Effect of exercise on coronary endothelial function in patients with coronary artery disease

Inflammatory markers and exercise: differences related to exercise type

PURPOSE

To examine the relationship between elevated inflammatory markers (CRP, fibrinogen, and white blood cell levels) and various forms of exercise for the adult U.S. population while controlling for factors that might influence the relationship.

METHODS

An analysis of the adults age 17 and over who participated in the National Health and Nutrition Examination Survey (NHANES) III was conducted. The main goal of the analysis was to determine whether exercise type was associated with systemic markers of inflammation. Bivariate statistics using chi-square to evaluate different types of exercise according to the presence of elevated and nonelevated inflammatory markers was initially performed. In addition, multivariate models were constructed using each type of exercise activity as the predictor variable and each inflammatory marker as the dependent variable.

RESULTS

A total of 4072 people were included in the analysis. In bivariate analyses, compared with nonexercisers in a specific exercise type, a significant lower likelihood of elevated inflammatory markers was found among regular participants in jogging, swimming, cycling, aerobic dancing, calisthenics, and weight lifting but not for gardening. After controlling for possible confounding factors including age, race, sex, body mass index, smoking, and health status in logistic regression analysis, only regular participants in jogging and aerobic dancing remained significantly less likely to have elevated cardiovascular markers.

CONCLUSIONS

The results of this study indicate that some forms of physical activity are associated with a lower likelihood of elevation of inflammatory markers, although we cannot exclude the possibility that differences may be due to exercise intensity or duration. Future research should be directed toward further exploration of the effects of different types of exercise activity on inflammatory markers and the role of exercise in the prevention of cardiovascular disease.

Impaired cardiac response to exercise in post-menopausal women: relationship with peripheral vascular function

Endothelial dysfunction has been demonstrated in post-menopausal women. To assess the relationship between peripheral vascular reserve and cardiac function during exercise in post-menopausal women, 91 subjects, who had no ischaemic findings on myocardial SPECT, were assigned to four groups: pre-menopausal women (n=13), post-menopausal women (n=33), younger men aged < or =50 years (n=10), and older men aged >50 years (n=35). First-pass radionuclide angiography was performed before and during bicycle exercise to calculate ejection fraction (EF) and peripheral vascular resistance (VR). There were no differences in haemodynamic variables among the groups at baseline. The per cent increase in EF=(exercise EF - resting EF)x100/resting EF, and the per cent decrease in VR=(resting VR - exercise VR)x100/resting VR were depressed in the post-menopausal women (0.4+/-2% and 35+/-3%, respectively) compared to the pre-menopausal women (10+/-3% and 47+/-3%, respectively; P<0.05 each). Although the age dependent impairment is thought to cause this depression, neither the per cent increase in EF nor the per cent decrease in VR in the older men was significantly different from that in the younger men. Post-menopausal women exhibited depressed cardiac function during exercise, which may be related to the impairment of peripheral vascular function after menopause.

Relative intensity of physical activity and risk of coronary heart disease

BACKGROUND

Current recommendations prescribe at least moderate-intensity physical activity, requiring >or=3 METs (metabolic equivalents) for >or=30 minutes almost daily, generating approximately 1000 kcal/wk. Defining intensity using an absolute scale in METs may be limited because it neglects variations in physical fitness: an activity requiring a particular MET value commands greater physical effort among less fit than more fit persons. It is unknown whether moderate-intensity exercise, relative to an individual's capacity, is associated with reduced coronary heart disease (CHD) rates.

METHODS AND RESULTS

We followed 7337 men (mean age, 66 years) from 1988 to 1995. At baseline, men reported their actual activities and, using the Borg Scale, the perceived level of exertion when exercising (relative intensity). During follow-up, 551 men developed CHD. After multivariate adjustment, the relative risks of CHD among men who perceived their exercise exertion as "moderate," "somewhat strong," and "strong" or more intense were 0.86 (95% confidence interval, 0.66 to 1.13), 0.69 (0.51 to 0.94), and 0.72 (0.52 to 1.00), respectively (P(trend)=0.02), compared with "weak" or less intense. This inverse association extended to men not fulfilling current recommendations, ie, expending <1000 kcal/wk in physical activity or not engaging in activities of >or=3 METs (P(trend)=0.03 and 0.007, respectively).

CONCLUSIONS

There is an inverse association between relative intensity of physical activity (an individual's perceived level of exertion) and risk of CHD, even among men not satisfying current activity recommendations. Recommendations for "moderate"-intensity physical activity may need to consider individual fitness levels instead of globally prescribing activities of >or=3 METs.

Endothelium and the lipid metabolism: the current understanding

The endothelium is a dynamic organ and responds to various physical and humoral conditions. The endothelium secretes several biologically active substances, both vasoconstrictors and vasodilators, which control these processes. Endothelial function is most commonly assessed as the vasodilatory response to stimuli. Several endothelium-dependent agonists have been identified, each of which acts through a membrane receptor. Nitric oxide which is continuously synthesized by the endothelium has a wide range of biological properties that maintain vascular homeostasis. It is a potent vasodilator and inhibitor of platelet aggregation and thus has an important protective role. Endothelial dysfunction in hypercholesterolemic patients is in large part due to a reduced bioavailability of NO. Traditional coronary risk factors, especially hypercholesterolemia, produce endothelial dysfunction even in patients with normal blood vessels. The underlying mechanisms involve a local inflammatory response, release of cytokines and growth factors, activation of oxidation-sensitive mechanisms in the arterial wall, modulation of intracellular signaling pathways, increased oxidation of low-density lipoprotein cholesterol, and quenching of nitric oxide. Clinical studies have shown a significant improvement in endothelial dysfunction following lowering of serum cholesterol levels, infusion of nitric oxide donors like L-arginine and exercise training. Clinical trials are underway examining the role of endothelin-1 receptor antagonists like bosentan in the prevention of graft atherosclerosis.

