Randomized trial of a hospital-based exercise training program after acute myocardial infarction: cardiac autonomic effects

Acute responses and chronic adaptations to exercise in humans: a look from the autonomic nervous system window

The objective of this review was to give an overview on the current knowledge on the neural mechanisms of cardiovascular regulation during acute exercise and the autonomic adaptations brought about by chronic exercise, that is, exercise training. Evidence derived mainly from human studies, which supports the contribution of the different control mechanisms, namely the centralcommand, the reflex drive from active muscles and the arterial baroreflex, with the attendant modifications in autonomic nervous system activity, in determining the acute cardiovascular responses to exercise are discussed, along with some controversial issues and evolving concepts in exercise physiology. In particular, data that show how the various neural mechanisms involved in cardiovascular regulation during exercise are differently modulated by factors related to the muscular activity being performed, such as the type and intensity of exercise and the size of the active muscle masses are presented, stressing the plasticity of the neural network. Thereafter, the clinical implications pertaining neural cardiovascular adaptations to exercise training are presented and discussed, in the context of cardiac diseases. In particular, I will summarize a series of investigations performed in our laboratory that utilized a new training methodology and different exercise formats to quantify the training load in cardiac patients. The way by which individualized exercise training doses affects the autonomic nervous system and the cardiorespiratory adaptations is highlighted.

The effect of home-based cardiac rehabilitation on arterial stiffness and peak oxygen consumption in patients with myocardial infarction

Objectives

This study aims to investigate the effectiveness of home-based cardiac rehabilitation (CR) on arterial stiffness in patients with acute myocardial infarction (AMI).

Patients and methods

Between January 2015 and December 2017, a total of 135 patients (120 males, 15 females; mean age: 58.8±11.1 years) with AMI who were referred for CR were included. Home-based CR was prescribed based on a cardiopulmonary exercise test (CPET) for at least six months. All patients completed three consecutive CPETs and brachial-ankle pulse wave velocity (baPWV) measurements at one, four, and seven months after onset.

Results

After six months of CR, there was an improvement in peak oxygen consumption (pVO2) (Month 1, 28.7±6.4 mL/kg/min; Month 4, 31.6±6.3 mL/kg/min; Month 7, 31.2±7.1 mL/kg/min, p<0.001) and a reduction in baPWV (Month 1, left, 1546.0±311.2 cm/sec, right 1545.5±301.5 cm/sec; Month 4, left, 1374.9±282.5 cm/sec, right 1371.6±287.5 cm/sec; Month 7, left, 1362.9±287.0 cm/sec, right 1365.5±281.1 cm/sec, p<0.001).

Conclusion

In patients with AMI, arterial stiffness and aerobic capacity improved after six months of home-based CR, particularly in the early stages of rehabilitation. These results suggest that changes in baPWV are useful in determining the effectiveness of CR and pVO2 in the initial stages of CR.

Effects of physical exercise on the autonomic nervous system in patients with coronary artery disease: a systematic review

BACKGROUND

Imbalance in autonomic modulation can occur after a cardiac event, which can lead to deleterious consequences. Exercise has proven to be a therapy which affects this modulation and can be assessed through heart rate variability (HRV).

AREAS COVERED

The objective of this systematic review was to investigate the effects of physical exercise on heart rate variability in individuals with coronary artery disease (CAD). The PubMed, PEDro, Scielo, Lilacs and Cochrane databases were systematically searched, for articles which performed supervised exercises in phase II of cardiac rehabilitation in patients with CAD.

EXPERT OPINION

Given the differences between studies on interventions and population characteristics, it is difficult to justify similarities or divergences in terms of results. In addition to the variation in sample size, intervention duration, carrying out an additional program at home, and patients with different clinical presentations, it can be inferred that responses to exercise may vary for certain types/clinical profile of individuals with CAD. Thus, it is necessary to carry out more studies with greater methodological rigor, greater standardization of the variables studied and the evaluation forms, in order to increase the veracity of the results and the consequent clinical relevance and therapeutic application.

Exercise-based cardiac rehabilitation and parasympathetic function in patients with coronary artery disease: a systematic review and meta-analysis

PURPOSE

The effects of exercise-based cardiac rehabilitation (CR) on parasympathetic modulation are controversial. This systematic review and meta-analysis aims to (a) determine the effect of exercise-based CR on heart-rate-derived indices associated with cardiac parasympathetic modulation in resting and post-exercise conditions in coronary artery disease (CAD) patients and (b) identify the possible moderator variables of the effect of exercise-based CR on parasympathetic modulation.

METHODS

We searched CENTRAL and Web of Science up to November 2018 for the following terms: adult CAD patients, controlled exercise-based CR interventions and parasympathetic modulation measured in resting (vagal-related heart rate variability [HRV] indices of the root mean square of the differences in successive in RR interval [RMSSD] and high frequency [HF]) and post-exercise (heart rate recovery [HRR]) pre- and post-intervention. We estimated a random-effects model of standardised mean difference (SMD) and mean difference (MD) for vagal-related HRV indices and HRR, respectively. We assessed the influence of categorical and continuous variables.

RESULTS

The overall effect size showed significant differences in RMSSD (SMD₊ = 0.30; 95% confidence interval [CI] = 0.12-0.49) and HRR (MD₊ = 5.35; 95% CI = 4.08-6.61 bpm) in favour of the exercise-based CR group. The overall effect size showed no differences in HF between groups (SMD₊ = 0.14; 95% CI,  -0.12-0.40). Heterogeneity analyses reached statistical significance, with high heterogeneity for HF (p < 0.001; I² = 70%) and HRR (p < 0.001; I² = 85%). Analysis of the moderator variables showed that the effect on HRR is greater in young patients (p = 0.008) and patients treated with percutaneous intervention (p = 0.020).

CONCLUSIONS

Exercise-based CR improves the post-exercise parasympathetic function, with greater effects in younger CAD patients and in those who were revascularised with percutaneous intervention. The effects on resting parasympathetic function are more controversial due to methodological inconsistencies in measuring HRV, with the use of RMSSD recommended instead of HF because its results show higher consistency. Future studies involving women, focusing on methodological issues, and performing other training methods are needed to increase our knowledge about this topic.

Are Trait Emotional Competencies and Heart Rate Variability Linked to Mental Health of Coronary Heart Disease Patients?

PURPOSE

Depression and anxiety have been extensively associated with adverse outcomes in coronary heart disease patients. However, psychological and physiological processes underlying the persistence of these troubles in coronary heart disease patients attending cardiac rehabilitation are poorly investigated. Trait emotional competencies and heart rate variability could be some of these processes. Thus, the aim of this study was to assess the predictive value of trait emotional competencies and heart rate variability on depression and anxiety symptoms persistence in coronary heart disease patients.

METHODS

Eighty-four patients who recently presented a myocardial infarction were evaluated at the beginning of cardiac rehabilitation. Forty-two patients continued their rehabilitation program and were then assessed three months later. They completed the Profile of Emotional Competence as well as the Hospital Anxiety and Depression Scale and underwent a 5-minute resting heart rate variability measure.

RESULTS

Low trait emotional competencies score predicted depression symptoms persistence, but unexpectedly, high trait emotional competencies score was also associated with withdrawal from cardiac rehabilitation. Contrary to our expectations, heart rate variability did not predict depression or anxiety symptoms persistence and was not associated with trait emotional competencies.

CONCLUSIONS

This study is the first to report an association between trait emotional competencies and depression symptoms persistence in coronary heart disease patients. However, heart rate variability was not associated with either depression or anxiety supporting the idea of mixed literature and highlighting the need of future research.

