Physical training improves endothelial function in patients with chronic heart failure

Effects of exercise training on vascular function and myocardial perfusion

It has long been unclear how exercise training improves myocardial perfusion in patients with stable CAD. Regression of coronary atherosclerosis and collateral formation have been favorite theories; however, angiographic techniques have so far failed to document any significant increase in coronary collaterals at rest. Although net regression of stenotic lesions may be achieved in high-intensity exercise training, it is unlikely that it causes the significant improvement in myocardial perfusion that is seen much earlier than plaque regression. The novel tools to examine coronary endothelial function in vivo and in vitro have now made it clear that exercise training enhances myocardial perfusion by increasing both eNOS and ecSOD expression, which attenuates the premature breakdown of NO by ROS. These increases in local NO production and half-life improve endothelium-dependent vasodilation in response to flow or acetylcholine. These functional changes will occur rather rapidly after the initiation of an exercise training program, although no studies are available on their precise time course. Anatomic changes, such as augmentation of the capillary bed and slowing of the progression of coronary atherosclerosis, may require more extended periods of training (Fig. 4). Recently, first reports about a possible association between endothelial dysfunction and the frequency of clinical events has been documented. Further prospective studies are needed to establish whether endothelial dysfunction is just an indicator of plaque instability or an independent prognostic marker. If it turns out to be the latter, exercise training may be promoted from a symptomatic intervention to a preventive strategy with long-term prognostic benefits.

Physical training in patients with chronic heart failure enhances the expression of genes encoding antioxidative enzymes

OBJECTIVES

We sought to determine whether the benefit of training for vasodilation in the skeletal muscle vasculature of patients with chronic heart failure (CHF) is likely to be caused at the molecular level primarily by increased nitric oxide (NO) production or decreased inactivation of NO.

BACKGROUND

Physical training reverses endothelium dysfunction in patients with CHF, mediated by increased NO bioactivity. Some animal studies support a mechanism whereby training results in increased vascular NO levels by sustained transcriptional activation of the endothelial NO synthase (eNOS) gene, presumably due to shear stress. The mechanism has not been addressed in patients with CHF.

METHODS

The steady state transcript levels for eNOS and two other shear stress regulated genes (angiotensin-converting enzyme [ACE] and prostacyclin synthase [PGI2S]) were measured in samples of skeletal muscle from patients with CHF before and after 12 weeks of training. Transcript levels were measured in the same samples for two genes encoding antioxidant enzymes, copper zinc superoxide dismutase (Cu/Zn SOD) and glutathione peroxidase (GSH-Px). Untrained patients served as controls.

RESULTS

As expected, training significantly enhanced peak oxygen uptake in the patients with CHF. Training did not increase steady-state transcript levels for eNOS, ACE or PGI2S. In striking contrast, training increased the expression of the antioxidative enzyme genes by approximately 100%.

CONCLUSIONS

Our results do not support a model of benefit from training by increased eNOS expression. However, the data are entirely consistent with the alternative hypothesis, that reduced oxidative stress may account for the increase in vascular NO-mediated vasodilation. Insight into the mechanism may be relevant when considering therapies for exercise-intolerant patients with CHF.

Uric acid in cachectic and noncachectic patients with chronic heart failure: relationship to leg vascular resistance

BACKGROUND

Chronic heart failure (CHF) is a hyperuricemic state, and capillary endothelium is the predominant site of xanthine oxidase in the vasculature. Upregulated xanthine oxidase activity (through production of toxic free radicals) may contribute to impaired regulation of vascular tone in CHF. We aimed to study the relationship between serum uric acid levels and leg vascular resistance in patients with CHF with and without cachexia and in healthy control subjects.

METHODS

In 23 cachectic and 44 noncachectic patients with CHF (age, 62 +/- 1 years, mean +/- SEM) and 10 healthy control subjects (age, 68 +/- 1 years), we assessed leg resting and postischemic peak vascular resistance (calculated from mean blood pressure and leg blood flow by venous occlusion plethysmography).

RESULTS

Cachectic patients, compared with noncachectic patients and control subjects, had the highest uric acid levels (612 +/- 36 vs 459 +/- 18 and 346 +/- 21 micromol/L, respectively, both P <.0001) and the lowest peak leg blood flow and vascular reactivity (reduction of leg vascular resistance from resting to postischemic conditions: 83% vs 88% and 90%, both P <.005). In all patients, postischemic vascular resistance correlated significantly and independently of age with uric acid (r = 0.61), creatinine (r = 0.47, both P <.0001), peak VO2 (r = 0.34), and New York Heart Association class (r = 0.33, both P <.01). This correlation was not present in healthy control subjects (r = -0.04, P =.9). In multivariate and stepwise regression analyses, serum uric acid emerged as the strongest predictor of peak leg vascular resistance (standardized coefficient = 0.61, P <.0001) independent of age, peak VO2, creatinine, New York Heart Association class, and diuretic dose.

CONCLUSIONS

Hyperuricemia and postischemic leg vascular resistance are highest in cachectic patients with CHF, and both are directly related independent of diuretic dose and kidney function. The xanthine oxidase metabolic pathway may contribute to impaired vasodilator capacity in CHF.

Association between wall shear stress and flow-mediated vasodilation in healthy men

Wall shear stress contributes to the endothelial production of vasoactive mediators, like nitric oxide (NO). Brachial artery vasodilation that follows increased blood flow is regulated by NO release. Aim of the present study was to investigate whether resting wall shear stress of the brachial artery is related to flow-mediated vasodilation (FMD) induced by forearm ischemia. Wall shear stress was calculated according to the following formula: Wall shear stress=Blood viscosity x Blood velocity/Internal diameter. FMD was calculated as percentage change of brachial artery diameter following forearm ischemia. Twenty-seven healthy male subjects were investigated. Peak wall shear stress and FMD were 37.3+/-12.8 dynes/cm(2) and 110.7+/-5.6%, respectively (mean+/-S.D.). In simple regression analyses, age was inversely associated with wall shear stress (r=48, P<0.01) and, marginally, with FMD (r=0.33, P=0.08). Wall shear stress and FMD were directly related (r=0.60, P<0.001). In multiple regression analysis, including wall shear stress, age, blood pressure, lipids, glucose and Body Mass Index as independent variables, wall shear stress was the only variable independently associated with FMD (standardized beta coefficient=0.690, P</=0.005). To avoid the influence of brachial artery size on FMD, the regression analysis was restricted to subjects with similar diameter (n=12). In these subjects wall shear stress continued to be significantly associated with FMD (r=0.69, P=0.01). Our results demonstrate a strong association between resting wall shear stress and FMD in the brachial artery in healthy men in vivo. This association is independent of age and vessel diameter.

Endothelin receptor antagonists in congestive heart failure: a new therapeutic principle for the future?

Congestive heart failure (CHF) is characterized by impaired left ventricular function, increased peripheral and pulmonary vascular resistance and reduced exercise tolerance and dyspnea. Thus, mediators involved in the control of myocardial function and vascular tone may be involved in its pathophysiology. The family of endothelins (ET) consists of four closely related peptides, ET-1, ET-2, ET-3 and ET-4, which cause vasoconstriction, cell proliferation and myocardial effects through activation of ETA receptors. In contrast, endothelial ETB receptors mediate vasodilation via release of nitric oxide and prostacyclin. In addition, ETB receptors in the lung are a major pathway for the clearance of ET-1 from plasma. Thus, infusion of an ETA-receptor antagonist into the brachial artery in healthy humans leads to vasodilation, whereas infusion of an ETB-receptor antagonist causes vasoconstriction. Endothelin-1 plasma levels are elevated in CHF and correlate both with hemodynamic severity and symptoms. Plasma levels of ET-1 and its precursor, big ET-1, are strong independent predictors of death after myocardial infarction as well as in CHF. Endothelin-1 contributes to increased systemic and pulmonary vascular resistance, vascular dysfunction, myocardial ischemia and renal impairment in CHF. Selective ETA, as well as combined ETA/B-receptor antagonists, have been studied in patients with CHF, and their use has shown impressive hemodynamic improvement (i.e., reduced peripheral vascular and pulmonary resistance as well as increased cardiac output). These results indicate that ET-receptor antagonists, indeed, have a potential to improve hemodynamics, symptoms and, potentially, prognosis in patients with CHF, which still carries a high mortality.