Effect of regular exercise on coronary endothelial function in patients with recent myocardial infarction

Exercise training improves the endothelial function of arteries in skeletal muscle, but few studies have examined its clinical effect on human coronary endothelial function. Non-infarct-related coronary arteries in 41 patients with a recent myocardial infarction who underwent successful percutaneous transluminal coronary angioplasty were studied. Patients were divided into 2 groups: regular exercisers (n=24, 17 males, mean age: 58 years), and non-exercisers (n=17, 12 males, mean age: 58 years). Acetylcholine (ACh) was infused into the non-infarct-related coronary artery and its diameter was measured by quantitative angiography at baseline and at 6 months after angioplasty. ACh, given in doses of 1, 3, 10, 30 microg/min, increased the coronary artery diameter in a dose-dependent manner in both groups. The mean percent change in the diameter at the site of stenosis change (%DS) was less in the regular exercisers than in the non-exercisers (11%+/-12 vs 41%+/-36, p<0.05). Multivariate analysis showed that regular exercise was the only significant determinant of improvement in endothelial function (p=0.01). These findings suggest that regular exercise improves endothelial function in the coronary arteries following myocardial infarction.

Endothelial dysfunction: a marker of atherosclerotic risk

Endothelial dysfunction is a systemic disorder and a key variable in the pathogenesis of atherosclerosis and its complications. Current evidence suggests that endothelial status is not determined solely by the individual risk factor burden but rather, may be regarded as an integrated index of all atherogenic and atheroprotective factors present in an individual, including known as well as yet-unknown variables and genetic predisposition. Endothelial dysfunction reflects a vascular phenotype prone to atherogenesis and may therefore serve as a marker of the inherent atherosclerotic risk in an individual. In line with this hypothesis, dysfunction of either the coronary or peripheral vascular endothelium was shown to constitute an independent predictor of cardiovascular events, providing valuable prognostic information additional to that derived from conventional risk factor assessment. Interventions like risk factor modification and treatment with various drugs, including statins and angiotensin-converting enzyme inhibitors, may improve endothelial function and thereby, potentially prognosis. Hence, given its reversibility and granted the availability of a diagnostic tool to identify patients at risk and to control the efficacy of therapy in clinical practice, endothelial dysfunction may be an attractive primary target in the effort to optimize individualized therapeutic strategies to reduce cardiovascular morbidity and mortality.

Serum fatty acid levels, dietary style and coronary heart disease in three neighbouring areas in Japan: the Kumihama study

CHD mortality is extremely low in Japan, particularly in rural districts, when compared with that in Western countries. This has been partly attributed to the difference in dietary lifestyle. We investigated the factors influencing CHD mortality in a rural coastal district of Japan, comprising mercantile, farming, and fishing areas with distinct dietary habits. We prospectively examined the incidence of CHD from 1994 to 1998, as well as coronary risk factors and serum fatty acid concentrations. The incidence of angina pectoris was significantly (P=0.01) lower in the fishing area than in the mercantile and farming areas. Blood pressure, physical activity, prevalence of diabetes, serum levels of uric acid and HDL-cholesterol were similar between the three areas. Total- and LDL-cholesterol levels were significantly lower but the smoking rate was markedly higher in the fishing area than in the other two areas. Serum levels of saturated fatty acids and n-6 polyunsaturated fatty acids (PUFA) were lowest in the fishing area, but n-3 PUFA did not differ significantly. The n-6:n-3 PUFA ratio was lowest and eicosapentaenoic:arachidonic acid was highest in the fishing area. Although many previous studies have emphasized the beneficial effect of n-3 PUFA in preventing CHD, the present study indicated that a lower intake of n-6 PUFA and saturated fatty acids has an additional preventive effect on CHD even when the serum level of n-3 PUFA is high because of high dietary fish consumption.

Cardiac rehabilitation secondary prevention programs

Contemporary cardiac rehabilitation programs are more accurately described as "secondary prevention centers." They offer comprehensive care for the patient with cardiovascular disease, resulting in decreased mortality, improvement of most cardiac risk factors, and an enhanced quality of life. Although overall participation has increased with enhanced recognition of the importance of secondary prevention, 80% of eligible patients still do not participate, in part due to lack of insurance reimbursement. This rate can be significantly increased by specific endorsement from the physician.

Exercise considerations in coronary artery disease, peripheral vascular disease, and diabetes mellitus

Physical inactivity is a risk factor for cardiovascular disease. Regular aerobic and resistance training increases exercise capacity and plays a role both in the primary and secondary prevention of cardiovascular disease. Patients with coronary artery disease, peripheral vascular disease, or diabetes mellitus must be considered individually when prescribing exercise because their clinical status can vary greatly. In addition, a majority of these patients have multiple comorbid disorders such as renal, neurologic, and retinal disease that may affect their ability to exercise safely. Therefore, a preparticipation medical evaluation is required. An exercise prescription should be tailored to each person's unique set of circumstances and reflect an effort to maximize the anticipated benefits while minimizing the risks.

Short-term training enhances endothelium-dependent dilation of coronary arteries, not arterioles

Our objective was to test the hypothesis that short-term exercise training (STR) of pigs increases endothelium-dependent dilation (EDD) of coronary arteries but not coronary arterioles. Female Yucatan miniature swine ran on a treadmill for 1 h, at 3.5 mph, twice daily for 7 days (STR; n = 28). Skeletal muscle citrate synthase activity was increased in STR compared with sedentary controls (Sed; n = 26). Vasoreactivity was evaluated in isolated segments of conduit arteries (1-2 mm ID, 3-4 mm length) mounted on myographs and in arterioles (50-100 microm ID) isolated and cannulated with micropipettes with intraluminal pressure set at 60 cmH(2)O. EDD was assessed by examining responses to increasing concentrations of bradykinin (BK) (conduit arteries 10(-12)-10(-6) M and arterioles 10(-13)-10(-6) M). There were no differences in maximal EDD or BK sensitivity of coronary arterioles from Sed and STR hearts. In contrast, sensitivity of conduit arteries (precontracted with PGF(2alpha)) to BK was increased significantly (P < 0.05) in STR (EC(50), 2.33 +/- 0.62 nM, n = 12) compared with Sed animals (EC(50), 3.88 +/- 0.62 nM, n = 13). Immunoblot analysis revealed that coronary arteries from STR and Sed animals had similar levels of endothelial nitric oxide synthase (eNOS). In contrast, eNOS protein was increased in STR aortic endothelial cells. Neither protein nor mRNA levels of eNOS were different in coronary arterioles from STR compared with Sed animals. STR did not alter expression of superoxide dismutase (SOD-1) protein in any artery examined. We conclude that pigs exhibit increases in EDD of conduit arteries, but not in coronary arterioles, at the onset of exercise training. These adaptations in pigs do not appear to be mediated by alterations in eNOS or SOD-1 expression.