Effects of 6 Months of Exercise-Based Cardiac Rehabilitation on Autonomic Function and Neuro-Cardiovascular Stress Reactivity in Coronary Artery Disease Patients

Background Autonomic dysregulation represents a hallmark of coronary artery disease (CAD). Therefore, we investigated the effects of exercise-based cardiac rehabilitation (CR) on autonomic function and neuro-cardiovascular stress reactivity in CAD patients. Methods and Results Twenty-two CAD patients (4 women; 62±8 years) were studied before and following 6 months of aerobic- and resistance-training-based CR. Twenty-two similarly aged, healthy individuals (CTRL; 7 women; 62±11 years) served as controls. We measured blood pressure, muscle sympathetic nerve activity, heart rate, heart rate variability (linear and nonlinear), and cardiovagal (sequence method) and sympathetic (linear relationship between burst incidence and diastolic blood pressure) baroreflex sensitivity during supine rest. Furthermore, neuro-cardiovascular reactivity during short-duration static handgrip (20s) at 40% maximal effort was evaluated. Six months of CR lowered resting blood pressure (P<0.05), as well as muscle sympathetic nerve activity burst frequency (48±8 to 39±11 bursts/min; P<0.001) and burst incidence (81±7 to 66±17 bursts/100 heartbeats; P<0.001), to levels that matched CTRL and improved sympathetic baroreflex sensitivity in CAD patients (P<0.01). Heart rate variability (all P>0.05) and cardiovagal baroreflex sensitivity (P=0.11) were unchanged following CR, yet values were not different pre-CR from CTRL (all P>0.05). Furthermore, before CR, CAD patients displayed greater blood pressure and muscle sympathetic nerve activity reactivity to static handgrip versus CTRL (all P<0.05); yet, responses were reduced following CR (all P<0.05) to levels observed in CTRL. Conclusions Six months of exercise-based CR was associated with marked improvement in baseline autonomic function and neuro-cardiovascular stress reactivity in CAD patients, which may play a role in the reduced cardiac risk and improved survival observed in patients following exercise training.

What is the effect of aerobic exercise intensity on cardiorespiratory fitness in those undergoing cardiac rehabilitation? A systematic review with meta-analysis

OBJECTIVE

Assess the role of exercise intensity on changes in cardiorespiratory fitness (CRF) in patients with cardiac conditions attending exercise-based cardiac rehabilitation.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

MEDLINE, Embase, CINAHL, SPORTDiscus, PsycINFO and Web of Science.

ELIGIBILITY CRITERIA FOR SELECTION

Studies assessing change in CRF (reported as peak oxygen uptake; V̇O_2peak) in patients post myocardial infarction and revascularisation, following exercise-based cardiac rehabilitation. Studies establishing V̇O_2peak via symptom-limited exercise test with ventilatory gas analysis and reported intensity of exercise during rehabilitation were included. Studies with mean ejection fraction <40% were excluded.

RESULTS

128 studies including 13 220 patients were included. Interventions were classified as moderate, moderate-to-vigorous or vigorous intensity based on published recommendations. Moderate and moderate-to-vigorous-intensity interventions were associated with a moderate increase in relative V̇O_2peak (standardised mean difference±95% CI=0.94±0.30 and 0.93±0.17, respectively), and vigorous-intensity exercise with a large increase (1.10±0.25). Moderate and vigorous-intensity interventions were associated with moderate improvements in absoluteV̇O_2peak (0.63±0.34 and 0.93±0.20, respectively), whereas moderate-to-vigorous-intensity interventions elicited a large effect (1.27±0.75). Large heterogeneity among studies was observed for all analyses. Subgroup analyses yielded statistically significant, but inconsistent, improvements in CRF.

CONCLUSION

Engagement in exercise-based cardiac rehabilitation was associated with significant improvements in both absolute and relative V̇O_2peak. Although exercise of vigorous intensity produced the greatest pooled effect for change in relative V̇O_2peak, differences in pooled effects between intensities could not be considered clinically meaningful.

REGISTRATION

Prospero CRD42016035638.

Changes in Oxygen Consumption and Heart Rate After Acute Myocardial Infarction During 6-Month Follow-up

BACKGROUND

Exercise intensity is a particularly important determinant of physiological responses to exercise training in patients with acute myocardial infarction. Heart rate (HR) is commonly used as a practical way of prescribing and monitoring exercise as specific intensities based on a linear relationship between the percentage of maximum HR (%HR_max) and the percentage of maximum oxygen consumption (%VO_2max) regardless of age, gender, or exercise mode.

OBJECTIVE

To examine the change in variability in the correlation between %HR_max and %VO_2max after acute myocardial infarction.

DESIGN

Retrospective study.

SETTING

Regional cardio-cerebrovascular center at a tertiary hospital.

PATIENTS

A total of 66 patients were enrolled who were referred for cardiac rehabilitation (CR) after percutaneous intervention, and who had reached stage 3 of the modified Bruce Protocol (mBP) on an exercise tolerance test (ETT).

METHODS

There were 54 men and 12 women with an average age of 56.7 ± 9.48 years, ejection fraction (EF) of 56.4% ± 8.89%, and body mass index (BMI) of 24.73 ± 2.86 kg/m². All patients participated in a 4-week outpatient CR program and underwent ETT with a gas analyzer to determine maximal heart rate and maximal oxygen consumption before CR and 1 month, 3 months, and 6 months after CR.

MAIN OUTCOME MEASUREMENTS

VO_2max and HR_max were defined as the highest values attained during the ETT. The HR and VO₂ values at each stage of the mBP were expressed as percentages of their maximum. %HR_max and %VO_2max were calculated at each stage of the mBP.

RESULTS

The maximum METs and VO_2max significantly improved at 1 month after CR, but not significantly at 3 and 6 months after CR. The correlation between VO_2max and HR_max progressively changed in a favorable manner during CR. The relationship between %HR_max and %VO_2max indicated a coefficient of variation before and 1, 3, and 6 months after of 0.800, 0.826, 0.832, and 0.880, respectively.

CONCLUSIONS

This study showed that the %HR_max correlates better with the %VO_2max in the late-stage post-AMI than in the initial stage. We should therefore set and monitor the exercise intensity using maximal oxygen consumption in the early stage of exercise training after onset of acute myocardial infarction.

LEVEL OF EVIDENCE

IV.

Adherence to lifestyle modifications after a cardiac rehabilitation program and endothelial progenitor cells

An increase of endothelial progenitor cells (EPCs) among acute myo-cardial infarction (AMI) patients participating in a cardiac rehabilitation (CR) program has been reported, but no data on the impact of adherence to lifestyle recommendations provided during a CR program on EPCs are available. It was our aim to investigate the effect of adherence to lifestyle recommendations on EPCs, inflammatory and functional parameters after six months of a CR program in AMI patients. In 110 AMI patients (90 male/20 female; mean age 57.9 ± 9.4 years) EPCs, high sensitivity C-reactive protein (hsCRP), N-terminal pro-brain natriuretic peptide (NT-ProBNP) levels, and cardiopulmonary testings were determined at the end of the CR (T1) and at a six-month follow-up (T2). At T2 we administered a questionnaire assessing dietary habits and physical activity. At T2, we observed a decrease of EPCs (p<0.05), of hsCRP (p=0.009) and of NT-ProBNP (p<0.0001). Patient population was divided into three categories by Healthy Lifestyle (HL) score (none/low, moderate and high adherence to lifestyle recommendations). We observed a significant association between adherence to lifestyle recommendations, increase in EPCs and exercise capacity between T1 and T2 (Δ EPCs p for trend <0.05; ΔWatt max p for trend=0.004). In a multivariate logistic regression analyses, being in the highest tertile of HL score affected the likelihood of an increase of EPC levels at T2 [OR (95% confidence interval): 3.36 (1.0–10.72) p=0.04]. In conclusion, adherence to lifestyle recommendations provided during a CR program positively influences EPC levels and exercise capacity.

Heart rate recovery, cardiac rehabilitation and erectile dysfunction in males with ischaemic heart disease

Objective:

Heart rate recovery (HRR) is a recognised marker used in clinical practice for assessing the risk of sudden cardiac death. Physical exercise leads to an improvement in HRR and has a proven beneficial effect on erection quality (EQ) related to the activity of the autonomic nervous system in men with ischaemic heart disease (IHD). This paper evaluates the relationship between HRR and EQ in patients with IHD and erectile dysfunction (ED) who underwent cardiac rehabilitation.

Methods:

The main analysis was based on the Mann–Whitney U test, Wilcoxon signed-rank test, Spearman correlation coefficient, Pearson’s chi-square test, chi-square test, with the Yates correction and (if possible) parametric tests were used. This prospective, non-randomised intervention study included 124 men with IHD and ED [International Index of Erectile Function (IIEF-5) scores of ≤21]. Of these, 89 patients underwent a 6-month cardiac rehabilitation phase III programme, whereas 35 did not. The results of the participants’ total IIEF-5 scores and their HRR, demographic and clinical data were analysed.