Cost-effectiveness analysis of long-term moderate exercise training in chronic heart failure

The purpose of this study is to perform a cost-effectiveness analysis of long-term moderate exercise training (ET) in patients with stable chronic heart failure. In particular, the study focuses on the survival analysis and cost savings from the reduction in the hospitalization rate in the exercise group. In the past 10 years, ET has been shown to be beneficial for patients with stable class II and III heart failure in many randomized clinical trials. However, the cost-effectiveness of a long-term ET program has not been addressed for outcomes related to morbidity/mortality end points or health care utilization. We examined the cost-effectiveness of a 14-month long-term training in patients with stable chronic heart failure. The estimated increment cost for the training group, $3,227/patient, was calculated by subtracting the averted hospitalization cost, $1,336/patient, from the cost of ET and wage lost due to ET, estimated at $4,563/patient. For patients receiving ET, the estimated increment in life expectancy was 1.82 years/person in a time period of 15.5 years, compared with patients in the control group. The cost-effectiveness ratio for long-term ET in patients with stable heart failure was thus determined at $1,773/life-year saved, at a 3% discount rate. Long-term ET in patients with stable chronic heart failure is cost-effective and prolongs survival by an additional 1.82 years at a low cost of $1,773 per/life-year saved.

L-arginine enhances aerobic exercise capacity in association with augmented nitric oxide production

We tested whether supplementation with L-arginine can augment aerobic capacity, particularly in conditions where endothelium-derived nitric oxide (EDNO) activity is reduced. Eight-week-old wild-type (E(+)) and apolipoprotein E-deficient mice (E(-)) were divided into six groups; two groups (LE(+) and LE(-)) were given L-arginine (6% in drinking water), two were given D-arginine (DE(+) and DE(-)), and two control groups (NE(+) and NE(-)) received no arginine supplementation. At 12-16 wk of age, the mice were treadmill tested, and urine was collected after exercise for determination of EDNO production. NE(-) mice demonstrated a reduced aerobic capacity compared with NE(+) controls [maximal oxygen uptake (VO(2 max)) of NE(-) = 110 +/- 2 (SE) vs. NE(+) = 122 +/- 3 ml O(2). min(-1). kg(-1), P < 0.001]. This decline in aerobic capacity was associated with a diminished postexercise urinary nitrate excretion. Mice given L-arginine demonstrated an increase in postexercise urinary nitrate excretion and aerobic capacity in both groups (VO(2 max) of LE(-) = 120 +/- 1 ml O(2). min(-1). kg(-1), P < 0.05 vs. NE(-); VO(2 max) of LE(+) = 133 +/- 4 ml O(2). min(-1). kg(-1), P < 0.01 vs. NE(+)). Mice administered D-arginine demonstrated an intermediate increase in aerobic capacity in both groups. We conclude that administration of L-arginine restores exercise-induced EDNO synthesis and normalizes aerobic capacity in hypercholesterolemic mice. In normal mice, L-arginine enhances exercise-induced EDNO synthesis and aerobic capacity.

Skeletal muscle training in chronic heart failure

Patients with heart failure are limited in their ability to tolerate exercise. Recent research has suggested that this limitation cannot be entirely attributed to cardiac or lung impairment but rather that changes in peripheral muscles may play an important role. There are objective similarities between heart failure and muscular deconditioning. Deficiencies in peripheral blood flow and skeletal muscle function, morphology, metabolism and function are present in both conditions. Moreover, an exaggerated activity of the receptors sensitive to exercise-derived metabolic signals (muscle ergoreceptors and peripheral and central chemoreceptors) leads to early and profound exercise-induced fatigue and dyspnoea. These muscle afferents contribute to the ventilatory, haemodynamic and autonomic responses to exercise both in physiological and pathological conditions, including chronic heart failure. Against this background, a skeletal muscle origin of symptoms in heart failure has been proposed. The protective effects of physical training have been described in many recent studies: training improves ventilatory control, skeletal muscle metabolism and autonomic nervous system activity. The exercise training appears to induce its beneficial effects on skeletal muscle both directly (on muscle function, histological and biochemical features) and indirectly (by reducing the activation of the muscle afferents). The metabolic mediators of these muscle afferents may become a potential target in the future therapy of heart failure symptoms.

Peripheral arterial vascular function at altitude: sea-level natives versus Himalayan high-altitude natives

OBJECTIVES

Regulation of the vascular system may limit physical performance and contribute to adaptation to high altitude. We evaluated vascular function in 10 Himalayan high-altitude natives and 10 recently acclimatized sea-level natives at an altitude of 5,050 m.

METHODS

We registered electrocardiogram, blood flow velocity in the common femoral artery, and blood pressure in the radial artery using non-invasive methods under baseline conditions, and during maximal vasodilation after 2 min leg occlusion. Vascular mechanics were characterized by estimating pulse wave velocity and input impedance.

RESULTS

Pulse wave velocity and parameters of input impedance did not differ between groups under baseline conditions. In the post-ischemic period, the ratio between maximal hyperemic and baseline blood flow velocity was significantly higher in the high-altitude than in the sea-level natives (5.7 +/- 2.5 versus 3.8 +/- 1.2, P < 0.05). The leg vascular resistance decreased in the post-occlusive period without differences between groups. Characteristic impedance decreased in the post-ischemic period by about one third of the baseline level without differences between groups. The post-ischemic decrease of input impedance modulus was more marked in the high-altitude than in the sea-level natives at low frequencies (28 +/- 12 versus 6.4 +/- 20% at 2 Hz, P < 0.01).

CONCLUSIONS

Our results demonstrate a superior ability to increase blood flow velocity as a response to muscular ischemia in high-altitude natives compared to sea-level natives. This phenomenon may be associated with a more effective coupling between blood pressure and blood flow which is probably caused by differences in conduit vessel function.

Effects of exercise rehabilitation on endothelial reactivity in older patients with peripheral arterial disease

Peripheral arterial disease (PAD) is a major cause of morbidity and mortality. Endothelial function, which is a measure of vascular health, is impaired in patients with PAD. We examined the effects of 6 months of aerobic exercise rehabilitation on brachial artery endothelial function, assessed using high-frequency ultrasonography, and calf blood flow in 19 older PAD patients (age 69 +/- 1 years, mean +/- SEM) with intermittent claudication (ankle to brachial artery index of 0.73 +/- 0.04). After exercise, the time to onset of claudication pain increased by 94%, from 271 +/- 49 to 525 +/- 80 seconds (p <0.01), and the time to maximal claudication pain increased by 43%, from 623 +/- 77 to 889 +/- 75 seconds (p <0.05). Exercise rehabilitation increased the flow-mediated brachial arterial diameter by 61%, from 0.18 +/- 0.03 to 0.29 +/- 0.04 mm (p <0.005), as well as the relative change in brachial arterial diameter from the resting state by 60%, from 4.81 +/- 0.82% to 7.97 +/- 1.03% (p <0.005). Maximal calf blood flow (14.2 +/- 1.0 vs 19.2 +/- 2.0 ml/100 ml/min; p = 0.04), and postocclusive reactive hyperemic blood flow (9.8 +/- 0.8 vs 11.3 +/- 0.7 ml/100 ml/min; p = 0.1) increased 35% and 15%, respectively. In conclusion, exercise rehabilitation improved ambulatory function, endothelial-dependent dilation, and calf blood flow in older PAD patients with intermittent claudication.