Physical activity and coronary heart disease: prevention and effect on risk factors

The general public recommendation to accumulate 30 minutes of daily physical activity on most, preferably all, days of the week was recently modified by the National Academy of Science Institute of Medicine to at least 60 minutes of cumulative daily physical activity to maintain cardiovascular health at a maximal level. Data suggest that regular physical activity, even as little as 30 minutes daily, can positively impact cardiovascular health by improving many of the major risk factors associated with coronary heart disease, including hypertension, dyslipidemia, obesity, insulin resistance, and endothelial function. With the recent and rapid rise in the rate of obesity in the United States, a doubling of the dose of physical activity daily may help offset the trend of increased caloric intake that has contributed to this epidemic. We briefly review the evidence regarding the amount and intensity of physical activity necessary to alter these cardiovascular risk factors with the goal of reducing coronary events.

Strength/endurance training versus endurance training in congestive heart failure

PURPOSE

The aim of this study was to compare the effects of endurance training alone (ET) with combined endurance and strength training (CT) on hemodynamic and strength parameters in patients with congestive heart failure (CHF).

METHODS

Twenty male patients with CHF were randomized into one of two training regimens consisting of endurance training or a combination of endurance and resistance training. Group ET had 40-min interval cycle ergometer endurance training three times per week. Group CT combined endurance and strength training with the same interval endurance training for 20 min, followed by 20 min of strength training. Left ventricular function was assessed at baseline and after 40 training sessions by echocardiography and radionuclide ventriculography. Work capacity was measured with cardiopulmonary exercise test (CPX) and lactate determination. Strength was measured with an isokinetic dynamometer.

RESULTS

After 40 sessions, the ET group improved functional class, work capacity, peak torque, and muscular endurance. However, peak O2 remained unchanged. Left ventricular ejection fraction (LVEF) and fractional shortening (FS) decreased, whereas left ventricular end-diastolic diameter (LVED) increased. The CT group improved NYHA score, working capacity, peak O2, and peak lactate; peak torque and muscular endurance, LVEF, and FS increased, whereas LVED decreased. Compared with ET, CT was significantly (P < 0.05) better in improving LV function.

CONCLUSION

Combined endurance/strength training was superior to endurance training alone concerning improvement of LV function, peak VO2, and strength parameters. It appears that for stable CHF patients, a greater benefit can be derived from this training modality.

Increased myocardial ischemia after food is not explained by endothelial dysfunction

BACKGROUND

Recent studies suggest that a high-fat meal can impair endothelial function. The aim of this study was to determine whether greater myocardial ischemia after either a low-fat or a high-fat meal is associated with an increase in brachial artery endothelial dysfunction.

METHODS

Twenty subjects with coronary artery disease and > or =1-mm ST-segment depression during exercise were studied. In a randomized, double-blind, crossover design, ST-segment changes during treadmill exercise and brachial artery diameter and flow-mediated dilation were measured before and 3 hours after a low-fat milkshake meal or the same meal supplemented with 64 grams of cooked fat.

RESULTS

After the low-fat but not the high-fat meal, resting brachial artery diameter decreased (before meal 4.72 +/-0.50 mm, after low fat meal 4.62 +/-0.49 mm, P =.001; after high fat meal 4.70 +/-0.51 mm, not significant). High-flow brachial artery diameter was similar before (4.81 +/- 0.48 mm) and after the low-fat (4.82 +/- 0.48 mm) and high-fat (4.84 +/- 0.48 mm) meals (P >.05 for all). Brachial artery flow-mediated dilation was not impaired after either meal. Exercise duration decreased more after the low-fat meal (mean change 39 seconds, 95% CI -14 to -63 seconds, P =.004) than after the high-fat meal (-7 seconds, 95% CI +19 to -34 seconds, not significant). ST-segment depression during equivalent exercise was greater after compared with before both meals (before meals 1.03 +/- 0.69 mm, after low fat 1.27 +/- 0.80 mm, P =.03; after high fat 1.24 +/- 0.74 mm, P =.04).

CONCLUSIONS

Increased myocardial ischemia after food is caused by mechanisms other than endothelial dysfunction and by meal components other than cooked fat.

Cardiorespiratory fitness and physical activity as risk predictors of future atherosclerotic cardiovascular diseases

Physical fitness and activity status are well-documented risk predictors of cardiovascular and total mortality. The purpose of this article is to show how cardiorespiratory fitness predicts atherosclerotic cardiovascular diseases. Measurement of maximum oxygen consumption (VO(2max)), defined with or without ventilatory gas analysis during exercise testing, can provide a good estimate for cardiorespiratory fitness, which is an independent marker of the early disease. Low VO(2max) has been shown to be comparable with elevated systolic blood pressure, smoking, obesity, and diabetes in importance as a risk factor for mortality, as well as a predictor of coronary artery disease and the progression of atherosclerosis. Cardiorespiratory fitness represents one of the strongest predictors of mortality, emphasizing the importance of exercise testing in everyday clinical practice. In the future, well-defined, disease-specific training programs for exercise prescriptions in different risk groups are needed as a clinical tool.

A hypothesis out-of-date. the diet-heart idea

An almost endless number of observations and experiments have effectively falsified the hypothesis that dietary cholesterol and fats, and a high cholesterol level play a role in the causation of atherosclerosis and cardiovascular disease. The hypothesis is maintained because allegedly supportive, but insignificant findings, are inflated, and because most contradictory results are misinterpreted, misquoted or ignored.

