Heart rate recovery predicts sudden cardiac death in heart failure

doi:10.1016/j.ijcard.2008.12.149

International Journal of Cardiology

Volume 144, Issue 1, 24 September 2010, Pages 121-123

https://doi.org/10.1016/j.ijcard.2008.12.149 Get rights and content

Abstract

The purpose of this investigation was to examine the ability of heart rate recovery (HRR) to predict mortality secondary to pump failure or sudden cardiac death (SCD) in patients with heart failure (HF). Kaplan–Meier analysis revealed a significant difference in survival for both SCD (100% vs. 73.9%, log-rank: 50.5, p < 0.001) and pump failure (96.1% vs. survival = 78.4%, log-rank: 24.4, p < 0.001) endpoints according to a </≥ 17 bpm HRR threshold. The results of the present study indicate HRR is a significant predictor of both SCD and pump failure mortality in patients with HF although its ability to predict SCD was superior.

Introduction

Heart rate recovery (HRR) following exercise appears to reflect the rate at which parasympathetic tone is reestablished [1], [2]. Given this link between physiology and HRR, it is not surprising that this exercise test variable has been shown to be an important prognostic marker in groups with varying levels of autonomic dysfunction favoring the sympathetic nervous system [3], [4], [5], [6], including patients with heart failure(HF) [7], [8]. In patients with HF, the cause of death can be divided into non-arrhythmic (i.e. pump failure) and arrhythmic (sudden cardiac death; SCD), the latter of which may be more influenced by the level of autonomic dysfunction [9]. We have previously demonstrated that the prognostic ability of cardiopulmonary exercise testing variables (exercise oscillatory ventilation and ventilatory efficiency) differ according to cause of death in a HF cohort [10]. This previous analysis demonstrated that exercise oscillatory ventilation, which has been linked to autonomic function, was the strongest predictor SCD, while ventilatory efficiency (the VE/VCO₂ slope) was the strongest predictor of pump failure. Given the link between HRR and autonomic tone, the predictive ability of this exercise test variable may likewise differ according to mechanism of death. The purpose of the present investigation was to therefore assess the ability of HRR to predict mortality secondary to pump failure and SCD in a group of subjects with HF.

Section snippets

Methods

Two-hundred and forty-three subjects (190 male/53 female, age: 62.2 ± 9.7 years, ejection fraction: 35.6 ± 11.0%) with compensated HF were enrolled in this study. Etiology of HF was ischemic in 63% and non-ischemic in the remaining 37%. Beta-blocker, ACE inhibitor and anti-aldosterone prescriptions were recorded in 57%, 79% and 42% of the subjects, respectively.

Statistical analysis

Analysis of Variance compared HRR₁ between survivors and deaths secondary to either pump failure or SCD. Tukey's honestly significant difference was used to determine which groups were significantly different from one-another. Receiver operating characteristic (ROC) curve analysis was used to assess the pump failure and SCD prognostic classification schemes for HRR₁ and to determine optimal threshold values. Kaplan Meier analysis assessed differences in both non-arrhythmic and arrhythmic death

Results

Mean resting HR, peak HR and HRR₁ for the overall group were 74.0 ± 9.1, 129.2 ± 16.4 and 18.0 ± 3.3 beats per minute (bpm), respectively. There were 48 cardiac-related deaths during the 23.2 ± 21.1 month tracking period (annual mortality rate: 9.4%). Twenty-three of the deaths were classified as SCD while the other 25 were classified as pump failure. HRR₁ was significantly greater in survivors (18.7 ± 3.0 bpm) compared to both pump failure (15.2 ± 2.2 bpm) and SCD (14.4 ± 1.5 bpm) subgroups (p < 0.001). HRR₁

Discussion

The results of the present study indicate HRR is a significant prognostic marker for both pump failure and SCD in patients with HF. Moreover, the optimal HRR threshold for identifying patients at elevated risk was the same for both mechanisms of death. This exercise test variable was, however, a stronger predictor of the latter endpoint, as indicated by ROC curve and Kaplan–Meier analysis. Of note, none of the subjects with a HRR₁ ≥ 17 bpm suffered a SCD.

Other groups have identified measures of

Acknowledgement

The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology [11].

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To determine whether the time for peak exercise heart rate to return to resting heart rate after the 6-minute walk test (6MWT) can predict cardiac events in patients with heart failure (HF) within 2 years.
Prospective cohort study.
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Seventy-six patients with HF, New York Heart Association functional classification II and III, and left ventricular ejection fraction <50%.
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Thirty-four patients had cardiac events during the 2-year follow-up period. However, there was a significant difference in the time to return to resting heart rate between the groups with and without cardiac events {with 3.6 (SD 1.1) vs without 2.8 (SD 1.1) minutes; mean difference of 0.79 (95% confidence interval (CI) of the difference 0.28 to 1.28; P = 0.003}. No significant differences between patients with and without cardiac events were found for mean walking distance, mean heart rate recovery at 1 minute and mean heart rate recovery at 2 minutes. The receiver operating curve discriminated between patients with and without cardiac events (área under the curve 0.71, 95% CI 0.61 to 0.81; P < 0.001). Using logistic regression analysis, prolonged time to return to resting heart rate (≥3 minutes) independently increased the risk for cardiac events 6.9-fold (95% CI 2.34 to 20.12; P < 0.001). The Kaplan–Meier curve showed more cardiac events in patients with prolonged time to return to resting heart rate (P = 0.028).
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Citation Excerpt :
Finally, failure to normalize HRR after cardiac rehabilitation predicted a higher mortality [31]. The above results and other studies of HRR in patients with HF have utilized symptom limited exercise tests; no previous study to our knowledge has examined the effects of exercise effort on the prognostic value of HRR [24–31]. We have observed that the prognostic significance of HRR is not dependent on maximal effort in patients with HF.
Heart rate recovery (HRR) has been observed to be a significant prognostic measure in patients with heart failure (HF). However, the prognostic value of HRR has not been examined in regard to the level of patient effort during exercise testing. Using the peak respiratory exchange ratio (RER) and a large multicenter HF database we examined the prognostic utility of HRR.
Cardiopulmonary exercise testing (CPX) was performed in 806 HF patients who then underwent an active cool-down of at least 1 min. Peak oxygen consumption (VO₂), ventilatory efficiency (VE/VCO₂ slope), and peak RER were determined with subjects categorized into subgroups according to peak RER (< 1.00, 1.00–1.09, ≥ 1.10). HRR was defined as the difference between heart rate at peak exercise and 1 min following test termination. Patients were followed for major cardiac events for up to four years post-CPX.
There were 163 major cardiac events (115 deaths, 20 left ventricular assist device implantations, and 28 transplantations) during the four year tracking period. Univariate Cox regression analysis results identified HRR as a significant (p < 0.05) univariate predictor of adverse events regardless of the RER achieved. Multivariate Cox regression analysis in the overall group revealed that the VE/VCO₂ slope was the strongest predictor of adverse events (chi-square: 110.9, p < 0.001) with both HRR (residual chi-square: 16.7, p < 0.001) and peak VO₂ (residual chi-square: 10.4, p < 0.01) adding significant prognostic value.
HRR after symptom-limited exercise testing performed at sub-maximal efforts using RER to categorize level of effort is as predictive as HRR after maximal effort in HF patients.
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Letter to the EditorHeart rate recovery predicts sudden cardiac death in heart failure