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

Do antioxidant vitamins ameliorate the beneficial effects of exercise training on insulin sensitivity?

PURPOSE

Exercise training has numerous health benefits, and in patients with type 2 diabetes mellitus and metabolic syndrome, it can improve insulin sensitivity and glucose control. A recent publication suggests that antioxidant vitamins (C and E) block these effects on blood glucose. This investigation was undertaken to determine whether antioxidant vitamins ameliorate the beneficial effects of cardiac rehabilitation and exercise training (CRET) on insulin sensitivity and glucose metabolism in patients with coronary heart disease (CHD).

METHODS

We assessed CHD risk factors, including clinical indices of glucose metabolism, and evaluated the effects of exercise training in 315 patients with CHD with diabetes mellitus and/or metabolic syndrome before and after a 3-month program of CRET. Patients were divided into 2 groups based on self-reported antioxidant vitamin (vitamins C and E) consumption.

RESULTS

Both groups, 113 patients (36%) consuming vitamins (Vits group) and 202 patients (64%) who reported no vitamin use (no-Vits group) were statistically similar at baseline. Following CRET, patients improved exercise capacity (10%, P < .0001), fasting blood glucose (-7%, P < .0001), percent body fat (-3%, P = .0001), high-sensitive Creactive protein (-31%, P = .003), and various lipids and behavioral parameters, but there was no significant improvement in glycosylated hemoglobin following formal CRET. Both Vits group and no-Vits group achieved statistically similar improvements in fasting blood glucose, body fat, and other CHD risk factors.

CONCLUSIONS

Commercially available antioxidant supplements (mean dose of 400 IU of vitamin E and 500 mg of vitamin C) do not ameliorate the health benefits of exercise training, including fasting blood glucose, in CHD patients

Psychological risk factors and cardiovascular disease: is it all in your head?

Psychological stress has been shown to be associated with cardiovascular disease. Over the past few decades, there has been an increasing interest in this relationship, leading to a growing pool of clinical and epidemiological data on the subject. Psychological stress has multiple etiologies, which include behavioral causes, acute events or stressors, and/or chronic stress. Cardiac rehabilitation and exercise therapy have been shown to provide protection in primary and secondary coronary heart disease prevention, as well as improve overall morbidity and mortality. In this article, we review the available data regarding the association between psychological stress and cardiovascular disease, as well as the impact of cardiac rehabilitation and exercise therapy on psychological stress-related cardiovascular events.

Cardiac rehabilitation and exercise training in secondary coronary heart disease prevention

Substantial evidence indicates that increased levels of physical activity, exercise training, and overall cardiorespiratory fitness provide protection in primary and secondary coronary heart disease (CHD) prevention. Clearly, cardiac rehabilitation and exercise training (CRET) programs have been greatly underused in patients with CHD. We review the benefits of formal CRET programs on CHD risk factors including exercise capacity, obesity indices, plasma lipids, inflammation, and psychosocial stress as well as overall morbidity and mortality. These data support the fact that patients with CHD, especially after major CHD events, need routine referral to CRET programs; and patients should be vigorously encouraged to attend these valuable programs.

Autonomic effects of exercise-based cardiac rehabilitation

PURPOSE

One hypothesis by which exercise-based cardiac rehabilitation (CR) reduces mortality and cardiac events in patients with coronary artery disease invokes a beneficial effect of exercise on autonomic modulation. This study aimed to evaluate the autonomic effects of CR in patients with coronary artery disease.

METHODS

Participants referred to phase 2 CR underwent 4 bicycle stress tests, 2 before starting CR and 2 after. On visits 1 and 3, a symptom-limited bicycle stress test was performed. On visits 2 and 4, the subject exercised to the same workload, but atropine was administered during maximal exercise to achieve parasympathetic blockade. Parasympathetic effect in exercise recovery was computed before and after CR. Heart rate variability for each segment was also quantified. Plasma catecholamine levels were obtained at baseline, peak exercise, and during recovery.

RESULTS

Seventeen subjects (age 56 ± 10 years; 4 women) were enrolled. Six completed the post-CR testing. There was a significant increase in parasympathetic effect during exercise recovery post-CR (P < .001). There was also a significant increase in heart rate variability during exercise recovery post-CR (P < .001). Resting catecholamine levels were not different pre- and post-CR (NS). Post-CR, there was a blunted increase in peak exercise plasma catecholamine levels compared with those seen pre-CR, but this was not statistically significant.

CONCLUSIONS

We demonstrated a shift toward increased parasympathetic and possibly, blunted sympathetic effect in this cohort after completion of an exercise-based CR program. Our findings provide insight into the mechanism for the observed changes in exercise parameters following exercise training, and the improved outcomes seen after CR.

Depression, autonomic function, and cardiorespiratory fitness: comment on Hughes, et al. (2010)

A recent paper by Hughes and colleagues suggested that dysfunction of the autonomic nervous system in depressed cardiac patients was partly explained by reduced physical activity and fitness. Other data demonstrate that exercise training and improvements in fitness not only lead to improvements in autonomic function in coronary patients but also reduce depression and depression-related increased mortality.

