortality, an association that is not necessarily negated by accelerating heart rate with atrial pacing. This apparent conundrum challenges the use of heart rate as a therapeutic target in patients with ventricular dysfunction.
Trial Registration:
http://www.clinicaltrials.gov NCT00187187.
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