[Role of rehabilitation in the treatment of chronic heart insufficiency]

Rehabilitation is an important component of the modern comprehensive care plan for patients with chronic heart failure. Cardiac rehabilitation combines exercise training with therapeutical adaptations, behavioral modifications and psychosocial interventions. Based on these data, patients with controlled heart failure should be involved in cardiac rehabilitation programs. Training prescription needs a strict previous cardiac evaluation. Exercise training monitoring must be adjusted to the physical tolerance of each patient. Cardiac rehabilitation has been found to improve functional capacity, reduce symptoms, and finally reduce cardiac morbidity and mortality. These beneficial effects were associated with muscular, endothelial and ventilatory improvements. Reduced sympathetic tone may decrease arrhythmias and may limit the progression of left ventricular dysfunction.

Endothelial dysfunction in patients with chronic heart failure: systemic effects of lower-limb exercise training

OBJECTIVES

We sought to analyze the systemic effects of lower-limb exercise training (ET) on radial artery endothelial function in patients with chronic heart failure (CHF).

BACKGROUND

Local ET has the potential to improve local endothelial dysfunction in patients with CHF. However, it remains unclear whether the systemic effects can be achieved by local ET.

METHODS

Twenty-two male patients with CHF were prospectively randomized to either ET on a bicycle ergometer (ET group, n = 11; left ventricular ejection fraction [LVEF] 26 +/- 3%) or an inactive control group (group C, n = 11; LVEF 24 +/- 2%). At the beginning of the study and after four weeks, endothelium-dependent and -independent vasodilation of the radial artery was determined by intra-arterial infusion of acetylcholine (ACh-7.5, 15 and 30 microg/min) and nitroglycerin (0.2 mg/min). The mean internal diameter (ID) of the radial artery was assessed using a high resolution ultrasound system (NIUS-02, Asulab Research Laboratories, Neuchâtel, Switzerland) with a 10-MHz probe.

RESULTS

After four weeks of ET, patients showed a significant increase in the baseline-corrected mean ID in response to ACh (30 microg/min), from 33 +/- 10 to 127 +/- 25 microm (p < 0.001 vs. control group at four weeks). In the control group, the response to ACh (30 microg/min) remained unchanged. Endothelium-independent vasodilation was similar in both groups at the beginning of the study and at four weeks. In the training group, increases in agonist-mediated, endothelium-dependent vasodilation correlated to changes in functional work capacity (r = 0.63, p < 0.05).

CONCLUSIONS

In patients with stable CHF, bicycle ergometer ET leads to a correction of endothelial dysfunction of the upper extremity, indicating a systemic effect of local ET on endothelial function.

Comparison of ultrasound assessment of flow-mediated dilatation in the radial and brachial artery with upper and forearm cuff positions

In the published literature relating to flow-mediated dilatation (FMD), there are substantial differences between centres in terms of normal FMD amongst healthy subjects. This present study attempts to identify the effect of differing methodologies on FMD. High frequency ultrasound was used to measure blood flow and percentage brachial and radial artery dilatation after reactive hyperaemia induced by forearm or upper arm cuff occlusion in 24 healthy subjects, less than 40 years, without known cardiovascular risk factors. FMD of the brachial artery was significantly higher after upper arm occlusion, compared with forearm occlusion, 6.4 (3.3) and 3.9 (2.6)% (P<0.05), respectively. FMD of the radial artery was significantly higher after forearm occlusion, compared with upper arm occlusion, 10.0 (4.6) and 7.9 (3.5)% (P<0.05), respectively. The percentage blood flow increase in the brachial and radial arteries after forearm and upper arm occlusion were similar. After forearm and upper arm occlusion, the radial artery percentage dilatation was greater than the brachial artery. In conclusion dilatation of the brachial artery, after reactive hyperaemia induced by upper arm occlusion, was significantly more pronounced compared with dilatation of the brachial artery after forearm occlusion, despite a similar percentage blood flow increase. The local ischaemia of the brachial artery with a proximal occlusion may explain why the brachial artery dilated more after upper arm occlusion compared with after forearm occlusion. The study has also shown that FMD of the radial artery could be assessed by B-mode ultrasound technique. FMD was greater using the radial artery compared with the brachial artery, suggesting that the radial artery may be a useful way to assess FMD in future clinical studies.

Effects of physical training of the dominant arm on ipsilateral radial artery distensibility and structure

BACKGROUND

Exercise training induces cardiovascular changes that are both generalized and restricted to the microcirculation of the tissues more actively involved in the exercise itself. Whether the local effect of exercise extends to larger arteries is unknown, however.

METHODS

In the right and left upper limb of 17 right-handed subjects performing an asymmetric training of the upper limbs (hammer throwers and baseball players) and 16 age-matched sedentary controls, we continuously measured radial artery diameter, distensibility and wall thickness by an echotracking and a beat-to-beat finger blood pressure device. Arterial distensibility was calculated by the arctangent model of Langewouters and expressed as continuous values from diastolic to systolic blood pressure. Measurements were made: (1) in baseline conditions; (2) after release from prolonged proximal ischaemia; and (3) after an increase in radial artery blood flow caused by a short (4 min) distal ischaemia to determine the endothelial involvement in the training-induced change in arterial distensibility.

RESULTS

In athletes the radial artery distensibility was markedly greater in the right than in the left arm, the latter showing values slightly greater than those seen in the two arms of sedentary subjects. In both arms and groups radial artery distensibility increased markedly after prolonged ischaemia, the between arm and group differences being preserved, however. The radial artery response to distal short ischaemia was, on the other hand, similar in the two arms of the athletes, although greater in these subjects than in the sedentary ones. Radial artery wall thickness was greater in the trained than in the untrained arm of athletes, both values being greater than in sedentary subjects.

CONCLUSIONS

Asymmetrical training of the upper limbs is accompanied by a greater distensibility of the middle-sized arteries of the more trained side. This is not associated with asymmetrical changes in endothelial structure or function. It is associated with a greater wall thickness in the trained side, suggesting that, at least in part, a training-induced asymmetrical change in wall structure (possibly with a predominance of more distensible tissues such as elastine and smooth muscle) is responsible.

Repeated Thermal Therapy Upregulates Arterial Endothelial Nitric Oxide Synthase Expression in Syrian Golden Hamsters

It has been previously reported that sauna therapy, a thermal therapy, improves the hemodynamics and clinical symptoms in patients with chronic heart failure and also improves endothelial function, which is impaired in such patients. The present study investigated whether the improvements observed with sauna therapy are through modulation of arterial endothelial nitric oxide synthase (eNOS) expression. Eight male Syrian golden hamsters underwent sauna therapy, using an experimental far infrared-ray dry sauna system, at 39 degrees C for 15 min followed by 30 degrees C for 20 min daily for 4 weeks. Control group hamsters were placed in the sauna system switched off at room temperature of 24 degrees C for 35 min. Immunohistochemistry found greater amounts of the immunoreactive products of eNOS in the endothelial cells of the aorta and carotid, femoral and coronary arteries in the sauna group than in the control group. Western blot analysis also revealed that 4-week sauna therapy significantly increased eNOS expression in aortas by 50% in 4 series of independent experiments with an identical protocol (p<0.01). In reverse transcription polymerase chain reaction assay, the eNOS mRNA in aortas was greater in the sauna group than in controls, with a peak at 1-week of sauna therapy (approximately 40-fold increase). In conclusion, repeated thermal therapy upregulates eNOS expression in arterial endothelium.

Heart failure etiology affects peripheral vascular endothelial function after cardiac transplantation

OBJECTIVES

The goal of this study was to examine the effect of heart failure etiology on peripheral vascular endothelial function in cardiac transplant recipients.

BACKGROUND

Peripheral vascular endothelial dysfunction occurs in patients with heart failure of either ischemic or nonischemic etiology. The effect of heart failure etiology on peripheral endothelial function after cardiac transplantation is unknown.