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.

Relationship between changes in heart rate recovery after cardiac rehabilitation on cardiovascular mortality in patients with myocardial infarction

BACKGROUND

Heart rate recovery (HRR) at predischarge exercise stress test predicts all-cause mortality in patients with myocardial infarction (MI), but the relationship between improvement in HRR with exercise training and clinical outcomes remains unclear.

OBJECTIVE

The purpose of this study was to evaluate the effect of change in HRR after exercise training on clinical outcomes in MI patients.

METHODS

The study included 386 consecutive patients with recent MI who were enrolled into our cardiac rehabilitation program. All patients underwent symptom-limited treadmill testing at baseline and after exercise training, and were prospectively followed-up in the outpatient clinic.

RESULTS

Treadmill testing revealed significant improvement in HRR after 8 weeks of exercise training (17.5 +/- 10.0 bpm to 19.0 +/- 12.3 bpm, P = .011). After follow-up of 79 +/- 41 months, 40 (10.4%) patients died of cardiac events. Multivariate Cox regression analysis revealed that diabetes (hazard ratio [HR] 2.28, 95% confidence interval [CI] 1.01-5.19, P = .049), statin use (HR 0.36, 95% CI 0.16-0.80, P = .012), baseline resting heart rate > or =65 bpm (HR 5.37, 95% CI 1.33-21.61, P = .018), post-training HRR <12 bpm (HR 2.49, 95% CI 1.10-5.63, P = .028), left ventricular ejection fraction < or =30% (HR 4.70, 95% CI 1.34-16.46, P = .016), and exercise capacity < or =4 metabolic equivalents (HR 3.63, 95% CI 1.17-11.28, P = .026) were independent predictors of cardiac death. Patients who failed to improve HRR from <12 bpm to > or =12 bpm after exercise training had significantly higher mortality (HR 6.2, 95% CI 1.3-29.2, P = .022).

CONCLUSION

Exercise training improved HRR in patients with recent MI, and patients with HRR increased to > or =12 bpm had better cardiac survival.

The obesity paradox, weight loss, and coronary disease

PURPOSE

Because obesity is a cardiovascular risk factor but is associated with a more favorable prognosis among cohorts of cardiac patients, we assessed this "obesity paradox" in overweight and obese patients with coronary heart disease enrolled in a cardiac rehabilitation and exercise training (CRET) program, making this assessment in patients classified as overweight/obese using both traditional body mass index (BMI) and percent body fat assessments. Additionally, we assessed the efficacy and safety of purposeful weight loss in overweight and obese coronary patients.

PATIENTS AND METHODS

We retrospectively studied 529 consecutive CRET patients following major coronary events before and after CRET, and compared baseline and post program data in 393 overweight and obese patients (body mass index [BMI] > or =25 kg/m(2)) divided by median weight change (median=-1.5%; mean +2% vs -5%, respectively). In addition, we assessed 3-year total mortality in various baseline BMI categories as well as compared mortality in those with high baseline percent fat (>25% in men and >35% in women) versus those with low baseline fat.

RESULTS

Following CRET, the overweight and obese with greater weight loss had improvements in BMI (-5%; P <.0001), percent fat (-8%; P <.0001), peak oxygen consumption (+16%; P <.0001), low-density lipoprotein cholesterol (-5%; P <.02), high-density lipoprotein cholesterol (+10%; P <.0001), triglycerides (-17%; P <.0001), C-reactive protein (-40%; P <.0001), and fasting glucose (-4%; P=.02), as well as marked improvements in behavioral factors and quality-of-life scores. Those with lower weight loss had no significant improvements in percent fat, low-density lipoprotein cholesterol, triglycerides, C-reactive protein, and fasting glucose. During 3-year follow-up, overall mortality trended only slightly lower in those with baseline overweightness/obesity who had more weight loss (3.1% vs 5.1%; P=.30). However, total mortality was considerably lower in the baseline overweight/obese (BMI > or =25 kg/m(2)) than in 136 CRET patients with baseline BMI <25 kg/m(2) (4.1% vs 13.2%; P <.001), as well as in those with high baseline fat compared with those with low fat (3.8% vs 10.6%; P <.01).

CONCLUSIONS

Purposeful weight loss with CRET in overweight/obese coronary patients is associated with only a nonsignificant trend for lower mortality but is characterized by marked improvements in obesity indices, exercise capacity, plasma lipids, and inflammation, as well as behavioral factors and quality of life. Although an "obesity paradox" exists using either baseline BMI or baseline percent fat criteria, these results support the safety and potential long-term benefits of purposeful weight loss in overweight and obese patients with coronary heart disease.

Reducing psychosocial stress: a novel mechanism of improving survival from exercise training

BACKGROUND

Exercise training reduces mortality in patients with coronary artery disease. Behavioral characteristics, including depression, hostility, and overall psychosocial stress, have been shown to be independent risk factors for recurrent myocardial infarction and death in these patients. Exercise training can reduce these high-risk behaviors, but it remains uncertain as to what extent the health benefits of exercise training can be attributed to improving these behaviors.