Results:

The results of the 89 rehabilitated patients (mean age: 60.44±9.29 years) and 35 controls (mean age: 61.43±8.81 years) were analysed. In the rehabilitated patients, the mean baseline IIEF-5 score was 13.15±5.76 (95% CI: 11.93–14.36) and HRR was 16.49±7.68/min (95% CI: 14.88–18.11). After cardiac rehabilitation, the parameters of ED and HRR improved significantly and were significantly higher than those of the controls; the mean IIEF-5 score of the rehabilitated group increased to 15.36±6.51 (95% CI: 13.99–16.73), while HRR increased to 21.40±7.25/min (95% CI: 19.88–22.93). A significant correlation was found between ∆HRR and ∆EQ (r=0.409791) as a result of the 6-month cardiac training programme

Conclusion:

Cardiac rehabilitation assessed by HRR has a sizable effect on autonomic balance in patients with IHD and ED, which plays a significant role in the mechanism of erection improvement.

Effect of Endurance Cardiovascular Training Intensity on Erectile Dysfunction Severity in Men With Ischemic Heart Disease

The protective effect of physical activity on arteries is not limited to coronary vessels, but extends to the whole arterial system, including arteries, in which endothelial dysfunction and atherosclerotic changes are one of the key factors affecting erectile dysfunction development. The objective of this study was to report whether the endurance training intensity and training-induced chronotropic response are linked with a change in erectile dysfunction intensity in men with ischemic heart disease. A total of 150 men treated for ischemic heart disease, who suffered from erectile dysfunction, were analyzed. The study group consisted of 115 patients who were subjected to a cardiac rehabilitation program. The control group consisted of 35 patients who were not subjected to any cardiac rehabilitation. An IIEF-5 (International Index of Erectile Function) questionnaire was used for determining erectile dysfunction before and after cardiac rehabilitation. Cardiac training intensity was objectified by parameters describing work of endurance training. The mean initial intensity of erectile dysfunction in the study group was 12.46 ± 6.01 (95% confidence interval [CI] = 11.35-13.57). Final erectile dysfunction intensity (EDI) assessed after the cardiac rehabilitation program in the study group was 14.35 ± 6.88 (95% CI = 13.08-15.62), and it was statistically significantly greater from initial EDI. Mean final training work was statistically significantly greater than mean initial training work. From among the parameters describing training work, none were related significantly to reduction of EDI. In conclusion, cardiac rehabilitation program-induced improvement in erection severity is not correlated with endurance training intensity. Chronotropic response during exercise may be used for initial assessment of change in cardiac rehabilitation program-induced erection severity.

Effect of 8-week exercise-based cardiac rehabilitation on cardiac autonomic function: A randomized controlled trial in myocardial infarction patients

PURPOSE

The purpose of this study is to evaluate the effects of an 8-week exercise-based cardiac rehabilitation program on traditional and nonlinear heart rate variability (HRV) indexes, assessing the potential confounding influences of habitual physical activity (PA) and dietary intake.

METHODS

In this parallel-group trial, 96 patients (56 ± 10 years old) were randomized to the exercise group (EG) or to the control group (CG) 4 weeks after an acute myocardial infarction. Exercise-based cardiac rehabilitation program consisted of aerobic exercise at 70% to 85% of maximal heart rate for 3 sessions per week plus usual care. The CG received only usual care. The baseline and final assessments comprised resting short-term HRV (primary outcome) by a Polar R-R recorder under controlled breathing (12 breaths per minute), habitual PA by accelerometers, and dietary intake by a 4-day food diary.

RESULTS

Two patients in each group dropped out and were not included in the intention-to-treat analysis. In the remaining 92 patients (EG = 47 and CG = 45), at baseline, only a difference in the proportion of nitrate medication use was significant between groups. After 8 weeks, no significant changes were found between groups on traditional and nonlinear HRV indexes (eg, ln HF, EG from 5.7 ± 1.5 to 5.9 ± 1.3 and CG from 5.5 ± 1.6 to 5.5 ± 1.5), habitual PA, and dietary intake.

CONCLUSION

Eight weeks of exercise-based cardiac rehabilitation program is an insufficient stimulus to improve cardiac autonomic function in post-myocardial infarction patients under optimal medication and with high levels of traditional and nonlinear HRV indexes at baseline.

The influence of endurance training intensity on dynamics of post-exertional heart rate recovery adaptation in patients with ischemic heart disease

PURPOSE

The intensity of post-exertion heart rate recovery, evaluated in the first minute of the recovery period (HRR₆₀), is considered to be a strong predictor of risk for cardiac death. Intensification of physical activity performed as part of cardiac rehabilitation (CR) increases the HRR₆₀ value in ischemic heart disease (IHD) patients. In this context, the impact of endurance training intensity (ETI) on change in HRR₆₀ intensity seems to be an interesting issue.

MATERIAL/METHODS

The study group consisted of 251 patients who were subjected to a CR cycle. 45 patients of this group participated in CR twice. The control group consisted of 35 patients who were not subjected to any CR. ETI was estimated by the training work. In all patients an exertion test on a treadmill was performed twice within six months, analyzing the initial and final HRR₆₀ value and ΔHRR₆₀.

RESULTS

After a six-month observation, there was a statistically significant increase in the HRR₆₀ value (17.98±8.33/min vs. 22.72±7.72/min, p<0.01) in the test group, which was not observed in the control group. Mean ΔHRR₆₀ value in the test group was statistically significantly greater than in the control group. In the subgroup subjected to the two CR cycles, only the first cycle led to a statistically significant increase in the mean HRR₆₀ value.

CONCLUSIONS

A six-month CR cycle significantly increased the HRR₆₀ value, while cardiac training intensity did not affect the exertion-evoked change in its intensity. Continuation of the CR cycle beyond 6 months no longer significantly affected the change in the HRR₆₀ value.

Exercise is the real polypill

The concept of a "polypill" is receiving growing attention to prevent cardiovascular disease. Yet similar if not overall higher benefits are achievable with regular exercise, a drug-free intervention for which our genome has been haped over evolution. Compared with drugs, exercise is available at low cost and relatively free of adverse effects. We summarize epidemiological evidence on the preventive/therapeutic benefits of exercise and on the main biological mediators involved.

Heart rate variability in myocardial infarction patients: effects of exercise training

Heart rate variability (HRV) is a simple and noninvasive measure that estimates cardiac autonomic modulation, mainly the parasympathetic contribution. Increased sympathetic and/or decreased parasympathetic nervous activity is seen in post-myocardial infarction (MI) patients. Consequently, these patients present reduced HRV, which has been associated with increased risk of adverse events and mortality. Exercise training, recommended as a complementary therapy for patients with cardiovascular disease, has shown numerous beneficial effects. The main aim of the present manuscript was to provide a critical review of studies investigating the effects of exercise training on cardiac autonomic modulation, through HRV, in MI patients and the possible mechanisms involved. Despite conflicting evidence, exercise training appears to be a useful therapeutic intervention to improve the unbalanced autonomic function of MI patients. Finally, the mechanisms involved are not yet well understood, but nitric oxide bioavailability and angiotensin II levels seem to play an important role.

Effects of Short-term Exercise Training on Cardiorespiratory Fitness of Male Adults with Myocardial Infarction

[Purpose] The purpose of this study was to determine the effects of short-term exercise training on the cardiorespiratory fitness (CRF) of individuals suffering from myocardial infarction. [Subjects] A total of 60 participants were divided into experimental (EXP; n=30, mean age 56.7 ± 2.8 years, body mass 80.7 ± 10.7 kg, body height 171.9 ± 7.2 cm) and control (CON; n=30, mean age 56.5 ± 3.1 years, body mass 84.4 ± 12.4 kg, body height 171.5 ± 12.4 cm) groups. [Methods] The members of the EXP group took part in an organized daily physical exercise program (Monday through Sunday), for a period of 3 weeks. The exercise program consisted of 60 min daily specialized fitness exercises with an intensity ranging from 55-70% of the maximum heart rate, which was determined by test on a bicycle ergometer. The effects of the exercise were monitored by means of the following parameters: maximum oxygen uptake (VO2peak), resting heart rate, systolic blood pressure and diastolic blood pressure. [Results] The results indicate statistically significant post-exercise improvements in heart rate, relative oxygen uptake and systolic blood pressure, among the members of the EXP group. The results indicate that at the initial measurement of cardiorespiratory fitness no statistically significant differences were found between the groups at the multivariate level (Wilk's λ=0.83), while statistically significant differences in the cardiorespiratory fitness were found at the final measurement (Wil's λ=0.430). [Conclusion] The obtained results indicate that the exercise program, which lasted for a period of 21 days, though shorter in duration than other programs still led to statistically significant changes in the CRF of individuals suffering from MI.