METHODS

Using brachial artery ultrasound, endothelium-dependent, flow-mediated dilation (FMD) was assessed in patients with heart failure with either nonischemic cardiomyopathy (n = 10) or ischemic cardiomyopathy (n = 7), cardiac transplant recipients with prior nonischemic cardiomyopathy (n = 10) or prior ischemic cardiomyopathy (n = 10) and normal controls (n = 10).

RESULTS

Patients with heart failure with either ischemic cardiomyopathy or nonischemic cardiomyopathy had impaired FMD (3.6 +/- 1.0% and 5.1 +/- 1.2%, respectively, p = NS) compared with normal subjects (13.9 +/- 1.3%, p < 0.01 compared with either heart failure group). In transplant recipients with antecedent nonischemic cardiomyopathy, FMD was markedly higher than that of heart failure patients with nonischemic cardiomyopathy (13.0 +/- 2.4%, p < 0.001) and similar to that of normal subjects (p = NS). However, FMD remained impaired in transplant recipients with prior ischemic cardiomyopathy (5.5 +/- 1.5%, p = 0.001 compared with normal, p = 0.002 vs. transplant recipients with previous nonischemic cardiomyopathy).

CONCLUSIONS

Peripheral vascular endothelial function is normal in cardiac transplant recipients with antecedent nonischemic cardiomyopathy, but remains impaired in those with prior ischemic cardiomyopathy. In contrast, endothelial function is uniformly abnormal for patients with heart failure, regardless of etiology. These findings indicate that cardiac transplantation corrects peripheral endothelial function for patients without ischemic heart disease, but not in those with prior atherosclerotic coronary disease.

The hemodynamic effects of isotonic exercise using hand-held weights in patients with heart failure

BACKGROUND

Controversy surrounds the use of resistance exercise in patients with heart failure because of concerns that increases in rate-pressure product and systemic vascular resistance might lead to increased afterload and decreased cardiac output.

METHODS

Following pharmacologic left ventricular unloading therapy using a pulmonary artery catheter, 34 patients with advanced heart failure performed isotonic weightlifting exercise at 50%, 65%, and 80% of the calculated one repetition maximum. Measurements were made of hemodynamics, ST segment, rate-pressure product, serum norepinephrine, rating of perceived exertion, and dysrhythmias following each exercise set.

RESULTS

Repeated analysis of variance showed significant increases in systolic blood pressure (p = 0.0005), diastolic blood pressure (p = 0.01), rate-pressure product (p = 0.005); serum norepinephrine (p = 0.004), and rating of perceived exertion (p = 0.0005). However, systemic vascular resistance and cardiac output did not change significantly (p>0.05). Pulmonary capillary wedge pressures, the incidence of dysrhythmias, and ST segments did not significantly differ from baseline. No patients experienced angina or dyspnea during the study.

CONCLUSIONS

Isotonic exercise using hand-held weights was well tolerated hemodynamically and clinically, and no patients experienced adverse outcomes during exercise.

Contribution of endogenous nitric oxide to basal vasomotor tone of peripheral vessels and plasma B-type natriuretic peptide levels in patients with congestive heart failure

OBJECTIVES

We examined whether a relationship exists between the vasoconstrictive response to endogenous nitric oxide (NO) synthesis inhibition and the severity of heart failure in patients with congestive heart failure (CHF).

BACKGROUND

Controversy exists as to whether the vasoconstrictive response to NO synthesis inhibition in patients with CHF is comparable to that in normal subjects or is enhanced.

METHODS

Forearm blood flow (FBF) and calculated forearm vascular conductance (FVC) were obtained using plethysmography before and after administration of the NO synthesis inhibitor L-NMMA (NG-monomethyl-L-arginine) in 40 patients with CHF due to dilated cardiomyopathy and in 16 normal control subjects. Basal plasma B-type natriuretic peptide (BNP) and nitric oxide concentrations were measured in all subjects.

RESULTS

Plasma BNP and nitrite/nitrate (NOx) levels in the patients group were significantly greater and baseline FBF was significantly less. Administration of L-NMMA significantly decreased FBF and FVC in both groups. The percent changes in FBF (%FBF) and FVC (%FVC) from the baseline after L-NMMA correlated significantly with plasma BNP level (%FBF: r = 0.72; %FVC: r = 0.76; both p < 0.001). Percent changes in both FBF and FVC were greater in patients with BNP > or = 100 pg/ml than in normal subjects; however, in patients with BNP < 100 pg/ml they were comparable to those in normal subjects.

CONCLUSIONS

Vasoconstrictive response to L-NMMA in patients with CHF was preserved or enhanced in proportion to the basal plasma BNP level, indicating a close relationship between the contribution of endogenous NO to basal vasomotor tone and the severity of heart failure.

Flow-mediated dilatation

Arterial endothelial dysfunction is one of the key early events in atherogenesis, preceding structural atherosclerotic changes. It is also important in the late stages of obstructive atherosclerosis, predisposing to constriction and/or thrombosis. Endothelial function can be measured in coronary arteries and in the periphery by measuring vasomotor function after intra-arterial infusion of pharmacologic substances which enhance the release of endothelial nitric oxide. The disadvantage of these methods is their invasive nature, which generally makes them unsuitable for studies involving asymptomatic subjects. For this reason, noninvasive tests of endothelial function have been developed. In the most widely used of these, an ultrasound-based method, arterial diameter is measured in response to an increase in shear stress, which causes endothelium-dependent dilatation. Endothelial function assessed by this method correlates with invasive testing of coronary endothelial function, as well as with the severity and extent of coronary atherosclerosis. This noninvasive endothelial function testing has provided valuable insights into early atherogenesis, as well as into the potential reversibility of endothelial dysfunction by various strategies, including pharmacological agents (lipid lowering, ACE inhibition), L-arginine, antioxidants and hormones.

Effect of aerobic and resistance exercise training on vascular function in heart failure

Exercise training of a muscle group improves local vascular function in subjects with chronic heart failure (CHF). We studied forearm resistance vessel function in 12 patients with CHF in response to an 8-wk exercise program, which specifically excluded forearm exercise, using a crossover design. Forearm blood flow (FBF) was measured using strain-gauge plethysmography. Responses to three dose levels of intra-arterial acetylcholine were significantly augmented after exercise training when analyzed in terms of absolute flows (7.0 +/- 1.8 to 10.9 +/- 2.1 ml x 100 ml(-1) x min(-1) for the highest dose, P < 0.05 by ANOVA), forearm vascular resistance (21.5 +/- 5.0 to 15.3 +/- 3.9 ml x 100 ml forearm(-1) x min(-1), P < 0.01), or FBF ratios (P < 0.01, ANOVA). FBF ratio responses to sodium nitroprusside were also significantly increased after training (P < 0.05, ANOVA). Reactive hyperemic flow significantly increased in both upper limbs after training (27.9 +/- 2.7 to 33.5 +/- 3.1 ml x 100 ml(-1) x min(-1), infused limb; P < 0.05 by paired t-test). Exercise training improves endothelium-dependent and -independent vascular function and peak vasodilator capacity in patients with CHF. These effects on the vasculature are generalized, as they were evident in a vascular bed not directly involved in the exercise stimulus.