Exercise training improves vascular endothelial function in patients with type 1 diabetes

OBJECTIVE-Impaired endothelial function of resistance and conduit arteries can be detected in patients with type 1 diabetes. We studied whether a persistent improvement of endothelial function can be achieved by regular physical training. RESEARCH DESIGN AND METHODS-The study included 26 patients with type 1 diabetes of 20 +/- 10 years' duration and no overt angiopathy; 18 patients (42 +/- 10 years old) participated in a bicycle exercise training program, and 8 patients with type 1 diabetes (33 +/- 11 years old) served as control subjects. Vascular function of conduit arteries was assessed by flow-mediated and endothelium-independent dilation of the brachial artery and of resistance vessels by the response of ocular fundus pulsation amplitudes to intravenous N(G)-monomethyl-L-arginine (L-NMMA) at baseline, after 2 and 4 months of training, and 8 months after cessation of regular exercise. RESULTS-Training increased peak oxygen uptake (VO(2max)) by 13% after 2 months and by 27% after 4 months (P = 0.04). Flow-mediated dilation (FMD) of the brachial artery increased from 6.5 +/- 1.1 to 9.8 +/- 1.1% (P = 0.04) by training. L-NMMA administration decreased fundus pulsation amplitude (FPA) by 9.1 +/- 0.9% before training and by 13.4 +/- 1.5% after 4 months of training (P = 0.02). VO(2max), FMD, and FPA were unchanged in the control group. Vascular effects from training were abrogated 8 months after cessation of exercise. CONCLUSIONS-Our study demonstrates that aerobic exercise training can improve endothelial function in different vascular beds in patients with long-standing type 1 diabetes, who are at considerable risk for diabetic angiopathy. However, the beneficial effect on vascular function is not maintained in the absence of exercise.

Exercise and gene expression: physiological regulation of the human genome through physical activity

The current human genome was moulded and refined through generations of time. We propose that the basic framework for physiologic gene regulation was selected during an era of obligatory physical activity, as the survival of our Late Palaeolithic (50 000-10 000 BC) ancestors depended on hunting and gathering. A sedentary lifestyle in such an environment probably meant elimination of that individual organism. The phenotype of the present day Homo sapiens genome is much different from that of our ancient ancestors, primarily as a consequence of expressing evolutionarily programmed Late Palaeolithic genes in an environment that is predominantly sedentary. In this sense, our current genome is maladapted, resulting in abnormal gene expression, which in turn frequently manifests itself as clinically overt disease. We speculate that some of these genes still play a role in survival by causing premature death from chronic diseases produced by physical inactivity. We also contend that the current scientific evidence supports the notion that disruptions in cellular homeostasis are diminished in magnitude in physically active individuals compared with sedentary individuals due to the natural selection of gene expression that supports the physically active lifestyle displayed by our ancestors. We speculate that genes evolved with the expectation of requiring a certain threshold of physical activity for normal physiologic gene expression, and thus habitual exercise in sedentary cultures restores perturbed homeostatic mechanisms towards the normal physiological range of the Palaeolithic Homo sapiens. This hypothesis allows us to ask the question of whether normal physiological values change as a result of becoming sedentary. In summary, in sedentary cultures, daily physical activity normalizes gene expression towards patterns established to maintain the survival in the Late Palaeolithic era.

Toward a better understanding of the influences on physical activity: the role of determinants, correlates, causal variables, mediators, moderators, and confounders

BACKGROUND

For research on physical activity interventions to progress systematically, the mechanisms of action must be studied. In doing so, the research methods and their associated concepts and terminology become more complex. It is particularly important to clearly distinguish among determinants, correlates, mediators, moderators, and confounder variables used in physical activity research. This article examines the factors that are correlated with and that may have a causal relationship to physical activity.

METHODS AND RESULTS

We propose that the term "correlate" be used, instead of "determinant," to describe statistical associations or correlations between measured variables and physical activity. Studies of the correlates of physical activity are reviewed. The findings of these studies can help to critique existing theories of health behavior change and can provide hypotheses to be tested in intervention studies from which it is possible to draw causal inferences. Mediator, moderator, and confounder variables can act to influence measured changes in physical activity. Intervening causal variables that are necessary to complete a cause-effect pathway between an intervention and physical activity are termed "mediators." The relationship between an intervention and physical activity behaviors may vary for different groups; the strata by which they vary are levels of "moderators" of the relationship. Other factors may distort or affect the observed relationships between program exposure and physical activity, and are known as "confounders."

CONCLUSIONS

Consistent use of terms and additional research on mediators and moderators of intervention effects will improve our ability to understand and influence physical activity.

Effect of exercise on upper and lower extremity endothelial function in patients with coronary artery disease

Aerobic exercise training improves endothelial vasomotor function in the coronary circulation of patients with coronary artery disease (CAD), an effect that has been attributed to local repetitive increases in shear stress on the endothelium. To study the effects of exercise on endothelial function in the peripheral circulation, we used vascular ultrasound to examine flow-mediated dilation and nitroglycerin-mediated dilation in the brachial and posterior tibial arteries of 58 subjects with CAD. Studies were performed at baseline and after 10 weeks in 40 subjects (aged 59 +/- 10 years) who participated in a supervised cardiac rehabilitation program that predominantly involved moderate intensity leg exercise (three 30-minute sessions/week), and 18 matched patients who did not exercise and maintained a sedentary lifestyle. Exercise was associated with a 29% increase in functional capacity (7.3 +/- 2.2 vs 9.4 +/- 2.7 METs, p <0.001), and significant improvement in endothelium-dependent, flow-mediated dilation in a conduit artery of the leg, but not the arm. Nitroglycerin-mediated dilation in the upper arm and lower extremity was unaffected. These findings suggest that exercise improves endothelial function in peripheral conduit arteries of patients with CAD and that the beneficial effect may be more marked in the vascular beds of the exercised limbs.

Waging war on physical inactivity: using modern molecular ammunition against an ancient enemy

A hypothesis is presented based on a coalescence of anthropological estimations of Homo sapiens' phenotypes in the Late Paleolithic era 10,000 years ago, with Darwinian natural selection synergized with Neel's idea of the so-called thrifty gene. It is proposed that humans inherited genes that were evolved to support a physically active lifestyle. It is further postulated that physical inactivity in sedentary societies directly contributes to multiple chronic health disorders. Therefore, it is imperative to identify the underlying genetic and cellular/biochemical bases of why sedentary living produces chronic health conditions. This will allow society to improve its ability to effect beneficial lifestyle changes and hence improve the overall quality of living. To win the war against physical inactivity and the myriad of chronic health conditions produced because of physical inactivity, a multifactorial approach is needed, which includes successful preventive medicine, drug development, optimal target selection, and efficacious clinical therapy. All of these approaches require a thorough understanding of fundamental biology and how the dysregulated molecular circuitry caused by physical inactivity produces clinically overt disease. The purpose of this review is to summarize the vast armamentarium at our disposal in the form of the extensive scientific basis underlying how physical inactivity affects at least 20 of the most deadly chronic disorders. We hope that this information will provide readers with a starting point for developing additional strategies of their own in the ongoing war against inactivity-induced chronic health conditions.