Dose-response relationship of baroreflex sensitivity and heart rate variability to individually-tailored exercise training in patients with heart failure

BACKGROUND

Heart Rate Variability (HRV) and Baroreflex Sensitivity (BRS) are impaired in patients with Chronic Heart Failure (CHF) and carry negative prognosis. Exercise training improves these parameters. However, the relationship between exercise training with HRV and BRS has been investigated without regard for individual training loads. We tested the hypothesis that in CHF patients changes in HRV and BRS are dose-response related to individual volume/intensity training load (TL).

METHODS

Twenty patients with stable postinfarction CHF under optimal medical treatment were randomized to either aerobic continuous training (ACT) or aerobic interval training (AIT) for 12weeks. Individualized TL was monitored by the Training Impulses (TRIMPi) method, which was determined using the individual HR and lactate profiling determined during a treadmill test at baseline. HRV (standard deviation of mean R-R interval) and BRS were assessed at rest and 3weeks apart, throughout the study.

RESULTS

HRV, BRS and R-R interval increased significantly with training, being very highly correlated to the dose of exercise with a second-order regression model (r(2) ranged from 0.75 to 0.96; P<0.001), resembling a bell-shaped in the ACT, and an asymptotic-shaped curve in the AIT groups, respectively. These changes were accompanied by a significant increase in functional capacity. No significant differences were detected between ACT and AIT in any variable.

CONCLUSIONS

These results suggest that improvements in HRV and BRS by exercise training in CHF patients are dose related to TL in a non-linear fashion on an individual basis, with optimal results at moderate doses of exercise.

Endurance exercise training reduces cardiac sodium/calcium exchanger expression in animals susceptible to ventricular fibrillation

Aim: Increased sodium/calcium exchanger activity (NCX1, an important regulator of cardiomyocyte cystolic calcium) may provoke arrhythmias. Exercise training can decrease NCX1 expression in animals with heart failure improving cytosolic calcium regulation, and could thereby reduce the risk for ventricular fibrillation (VF). Methods: To test this hypothesis, a 2-min coronary occlusion was made during the last minute of exercise in dogs with healed myocardial infarctions; 23 had VF (S, susceptible) and 13 did not (R, resistant). The animals were randomly assigned to either 10-week exercise training (progressively increasing treadmill running; S n = 9; R n = 8) or 10-week sedentary (S n = 14; R n = 5) groups. At the end of the 10-week period, the exercise + ischemia test provoked VF in sedentary but not trained susceptible dogs. On a subsequent day, cardiac tissue was harvested and NCX1 protein expression was determined by Western blot. Results: In the sedentary group, NCX1 expression was significantly (ANOVA, P < 0.05) higher in susceptible compared to resistant dogs. In contrast, NCX1 levels were similar in the exercise trained resistant and susceptible animals. Conclusion: These data suggest that exercise training can restore a more normal NCX1 level in dogs susceptible to VF, improving cystolic calcium regulation and could thereby reduce the risk for sudden death following myocardial infarction.

Home-based cardiac rehabilitation is as effective as centre-based cardiac rehabilitation among elderly with coronary heart disease: results from a randomised clinical trial

BACKGROUND

participation in centre-based cardiac rehabilitation (CR) is known to reduce morbidity and mortality but participation rates among the elderly are low. Establishing alternative programmes is important, and home-based CR is the predominant alternative. However, no studies have investigated the effect of home-based CR among a group of elderly patients with coronary heart disease with a long-term follow-up.

METHODS

randomised clinical trial comparing home-based CR with comprehensive centre-based CR among patients ≥ 65 years with coronary heart disease.

RESULTS

seventy-five patients participated. There were no significant differences in exercise capacity after the intervention between home and centre-based CR. Adjusted mean differences of peak VO₂ = 0.9 ml/kg/min (95% CI -0.7, 2.4) and of 6 min walk test = -18.7 m (95% CI -56.4, 18.9). In addition, no differences were found in the secondary outcomes of systolic blood pressure (-0.6 mmHg, 95% CI -11.3, 10.0), LDL cholesterol (0.3 mmol/l, 95% CI -0.04, 0.7), HDL cholesterol (0.2 mmol/l, 95% CI -0.01, 0.3), body composition, proportion of smokers and health-related quality of life. A group of patients who did not have an effect of either programmes were characterised by higher age, living alone and having COPD. At 12 months of follow-up, both groups had a significant decline in exercise capacity.

CONCLUSIONS

home-based CR is as effective as centre-based CR in improving exercise capacity, risk factor control and health-related quality of life. However, a group of patients did not improve regardless of the type of intervention. Continued follow-up is essential in order to maintain the gained improvements.

Effects of long-term exercise training on cardiac baroreflex sensitivity in patients with coronary artery disease: a randomized controlled trial

Objective: To investigate whether a structured long-term exercise training programme in patients with coronary artery disease affects baroreflex function and cardiorespiratory efficiency.

Patients: Twenty-five elderly male patients with coronary artery disease.

Methods: The patients were randomized into exercise (group A) or control group (group B). Group A followed a seven-month supervised exercise programme, consisting of three sessions of aerobic interval training weekly at moderate intensity. Twenty patients completed the study (group A: 10 patients and group B: 10 patients). At the beginning and end of the study, all subjects underwent a tilt test for the baroreflex sensitivity assessment and a graded exercise treadmill test with spiroergometry for the evaluation of their cardiorespiratory efficiency.

Results: There were no differences between the two groups for any baseline variable. After training in group A, peak oxygen consumption, maximal treadmill tolerance time and anaerobic threshold were significantly increased by 21.9% ( P < 0.001), 19.8% ( P < 0.001) and 18.6% ( P < 0.05), respectively. There were also significant increases in baroreflex sensitivity by 21.2% ( P < 0.01), in baroreflex effectiveness index by 23.9% ( P < 0.01), in event count by 45.1% ( P < 0.01) and in ramp count by 13.2% ( P < 0.05). Moreover, significant correlations were observed between the autonomic and cardiorespiratory parameters in group A at the end.

Conclusion: The results suggest that long-term exercise training leads to beneficial effects on baroreflex activity and cardiorespiratory performance in coronary patients, and thus could constitute an efficient nonpharmacological intervention in this population.

Improvements in heart rate variability with exercise therapy

Heart rate variability (HRV) is a noninvasive, practical and reproducible measure of autonomic nervous system function. A heart rate that is variable and responsive to demands is believed to bestow a survival advantage, whereas reduced HRV may be associated with poorer cardiovascular health and outcomes. In recent years, many researchers have investigated the prognostic implications of HRV in a variety of clinical populations. Evidence suggests that reduced HRV has prognostic significance for individuals with myocardial infarction, chronic heart failure, unstable angina and diabetes mellitus. Interventions to increase HRV, such as exercise therapy, have also been examined. The findings of the present review suggest that exercise therapy may improve HRV in myocardial infarction, chronic heart failure and revascularization patients by increasing vagal tone and decreasing sympathetic activity. One hypothesis is that a shift toward greater vagal modulation may positively affect the prognosis of these individuals. While the underlying mechanisms by which exercise training improves vagal modulation are speculative at present, angiotensin II and nitric oxide may be potential mediators.

Testing an exercise intervention to improve aerobic conditioning and autonomic function after an implantable cardioverter defibrillator (ICD)

BACKGROUND

Implantable cardioverter defibrillators (ICDs) are an increasingly common treatment for survivors of sudden cardiac arrest or others with life-threatening ventricular arrhythmias. Health-care providers are often reluctant to prescribe exercise for this group because of the belief that it will provoke ventricular arrhythmias and cardiac arrest; patients are often afraid to exercise because of concern over receiving an ICD shock. A social cognitive theory-driven exercise intervention aimed at stabilizing cardiac arrhythmias and reducing ICD shocks by increasing parasympathetic autonomic nervous system control is described.

METHODS

The exercise intervention has two phases that include an 8-week aerobic conditioning component followed by a 16-week exercise maintenance component. The aerobic exercise intervention is expected to have significant impact on cardiopulmonary function, ventricular arrhythmias, cardiac autonomic function, and self-efficacy in persons who have an ICD. The exercise intervention is currently being tested using a randomized clinical trial format, the results of which will be available in 2012.

CONCLUSION

The exercise after ICD trial is one of the first clinical trials to test the effects of aerobic exercise on cardiopulmonary outcomes after receiving an ICD for primary or secondary prevention of sudden cardiac arrest.