METHODS

We evaluated the impact of exercise training during cardiac rehabilitation on mortality in 53 patients with coronary artery disease with high levels of psychosocial stress and in 469 patients with coronary artery disease with low levels of psychosocial stress and compared them with 27 control patients with high psychosocial stress who did not undergo formal cardiac rehabilitation and exercise training.

RESULTS

Mortality was approximately 4-fold greater in patients with high psychosocial stress than in those with low psychosocial stress (22% vs 5%; P = .003). Exercise training decreased the prevalence of psychosocial stress from 10% to 4% (P<.0001) and similarly improved peak oxygen uptake in patients with high and low psychosocial stress. Mortality in patients who improved exercise capacity by>or=10% (high exercise change) was 60% lower than in patients who had<10% improvement in exercise capacity (low exercise change) (P=.009). Mortality was lower in patients with high psychosocial stress with high exercise change compared with patients with high psychosocial stress with low exercise change (0% vs 19%; P=.009). In contrast, there was no significant improvement in mortality in patients with high versus low exercise change with low psychosocial stress (4% vs 8%; P=.14).

CONCLUSION

Psychosocial stress is an independent risk factor for mortality in patients with coronary artery disease, and exercise training can effectively reduce its prevalence. Exercise training reduces mortality in patients with coronary artery disease, and this effect seems to be mediated in part because of the salutary effects of exercise on psychosocial stress.

Cardiovascular rehabilitation increase arterial compliance in type 2 diabetic patients with coronary artery disease

AIMS

The effect of a cardiovascular rehabilitation program on arterial compliance in type 2 diabetes mellitus with coronary disease was studied.

METHODS

Hemodynamic data and arterial compliance were measured with a tonometer (HDI/Pulse wave CR-2000) in coronary artery disease patients with (n=32) and without (n=24) type 2 diabetes before and after a 6-week multidisciplinary cardiac rehabilitation program.

RESULTS

A decrease in heart rate and an increase in stroke volume without significant change in resting cardiac output were obtained in diabetic patients. Arterial compliance of both small and large arteries was significantly increased. In 10 diabetic patients, this increase could be related to an increase in the anti-hypertensive treatment and to the decreased blood pressure. In the 22 remainders, the small artery compliance was significantly increased independently of blood pressure change.

CONCLUSIONS

Exercise training as well as optimization of diabetes and dyslipidemia treatment could explain the improvement of arterial compliance. If these changes are long-lasting and if they improve prognosis remains to be evaluated.

Long-term secondary prevention programs after cardiac rehabilitation for the reduction of future cardiovascular events: focus on regular physical activity

Cardiac rehabilitation/secondary prevention programs are recognized as integral to the comprehensive care of patients with coronary heart disease, and as such are recommended in most contemporary clinical practice guidelines. The interventions are aimed at reducing disability, optimizing cardiovascular risk reduction by drug therapy and promoting healthy behavior. Healthy lifestyle habits must be recognized as capable of substantially reducing the risk for cardiovascular events in patients with coronary heart disease. This review highlights the recommended components of cardiac rehabilitation/secondary prevention programs, with special emphasis on regular physical activity.

Exercise training and cardiac rehabilitation in primary and secondary prevention of coronary heart disease

Substantial data have established a sedentary lifestyle as a major modifiable risk factor for coronary heart disease (CHD). Increased levels of physical activity, exercise training, and overall cardiorespiratory fitness have provided protection in the primary and secondary prevention of CHD. This review surveys data from observational studies supporting the benefits of physical activity, exercise training, and overall cardiorespiratory fitness in primary prevention. Clearly, cardiac rehabilitation/secondary prevention (CRSP) programs have been greatly underused by patients with CHD. We review the benefits of CRSP programs on CHD risk factors, psychological factors, and overall CHD morbidity and mortality. These data support the routine referral of patients with CHD to CRSP programs. Patients should be vigorously encouraged to attend these programs.

Cardiac autonomic function and baroreflex changes following 4 weeks of resistance versus aerobic training in individuals with pre-hypertension

AIM

Cardiac autonomic modulation and baroreflex sensitivity (BRS) are altered in individuals with hypertension. Aerobic exercise (AE) training has been shown to improve both measures, yet little is known about the effects of resistance exercise (RE). The purpose of this study was to examine the heart rate variability (HRV) and BRS following 4 weeks of resistance or aerobic training in a population with borderline high blood pressure (BP).

METHODS

Twenty-nine mild hypertensives were recruited and randomly assigned to 4 weeks of RE or AE training. Before and after training, resting measures of HRV frequencies and BRS were obtained.