Exercise following heart transplantation

During the past 2 decades, heart transplantation has evolved from an experimental procedure to an accepted life-extending therapy for patients with endstage heart failure. However, with dramatic improvements in organ preservation, surgery and immunosuppressive drug management, short term survival is no longer the pivotal issue for most heart transplant recipients (HTR). Rather, a return to functional lifestyle with good quality of life is now the desired procedural outcome. To achieve this outcome, aggressive exercise rehabilitation is essential. HTR present unique exercise challenges. Preoperatively, most of these patients had chronic debilitating cardiac illness. Many HTR have had prolonged pretransplantation hospitalisation for inotropic support or a ventricular assist device. Decrements in peak oxygen consumption (VO2peak) and related cardiovascular parameters regress approximately 26% within the first 1 to 3 weeks of sustained bed rest. Consequently, extremely poor aerobic capacity and cardiac cachexia are not unusual occurrences in HTR who have required mechanical support or been confined to bed rest. Moreover, HTR must also contend with de novo exercise challenges conferred by chronic cardiac denervation and the multiple sequelae resulting from immunosuppression therapy. There is ample evidence that both endurance and resistance training are well tolerated in HTR. Moreover, there is growing clinical consensus that specific endurance and resistance training regimens in HTR can be efficacious adjunctive therapies in the prevention of immunosuppression-induced adverse effects and the reversal of pathophysiological consequences associated with cardiac denervation and antecedent heart failure. For example, some HTR who remain compliant during strenuous long term endurance training programmes achieve peak heart rate and VO2peak values late after transplantation that approach age-matched norms (up to approximately 95% of predicted). These benefits are not seen in HTR who do not participate in structured endurance exercise training. Rather, peak heart rate and VO2peak values in untrained HTR remain approximately 60 to 70% of predicted indefinitely. However, the mechanisms responsible for improved peak heart rate, VO2peak and total exercise time are not completely understood and require further investigation. Recent studies have also demonstrated that resistance exercise training may be an effective countermeasure for corticosteroid-induced osteoporosis and skeletal muscle myopathy. HTR who participate in specific resistance training programmes successfully restore bone mineral density (BMD) in both the axial and appendicular skeleton to pretransplantation levels, increase lean mass to levels greater than pretransplantation, and reduce body fat. In contrast, HTR who do not participate in resistance training lose approximately 15% BMD from the lumbar spine early in the postoperative period and experience further gradual reductions in BMD and muscle mass late after transplantation.

Nitric oxide-mediated metabolic regulation during exercise: effects of training in health and cardiovascular disease

Accumulating data suggest that nitric oxide (NO) is important for both coronary and peripheral hemodynamic control and metabolic regulation during exercise. Although still controversial, NO of endothelial origin may potentiate exercise-induced hyperemia. Mechanisms of release include both acetylcholine derived from the neuromuscular junction and elevation in vascular shear stress. A splice variant of neuronal nitric oxide synthase (NOS), nNOSmu, is expressed in human skeletal muscle. In addition to being a potential modulator of blood flow, NO from skeletal muscle regulates muscle contraction and metabolism. In particular, recent human data indicate that NO plays a role in muscle glucose uptake during exercise independently of blood flow. Exercise training in healthy individuals elevates NO bioavailability through a variety of mechanisms including increased NOS enzyme expression and activity. Such adaptations likely contribute to increased exercise capacity and cardiovascular protection. Cardiovascular risk factors including hypercholesterolemia, hypertension, diabetes, and smoking as well as established disease are associated with impairment of the various NO systems. Given that NO is an important signaling mechanism during exercise, such impairment may contribute to limitations in exercise capacity through inadequate coronary or peripheral perfusion and via metabolic effects. Exercise training in individuals with elevated cardiovascular risk or established disease can increase NO bioavailability and may represent an important mechanism by which exercise training conveys benefit in the setting of secondary prevention.

Cardiac rehabilitation and secondary prevention programs for elderly cardiac patients

The utility of cardiac rehabilitation for elderly cardiac patients is controversial, and cost, logistic barriers, and encumbering comorbidities often seem disproportionate. Many clinicians view the emphasis of cardiac rehabilitation on behavior modification and risk-factor reduction as irrelevant for very old adults and consider pure exercise programs as appropriate alternatives. The strong rationale for cardiac rehabilitation and secondary prevention is elucidated, and available corroborating data are presented. The benefits of exercise prescription in cardiac rehabilitation and synchronized risk-factor reduction are pertinent to aging and age-related heart disease, including coronary heart disease and heart failure.

Regulation of the vascular extracellular superoxide dismutase by nitric oxide and exercise training

The bioactivity of endothelium-derived nitric oxide (NO) reflects its rates of production and of inactivation by superoxide (O(2)(*-)), a reactive species dismutated by extracellular superoxide dismutase (ecSOD). We have now examined the complementary hypothesis, namely that NO modulates ecSOD expression. The NO donor DETA-NO increased ecSOD expression in a time- and dose-dependent manner in human aortic smooth muscle cells. This effect was prevented by the guanylate cyclase inhibitor ODQ and by the protein kinase G (PKG) inhibitor Rp-8-CPT-cGMP. Expression of ecSOD was also increased by 8-bromo-cGMP, but not by 8-bromo-cAMP. Interestingly, the effect of NO on ecSOD expression was prevented by inhibition of the MAP kinase p38 but not of the MAP kinase kinase p42/44, suggesting that NO modulates ecSOD expression via cGMP/PKG and p38MAP kinase-dependent pathways, but not through p42/44MAP kinase. In aortas from mice lacking the endothelial nitric oxide synthase (eNOS), ecSOD was reduced more than twofold compared to controls. Treadmill exercise training increased eNOS and ecSOD expression in wild-type mice but had no effect on ecSOD expression in mice lacking eNOS, suggesting that this effect of exercise is meditated by endothelium-derived NO. Upregulation of ecSOD expression by NO may represent an important feed-forward mechanism whereby endothelial NO stimulates ecSOD expression in adjacent smooth muscle cells, thus preventing O(2)(*-)-mediated degradation of NO as it traverses between the two cell types.

Nitric oxide as a metabolic regulator during exercise: effects of training in health and disease

1. Accumulating animal and human data suggest that nitric oxide (NO) is important for both coronary and peripheral haemodynamic control and metabolic regulation during performance of exercise. 2. While still controversial, NO of endothelial origin is thought to potentiate exercise-induced hyperaemia, both in the peripheral and coronary circulations. The mechanism of release may include both acetylcholine derived from the neuromuscular junction and vascular shear stress. 3. A splice variant of neuronal nitric oxide synthase (NOS), nNOSmicro, incorporating an extra 34 amino acids, is expressed in human skeletal muscle. In addition to being a potential modulator of blood flow, skeletal muscle-derived NO is an important regulator of muscle contraction and metabolism. In particular, recent human data indicate that NO modulates muscle glucose uptake during exercise, independently of blood flow. 4. Exercise training in healthy individuals promotes adaptations in the various NO systems, which can increase NO bioavailability through a variety of mechanisms, including increased NOS enzyme expression and activity. Such adaptations likely contribute to increased exercise capacity and protection from cardiovascular events. 5. Cardiovascular risk factors, including hypercholesterolaemia, hypertension, diabetes and smoking, as well as established disease, are associated with impairment of the various NO systems. Given that NO is an important signalling mechanism during exercise, such impairment may contribute to limitations in exercise capacity through inadequate coronary or peripheral blood delivery and via metabolic effects. 6. Exercise training in individuals with elevated cardiovascular risk or established disease can increase NO bioavailability and may represent an important mechanism by which exercise training provides benefit in the setting of secondary prevention.

Endothelial dysfunction in patients with heart failure: relationship to disease severity

BACKGROUND

Heart failure is associated with abnormal endothelium-dependent vasodilation. However, the relationship of this abnormality to heart failure severity has not been well defined.