Cardiac autonomic neural remodeling and susceptibility to sudden cardiac death: effect of endurance exercise training

Sudden cardiac death resulting from ventricular tachyarrhythmias remains the leading cause of death in industrially developed countries, accounting for between 300,000 and 500,000 deaths each year in the United States. Yet, despite the enormity of this problem, both the identification of factors contributing to ventricular fibrillation as well as the development of safe and effective antiarrhythmic agents remain elusive. Subnormal cardiac parasympathetic regulation coupled with an elevated cardiac sympathetic activation may allow for the formation of malignant ventricular arrhythmias. In particular, myocardial infarction can reduce cardiac parasympathetic regulation and alter beta-adrenoceptor subtype expression enhancing beta(2)-adrenoceptor sensitivity that can lead to intracellular calcium dysregulation and arrhythmias. As such, myocardial infarction can induce a remodeling of cardiac autonomic regulation that may be required to maintain cardiac pump function. If alterations in cardiac autonomic regulation play an important role in the genesis of life-threatening arrhythmias, then one would predict that interventions designed to either augment parasympathetic activity and/or reduce cardiac adrenergic activity would also protect against ventricular fibrillation. Recently, studies using a canine model of sudden death demonstrate that endurance exercise training (treadmill running) enhanced cardiac parasympathetic regulation (increased heart rate variability), restored a more normal beta-adrenoceptor balance (i.e., reduced beta(2)-adrenoceptor sensitivity and expression), and protected against ventricular fibrillation induced by acute myocardial ischemia. Thus exercise training may reverse the autonomic neural remodeling induced by myocardial infarction and thereby enhance the electrical stability of the heart in individuals shown to be at an increased risk for sudden cardiac death.

Changes in short-term measures of heart rate variability after eight weeks of cardiac rehabilitation

BACKGROUND

In coronary artery disease (CAD) and following myocardial infarction (MI), activity of the autonomic nervous system is altered. Reduced heart rate variability (HRV) is a risk factor for future cardiac event. Studies reporting changes in HRV post-cardiac rehabilitation (CR) are heterogeneous, due possibly to varied data collection and analysis protocols.

AIM

To evaluate changes in spectral measures of HRV derived from 5-minute ECG recordings in patients completing an 8 weeks CR programme.

METHODS

Thirty-eight patients (21 males, 17 females, aged 65.6 +/- 11.6 years) underwent 5 minutes, supine ECG recordings and standard physiological and psychological assessment pre- and post-CR. A further 23 patients (14 males, 9 females aged 64.9 +/- 9 years) acted as controls. Outcome measures were: low frequency power, (LF, 0.04-0.15 Hz) high frequency power (HF, 0.15-0.40 Hz), LF:HF ratio and mean RR interval. Change was assessed by ANCOVA and paired t-tests.

RESULTS

When compared with the CT group, the CR group showed significant increases in: SDNN (Delta +6 ms, CR vs. 0 ms CT), HFln (Delta 0.4 log units CR vs. 0 log units CT), LFln (Delta +0.6 log units CR, vs. +0.1 log units CT) and RR interval (Delta +30 ms, CR vs. -28 ms CT).

CONCLUSIONS

This is the first study to show significant increases in raw LF and HF power derived from short-term ECG recordings in CR patients. These measures are risk factors for future cardiac event. As CR is associated with increases in these measures it may be viewed as an effective therapy capable of bringing about favourable alterations in autonomic control.

Analysis of Alteration of Blood Pressure Response to Exercise through Baroreflex

BACKGROUND

The baroreflex has been reported to play an important role in hemodynamic regulation during exercise. Therefore, impairment of baroreflex function can induce an abnormal response of systolic blood pressure (SBP) to exercise, including exercise-induced hypertension. To clarify whether baroreflex function alters SBP response, we examined the relationship of baroreflex sensitivity (BRS) with SBP response to exercise.

METHODS

In 22 subjects without cardiac dysfunction, BRS (ms/mmHg) was measured by the phenylephrine method, and a treadmill exercise test was administered according to Bruce's protocol.

RESULTS

1) The chronotropic response to exercise was higher in the normal BRS group than in the reduced BRS group (p<0.01). The SBP at the initial phase of exercise (1 min after the start of exercise) showed a smaller increase in the normal BRS group than in the reduced BRS group (p<0.01). During the initial phase of exercise, BRS had negative correlation with the SBP increment from rest (r=-0.408, p<0.05). During submaximal exercise (6 min after the start of exercise), a positive correlation between BRS and SBP response (r=0.422, p<0.05) was shown. 2) Subjects were divided into 2 groups: 12 subjects with normal BRS (> or =5 ms/mmHg) and 10 subjects with reduced BRS (<5 ms/mmHg). During the initial exercise phase, the negative correlation between BRS and SBP response was stronger in the normal BRS group (r=-0.398) than in the reduced BRS group (r= -0.126). During submaximal exercise, BRS had a positive correlation with BP response to exercise in subjects with normal BRS (r=0.462).

CONCLUSION

Preserved baroreflex function is thought to be related to the pressor response to submaximal exercise, although the baroreflex is thought to be associated with the stabilization of blood pressure change during the initial exercise phase. These findings suggest that exercise-induced hypertension develops through the baroreflex mechanism.

Effect of endurance exercise training on heart rate onset and heart rate recovery responses to submaximal exercise in animals susceptible to ventricular fibrillation

Both a large heart rate (HR) increase at exercise onset and a slow heart rate (HR) recovery following the termination of exercise have been linked to an increased risk for ventricular fibrillation (VF) in patients with coronary artery disease. Endurance exercise training can alter cardiac autonomic regulation. Therefore, it is possible that this intervention could restore a more normal HR regulation in high-risk individuals. To test this hypothesis, HR and HR variability (HRV, 0.24- to 1.04-Hz frequency component; an index of cardiac vagal activity) responses to submaximal exercise were measured 30, 60, and 120 s after exercise onset and 30, 60, and 120 s following the termination of exercise in dogs with healed myocardial infarctions known to be susceptible (n = 19) to VF (induced by a 2-min coronary occlusion during the last minute of a submaximal exercise test). These studies were then repeated after either a 10-wk exercise program (treadmill running, n = 10) or an equivalent sedentary period (n = 9). After 10 wk, the response to exercise was not altered in the sedentary animals. In contrast, endurance exercise increased indexes of cardiac vagal activity such that HR at exercise onset was reduced (30 s after exercise onset: HR pretraining 179 +/- 8.4 vs. posttraining 151.4 +/- 6.6 beats/min; HRV pretraining 4.0 +/- 0.4 vs. posttraining 5.8 +/- 0.4 ln ms(2)), whereas HR recovery 30 s after the termination of exercise increased (HR pretraining 186 +/- 7.8 vs. posttraining 159.4 +/- 7.7 beats/min; HRV pretraining 2.4 +/- 0.3 vs. posttraining 4.0 +/- 0.6 ln ms(2)). Thus endurance exercise training restored a more normal HR regulation in dogs susceptible to VF.

Reduced susceptibility to ventricular tachyarrhythmias in rats selectively bred for high aerobic capacity

Reperfusion after a brief period of cardiac ischemia can lead to potentially lethal arrhythmias. Human epidemiological studies and experimental work with animals indicate that regular physical activity is associated with reductions in cardiovascular disease (CVD) risk factors and sudden cardiac death. Similarly, artificial selection of rats for high aerobic treadmill-running capacity (high-capacity runners; HCR) has been shown to reduce CVD risk factors relative to rats selected as low-capacity runners (LCR). Therefore, we tested the hypothesis that HCR, relative to LCR rats, would be less susceptible to ischemia-reperfusion-mediated ventricular tachyarrhythmias. To test this hypothesis, we measured the susceptibility to ventricular tachyarrhythmias produced by 3 min of occlusion and reperfusion of the left main coronary artery in conscious LCR and HCR rats. Results document a significantly lower incidence of ventricular tachyarrhythmias in HCR (3 of 11, 27.3%) relative to LCR (6 of 7, 85.6%) rats. The decreased susceptibility to tachyarrhythmias in HCR rats was associated with a reduced cardiac metabolic demand during ischemia (lower rate-pressure product and ST segment elevation) as well as a wider range for the autonomic control of heart rate. The HCR and LCR represent a unique substrate for evaluation of the mechanisms underlying ischemia-mediated cardiac arrhythmogenesis.

Home-based cardiac rehabilitation compared with centre-based rehabilitation and usual care: A systematic review and meta-analysis

BACKGROUND

To determine the effectiveness of home-based cardiac rehabilitation programmes compared with (i) usual care and (ii) supervised centre-based cardiac rehabilitation on mortality, health related quality of life and modifiable cardiac risk factors of patients with coronary heart disease.