RESULTS

There was a significant decrease in resting systolic BP for both exercise training modes (RE 136 +/- 3.0 pre- to 132 +/- 3.4 post-training vs. AE 142 +/- 4.0 pre- to 137 +/- 3.6 mmHg post-training, P = 0.019). Diastolic BP decreased significantly following both exercise training modes (RE 78 +/- 1.31 pre to 74 +/- 1.1 post vs. AE 80 +/- 1.7 pre to 77 +/- 1.6 mmHg post, P = 0.002). A significant time by training mode interaction for low frequency : high frequency (HF) ratio (P = 0.017) with AE decreasing the ratio (275.21 +/- 67.28 to 161.26 +/- 61.49) and RE increasing this ratio (143.73 +/- 65.00 to 227.83 +/- 59.41). Natural log-transformed (ln) HRV values showed a time-by-training mode interaction for ln HF (P = 0.05) as ln HF increased (4.7 +/- 0.38 to 5.4 +/- 0.35 ms(2)) following AE and decreased (5.98 +/- 0.37 to 5.76 +/- 0.42 ms(2)) following RE. BRS increased following aerobic training and decreased after resistance training (6.74 +/- 1.2 to 7.94 +/- 1.3 and 10.44 +/- 1.2 to 9.1 +/- 1.2 ms mmHg(-1) respectively, P = 0.021).

CONCLUSIONS

Aerobic exercise improved the autonomic nervous system (increasing vagal tone, reducing sympathovagal balance while increasing BRS) while RE showed no improvements in cardiac autonomic tone and decreased BRS.

Effects of cyclooxygenase-2 gene inactivation on cardiac autonomic and left ventricular function in experimental diabetes

Glucose-mediated oxidative stress and the upregulation of cyclooxygenase (COX)-2 pathway activity have been implicated in the pathogenesis of several vascular complications of diabetes including diabetic neuropathy. However, in nondiabetic subjects, the cardiovascular safety of selective COX-2 inhibition is controversial. The aim of this study was to explore the links between hyperglycemia, oxidative stress, activation of the COX-2 pathway, cardiac sympathetic integrity, and the development of left ventricular (LV) dysfunction in experimental diabetes. R wave-to-R wave interval (R-R interval) and parameters of LV function measured by echocardiography using 1% isoflurane, LV sympathetic nerve fiber density, LV collagen content, and markers of myocardial oxidative stress, inflammation, and PG content were assessed after 6 mo in control and diabetic COX-2-deficient (COX-2(-/-)) and littermate, wild-type (COX-2(+/+)) mice. There were no differences in blood glucose, LV echocardiographic measures, collagen content, sympathetic nerve fiber density, and markers of oxidative stress and inflammation between nondiabetic (ND) COX-2(+/+) and COX-2(-/-) mice at baseline and thereafter. After 6 mo, diabetic COX-2(+/+) mice developed significant deteriorations in the R-R interval and signs of LV dysfunction. These were associated with a loss of LV sympathetic nerve fiber density, increased LV collagen content, and a significant increase in myocardial oxidative stress and inflammation compared with those of ND mice. Diabetic COX-2(-/-) mice were protected against all these biochemical, structural, and functional deficits. These data suggest that in experimental diabetes, selective COX-2 inactivation confers protection against sympathetic denervation and LV dysfunction by reducing intramyocardial oxidative stress, inflammation, and myocardial fibrosis.

Heart rate variability explored in the frequency domain: a tool to investigate the link between heart and behavior

The neural regulation of circulatory function is mainly effected through the interplay of the sympathetic and vagal outflows. This interaction can be explored by assessing cardiovascular rhythmicity with appropriate spectral methodologies. Spectral analysis of cardiovascular signal variability, and in particular of RR period (heart rate variability, HRV), is a widely used procedure to investigate autonomic cardiovascular control and/or target function impairment. The oscillatory pattern which characterizes the spectral profile of heart rate and arterial pressure short-term variability consists of two major components, at low (LF, 0.04-0.15Hz) and high (HF, synchronous with respiratory rate) frequency, respectively, related to vasomotor and respiratory activity. With this procedure the state of sympathovagal balance modulating sinus node pacemaker activity can be quantified in a variety of physiological and pathophysiological conditions. Changes in sympathovagal balance can be often detected in basal conditions, however a reduced responsiveness to an excitatory stimulus is the most common feature that characterizes numerous pathophysiological states. Moreover the attenuation of an oscillatory pattern or its impaired responsiveness to a given stimulus can also reflect an altered target function and thus can furnish interesting prognostic markers. The dynamic assessment of these autonomic changes may provide crucial diagnostic, therapeutic and prognostic information, not only in relation to cardiovascular, but also non-cardiovascular disease. As linear methodologies fail to provide significant information in conditions of extremely reduced variability (e.g. strenuous exercise, heart failure) and in presence of rapid and transients changes or coactivation of the two branches of autonomic nervous system, the development of new non-linear approaches seems to provide a new perspective in investigating neural control of cardiovascular system.

Heart rate variability characteristics in sedentary postmenopausal women following six months of exercise training: the DREW study

BACKGROUND

Decreased heart rate variability (HRV) is associated with a higher risk of mortality. Overall, postmenopausal women have lower levels of HRV than premenopausal women, which may be additionally complicated by lifestyle related behaviors such as physical inactivity and obesity. Though cardiorespiratory exercise training increases HRV, little is known regarding the exercise dose necessary to promote this improvement.