METHODS AND RESULTS

We used strain-gauge plethysmography to assess forearm blood flow (FBF) responses to endothelium-dependent, endothelium-independent, and reactive hyperemic stimuli in normal subjects (n = 29) and in patients with mild (n = 26) and severe (n = 41) heart failure. FBF responses to intra-arterial methacholine (0.3, 1.5, 3.0 microg/min) were significantly (P < .005) and similarly reduced in patients with mild (2.8 +/- 0.4, 5.9 +/- 0.7, and 7.7 +/- 1.1 mL/min/dL) and severe (2.7 +/- 0.4, 5.4 +/- 0.7, and 6.9 +/- 0.9) heart failure compared with normal subjects (4.5 +/- 0.4, 9.4 +/- 1.0, and 12.0 +/- 1.1). FBF responses to nitroprusside (1, 5, 10 microg/min) were significantly reduced in mild (2.4 +/- 0.3, 6.7 +/- 1.1, and 11.9 +/- 2.0, P < .05) and severe (1.9 +/- 0.2, 5.1 +/- 0.5, and 7.3 +/- 0.9, P < .001) heart failure groups compared with normal subjects (3.8 +/- 0.5, 10.8 +/- 1.2, and 14.9 +/- 1.2). However, FBF responses were reduced to a greater extent (P < .001) in mild heart failure compared with severe heart failure. Peak reactive hyperemia was significantly impaired only in severe heart failure. There was no correlation between methacholine responses and ejection fraction, maximum oxygen consumption, wedge pressure, or serum norepinephrine.

CONCLUSION

Impaired endothelium-dependent vasodilation is present and near maximum in mild heart failure. Endothelial dysfunction may be an early finding in human heart failure.

Chronic exercise training preserves prostaglandin-induced dilation of epicardial coronary artery during development of heart failure in awake dogs

Although it has been shown that long-term exercise training preserves endothelium-mediated nitric oxide vasodilator function in chronic heart failure (CHF), whether exercise training exerts similar beneficial effects on endothelial/prostaglandin-mediated vasodilator capacity in coronary circulation during the development of CHF has not been determined. Fifteen mongrel dogs were surgically instrumented for measurement of left ventricular pressure, aortic pressure, coronary blood flow and left circumflex coronary artery diameter. Dogs (n = 5) who underwent 4 weeks of cardiac pacing (210 b/min for 3 weeks and 240 b/min for the 4th week) developed CHF as characterized by significant reduction in left ventricular systolic pressure, mean arterial pressure and left ventricular dP/dt, increases in left ventricular end-diastolic pressure and heart rate, as well as clinical signs of CHF. Endothelial prostaglandin-mediated vasodilation of the epicardial coronary artery was impaired, as manifested by an attenuated arachidonic acid (AA)-induced dilation of the artery (epicardial artery diameter increased by: 0.78 +/- 0. 84% in CHF versus 4.6 +/- 0.89% in normal, P < 0.05); however, prostacyclin (PGI(2))-induced and nitroglycerin-induced vasodilation of the coronary circulation were not altered. In contrast, dogs (n = 6) with cardiac pacing plus daily exercise training (4.4 +/- 0.3 km/h, 2 h/day) only developed mild cardiac dysfunction, and the response of the epicardial coronary artery diameter to AA was preserved (epicardial artery diameter increased by 4.2 +/- 0.98% from baseline, P 0.05 compared to its respective control). Thus, long-term exercise training preserves endothelial/prostaglandin-mediated dilation of epicardial coronary artery during development of CHF.

Correction of endothelial dysfunction in chronic heart failure: additional effects of exercise training and oral L-arginine supplementation

OBJECTIVES

The aim of this study was to analyze whether L-arginine (L-arg.) has comparable or additive effects to physical exercise regarding endothelium-dependent vasodilation in patients with chronic heart failure (CHF).

BACKGROUND

Endothelial dysfunction in patients with CHF can be corrected by both dietary supplementation with L-arg. and regular physical exercise.

METHODS

Forty patients with severe CHF (left ventricular ejection fraction 19 +/- 9%) were randomized to an L-arg. group (8 g/day), a training group (T) with daily handgrip training, L-arg. and T (L-arg. + T) or an inactive control group (C). The mean internal radial artery diameter was determined at the beginning and after four weeks in response to brachial arterial administration of acetylcholine (ACh) (7.5, 15, 30 microg/min) and nitroglycerin (0.2 mg/min) with a transcutaneous high-resolution 10 MHz A-mode echo tracking system coupled with a Doppler device. The power of the study to detect clinically significant differences in endothelium-dependent vasodilation was 96.6%.

RESULTS

At the beginning, the mean endothelium-dependent vasodilation in response to ACh, 30 microg/min was 2.54 +/- 0.09% (p = NS between groups). After four weeks, internal radial artery diameter increased by 8.8 +/- 0.9% after ACh 30 microg/min in L-arg. (p < 0.001 vs. C), by 8.6 +/- 0.9% in T (p < 0.001 vs. C) and by 12.0 +/- 0.3% in L-arg. +/- T (p < 0.005 vs. C, L-arg. and T). Endothelium-independent vasodilation as assessed by infusion of nitroglycerin was similar in all groups at the beginning and at the end of the study.

CONCLUSIONS

Dietary supplementation of L-arg. as well as regular physical exercise improved agonist-mediated, endothelium-dependent vasodilation to a similar extent. Both interventions together seem to produce additive effects with respect to endothelium-dependent vasodilation.

Arteriolar reactivity and capillarization in chronically stimulated rat limb skeletal muscle post-MI

The purpose of this study was to assess whether electrical stimulation-induced increases in muscular activity could improve capillary supply and correct previously documented abnormal vasodilator and vasoconstrictor responses of arterioles in limb skeletal muscle post-myocardial infarction (MI). Extensor digitorum longus (EDL) muscle from rats with surgically induced MI ( approximately 30% of the left ventricle) was chronically stimulated (Stim) 8 h/day for 6 +/- 1 days, at 11 wk post-MI. Third- (3A) and fourth-order (4A) arterioles in EDL from nine MI rats and four MI+Stim rats were compared with those of 11 controls (Con). Compared with Con rats, MI alone caused a reduction in the resting diameter of 3A and 4A arterioles, which was completely reversed by MI+Stim. However, Stim did not correct the attenuated vasodilator response to 10(-4) M adenosine seen in 4A arterioles from MI rats compared with Con. The constrictor response of both 3A and 4A vessels in MI rats to low doses of acetylcholine (10(-9) M, 10(-8) M) and norepinephrine (10(-9) M) was accentuated in MI+Stim. The proportion of oxidative fibers in EDL was unaffected by MI or MI+Stim combination. However, Stim significantly increased (P < 0.05) the capillary-to-fiber ratio in this muscle compared with Con. Thus, although the increase in muscle activity induced by chronic electrical stimulation normalized the reduction in resting vessel diameter seen after MI, it failed to correct the abnormalities in vasoreactivity of these same vessels.

Endothelial dysfunction in hypertension

Hypertension is an important risk factor for the development of atherosclerosis and endothelial dysfunction may be a key mechanism. The nitric oxide mediated vasodilator function of the endothelium has been widely studied as a test of endothelial integrity in patients with hypertension and impaired basal and muscarinic agonist stimulated components of nitric oxide mediated vascular tone have been found in coronary, forearm and cutaneous resistance vessels and in coronary and forearm conduit vessels. The underlying abnormalities of these changes are unknown but it is likely to be a secondary phenomenon due to increased blood pressure. However, endothelial dysfunction as assessed by response to muscarinic agonists does not occur in all patients and antihypertensive therapy so far has been mostly unable to reverse it. Although widely used the response to acetylcholine has some shortcomings and it remains to be established what parameter best reflects endothelial dysfunction. The relationship of such abnormalities to the present or future atherosclerosis needs to be defined.

