ClinicalGeneralRelationship between changes in heart rate recovery after cardiac rehabilitation on cardiovascular mortality in patients with myocardial infarction
Introduction
The autonomic nervous system plays an important role in regulating the cardiovascular system. Both high sympathetic and low parasympathetic tones have been shown to be associated with increased cardiovascular mortality.1, 2Heart rate recovery (HRR), defined as the fall in heart rate through the first minute after exercise, is a measure of the capacity of the cardiovascular system to reactivate the parasympathetic nervous system after exercise3, 4 and has been found to be an independent predictor of all-cause mortality in various populations.5, 6, 7 Previous studies have shown that HRR measured at predischarge exercise stress test (EST) predicts mortality among survivors of acute myocardial infarction (MI).8
HRR appears to be modifiable by regular exercise,9, 10, 11 presumably due to the favorable effect of exercise on autonomic regulation.12, 13 However, the relationship between improvement in HRR and clinical outcomes after MI remains unclear. The aim of this study was to evaluate the effect of exercise training on HRR in patients with recent MI and the impact of change in HRR on their clinical outcomes.
Section snippets
Study population
This prospective cohort study consisted of consecutive patients who were enrolled into our cardiac rehabilitation program from 1996 to 2007. All patients had confirmed diagnoses of acute MI based on World Health Organization criteria.14 A total of 446 patients who were able to perform symptom-limited EST on treadmill, completed phase 1 and phase 2 of the program with good attendance over 70%, no pacemaker implantation, and no change in medications between the two ESTs were recruited. Among
Study design
Among the 386 patients recruited, 334 underwent an 8-week exercise training program in phase 2 of our program, which consisted of twice-weekly 45-minute scheduled sessions of supervised exercise at an intensity based on individual assessment. The remaining 52 patients did not receive any exercise training because they were included into the control arm of our prior randomized study conducted between 1997 and 2002.15 Nevertheless, all 386 patients received the same magnitude of education,
Exercise testing
Symptom-limited ESTs were conducted in phase 1 (before exercise training) and at the end of phase 2 (after exercise training) using the modified Bruce protocol. Treadmill was terminated within 10 seconds after peak exercise, and patients were allowed to assume a sitting position immediately. Resting heart rate was defined as heart rate before EST during sitting. Peak heart rate was defined as heart rate achieved at peak exercise. Heart rate increment was defined as heart rate increase from
Statistical analysis
Continuous variables are expressed as mean ± SD, and categorical variables are presented in frequency tables. Statistical comparisons were performed using Student's t-test or Pearson Chi-square test, as appropriate. LVEF ≤30% was chosen as a predictive variable of cardiac death, in line with the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II).23 For all other variables, cutoff points were obtained from receiver operating characteristic curve analyses. Hazard ratio (HR) and
Results
Table 1 lists baseline clinical demographic features of the study population. A total of 334 (86.5%) patients received exercise training. More patients in the exercise training group received antiplatelets or warfarin, statins, and revascularizations before enrollment compared to patients without exercise training. Their changes in EST parameters and LVEF during follow-up are listed in Table 2. Peak heart rate, heart rate increment, and HRR increased significantly after completion of phase 2 in
Discussion
Our results demonstrated exercise training improved HRR, LVEF, and exercise capacity in patients with recent MI. In this study, none of the parameters during baseline phase 1 EST, except resting heart rate, predicted cardiac death during long-term follow-up. In contrast, left ventricular dysfunction with LVEF ≤30%, impaired HRR <12 bpm, and exercise capacity ≤4 METs at phase 2 after training were shown to be independent predictors of cardiac death. Furthermore, persistently impaired HRR <12 bpm
Study limitations
First, our study recruited patients who completed phase 1 and phase 2 of the cardiac rehabilitation program with good attendance and were able to perform symptom-limited EST on treadmill. As a result, high-risk populations of patients who could not complete the program due to repeated hospitalizations or could not perform treadmill tests due to poor cardiovascular function were excluded. Indeed, the cardiac death rate was 21% and sudden cardiac death rate was 12.3% among patients excluded (n =
Conclusion
Our study demonstrated that exercise training improved HRR and that patients with persistently impaired HRR <12 bpm after rehabilitation had higher cardiac mortality during long-term follow-up, suggesting that modulation of cardiovascular autonomic control with exercise training may contribute to the long-term beneficial effects of a cardiac rehabilitation program. Its clinical application as a therapeutic target for exercise prescription and medication titration needs to be further addressed
References (35)
- et al.
Autonomic tone as a cardiovascular risk factor: the dangers of chronic fight or flight
Mayo Clin Proc
(2002) - et al.
Autonomic nervous system interaction with the cardiovascular system during exercise
Prog Cardiovasc Dis
(2006) - et al.