METHODOLOGY/PRINCIPAL FINDINGS

Our primary aim was to measure HRV in post-menopausal women following 6-months of exercise training. We examined supine resting HRV in 373 post-menopausal women (45-75 y) after 6-months of randomly assigned and double-blinded administered exercise training exercise training at 50%, 100% and 150% of the NIH Consensus Development Panel's recommended minimal physical activity level. This corresponded to 4, 8, or 12 kcal/kg per week (KKW) of energy expenditure. At baseline, we observed no significant differences in HRV or hormone replacement use between treatment groups. However, we did observe that Caucasian women and those taking antidepressant medications had lower levels of baseline HRV. After 6-months of exercise intervention, we observed a dose dependent increase in all parasympathetically derived time and frequency domain measurements across exercise groups after adjustment for age, ethnicity, antidepressants, and baseline rMSSD (all, P<0.001). For example, the parasympathetic index rMSSD was greater than control (23.19+/-1.0) for the 4-KKW (25.98+/-0.8; P = 0.14), 8-KKW (27.66+/-1.0; P<0.05), and 12-KKW (27.40+/-0.0; P<0.05) groups at follow-up.

CONCLUSIONS/SIGNIFICANCE

Moderate intensity exercise training exercise is sufficient to improve HRV in previously sedentary postmenopausal women in a dose-dependent manner, as 4-KKW is insufficient to improve parasympathetic indices of HRV, while 12-KKW conferred no greater improvement than 8-KKW.

TRIAL REGISTRATION

Clinicaltrials.gov NCT 00011193.

The role of exercise training in peripheral arterial disease

Peripheral arterial disease (PAD) is currently a major health problem affecting 8-12 million Americans, 15-40% of whom will have intermittent claudication that can lead to substantial impairment in their ability to carry out normal daily activities as well as perform the recommended cardiovascular exercise. Supervised exercise training is an effective tool in the treatment of claudication and is currently a recommended first-line therapy for patients with this condition. In addition to improving pain-free walking distance and quality of life, supervised exercise training can improve many cardiovascular risk factors, possibly reducing the risk for subsequent myocardial infarction, stroke, and death. This paper will review the benefits of supervised exercise training in patients with PAD.

Effects of exercise training on heart rate recovery in patients with chronic heart failure

BACKGROUND

Heart rate recovery (HRR) is a marker of vagal tone that is associated with survival, but little is known about the effects of exercise training on HRR in patients with heart failure (HF).

METHODS

Twenty-four patients with HF were randomized to a 2-month residential rehabilitation program or to usual care. Symptom-limited exercise testing was performed at baseline and at discharge from the program. Heart rate recovery was expressed as the decline in heart rate from peak exercise through 6 minutes into recovery. In addition, HRR recovery curves were normalized to a range of 1 at peak heart rate and 0 at 6 minutes and adjusted for differences in heart rate reserve, facilitating the comparison of recovery curve shapes between groups.

RESULTS

Mean peak oxygen uptake and oxygen uptake at the lactate threshold increased 26% (P < .05) and 39% (P < .001), respectively, in the exercise group, whereas neither of these responses changed significantly among controls. Heart rate recovery was significantly more rapid in the exercise group after training (main effect 12.6 vs 2.6 beat/min in the trained and control groups, respectively, P = .005). The normalized curves showed that the largest improvement in recovery curve shape occurred in the exercise group, but most of the HRR improvement was accounted for by a widening of the difference between peak and resting heart rate.

CONCLUSION

Exercise training results in a faster HRR in patients with HF. Heart rate recovery, as a simple marker of autonomic function, is an easily acquired response that may be useful for evaluating patient outcomes in cardiac rehabilitation.

Exercise training for patients with cardiovascular disease

This review surveys effort training, a validated and recommended therapy, in patients with atheromatous cardiovascular disease. This true therapy reduces mortality by 25-35%, reduces clinical manifestations and complications (rhythm problems, thrombosis) and improves physical capacity, reintegration and quality of life. The effects are essentially linked to improved metabolic performance of muscles and reduced endothelial dysfunction, insulin resistance and neurohormonal abnormalities. Training also has an impact on the evolution of major risk factors, especially diabetes and arterial hypertension. The risks are limited as long as the contraindications are respected and the programmes supervised. The indications (stable angina, chronic heart failure, peripheral arterial disease) should be described more precisely by taking into account functional criteria: physical deconditioning, exclusion, compliance, mood swings, and seriousness of risk factors. The training programme should be tailor made and based on evaluation of the patient's adaptation to effort, in terms of frequency, intensity and duration of the exercises. Various types of exercise include overall or segmental physical training; concentric, eccentric, even isokinetic muscle contraction exercises; and proprioceptive rehabilitation. However, knowledge is lacking about the molecular mechanisms of the effects of training, the most effective intensity of effort, and strategies to develop physical activity in this ever-growing population for both primary and secondary prevention.