Endocrine response to exercise in young and old horses

Six young (mean + s.e., 5.3 +/- 0.8 years, 445 +/- 13 kg bwt) and 6 old (22.0 +/- 0.4 years, 473 +/- 18 kg bwt) Standardbred and Thoroughbred mares were used to test the hypothesis that age would alter the endocrine response to exercise. All of the mares were unconditioned but accustomed to the laboratory, to standing quietly and running on a treadmill, and to the standardised incremental exercise test (SET) used in the experiment. Two weeks prior to the experiment, each horse underwent a SET to determine maximal oxygen uptake (VO2max) and the speeds to be used in the actual experiment. A second graded exercise test (GXT) was performed without instrumentation for the measurement of plasma renin activity (PRA) and the plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), aldosterone (ALDO), and endothelin-1 (ET-1). Blood samples (30 ml) were collected at rest and at the end of each one minute step of the exercise test. Plasma concentrations of hormones were measured using radioimmunoassay kits. There were no differences (P > 0.05) between old vs. young mares for resting PRA (2.2 +/- 0.3 vs. 1.5 +/- 0.3 ng/ml/h), or the plasma concentrations of ANP (10.0 +/- 0.9 vs. 10.7 +/- 0.6 pg/ml); AVP (0.7 + 0.7 vs. 1.4 +/- 0.4 pg/ml); ALDO (39.2 +/- 10.3 vs. 22.7 +/- 4.6 pg/ml); or ET-1 (0.23 +/- 0.04 vs. 0.18 +/- 0.03 pg/ml). Exercise significantly increased PRA and the concentrations of ANP, AVP, and ALDO in both groups of horses; however, ET-1 was not altered (P > 0.05) by exercise in either group. There were differences (P < 0.05) between means obtained from the old and young groups for PRA (5.4 +/- 0.6 vs. 3.9 +/- 0.8 ng/ml/h and the concentrations of ANP (14.5 +/- 2.3 vs. 26.5 +/- 9.0 pg/ml), AVP (13.6 +/- 0.3 vs. 26.1 +/- 13.9 pg/ml, and ALDO (76.8 +/- 22.0 vs. 41.5 +/- 4.9 pg/ml) measured in samples obtained at the speed eliciting VO2max. These data suggest that older horses have an age-altered endocrine response to exercise.

Cardiovascular dynamics at the onset of exercise

At the onset of exercise, the cardiovascular system adapts with a series of integrated responses to meet the metabolic demands of the exercising muscles. The importance of rapid increases in cardiac output and local muscle blood flow has been established by showing that small decreases in O2 supply at the onset of exercise cause delays in the increase in O2 utilization. With the development of techniques that can be applied to instantaneous measurement of the cardiovascular response, the mechanisms that regulate increased muscle perfusion have recently been investigated. In this introduction to the symposium, a model of the within muscle distribution of blood flow is considered as a function of the measured responses across an exercising skeletal muscle. This model demonstrates the necessity of considering the distribution of blood flow to the working fibers very early in exercise. The symposium provides insight into our current understanding of the factors involved in the regulation of skeletal muscle blood flow at the onset of exercise. Our ability to study the impact of cardiovascular disease on exercise performance has improved with the development of selective pharmacological agents to block or stimulate specific components of the cardiovascular response. These advances should provide the basis for future research.

Resistance exercise training increases muscle strength, endurance, and blood flow in patients with chronic heart failure

Resistance exercise training was well tolerated in patients with stable, chronic heart failure, resulting in increased strength and endurance, and lower oxygen consumption at submaximum workloads but no improvement in VO2peak. There was also a significant increase in basal forearm blood flow following this form of exercise training.

Peripheral vascular remodeling in chronic heart failure: clinical relevance and new conceptualization of its mechanisms

Increased peripheral vascular tone is a critical factor in the deterioration of clinical stage and symptoms in chronic congestive heart failure (CHF) because of increased cardiac afterload and decreased nutritive skeletal muscle blood flow. Endothelial function as represented by nitric oxide (NO) production shows significant attenuation with the progression of clinical severity of CHF as determined by New York Heart Association class and exercise capacity parameters. This endothelial dysfunction emerges in the early stages of CHF. In the advanced stage of the condition, both endothelium-dependent and endothelium-independent dilator mechanisms are impaired in limb resistance vessels. This occurs because vascular endothelial function, especially NO production, is an important factor in the regulation of vasodilatory function, as well as making an important contribution to vascular structure. Furthermore, although such vasodilatory circulating factors as natriuretic polypeptides and newly discovered adrenomedullin are increased in heart failure, the vasodilatory potency of these polypeptide hormones in the limb vascular bed is significantly blunted. These observations suggest that peripheral circulatory failure in CHF is caused not only by simple arterial muscle constriction, but also by structural and functional changes, including receptor and postreceptor levels in the vasculature. This vascular remodeling may be an important mechanism underlying vasodilatory failure in both limb conduit and intraskeletal muscle vessels and may contribute significantly to left ventricular dysfunction and exercise intolerance in patients with heart failure.

Exercise training enhances endothelial function in young men

OBJECTIVES

The present study was designed to assess whether exercise training can enhance endothelium-dependent dilatation in healthy young men.

BACKGROUND

Exercise has been shown to reduce cardiovascular morbidity and mortality, but the mechanisms for this benefit are unclear. Endothelial dysfunction is an early event in atherogenesis, and animal studies have shown that exercise training can enhance endothelial function.

METHODS

We have examined the effect of a standardized, 10-week, aerobic and anaerobic exercise training program on arterial physiology in 25 healthy male military recruits, aged 17 to 24 (mean 20) years, of average fitness levels. Each subject was studied before starting, and after completing the exercise program. Baseline vascular reactivity was compared with that of 20 matched civilian controls. At each visit, the diameter of the right brachial artery was measured at rest, during reactive hyperemia (increased flow causing endothelium-dependent dilation) and after sublingual glyceryltrinitrate (GTN; an endothelium-independent dilator), using high-resolution external vascular ultrasound.

RESULTS

At baseline, flow-mediated dilatation (FMD) and GTN-mediated dilatation were similar in the exercise and control groups (FMD 2.2+/-2.4% and 2.4+/-2.8%, respectively, p = 0.33; GTN 13.4+/-6.2 vs. 16.7+/-5.9, respectively, p = 0.53). In the military recruits, FMD improved from 2.2+/-2.4% to 3.9+/-2.5% (p = 0.01), with no change in the GTN-mediated dilation (13.4+/-6.2% vs. 13.9+/-5.8%, p = 0.31) following the exercise program.

CONCLUSION

Exercise training enhances endothelium-dependent dilation in young men of average fitness. This may contribute to the benefit of regular exercise in preventing cardiovascular disease.

Clinical importance of coronary endothelial vasodilator dysfunction and therapeutic options

The vascular endothelium plays a key role in the control of vasomotor tone, local haemostasis and vascular wall proliferation processes. These responses are mediated by a variety of substances released from the endothelium in response to physiological stimuli, including prostacyclin, endothelin, and most importantly nitric oxide (NO). NO mediates vasodilation and furthermore inhibits platelet aggregation, expression of adhesion molecules for monocytes and adhesion of neutrophils, and it impairs growth of vascular smooth muscle cells. Risk factors for coronary atherosclerosis, such as hypercholesterolaemia, impair NO bioactivity, mainly due to an oxidative stress by superoxide radicals (O2-), which are able of rapidly inactivating endothelium-derived NO. Impaired NO bioactivity leads to unopposed paradoxical vasoconstriction of epicardial conductance vessels in response to physiological stimuli such as sympathetic activation as well as impaired vasodilator function of coronary resistance vessels. Therefore, endothelial dysfunction contributes to ischaemic manifestation of coronary artery disease. In addition, enhanced paradoxical vasoconstriction and a loss of endothelial antithrombotic activities might unfavourably modulate the course of acute coronary syndromes. Thus, the aim of therapeutic interventions is to increase NO bioavailability by either increasing NO production or decreasing O2- production in the endothelium. This goal can be reached, for example by ACE inhibitors, lipid-lowering drugs, increased shear-stress by physical exercise, oestrogens, and L-arginine, which have already been shown to improve endothelial vasodilator function. Nevertheless, it has to be determined whether ameliorated endothelial function will contribute to improved patients prognosis.