Heart rate recovery after exercise as a predictor of mortality among survivors of acute myocardial infarction
Am J Cardiol
(2003) - et al.
Effect of exercise training in supervised cardiac rehabilitation programs on prognostic variables from the exercise tolerance test
Am J Cardiol
(2008) - et al.
Heart rate recovery in heart failure patients after a 12-week cardiac rehabilitation program
Am J Cardiol
(2006) - et al.
Effects of cardiac rehabilitation and exercise training on autonomic regulation in patients with coronary artery disease
Am Heart J
(2002) - et al.
A short course of cardiac rehabilitation program is highly cost effective in improving long-term quality of life in patients with recent myocardial infarction or percutaneous coronary intervention
Arch Phys Med Rehabil
(2004) - et al.
Ergometric score systems after myocardial infarction: prognostic performance of the Duke Treadmill Score, Veterans Administration Medical Center Score, and of a novel score system, GISSI-2 Index, in a cohort of survivors of acute myocardial infarction
Am Heart J
(2003) - et al.
Prognostic evaluation by clinical exercise test scores in patients treated with primary percutaneous coronary intervention or fibrinolysis for acute myocardial infarction (a Danish Trial in Acute Myocardial Infarction-2 Sub-Study)
Am J Cardiol
(2007) - et al.
Prognostic value of training-induced change in peak exercise capacity in patients with myocardial infarcts and patients with coronary bypass surgery
Am J Cardiol
(1995)
Resting heart rate in cardiovascular disease
J Am Coll Cardiol
Comparison of baroreflex sensitivity and heart period variability after myocardial infarction
J Am Coll Cardiol
Decreased heart rate variability and its association with increased mortality after acute myocardial infarction
Am J Cardiol
Decreased heart rate recovery after exercise in patients with congestive heart failure: effect of beta-blocker therapy
J Card Fail
Autonomic nervous system and sudden cardiac deathExperimental basis and clinical observations for post-myocardial infarction risk stratification
Circulation
Autonomic changes in patients with heart failure and in post-myocardial infarction patients
Heart
Heart rate recovery and treadmill exercise score as predictors of mortality in patients referred for exercise ECG
JAMA
Cited by (30)
Acute and chronic effects of high-intensity interval and moderate-intensity continuous exercise on heart rate and its variability after recent myocardial infarction: A randomized controlled trial
2022, Annals of Physical and Rehabilitation MedicineCardiorespiratory fitness measured with cardiopulmonary exercise testing and mortality in patients with cardiovascular disease: A systematic review and meta-analysis
2021, Journal of Sport and Health ScienceCitation Excerpt :The follow-up length ranged from 1223 to 16824 months. The most common CVDs were coronary artery disease23–32 and heart failure,33–37 and other studies included patients diagnosed with aortic stenosis,22 hypertrophic cardiomyopathy,38 peripheral artery disease,39 and a combination of various pathologies.21,40–42 General characteristics of the 21 included studies are summarized in Table 1.
Effect of exercise training on heart rate recovery in patients post anterior myocardial infarction
2018, Egyptian Heart JournalCitation Excerpt :Our study showed statistically significant increase in mean HR recovery in 1st min (HRR1) and 2nd minute (HRR2) after exercise training program (18 ± 8.47 vs. 24.70 ± 7.57, p-value <0.001) and (30.52 ± 8.62 vs. 38.86 ± 10.13, p-value <0.001) respectively. These improvements in HR recovery was supported by Hai et al. who investigated the effect of change in HR recovery after exercise training on clinical outcomes in MI patients.6 The study included 386 consecutive patients with recent MI who were enrolled into CR program.
The prognostic value of heart rate recovery in patients with coronary artery disease: A systematic review and meta-analysis
2018, American Heart JournalCitation Excerpt :After reviewing 2,078 titles and abstracts, 66 studies were assessed full text for eligibility. In total, 4 studies met the inclusion criteria (Figure 1).7,18,22,23 No additional studies were identified by reference checking.
Effects of high-intensity interval versus continuous exercise training on post-exercise heart rate recovery in coronary heart-disease patients
2017, International Journal of CardiologyCitation Excerpt :Another interesting observation is that in the group of patients as a whole, we found a significant correlation of VO2peak between HHR1 and HHR2. In contrast to most previous research that analyzed only HRR1 [32–37], we measured the heart rate recovery in the 1 and 2 min post-exercise. Both points have shown associations with mortality risk, although the heart rate in min 2 post-exercise has proved to be the most powerful predictor [30], which suggests the need to add systematic evaluation of HRR2 in patients with cardiovascular disease.
Impact of Phase II cardiac rehabilitation on abnormal heart rate recovery
2014, Journal of the Chinese Medical Association