METHODS

Systematic review and meta-analysis of randomised controlled trials.

MAIN OUTCOME MEASURES

mortality, smoking cessation, exercise capacity, systolic blood pressure, total cholesterol, psychological status, and health related quality of life.

RESULTS

Eighteen included trials for home versus usual rehabilitation and six trials of home versus supervised centre-based rehabilitation were identified. The home-based interventions were clinically heterogeneous, trials often small, with quality poorly reported. Compared with usual care, home-based cardiac rehabilitation had a 4 mm Hg (95% CI 6.5, 1.5) greater reduction in systolic blood pressure, and a reduced relative risk of being a smoker at follow-up (RR 0.71, 95% CI 0.51, 1.00). Differences in exercise capacity, total cholesterol, anxiety and depression were all in favour of the home-based group. In patients post-myocardial infarction exercise capacity was significantly improved in the home rehabilitation group by 1.1 METS (95% CI 0.2, 2.1) compared to usual care. The comparison of home-based with supervised centre-based cardiac rehabilitation revealed no significant differences in exercise capacity, systolic blood pressure and total cholesterol.

CONCLUSIONS

Current evidence does not show home-based cardiac rehabilitation to be significantly inferior to centre-based rehabilitation for low-risk cardiac patients. However, the numbers of patients included are less than 750 and ongoing trials will contribute to the debate on the acceptability, effectiveness and cost-effectiveness of home-based cardiac rehabilitation.

[The role of physical training in patients after myocardial infarction]

INTRODUCTION

Physical training is an optimal method of rehabilitation of cardiovascular patients, especially in patients with myocardial infarction. The aim of this study was to evaluate the effects of physical training in patients with myocardial infarction during the post-hospital phase and prolonged rehabilitation by determining the test exercise parameters.

MATERIAL AND METHODS

This prospective clinical study included 230 patients after myocardial infarction. Group A (180 patients) participated in organized forms of exercise (post-hospital rehabilitation and prolonged rehabilitation at home) for 48 +/- 6.4 months, while the control group was without physical training. The first clinical examination and the exercise test were performed in group A after post-hospital rehabilitation and after 191 +/- 16.4 days in the control group. In all patients the last control was performed 48 +/- 6.4 months after myocardial infarction.

RESULTS

After the first control, the mean physical workload in group A was significantly higher compared with the control group (p < 0.05). After a 48 month follow-up period the physical workload was significantly higher in group A (p < 0.01), while in the control group a significant increase of workload was not observed (p > 0.05). Comparing the duration of exercise testing, significant differences were found after the first and last control (p < 0.05; p < 0.01, respectively). The double product was significantly higher in group A than in the control group after the first and last control (p < 0.05; p < 0.01, respectively).

CONCLUSION

Prolonged physical training is beneficial for patients after myocardial infarction, because it improves cardiovascular functions and physical work capacity, improves angina threshold and the patient's general health.

Cardiac vagal modulation of heart rate during prolonged submaximal exercise in animals with healed myocardial infarctions: effects of training

The present study investigated the effects of long-duration exercise on heart rate variability [as a marker of cardiac vagal tone (VT)]. Heart rate variability (time series analysis) was measured in mongrel dogs (n = 24) with healed myocardial infarctions during 1 h of submaximal exercise (treadmill running at 6.4 km/h at 10% grade). Long-duration exercise provoked a significant (ANOVA, all P < 0.01, means +/- SD) increase in heart rate (1st min, 165.3 +/- 15.6 vs. last min, 197.5 +/- 21.5 beats/min) and significant reductions in high frequency (0.24 to 1.04 Hz) power (VT: 1st min, 3.7 +/- 1.5 vs. last min, 1.0 +/- 0.9 ln ms(2)), R-R interval range (1st min, 107.9 +/- 38.3 vs. last min, 28.8 +/- 13.2 ms), and R-R interval SD (1st min, 24.3 +/- 7.7 vs. last min 6.3 +/- 1.7 ms). Because endurance exercise training can increase cardiac vagal regulation, the studies were repeated after either a 10-wk exercise training (n = 9) or a 10-wk sedentary period (n = 7). After training was completed, long-duration exercise elicited smaller increases in heart rate (pretraining: 1st min, 156.0 +/- 13.8 vs. last min, 189.6 +/- 21.9 beats/min; and posttraining: 1st min, 149.8 +/- 14.6 vs. last min, 172.7 +/- 8.8 beats/min) and smaller reductions in heart rate variability (e.g., VT, pretraining: 1st min, 4.2 +/- 1.7 vs. last min, 0.9 +/- 1.1 ln ms(2); and posttraining: 1st min, 4.8 +/- 1.1 vs. last min, 2.0 +/- 0.6 ln ms(2)). The response to long-duration exercise did not change in the sedentary animals. Thus the heart rate increase that accompanies long-duration exercise results, at least in part, from reductions in cardiac vagal regulation. Furthermore, exercise training attenuated these exercise-induced reductions in heart rate variability, suggesting maintenance of a higher cardiac vagal activity during exercise in the trained state.

Effects of endurance exercise training on heart rate variability and susceptibility to sudden cardiac death: protection is not due to enhanced cardiac vagal regulation

Low heart rate variability (HRV) is associated with an increased susceptibility to ventricular fibrillation (VF). Exercise training can increase HRV (an index of cardiac vagal regulation) and could, thereby, decrease the risk for VF. To test this hypothesis, a 2-min coronary occlusion was made during the last min of a 18-min submaximal exercise test in dogs with healed myocardial infarctions; 20 had VF (susceptible), and 13 did not (resistant). The dogs then received either a 10-wk exercise program (susceptible, n=9; resistant, n=8) or an equivalent sedentary period (susceptible, n=11; resistant, n=5). HRV was evaluated at rest, during exercise, and during a 2-min occlusion at rest and before and after the 10-wk period. Pretraining, the occlusion provoked significantly (P<0.01) greater increases in HR (susceptible, 54.9+/-8.3 vs. resistant, 25.0+/-6.1 beats/min) and greater reductions in HRV (susceptible, -6.3+/-0.3 vs. resistant, -2.8+/-0.8 ln ms2) in the susceptible dogs compared with the resistant animals. Similar response differences between susceptible and resistant dogs were noted during submaximal exercise. Training significantly reduced the HR and HRV responses to the occlusion (HR, 17.9+/-11.5 beats/min; HRV, -1.2+/-0.8, ln ms2) in the susceptible dogs; similar response reductions were noted during exercise. In contrast, these variables were not altered in the sedentary susceptible dogs. Posttraining, VF could no longer be induced in the susceptible dogs, whereas four sedentary susceptible dogs died during the 10-wk control period, and the remaining seven animals still had VF when tested. Atropine decreased HRV but only induced VF in one of eight trained susceptible dogs. Thus exercise training increased cardiac vagal activity, which was not solely responsible for the training-induced VF protection.

Cardiac rehabilitation and secondary prevention of coronary heart disease: an American Heart Association scientific statement from the Council on Clinical Cardiology (Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention) and the Council on Nutrition, Physical Activity, and Metabolism (Subcommittee on Physical Activity), in collaboration with the American association of Cardiovascular and Pulmonary Rehabilitation

This article updates the 1994 American Heart Association scientific statement on cardiac rehabilitation. It provides a review of recommended components for an effective cardiac rehabilitation/secondary prevention program, alternative ways to deliver these services, recommended future research directions, and the rationale for each component of the rehabilitation/secondary prevention program, with emphasis on the exercise training component.

Daily exercise-induced cardioprotection is associated with changes in calcium regulatory proteins in hypertensive rats

Epidemiological data document that regular exercise protects against the morbidity and mortality associated with ischemic heart disease. Therefore, we tested the hypothesis that daily exercise (DE) increases the ventricular arrhythmia threshold (VAT) induced by coronary artery occlusion and alters the expression of calcium regulatory proteins. The VAT was defined as the time from coronary occlusion to sustained ventricular tachycardia resulting in a reduction in arterial pressure. To test this hypothesis, we recorded the VAT in conscious sedentary normotensive, sedentary hypertensive, and DE hypertensive rats, and we associated these thresholds with the protein expression of the L-type calcium channel, Na+/Ca2+ exchanger, phospholamban, and sarco(endo)plasmic reticulum Ca2+-ATPase. Results document a significantly reduced time to ventricular arrhythmias (sedentary hypertensive, 3.7 ± 0.3 min vs. sedentary normotensive, 4.8 ± 0.3 min), an increased Na+/Ca2+ exchanger protein expression (47%), and a decreased phospholamban protein expression (−34%) in conscious hypertensive rats. DE increased the VAT (5.9 ± 0.2 min), decreased the protein expression of the Na+/Ca2+ exchanger, and normalized the protein expression of phospholamban in the hypertensive rats. Thus DE may be a primary prevention approach for reducing the incidence of arrhythmias by altering calcium regulatory proteins in hypertensive rats.