Impaired aerobic capacity in hypercholesterolemic mice: partial reversal by exercise training

The present study assessed whether impaired aerobic capacity previously observed in hypercholesterolemic mice is reversible by exercise training. Seventy-two 8-wk-old female C57BL/6J wild-type (+, n = 42) and apolipoprotein E-deficient (-, n = 30) mice were assigned to the following eight interventions: normal chow, sedentary (E+, n = 17; E-, n = 8) or exercised (E+ex, n = 13; E-ex, n = 7) and high-fat chow, sedentary (E+chol, n = 6; E-chol, n = 8) or exercised (E+chol-ex, n = 6; E-chol-ex, n = 7). Mice were trained on a treadmill 2 x 1 h/day, 6 days/wk, for 4 wk. Cholesterol levels correlated inversely with maximum oxygen uptake (r = -0.35; P < 0. 02), which was blunted in all hypercholesterolemic sedentary groups (all P < 0.05). Maximum oxygen uptake improved in all training groups but failed to match E+ex (all P < 0.05). Vascular reactivity and nitric oxide (NO) synthesis correlated with anaerobic threshold (r = 0.36; P < 0.025) and maximal distance run (r = 0.59; P < 0.007). We conclude that genetically induced hypercholesterolemia impairs aerobic capacity. This adverse impact of hypercholesterolemia on aerobic capacity may be related to its impairment of vascular NO synthesis and/or vascular smooth muscle sensitivity to nitrovasodilators. Aerobic capacity is improved to the same degree by exercise training in normal and genetically hypercholesterolemic mice, although there remains a persistent difference between these groups after training.

Impaired response of the forearm resistance but not conductance vessels to reactive hyperemia in hypertrophic cardiomyopathy

It has been suggested that in hypertrophic cardiomyopathy (HC), vascular abnormalities are not restricted to the heart. Flow-mediated dilation of peripheral conductance arteries (reflecting their endothelial function) has not yet been studied in HC. Our aim was to assess both flow-dependent dilation of the brachial artery and flow responses (dependent on resistance vessels) during forearm reactive hyperemia (RH) in nontreated HC patients. The authors studied 13 HC patients and 14 age- and sex-matched healthy controls. None of them exhibited any factors known to be associated with endothelial dysfunction. Using 7 MHz ultrasound, brachial artery diameter and Doppler flow velocity were measured continuously at baseline and throughout 1 min of RH following 5 min of forearm ischemia induced by inflation of a blood pressure cuff. Arterial diameter and RH flow are expressed as percent changes with respect to the baseline. Flow-dependent dilation was similar in the HC patients and control subjects (7.2 +/- 9.5% vs 9.9 +/- 10.4%, p>0.05). Compared to the control group, RH flow in HC was decreased; however, differences did not reach statistical significance until 60 sec of RH (112 +/- 102% vs 261 +/- 217%, p<0.05; HC vs controls). In HC patients, endothelial function of peripheral conductance arteries is preserved. Hence, a defect in the forearm arterial bed in HC seems to be limited to mechanisms maintaining the dilation of resistance vessels during decreasing RH flow.

Effect of intensive therapy for heart failure on the vasodilator response to exercise

OBJECTIVES

The purpose of the study was to evaluate the lower extremity vascular responsiveness to metabolic stimuli in patients with heart failure and to determine whether these responses improve acutely after intensive medical therapy.

BACKGROUND

Metabolic regulation of vascular tone is an important determinant of blood flow, and may be abnormal in heart failure.

METHODS

The leg blood flow responses were measured in 11 patients with nonedematous class III-IV heart failure before and after inpatient medical therapy and in 10 normal subjects. Venous occlusion plethysmography was used to measure peak blood flow and total hyperemia in the calf after arterial occlusion and also after isotonic ankle exercise. Measurements were repeated following short-term inpatient treatment with vasodilators and diuretics administered to decrease right atrial pressure (18+/-2 to 7+/-1 mm Hg), pulmonary wedge pressure (32+/-3 to 15+/-2 mm Hg), and systemic vascular resistance (1581+/-200 to 938+/-63 dynes.s.cm(-5), all p < 0.02).

RESULTS

Leg blood flow at rest, after exercise, and during reactive hyperemia was less in heart failure patients than in control subjects. Resting leg blood flow did not increase significantly after medical therapy, but peak flow after the high level of exercise increased by 59% (p = 0.009). Total hyperemic volume in the recovery period increased by 73% (p = 0.03). Similarly, the peak leg blood flow response to ischemia increased by 88% (p = 0.04), whereas hyperemic volume rose by 98% (p = 0.1).

CONCLUSIONS

The calf blood flow responses to metabolic stimuli are blunted in patients with severe heart failure, and improve rapidly with intensive medical therapy.

Influence of intensive physical training on urinary nitrate elimination and plasma endothelin-1 levels in patients with congestive heart failure

BACKGROUND

Congestive heart failure (CHF) is associated with increased peripheral vascular resistance. Exercise-induced shear stress may release endothelial relaxing factors, such as nitric oxide (NO), and inhibit the production of vasoconstrictors such as endothelin-1 (ET-1) thereby modulating vascular tone. We examined the effect of intensive training on ET-1 plasma concentrations and NO-metabolite elimination in patients with CHF after acute myocardial infarction.

METHODS

Seventeen patients with CHF after a myocardial infarction were randomized to an exercise group (n = 9), who performed physical training for 8 weeks, or a control group (n = 8) who received usual care. A physical examination, pulmonary function test, and a maximum exercise test were performed, and 24-hour urinary nitrate elimination and ET-1 in plasma were determined before and at the end of the study period.

RESULTS

Maximal oxygen uptake remained unchanged in controls (17.9 +/- 1.4 to 18.1 +/- 1.5 mL/(kg min) but increased in the exercise group (from 20.4 +/- 0.75 to 26.7 +/- 1.4 mL/(kg min). After 8 weeks the urinary nitrate elimination in controls was significantly decreased (1.25 +/- 0.20 to 1.03 +/- 0.22 mmol/24 hours; P < 0.001), while it was unchanged in the exercise group (1.26 +/- 0.23 to 1.39 +/- 0.28; P = 0.71). Plasma ET-1 levels did not change after 8 weeks (7.87 +/- 0.62 versus 7.57 +/- 0.75 and 7.13 +/- 0.6 versus 7.35 +/- 0.7 pg/mL for control and exercise groups, respectively).

CONCLUSION

In patients with CHF after acute myocardial infarction nitrate elimination decreases over the subsequent 2 months. This trend was reversed by training. Because nitrate elimination mirrors endogenous NO production, these results suggest that training may positively influence endothelial vasodilator function.

Exercise training in heart failure

Patients with heart failure challenge the clinician with a constellation of difficult clinical, pathophysiologic, and psychologic issues. As a result, until recently, exercise training was not considered a safe and effective treatment strategy to be used in these patients. However, in the past 10 years, data from both randomized and nonrandomized trials showed that regular exercise training in patients with stable Class II and III heart failure can safely improve exercise tolerance, attenuate an overactivated sympathetic nervous system, partially reverse skeletal muscle abnormalities, and enhance health-related quality of life. These outcomes are achievable with a relatively moderate dose of physical activity, such as 30 to 60 minutes of walking or cycling 3 to 5 days per week at an intensity equivalent to 60% to 70% of peak oxygen consumption. Sufficiently powered trials are needed to assess morbidity, mortality, and cost-effectiveness endpoints relative to exercise training in patients with heart failure.

Clinical implications of endothelial dysfunction

Endothelial dysfunction is increasingly recognized as an early event in the pathogenesis of cardiovascular disease. This observation is consistent with the growing appreciation of the role of endothelium in maintaining cardiovascular health. Endothelial dysfunction and coronary artery disease are both linked to hypertension, hypercholesterolemia, diabetes mellitus, and cigarette smoking. Modification of these conditions improves both endothelial function and coronary artery disease outcomes. Dietary and lifestyle modifications and antioxidant vitamin supplementation have a beneficial effect on endothelial function, as do angiotensin-converting enzyme inhibitors and lipid-lowering agents. Future studies will determine whether interventions that specifically target endothelial dysfunction can reduce rates of clinical disease.