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.

Obesity, atherosclerosis and the vascular endothelium: mechanisms of reduced nitric oxide bioavailability in obese humans

It is now well established that obesity is an independent risk factor for the development of coronary artery atherosclerosis. The maintenance of vascular homeostasis is critically dependent on the continued integrity of vascular endothelial cell function. A key early event in the development of atherosclerosis is thought to be endothelial cell dysfunction. A primary feature of endothelial cell dysfunction is the reduced bioavailability of the signalling molecule nitric oxide (NO), which has important anti atherogenic properties. Recent studies have produced persuasive evidence showing the presence of endothelial dysfunction in obese humans NO bioavailability is dependent on the balance between its production by a family of enzymes, the nitric oxide synthases, and its reaction with reactive oxygen species. The endothelial isoform (eNOS) is responsible for a significant amount of the NO produced in the vascular wall. NO production can be modulated in both physiological and pathophysiological settings, by regulation of the activity of eNOS at a transcriptional and post-transcriptional level, by substrate and co-factor provision and through calcium dependent and independent signalling pathways. The present review discusses general mechanisms of reduced NO bioavailability including factors determining production of both NO and reactive oxygen species. We then focus on the potential factors responsible for endothelial dysfunction in obesity and possible therapeutic interventions targetted at these abnormalities.

Effect of endurance training on coronary artery size and function in healthy men: an invasive followup study

In eight healthy male volunteers (cardiologists; age 36 +/- 5 yr), bicycle spiroergometry, Doppler echocardiography, and quantitative coronary angiography with intracoronary Doppler measurements before and after completion of a physical endurance exercise program of >5 mo duration were performed. Maximum oxygen uptake increased from 46 +/- 6 to 54 +/- 5 ml x kg(-1) x min(-1) (P = 0.04), maximum ergometric workload changed from 3.8 +/- 0.3 to 4.4 +/- 0.3 W/kg (P = 0.001), and left ventricular mass index increased from 82 +/- 18 to 108 +/- 29 g/m(2) (P = 0.001). The right, left main, and left anterior descending coronary artery cross-sectional area increased significantly in response to exercise. Before versus at the end of the exercise program, flow-induced left anterior descending coronary artery cross-sectional area was 10.1 +/- 3.5 and 11.0 +/- 3.9 mm(2), respectively (P = 0.03), nitroglycerin-induced left coronary calibers increased significantly, and coronary flow velocity reserve changed from 3.8 +/- 0.8 to 4.5 +/- 0.7 (P = 0.001). Left coronary artery correlated significantly with ventricular mass and maximum oxygen uptake, and coronary flow velocity reserve was significantly associated with maximum workload.

Myocardial perfusion and perfusion reserve in endurance-trained men

PURPOSE

This study was undertaken to determine whether endurance training is associated with changes in myocardial perfusion in humans.

METHODS

Myocardial perfusion was measured in eleven trained and nine sedentary men at rest and during adenosine-stimulated hyperemia using positron emission tomography (PET). Left ventricular (LV) dimensions and mass were measured using echocardiography. Myocardial work per gram of tissue was calculated as (cardiac output. mean arterial blood pressure)/LV mass.

RESULTS

LV mass was significantly higher and myocardial work per gram of tissue lower in the trained than in the untrained subjects. Basal (0.78 +/- 0.10 and 0.76 +/- 0.15 mL. min-1. g-1, P = NS) and adenosine-stimulated perfusion (3.46 +/- 0.91 and 3.14 +/- 0.70 mL. min-1. g-1, P = NS) were similar between trained and untrained men, respectively. Consequently, myocardial perfusion reserve was similar in both groups (4.4 +/- 1.2 and 4.1 +/- 0.7, P = NS). In addition, coronary resistance at baseline (115 +/- 17 vs 119 +/- 22, mm Hg. mL. min-1. g-1, P = NS) and during adenosine infusion (28 +/- 8 vs 30 +/- 8, mm Hg. mL. min-1. g-1, P = NS) were similar in both groups. Resting myocardial work correlated with resting myocardial perfusion in both groups, but the relationship between perfusion and work was different between the groups so that perfusion for a given myocardial work was significantly higher in trained subjects (0.56 +/- 0.04 and 0.34 +/- 0.05 mL. (mm Hg. L)-1, P < 0.001).

CONCLUSIONS

These findings suggest that endurance trained subjects do not have different resting or adenosine-stimulated myocardial perfusion. However, the relationship between myocardial perfusion and work appears altered in the athletes.

Regular physical exercise improves endothelial function in heart transplant recipients

BACKGROUND

Impaired endothelial function is detectable in heart transplant (HTX) recipients and regarded as risk factor for coronary artery disease. We have studied whether endothelial function can be improved in HTX patients participating in a regular physical training program as demonstrated in patients with chronic heart failure, hypertension and coronary artery disease.

METHODS

Male HTX patients and healthy, age-matched controls were studied. Seven HTX patients (age: 60 +/- 6 yr; 6 +/- 2 yr of HTX) participated in an outpatient training program, six HTX patients (age: 63 +/- 8 yr; 7 +/- 1 yr of HTX) maintained a sedentary lifestyle without regular physical exercise since transplantation. A healthy control group comprised six subjects (age: 62 +/- 6 yr). Vascular function was assessed by flow-mediated dilation of the brachial artery (FMD). Systemic haemodynamic responses to intravenous infusion of the endothelium independent vasodilator sodium nitroprusside (SNP) and to NG-monomethyl-L-arginine (L-NMMA), an inhibitor of constitutive nitric oxide synthase, were also measured.