Effects of exercise training on heart rate and QT interval in healthy young individuals: are there gender differences?

AIMS

The aim of the present study was to assess the effects of exercise training on heart rate, QT interval, and on the relation between ventricular repolarization and heart rate in men and women.

METHODS AND RESULTS

A 24 h Holter recording was obtained in 80 healthy subjects (40 males) who differed for the degree of physical activity. Trained individuals showed a lower heart rate and a higher heart rate variability than sedentary subjects, independent of the gender difference in basal heart rate. Mean 24 h QTc was similar in trained and non-trained men, while a significant difference was observed between trained and non-trained women. Exercise training reduced the QT/RR slope in both genders. This effect on the QT/RR relation was more marked in women; in fact, the gender difference in the ventricular repolarization duration at low heart rate observed in sedentary subjects was no longer present among trained individuals.

CONCLUSION

The results of this study suggest that the cardiovascular response to exercise training may be different in men and women. Women may benefit more from interventions aimed to increase physical activity as a tool for prevention of cardiovascular morbidity and mortality.

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.

Stress management at the worksite: reversal of symptoms profile and cardiovascular dysregulation

Work stress may increase cardiovascular risk either indirectly, by inducing unhealthy life styles, or directly, by affecting the autonomic nervous system and arterial pressure. We hypothesized that, before any apparent sign of disease, work-related stress is already accompanied by alterations of RR variability profile and that a simple onsite stress management program based on cognitive restructuring and relaxation training could reduce the level of stress symptoms, revert stress-related autonomic nervous system dysregulation, and lower arterial pressure. We compared 91 white-collar workers, enrolled at a time of work downsizing (hence, in a stress condition), with 79 healthy control subjects. Psychological profiles were assessed by questionnaires and autonomic nervous system regulation by spectral analysis of RR variability. We also tested a simple onsite stress management program (cognitive restructuring and relaxation training) in a subgroup of workers compared with a sham subgroup (sham program). Workers presented an elevated level of stress-related symptoms and an altered variability profile as compared with control subjects (low-frequency component of RR variability was, respectively, 65.2+/-2 versus 55.3+/-2 normalized units; P<0.001; opposite changes were observed for the high-frequency component). These alterations were largely reverted (low-frequency component of RR variability from 63.6+/-3.9 to 49.3+/-3 normalized units; P<0.001) by the stress management program, which also slightly lowered systolic arterial pressure. No changes were observed in the sham program group. This noninvasive study indicates that work stress is associated with unpleasant symptoms and with an altered autonomic profile and suggests that a stress management program could be implemented at the worksite, with possible preventive advantages for hypertension.

Clinical evidence for a health benefit from cardiac rehabilitation: an update

The recent decision by the Centers for Medicare and Medicaid Services to expand the indications for cardiac rehabilitation (CR) provides an opportunity to review the clinical evidence of the efficacy of exercise in the CR setting for patients who have experienced an acute myocardial infarction, coronary artery bypass graft surgery, stable angina, percutaneous coronary intervention, chronic heart failure, cardiac transplant, or cardiac valve repair/replacement. Evidence shows that physician-directed, exercise-based CR positively affects the basic pathophysiology of coronary artery disease, the extent of disability and level of quality of life, and the ability to potentially impact events of both morbidity and mortality. The role of CR, including regular exercise, lifestyle modification, and appropriate medical therapy, is effective in younger and older men and women with cardiac diagnoses. The efficacy of this important therapeutic modality warrants its more widespread application.

Exercise-based cardiac rehabilitation improves heart rate recovery in elderly patients after acute myocardial infarction

BACKGROUND

Heart rate recovery (HRR), defined as the fall in HR during the first minute after exercise, is a marker of vagal tone, which is a powerful predictor of mortality in patients with coronary artery disease and in older patients. Whether exercise training (ET) modifies HRR in elderly patients recovering from acute myocardial infarction (AMI) is still unknown. Therefore, this study aims at evaluating the effect of ET on HRR in elderly AMI patients.

METHODS

This was a prospective observational study including 268 older patients after AMI (217 men, 51 women), subdivided in two groups: Group A (n = 104), enrolled in an ET program; Group B (n = 164), discharged with generic instructions to continue physical activity. At baseline and at 3-month follow-up, all Group A and 54/164 Group B patients underwent a cardiopulmonary exercise stress test, whereas 110/164 Group B patients underwent an exercise stress test.

RESULTS

After completion of the ET program, in Group A we observed an improvement in oxygen consumption at peak exercise (VO2peak; from 14.7 +/- 1.3 to 17.6 +/- 1.9 mL/kg/min, p < .001), in the rate of increase of ventilation per unit of increase of carbon dioxide production (VE/VCO2slope; from 34.2 +/- 3.8 to 30.4 +/- 3.0, p < .001), and in HRR (from 13.5 +/- 3.7 to 18.7 +/- 3.5 beats/min, p < .001). The changes in VO2peak and in VE/VCO2slope after ET were correlated with the improvement of HRR (r = -0.865, p < .01; r = -0.594, p < .01, respectively). No changes in these parameters were observed in Group B patients.