Home versus center based physical activity programs in older adults

BACKGROUND

Physical inactivity is a leading cause of preventable death and morbidity in developed countries. In addition physical activity can potentially be an effective treatment for various medical conditions (e.g. cardiovascular disease, osteoarthritis). Many types of physical activity programs exist ranging from simple home exercise programs to intense highly supervised hospital (center) based programs.

OBJECTIVES

To assess the effectiveness of 'home based' versus 'center based' physical activity programs on the health of older adults.

SEARCH STRATEGY

The reviewers searched the Cochrane Central Register of Controlled Trials (CENTRAL) (1991-present), MEDLINE (1966-Sept 2002), EMBASE (1988 to Sept 2002), CINAHL (1982-Sept 2002), Health Star (1975-Sept 2002), Dissertation Abstracts (1980 to Sept 2002), Sport Discus (1975-Sept 2002) and Science Citation Index (1975-Sept 2002), reference lists of relevant articles and contacted principal authors where possible.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials of different physical activity interventions in older adults (50 years or older) comparing a 'home based' to a 'center based' exercise program. Study participants had to have either a recognised cardiovascular risk factor, or existing cardiovascular disease, or chronic obstructive airways disease (COPD) or osteoarthritis. Cardiac and post-operative programs within one year of the event were excluded.

DATA COLLECTION AND ANALYSIS

Three reviewers selected and appraised the identified studies independently. Data from studies that then met the inclusion/exclusion criteria were extracted by two additional reviewers.

MAIN RESULTS

Six trials including 224 participants who received a 'home based' exercise program and 148 who received a 'center based' exercise program were included in this review. Five studies were of medium quality and one poor. A meta-analysis was not undertaken given the heterogeneity of these studies. CARDIOVASCULAR. The largest trial (accounting for approximately 60% of the participants) looked at sedentary older adults. Three trials looked at patients with peripheral vascular disease (intermittent claudication). In patients with peripheral vascular disease center based programs were superior to home at improving distance walked and time to claudication pain at up to 6 months. However the risk of a training effect may be high. There are no longer term studies in this population. Notably home based programs appeared to have a significantly higher adherence rate than center based programs. However this was based primarily on the one study (with the highest quality rating of the studies found) of sedentary older adults. This showed an adherence rate of 68% in the home based program at two year follow-up compared with a 36% adherence in the center based group. There was essentially no difference in terms of treadmill performance or cardiovascular risk factors between groups. CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD). Two trials looked at older adults with COPD. In patients with COPD the evidence is conflicting. One study showed similar changes in various physiological measures at 3 months that persisted in the home based group up to 18 months but not in the center based group. The other study showed significantly better improvements in physiological measures in the center based group after 8 weeks but again the possibility of a training effect is high. OSTEOARTHRITIS. No studies were found. None of the studies dealt with measures of cost, or health service utilization.

AUTHORS' CONCLUSIONS

In the short-term, center based programs are superior to home based programs in patients with PVD. There is a high possibility of a training effect however as the center based groups were trained primarily on treadmills (and the home based were not) and the outcome measures were treadmill based. There is conflicting evidence which is better in patients with COPD. Home based programs appear to be superior to center based programs in terms of the adherence to exercise (especially in the long-term).

Heart rate variability in premenstrual dysphoric disorder

Measuring heart rate variability (HRV) is a way to assess the autonomic regulation of the heart. Decreased HRV, indicating reduced parasympathetic tone, has previously been found in depression and anxiety disorders. The objective of this study was to assess HRV in women with premenstrual dysphoric disorder (PMDD). To this end, time domain variables and frequency domain variables were assessed in 28 women with PMDD and in 11 symptom-free controls during both the symptomatic luteal phase and the non-symptomatic follicular phase of the menstrual cycle. Two variables reflecting vagal activity in the time domain, the root mean square of differences of successive normal RR intervals (rMSSD) and standard deviation of normal RR intervals (SDNN) were lower in PMDD patients, but this difference was statistically significant in the follicular phase only. The most important vagal measure in the frequency domain, supine high frequency (HF), also appeared lower in PMDD subjects during the follicular phase. It is suggested that PMDD may be associated with reduced vagal tone compared to controls and that this difference is most apparent in the non-symptomatic follicular phase of the menstrual cycle.

Exercise training improves baroreflex sensitivity in type 2 diabetes

Type 2 diabetes is a strong risk factor for coronary heart disease and sudden cardiac death. It is associated with reduced baroreflex sensitivity (BRS) and heart rate variability (HRV), which are indicators of increased risk for mortality and morbidity in various patient populations. This study was designed to assess the effects of exercise training on BRS, HRV, and hemodynamics in patients with type 2 diabetes. Subjects (50 men, mean age 53.3 +/- 5.1 years) with type 2 diabetes were randomized into either a control group, in which they received conventional treatment only, or an exercise group, in which they received conventional treatment together with heart rate-controlled endurance training twice a week and supervised muscle strength training twice a week for 12 months. Measurements taken at baseline and follow-up included VO(2max), standard time and frequency domain measures of HRV during 24-h recording, and BRS by the phenylephrine method. Cardiac index, systemic vascular resistance index, stroke index, and pulse wave velocity were measured by whole-body impedance cardiography. Significant improvements in VO(2max) (exercise group: +2.3 ml x kg(-1) x min(-1); P < 0.005 vs. control group), muscle strength, and glycemic control (exercise group: HbA(1c) -0.9%; P < 0.001 vs. control group) were observed in the exercise group. BRS increased in the exercise group, from 6.8 to 8.6 ms/mmHg, and decreased in the control group, from 7.5 to 6.4 ms/mmHg (95% CI for the difference between 0.05 and 4.36 ms/mmHg; P < 0.05). No significant changes in the time or frequency domain measures of HRV or in systemic hemodynamics were observed. We concluded that exercise training improves BRS sensitivity in type 2 diabetes subjects in addition to increasing the exercise capacity and muscle strength and improving glucose control. These beneficial effects in reflectory autonomic regulation and glucose control caused by exercise may be associated with improved prognosis of type 2 diabetes patients.

Arterial baroreflex function and cardiovascular variability: interactions and implications

The arterial baroreflex contributes importantly to the short-term regulation of blood pressure and cardiovascular variability. A number of factors (including reflex, humoral, behavioral, and environmental) may influence gain and effectiveness of the baroreflex, as well as cardiovascular variability. Many central neural structures are also involved in the regulation of the cardiovascular system and contribute to the integrity of the baroreflex. Consequently, brain injuries or ischemia may induce baroreflex impairment and deranged cardiovascular variability. Baroreflex dysfunction and deranged cardiovascular variability are also common findings in cardiovascular disease. A blunted baroreflex gain and impaired heart rate variability are predictive of poor outcome in patients with heart failure and myocardial infarction and may represent an early index of autonomic activation in left ventricular dysfunction. The mechanisms mediating these relationships are not well understood and may in part be the result of cardiac structural changes and/or altered central neural processing of baroreflex signals.

Exercise-induced increase in baroreflex sensitivity predicts improved prognosis after myocardial infarction

BACKGROUND

Despite the rational expectation for a survival benefit produced by exercise training among post-myocardial infarction (MI) patients, direct evidence remains elusive. Clinically, changes in autonomic balance toward lower vagal activity have consistently been associated with increased mortality risk; conversely, among both control and post-MI dogs, exercise training improved vagal reflexes and prevented sudden death. Accordingly, we tested the hypothesis that exercise training, if accompanied by a shift toward increased vagal activity of an autonomic marker such as baroreflex sensitivity (BRS), could reduce mortality in post-MI patients.