RESULTS

Resting heart rate was significantly lower (p < 0.05) in healthy controls (66 +/- 13) than in the HTX training group (83 +/- 11) and in non-training HTX patients (91 +/- 9), baseline blood pressure also tended to be lower in healthy subjects and in the training HTX patients. FMD was significantly higher (p < 0.05) in the control group (8.4 +/- 2.2%) and in the training group (7.1 +/- 2.4%), compared with non-training HTX patients (1.4 +/- 0.8%). The response of systolic blood pressure (p = 0.08) and heart rate (p < 0.05) to L-NMMA was reduced in sedentary HTX patients compared with healthy controls and heart rate response to SNP was also impaired in sedentary HTX patients.

DISCUSSION

Regular aerobic physical training restores vascular function in HTX patients, who are at considerable risk for developing vascular complications. This effect is demonstrable in conduit and systemic resistance arteries.

Isoflurane does not further impair microvascular vasomotion in a rat model of subarachnoid hemorrhage

PURPOSE

Since isoflurane is known to attenuate endothelium-dependent dilation (EDD) in normal cerebral arterioles, we examined whether the anesthetic has a similar effect and further impairs EDD in vessels exposed to SAH.

METHODS

Autologous blood was introduced in the subarachnoid space and the parietal lobe harvested. Control animals were sacrificed without introduction of blood. The response of microvessles to the endothelium-dependent dilator adenosine diphosphate (ADP) 10(-9)-10(-4) M, the endothelium-independent dilator nitroprusside 10(-9)-10(-4) M, and ET-1 10(-13)-10(-8) M was measured by videomicroscopy in the presence of 0-2 minimum alveolar concentration (MAC) of isoflurane.

RESULTS

Isoflurane attenuated EDD to ADP in control vessels [66 +/- 5% (control) vs 27 +/- 11% (2 MAC) dilation to ADP 10(-4) M, P < 0.05]. Although SAH was associated with reduced dilation to ADP, exposure to isoflurane did not further impair dilation to ADP after SAH [26 +/- 3% (SAH) vs 21 +/- 5% (SAH/2 MAC) dilation to ADP 10(-4) M, P = NS]. Dilation to nitroprusside was not affected by isoflurane or SAH. Constriction to ET-1 was reduced by 2 MAC of isoflurane [21 +/- 1% (control) vs 13 +/- 5% (2 MAC) constriction to ET-1 10(-8) M, P < 0.05], but not by 1 MAC of isoflurane in control vessels. Constriction to ET-1 was greatly attenuated by 1 or 2 MAC of isoflurane after SAH [32 +/- 5% (SAH) vs 18 +/- 4% (SAH/2 MAC) constriction to ET-1 10(-8) M, P < 0.05].

CONCLUSION

In rats, isoflurane does not further impair EDD after SAH and modulates the constrictive response to ET-1. Such an effect of isoflurane would not predispose the SAH-exposed vessels to vasospasm.

Retained fibrinolytic response and no coagulation activation after acute physical exercise in middle-aged women with previous myocardial infarction

Sudden physical exertion is associated with an increased risk of acute myocardial infarction (MI) and sudden cardiac death. In addition, activation of the coagulation cascade and/or reduced fibrinolytic capacity after physical exercise has been reported in patients with cardiovascular disease. We investigated the haemostatic responses to an acute submaximal physical exercise in middle-aged women with a history of MI compared with healthy, age-matched controls. Resting plasma von Willebrand factor antigen (vWF Ag) and tissue plasminogen activator (tPA) antigen concentrations and plasminogen activator inhibitor-1 (PAI-1) activity were higher in the patients compared with control subjects. After 30 min of submaximal exercise on a bicycle ergometer, small, but still significant, increases in fibrinogen and vWF Ag concentrations were found in both groups. However, exercise did not induce thrombin generation and fibrin formation, as assessed by thrombin-antithrombin complex and fibrin D-dimer, in either group. Both tPA antigen concentration and activity increased and PAI-1 activity decreased significantly with exercise in both groups. Interestingly, the magnitude of changes in these latter variables did not differ between the groups (P=.99, P=.88 and P=.24, respectively). The present study demonstrates that some middle-aged women with previous MI have no signs of coagulation activation and retained fibrinolytic response after submaximal exercise. The clinical implication of these results might be that women with stable coronary heart disease can participate in rehabilitative exercise training without exhibiting a procoagulative state.

An obligation for primary care physicians to prescribe physical activity to sedentary patients to reduce the risk of chronic health conditions

Physical inactivity increases the risk of many chronic disorders. Numerous studies have convincingly demonstrated that undertaking and maintaining moderate levels of physical activity (eg, brisk walking 3 hours a week) greatly reduces the incidence of developing many chronic health conditions, most notably type 2 diabetes mellitus, obesity, cardiovascular disease, and many types of cancers. However, the underlying mechanistic details of how physical activity confers such protective effects are not well understood and consequently constitute an active area of research. Although changing an individual's ingrained behavior is commonly perceived to be difficult, encouraging evidence suggests that intensive and repeated counseling by health care professionals can cause patients to become more physically active. Therefore, counseling patients to undertake physical activity to prevent chronic health conditions becomes a primary prevention modality. This article summarizes the vast epidemiologic and biochemical evidence supporting the many beneficial health implications of undertaking moderate physical activity and provides a rationale for incorporating physical activity counseling as part of routine practice in the primary care setting.

Physical activity and the presence and extent of calcified coronary atherosclerosis

PURPOSE

Regular physical activity leads to a more favorable cardiovascular risk factor profile and a lower risk of developing incident coronary heart disease (CHD). These correlations suggest that higher levels of physical activity should also attenuate the presence and extent of coronary atherosclerosis.

METHODS

Physical activity was measured using the Baecke Physical Activity Index in 630 consecutive asymptomatic men and women ages 39-45 without known heart disease. The degree of physical activity was compared with the cardiovascular risk factor profile and the presence and extent of subclinical atherosclerosis measured using electron beam computed tomography.