CONCLUSIONS

In older AMI patients, ET results in HRR improvement, which was correlated to the improvement in cardiopulmonary parameters. These findings may shed additional light on the possible mechanisms of the beneficial prognostic effects of ET in this patient population.

Cardiac Rehabilitation vs. Home Exercise After Coronary Artery Bypass Graft Surgery

OBJECTIVE

The autonomic dysfunction is known to adversely affect clinical outcome in patients with cardiovascular disease, and exercise training has been shown to modify the sympathovagal control of heart rate. The purposes of this study were to investigate the effect of cardiac rehabilitation on heart rate recovery in patients who received coronary artery bypass grafting (CABG) and compare the effect with that of a home-based exercise program.

DESIGN

Fifty-four male patients having undergone CABG were randomly assigned to a cardiac rehabilitation exercise program (n = 18), a home-based exercise program (n = 18), and a control group (n = 18) for 12 wks to evaluate the differences in heart rate recovery among groups.

RESULTS

Patients in the cardiac rehabilitation group had significant increases in heart rate recovery (19.1 +/- 6.2 vs. 14.0 +/- 5.4 beats/min, P = 0.022) compared with those in the control group. There were no significant differences in heart rate recovery between cardiac rehabilitation and home-based exercise groups (16.2 +/- 4.8 beats/min) or between home-based exercise and control groups. All three groups had significantly improved heart rate recovery compared with their baseline data (P < 0.001, < 0.001, and 0.007).

CONCLUSION

Our results point out that a cardiac rehabilitation exercise program has a positive effect on heart rate recovery in patients having undergone CABG and is consistent with the autonomic improvement. Although the home-based exercise group did not reveal statistical significances over those in the control group, it had comparable efficacy to that demonstrated in the cardiac rehabilitation group.

Fatigue et maladies cardiovasculaires

Fatigue is a frequent complaint during cardiovascular disease and can sometimes constitute the first clinical manifestation of this disease. It is responsible for deterioration of the quality of life and prognosis. Although physical and mental fatigue are often intimately interrelated, these two aspects of fatigue correspond to different pathophysiological mechanisms and different clinical features and the neurobiological links between the two are only just beginning to be studied. Physical fatigue is related to loss of efficacy of the effector muscle, due to multiple causes: mismatch of cardiac output during exercise, muscle and microcirculatory deconditioning, neuroendocrine dysfunction, associated metabolic disorders. Mental fatigue corresponds to predominantly depressive mood disorders with a particular entity, vital exhaustion. The diagnostic approach is designed to eliminate other organic causes of fatigue. Functional tests investigating physical (exercise capacity) and mental dimensions (mood disorders) can be used to analyse their respective roles and to propose personalized management, in which rehabilitation has an essential place due to its global approach. The objective of this reduction of fatigue is threefold: to improve independence, to improve quality of life and to limit morbidity and mortality.

Relationship between Daily Physical Activity and ANS Activity in Patients with CHF

PURPOSE

Heart rate variability (HRV) indices are powerful independent prognostic factors of cardiovascular events and all cause mortality in patients with chronic heart failure (CHF). This study evaluates the influence of lifestyle on HRV in CHF patients.

METHODS

Thirty-nine CHF patients (33 men, ischemic/dilated cardiomyopathy (18/21), 52.4 +/- 11.2 yr, NYHA I to III, LVEF 33.4 +/- 5.1%) filled out a physical activity questionnaire providing an individual complete qualitative and quantitative picture of their physical activity and daily energy expenditure (PAEE/DEE) corrected for age, weight, severity of the condition and autonomy. Frequency and time domain indices of HRV were calculated from ECG Holter recordings on a typical weekday. Nighttime indices were calculated in order to avoid the confounding factor of physical activity that might alter 24-h frequency analysis of HRV.

RESULTS

DEE was significantly different between classes I and II and classes I and III (P = 0.01 both) patients. Time spent in activities above 3 METs decreased significantly with the severity of the condition. Global and parasympathetic indices of 24-h HRV analysis were correlated to DEE and PAEE (Ptot24h = 78.80*PAEE (J x min x kg) -1061.80, R = 0.72, P < 0.0001). Multiple regression analysis revealed that PAEE was the sole independent factor on established HRV prognostic indices (P < 0.05) and especially within PAEE dimensions, only activities above 3 METs were correlated with established prognostic HRV indices (P < 0.05).

CONCLUSION

These results indicate that rather than total DEE, moderate to intensive physical activity may counteract the decline in HRV with chronic heart disease. This may be linked to longer time spent in higher intensity activities, and not to total activity time.

Indices de mesure de l'activité physique dans le domaine des affections cardiovasculaires

PURPOSE

To identify the more useful among many methods available for the measurement of physical activity in patients with cardiovascular disease. For practical and financial reasons only questionnaires and mechanical monitoring, which are appropriate for use in large studies, were assessed.