METHODS AND RESULTS

Ninety-five consecutive male patients surviving a first uncomplicated MI were randomly assigned to a 4-week endurance training period or to no training. Age (51+/-8 versus 52+/-8 years), site of MI (anterior 41% versus 43%), left ventricular ejection fraction (52+/-13 versus 51+/-14%), and BRS (7.9+/-5.4 versus 7.9+/-3.4 ms/mm Hg) did not differ between the two groups. After 4 weeks, BRS improved by 26% (P=0.04) in trained patients, whereas it did not change in nontrained patients. During a 10-year follow-up, cardiac mortality among the 16 trained patients who had an exercise-induced increase in BRS >or = 3 ms/mm Hg (responders) was strikingly lower compared with that of the trained patients without such a BRS increase (nonresponders) and that of the nontrained patients (0 of 16 versus 18 of 79 [23%], P=0.04). Cardiac mortality was also lower among responders irrespective of training (4% versus 24%, P=0.04).

CONCLUSIONS

Post-MI exercise training can favorably modify long-term survival, provided that it is associated with a clear shift of the autonomic balance toward an increase in vagal activity.

Mortality, cardiac vagal control and physical training--what's the link?

There is little doubt that regular exercise results in increases in life expectancy and protects against adverse cardiac events in both healthy subjects and patients with cardiovascular disease. The mechanism of action of physical training remains unclear but a variety of evidence points towards an enhancement in cardiac vagal activity protecting against lethal arrhythmias. Just how physical training increases cardiac vagal activity is an area that is ill understood but plausible mechanisms include mediation via angiotensin II or NO. Further research is needed in this area. Exercise training is demanding and difficult, particularly for patients with cardiac disease. If the mechanism of increase in cardiac vagal activity with training can be determined it may be possible to use pharmacological approaches to mimic the effects of exercise with potentially beneficial effects.

Effects of cardiac rehabilitation and exercise training on autonomic regulation in patients with coronary artery disease

BACKGROUND

Although cardiovascular rehabilitation and exercise training have substantial benefits in various ischemic heart disease (IHD) risk factors and subsequent prognosis after major IHD events, there is a paucity of information about its effects on autonomic regulation (such as heart rate variability [HRV] and baroreflex gain), particularly considering its arterial and cardiopulmonary components.

METHODS

We studied 40 patients (aged 60 +/- 6 y) after major IHD events, including 29 who underwent a comprehensive phase II cardiac rehabilitation and exercise training program and 11 controls who did not attend cardiac rehabilitation. Specifically, we determined whether active training improves prognostic indices of autonomic regulation of the SA node and whether changes in baroreflex gain could be ascribed to the arterial or to the cardiopulmonary component of the overall arterial pressure/heart period baroreflex.

RESULTS

Only patients with IHD undergoing active rehabilitation demonstrated a significant increase in R-R interval, in its variance, in overall gain of arterial pressure/heart period baroreflex (7.44 +/- 1.20 ms/mm Hg to 12.12 +/- 1.48 ms/mm Hg, P <.001) and in peak oxygen consumption (Delta = 2.45 mL/kg/min, P <.001). Separate examination of the selective arterial and cardiopulmonary components showed that only the latter increased significantly (6.17 +/- 1.09 ms/mm Hg to 10.62 +/- 1.56 ms/mm Hg; P <.01).

CONCLUSIONS

Cardiac rehabilitation is associated with significant improvements in autonomic markers of neural regulation of the SA node, such as increases in R-R variance and the gain of the overall spontaneous baroreflex, with specific improvements in the cardiopulmonary component as opposed to the arterial baroreflex component of this system. These improvements may further explain the reduction in morbidity and mortality noted after formal cardiac rehabilitation and exercise training programs.

Aerobic exercise conditioning: a nonpharmacological antiarrhythmic intervention

Sudden, unexpected cardiac death due to ventricular fibrillation is the leading cause of death in most industrially developed countries. Yet, despite the enormity of this problem, the development of safe and effective antiarrhythmic therapies has proven to be an elusive goal. In fact, many initially promising antiarrhythmic medications were subsequently found to increase rather than to decrease cardiac mortality. It is now known that cardiac disease alters cardiac autonomic balance and that the patients with the greatest changes in this cardiac neural regulation (i.e., decreased parasympathetic coupled with increased sympathetic activity) are also the patients at the greatest risk for sudden death. A growing body of experimental and epidemiological data demonstrates that aerobic exercise conditioning can dramatically reduce cardiac mortality, even in patients with preexisting cardiac disease. Conversely, the lack of exercise is strongly associated with an increased incidence of many chronic debilitating diseases, including coronary heart disease. Because it is well established that aerobic exercise conditioning can alter autonomic balance (increasing parasympathetic tone and decreasing sympathetic activity), a prudently designed exercise program could prove to be an effective and nonpharmacological way to enhance cardiac electrical stability, thereby protecting against sudden cardiac death.

Cardiac rehabilitation for community-based patients with myocardial infarction: factors predicting discharge recommendation and participation

Although there is substantial evidence that cardiac rehabilitation is beneficial for post myocardial infarction (MI) patients, such programs are currently under utilized. This study examined systematic criteria predicting physician referral to and patients' participation in cardiac rehabilitation programs. Patients discharged for MI were interviewed in-hospital and at 6-12 weeks post discharge to determine referral, participation, and completion. Stepwise logistic regression analyzed factors associated with rehabilitation. Factors associated with referral to rehab were catheterization (p < 0.001), bypass surgery (p < 0.01), cardiologist/cardiac surgeon appointment (p < 0.02), and age (p < 0.01). Participation was increased for those with bypass surgery (p < 0.001), and referral to cardiologist or cardiac surgeon (p < 0.001). Type of provider significantly influences referral to and participation in cardiac rehabilitation. This suggests that encouragement plays a strong role in attendance for rehabilitation. The same strong encouragement should be given to the broader range of MI patients who stand to benefit from cardiac rehabilitation.

Exercise and autonomic function in health and cardiovascular disease

Autonomic nervous system activity contributes to the regulation of cardiac output during rest, exercise, and cardiovascular disease. Measurement of HRV has been particularly useful in assessing parasympathetic activity, while its utility for assessing sympathetic function and overall sympathovagal balance remains controversial. Studies have revealed that parasympathetic tone dominates the resting state, while exercise is associated with prompt withdrawal of vagal tone and subsequent sympathetic activation. Conversely, recovery is characterized by parasympathetic activation followed by sympathetic withdrawal, although clarification of the normal trajectory and autonomic basis of heart rate decay following exercise is needed. Abnormalities in autonomic physiology--especially increased sympathetic activity, attenuated vagal tone, and delayed heart rate recovery--have been associated with increased mortality. Exercise training is associated with a relative enhancement of vagal tone, improved heart rate recovery after exercise, and reduced morbidity in patients with cardiovascular disease. However, whether exercise training leads to reduced mortality in this population because of its ability to specifically modulate autonomic function is unknown at the present time. Although the results of a recent randomized study in patients with CHF and a meta-analysis in the setting of a recent myocardial infarction determined that exercise training leads to improved outcomes in these populations, neither study measured autonomic function. Improved autonomic function due to exercise training is a promising rationale for explaining improvements in outcome, although more research is needed to confirm this hypothesis.

Intensive home-based exercise training in cardiac rehabilitation increases exercise capacity and heart rate variability

BACKGROUND

Reduced heart rate variability (HRV) is a risk factor for cardiac death. Animal studies have shown increased HRV and reduced mortality after physical training. We evaluated the change in exercise capacity and HRV in cardiac rehabilitation patients, randomised to routine or home-based intensive training. The design was prospective, stratified randomisation with pre-specified subgroup analysis.

METHODS

Maximal bicycle exercise test and 24-h Holter were performed 1 (baseline), 4 and 12 months after myocardial infarction (MI) or coronary artery by-pass surgery (CABG). Patients were randomised to physical training either two (N) or six (I) times per week for 3 months Sixty-two patients (43 MI and 19 CABG patients) were evaluated.

RESULTS

Exercise capacity increased significantly more after 3 months of training in group I (mean (S.E.)); 29.0 (3.4) vs. 7.2 (2.6) watts, P<0.001). One year later the difference in exercise capacity remained (26.5 (3.3) vs. 11.8 (3.8) watts, P<0.001). Global HRV measurements SDNN and SDANN increased significantly more in group I after training (17.1 (5.6) vs. 1.7 (3.7) and 16.2 (4.9) vs. 2.8 (3.1) ms, P<0.05) and 1 year later the differences were still significant. Subgroup analysis showed more pronounced HRV response in CABG than MI patients.

CONCLUSION

Intensive exercise training in cardiac rehabilitation increases exercise capacity and global HRV, which could be of prognostic significance.