RESULTS

Sports-related physical activity was associated with lower body mass index (r = -0.11; P = 0.001), higher high-density lipoprotein (HDL) cholesterol (r = 0.13; P = 0.003) and less glucose resistance as assessed by fasting serum insulin levels (r = -0.16; P = 0.001). Leisure-time and work-related physical activity were unrelated to any coronary risk variables. Calcified subclinical atherosclerosis was unrelated to all physical activity dimensions. Comparing the most sedentary (lowest quartile) and most active (highest quartile) patients, the prevalence of coronary calcium (17.0% vs 18.5%; P = 0.92) and mean coronary calcium scores (8 +/- 31 vs 5 +/- 15; P = 0.87) were similar. In a multivariate model controlling for standard cardiovascular risk factors and physical activity level, only low-density lipoprotein (LDL) cholesterol was associated with the presence of coronary calcium.

CONCLUSION

Physical activity, particularly high-intensity exercise in sports-related activities, promotes a healthy cardiovascular risk profile, including lower body mass index and insulin resistance, but is unrelated to coronary calcification. This suggests that the risk reduction associated with physical activity is mediated by factors other than retarding the development of calcified atherosclerosis.

Exercise and heart disease

Atherosclerotic coronary artery disease (CAD) is a leading cause of death in the United States. It accounts for myocardial infarction in approximately 1.5 million Americans annually and results in approximately 500,000 deaths yearly. Half of these deaths occur prior to patients being admitted to a hospital. A dramatic reduction in mortality related to atherosclerotic CAD has occurred in the last decade. This reduction has resulted from significant advances in both the medical and surgical management of this disease as well as from increased efforts to modify risk factors known to increase the likelihood of developing CAD. Modifiable risk factors include cigarette smoking, hypercholesterolemia, and hypertension. More recently, physical inactivity has been found to be a significant modifiable risk factor that can influence the development of CAD. This article reviews some of the observational data that support these conclusions, discusses the role of exercise in the prevention of CAD in select groups, and reviews some of the mechanisms by which exercise may modify the development of CAD.

Physical fitness and changes in mortality: the survival of the fittest

Physical fitness is a term describing maximal aerobic capacity adjusted for body size and composition, and is an integrated measure of cardiorespiratory and neuromusculo-skeletal function, oxygen transport and delivery, and psychological drive. Accordingly, high physical fitness requires that all these important body functions function normally, while low physical fitness suggests malfunction of one or more of them. High levels of physical fitness--maintained through heavy daily exercise--has probably been a necessary requirement for survival in the earlier history of humans. In modern, industrialised countries the demand for physical activity to sustain life is declining, and a decline in physical fitness is observed in many populations. Epidemiological studies over the past 50 years have unanimously shown that low physical activity and physical fitness is associated with high cardiovascular and total mortality. Recent data also suggest that low physical activity and physical fitness is followed by an increased incidence of diabetes mellitus and nonfatal cardiovascular diseases. A number of unfavourable biochemical and physiological aberrations following physical inactivity probably explain these observations. However, recent studies also indicate that changes in physical activity, and especially changes that bring increases in physical fitness, can reverse this rather pessimistic scenario. The Global Burden of Disease Study initiated by the World Health Organization included physical inactivity among the most important risk factors threatening global health. A sedentary life style may be as detrimental to health as smoking. Encouragement of physical activity is an important and difficult task, as society is becoming increasingly successful in reducing our need to move.

Exercise training improves diastolic perfusion time in patients with coronary artery disease

Exercise training elicits an improvement in work capacity and in left-ventricular function in patients with coronary artery disease. An improvement in myocardial oxygen supply accounts for these effects. The aim of this study was to test the hypothesis that exercise training could favorably influence diastolic perfusion time, a major determinant of subendocardial perfusion. Twenty-two male patients with coronary artery disease were randomized to a training or control group. At the study entry and after one year, all patients underwent an exercise stress test. After one year, rest heart rate was lower and diastolic perfusion time was higher in the training group but not in the control group. At peak of exercise, diastolic perfusion time increased and ST-segment depression decreased significantly in the training group but not in the control group. A significant relation was found between the R-R interval and the diastolic perfusion time either before or after training, with a difference in the intercepts of two regressions. Training shifted updown-line regression, effecting a higher value of diastolic perfusion time for a given value of heart rate. Thus, training increases diastolic perfusion time, independently from the effect on heart rate. This mechanism may contribute to the improvement of myocardial perfusion.

Association between self-reported physical activity and vascular reactivity in postmenopausal women

Short-term exercise training has been associated with improved endothelial-dependent vasodilation, but the impact of long-term habitual physical activity on vascular reactivity is not established. We studied the correlation between self-reported, habitual physical activity and vasoreactivity in non-smoking, non-diabetic, postmenopausal women (n=34, mean age 65.6+/-7.4 years). Vasoreactivity was evaluated by the percentage and absolute change in brachial artery diameter in response to reactive hyperemia induced by occlusion-release, and in response to cold pressor testing (CPT). Habitual physical activity was assessed by a standardized questionnaire based on participant recall. Our results indicate that 64.7% of the women were exercising-to-sweat > or =1x/week, 4.8 flights of stairs were climbed/day, 5.0 city blocks were walked/day and 29.4% participated in moderately physically demanding daily activity. There was a significant association between the number of city blocks walked daily and exercising-to-sweat > or =1x/week with brachial artery percentage and absolute change to CPT (P<0.05). Women who reported a moderately physically demanding daily activity had a significantly greater brachial reactivity percentage change in response to CPT compared with those performing less demanding daily activity (2.0+/-3.6 versus 1.4+/-7.0%, P<0.05). The response to reactive hyperemia was also greater in those women reporting moderately physically demanding daily activity compared to less active women (6.5+/-5.4 versus 5.8+/-5.9%, P=n.s.), but this did not reach statistical significance. Stepwise, multivariate analysis adjusting for body mass index and HDL-cholesterol eliminated the association between physical activity and brachial reactivity in response to CPT, suggesting that physical activity may affect vasoreactivity via these mechanisms. This study suggests that moderate levels of self-reported physical activity are associated with a greater brachial reactivity in response to CPT and supports the recommendation that moderate intensity physical activity may be cardioprotective in postmenopausal women.

Exercise training, vascular function, and functional capacity in middle-aged subjects

PURPOSE

The aim of this study was to investigate the effect of 8 wk of exercise training on functional capacity, muscular strength, body composition, and vascular function in sedentary but healthy subjects by using a randomized, crossover protocol.