METHODS

To select tools valuable for clinical and epidemiological measurement of physical activity, with sufficient validity, reproducibility and sensitivity, we reviewed the literature in Medline with use of keywords: accelerometry, ambulatory accelerometry, ambulatory monitoring, cardiovascular diseases, daily activity, heart disease, pedometer, physical activity, questionnaire.

RESULTS

Considering appropriate level of reproducibility and validity, 15 questionnaires are available. For measuring postures and motions during daily life, activity monitor seems to be more valid than pedometers or single accelerometers.

CONCLUSION

At present the preferred method is a questionnaire, provided it is valid, repeatable, easy to use and inexpensive. In the future mechanical monitoring (especially activity monitor) will be probably a good alternative.

Prevalence of hostility in young coronary artery disease patients and effects of cardiac rehabilitation and exercise training

OBJECTIVE

To determine the prevalence of hostility symptoms in young patients with coronary artery disease (CAD), the associated risk factor profile in these patients, and the effects of a formal phase 2 cardiac rehabilitation and exercise training program.

PATIENTS AND METHODS

Our study included consecutive CAD patients referred for cardiac rehabilitation from May 1999 through December 2000. At baseline and after rehabilitation, behavioral factors and quality of life were assessed by validated questionnaires, and standard CAD risk factors were measured, including exercise capacity. We specifically evaluated detailed data for young patients.

RESULTS

A total of 500 patients were included in the study. Hostility scores were 2.5 times higher (P<.001) in the 81 young patients (< 50 years; mean +/- SD age, 45 +/- 5 years) than in the 268 elderly patients (> or = 65 years; mean +/- SD age, 70 +/- 4 years), and the prevalence of hostility symptoms was 3.5 times higher in young patients (28% vs 8%; P<.001). Young patients with hostility symptoms also had more adverse CAD risk profiles, including higher total cholesterol levels, triglyceride levels, total cholesterol/high-density lipoprotein cholesterol ratios, fasting glucose levels, and glycosylated hemoglobin levels and lower quality-of-life scores compared with young patients with low hostility scores. After cardiac rehabilitation, young patients with hostility symptoms had marked improvements in CAD risk factors, behavioral characteristics (including hostility), and quality of life, and a nearly 50% (P=.005) reduction in the prevalence of hostility symptoms occurred.

CONCLUSIONS

Young CAD patients have a high prevalence of hostility symptoms and adverse CAD risk profiles. Reducing hostility symptoms and other parameters of psychological distress in young CAD patients should be emphasized, and the potential benefits of cardiac rehabilitation programs in the secondary prevention of CAD should be highlighted.

System identification: a multi-signal approach for probing neural cardiovascular regulation

Short-term, beat-to-beat cardiovascular variability reflects the dynamic interplay between ongoing perturbations to the circulation and the compensatory response of neurally mediated regulatory mechanisms. This physiologic information may be deciphered from the subtle, beat-to-beat variations by using digital signal processing techniques. While single signal analysis techniques (e.g., power spectral analysis) may be employed to quantify the variability itself, the multi-signal approach of system identification permits the dynamic characterization of the neural regulatory mechanisms responsible for coupling the variability between signals. In this review, we provide an overview of applications of system identification to beat-to-beat variability for the quantitative characterization of cardiovascular regulatory mechanisms. After briefly summarizing the history of the field and basic principles, we take a didactic approach to describe the practice of system identification in the context of probing neural cardiovascular regulation. We then review studies in the literature over the past two decades that have applied system identification for characterizing the dynamical properties of the sinoatrial node, respiratory sinus arrhythmia, and the baroreflex control of sympathetic nerve activity, heart rate and total peripheral resistance. Based on this literature review, we conclude by advocating specific methods of practice and that future research should focus on nonlinear and time-varying behaviors, validation of identification methods, and less understood neural regulatory mechanisms. Ultimately, we hope that this review stimulates such future investigations by both new and experienced system identification researchers.

Depressive mood after a cardiac event: gender inequality and participation in rehabilitation programme

BACKGROUND

Depressive mood after a cardiac event is common with serious consequences for the patient.

AIMS

To compare gender in depressive mood during the first year after a cardiac event and to evaluate the effect of participating in a multidimensional secondary prevention program on depressive mood.

METHODS

166 men and 54 women, <73 years, consecutively answered a questionnaire concerning depressive mood at 2 weeks, 6 weeks, 5 months and 1 year after discharge after a cardiac event. At 2 weeks, each patient met a nurse, and was informed about the disease and received individual support about lifestyle changes. Of those invited to participate in a secondary prevention program, 127 patients accepted, and 93 declined participation.

RESULTS

At each of the four follow-ups, women had significantly higher depression scores than men. Depressive mood in both women and men was significantly reduced at 6 weeks. Thereafter, it increased to the 2-week level in women and to above the 2-week level in men. No differences were seen in patients participating or not in secondary prevention programs.

CONCLUSION

Women had higher depressive mood scores than men and secondary prevention programs failed to improve depressive mood in both women and men.