METHODS

After familiarization sessions, 19 subjects aged 47 +/- 2 yr (mean +/- SE) undertook a randomized, crossover design study of the effect of 8 wk of supervised circuit training consisting of combined aerobic and resistance exercise. Peak oxygen uptake (.VO(2peak)), sum of 7 maximal voluntary contractions and the sum of 8 skinfolds and 5 segment girths were determined at entry, crossover, and 16 wk. Endothelium-dependent and -independent vascular function were determined by forearm strain-gauge plethysmography and intrabrachial infusions of acetylcholine (ACh) and sodium nitroprusside (SNP) in 16 subjects.

RESULTS

Training did not alter ACh or SNP responses. .VO(2peak), (28.6 +/- 1.1 to 32.6 +/- 1.3 mL.kg(-1).min(-1), P < 0.001), exercise test duration (17.4 +/- 1.1 to 22.1 +/- 1.2 min, P < 0.001), and muscular strength (465 +/- 27 to 535 +/- 27 kg, P < 0.001) significantly increased after the exercise program, whereas skinfolds decreased (144 +/- 10 vs 134 +/- 9 mm, P < 0.001).

CONCLUSION

These results suggest that moderate intensity circuit training designed to minimize the involvement of the arms improves functional capacity, body composition, and strength in healthy, middle-aged subjects without significantly influencing upper limb vascular function. This finding contrasts with previous studies in subjects with type 2 diabetes and heart failure that employed an identical training program.

Endothelial dysfunction, oxidative stress, and risk of cardiovascular events in patients with coronary artery disease

BACKGROUND

Endothelial function is impaired in coronary artery disease and may contribute to its clinical manifestations. Increased oxidative stress has been linked to impaired endothelial function in atherosclerosis and may play a role in the pathogenesis of cardiovascular events. This study was designed to determine whether endothelial dysfunction and vascular oxidative stress have prognostic impact on cardiovascular event rates in patients with coronary artery disease.

METHODS AND RESULTS

Endothelium-dependent and -independent vasodilation was determined in 281 patients with documented coronary artery disease by measuring forearm blood flow responses to acetylcholine and sodium nitroprusside using venous occlusion plethysmography. The effect of the coadministration of vitamin C (24 mg/min) was assessed in a subgroup of 179 patients. Cardiovascular events, including death from cardiovascular causes, myocardial infarction, ischemic stroke, coronary angioplasty, and coronary or peripheral bypass operation, were studied during a mean follow-up period of 4.5 years. Patients experiencing cardiovascular events (n=91) had lower vasodilator responses to acetylcholine (P<0.001) and sodium nitroprusside (P<0.05), but greater benefit from vitamin C (P<0.01). The Cox proportional regression analysis for conventional risk factors demonstrated that blunted acetylcholine-induced vasodilation (P=0.001), the effect of vitamin C (P=0.001), and age (P=0.016) remained independent predictors of cardiovascular events.

CONCLUSIONS

Endothelial dysfunction and increased vascular oxidative stress predict the risk of cardiovascular events in patients with coronary artery disease. These data support the concept that oxidative stress may contribute not only to endothelial dysfunction but also to coronary artery disease activity.

High level of physical activity preserves the cardioprotective effect of preinfarction angina in elderly patients

OBJECTIVES

The study investigated the effects of physical activity on preinfarction angina, a clinical equivalent of ischemic preconditioning (PC), in adult and elderly patients with acute myocardial infarction (AMI).

BACKGROUND

Preinfarction angina seems to confer protection against in-hospital mortality in adult but not in elderly patients. However, it has been experimentally demonstrated that exercise training restores the protective effect of PC in the aging heart.

METHODS

We retrospectively verified whether physical activity preserved the protective effect of preinfarction angina against in-hospital mortality in 557 elderly patients with AMI. Physical activity was quantified according to the Physical Activity Scale for the Elderly (PASE).

RESULTS

In-hospital mortality was 22.2% in elderly patients with preinfarction angina and 27.2% in those without (p = 0.20). When the PASE score was stratified in quartiles (0 to 40, 41 to 56, 57 to 90, >90), a high score was strongly associated with reduced in-hospital mortality (30.8%, 32.2%, 17.2% and 15.3%, respectively, p < 0.001 for trend). Interestingly, a high level of physical activity reduced in-hospital mortality in elderly patients with preinfarction angina (35.7%, 35.4%, 12.3% and 4.23%, respectively, p < 0.001 for trend) but not in those without (23.0%, 27.2%, 26.0% and 35.0%, respectively, p = 0.35 for trend). Accordingly, the protective role of preinfarction angina on in-hospital mortality was present only in elderly patients showing a high level of physical activity (adjusted odds ratio, 0.09; 95% confidence interval, 0.01 to 0.57; p < 0.05).

CONCLUSIONS

Physical activity and not preinfarction angina protects against in-hospital mortality in elderly patients with myocardial infarction. Nevertheless, the protective effect of preinfarction angina is preserved in elderly patients with a high level of physical activity.

Why vascular biology matters

Cardiovascular disease has been the leading cause of death for men and women in this country since 1921 and is currently the leading cause of death in the world. Adding to the sense of urgency about disease prevention is the recent finding that the initial lesions of atherosclerotic vascular disease may begin within the first year of life-or even earlier, during fetal growth. However, the pathobiology of atherosclerosis (and in particular, the key role of low-density lipoprotein cholesterol) is now well understood. Activation of 3 major oxidative systems as well as the renin-angiotensin system-all located in the vascular wall-is an early step. In fact, the effects of statins and angiotensin-converting enzyme inhibitors on the vascular wall (improved endothelial function, inhibition of platelet aggregation, and plaque stabilization) are an important mechanism of benefit, independent of their systemic effects. Several very positive trials with these agents have been completed. However, if this information is not incorporated into clinical practice in a timely manner, cardiovascular disease will continue to present a major cause of morbidity and mortality worldwide.

Exercise update 2001

Recent studies addressing the role of exercise in the detection, prevention, and treatment of coronary heart disease have significantly expanded our knowledge base in this area. This therapeutic review is focused on physiologic parameters in exercise, electrocardiogram testing, and the preventive impact of low-intensity regular exercise and the role of exercise training in selected patient populations.