Exercise performance and diastolic filling in essential hypertension

Central losartan administration increases cardiac workload during aerobic exercise

To assess the effects of central administration of losartan, an antagonist of angiotensin II AT₁ receptors, on cardiovascular function during aerobic exercise, heart rate, systolic and diastolic arterial pressures and rate pressure product of Wistar rats were measured as cardiac workload indexes. The animals ran on a treadmill until fatigue after an intracerebroventricular injection of losartan or saline. Pulsatile arterial pressure was recorded by a catheter implanted into the ascending aorta, from which were derived cardiovascular parameters to estimate the cardiac workload. Total exercise time and exercise workload were determined as performance indexes. The rats showed a more intense increase in heart rate after 8 min of exercise and sustained until fatigue (P < .05). Furthermore, the rats injected with losartan had a higher increase of both systolic and diastolic arterial pressures as well as rate pressure product from approximately 6 min of exercise until fatigued (P < .05). In addition, a 22% reduction in exercise time was found in losartan-rats (P < .01). This ergolytic effect induced by losartan was strongly inversely correlated with rate-pressure product during aerobic exercise (r = 0.78, P ≤ .01). The data shows that central administration of losartan augments the cardiac workload during aerobic exercise, which courses in parallel with the reduced exercise performance.

Correlation of cardiomyocyte apoptosis with duration of hypertension, severity of hypertension and caspase-3 expression in hypertensive rats

Correlation of cardiomyocyte apoptosis with duration of hypertension, severity of hypertension and caspase-3 expression in hypertensive rats was analyzed. Sixty male Sprague-Dawley (SD) rats were selected and randomly divided into the observation group (n=30) and control group (n=30), and the rat models of hypertension were established by virtue of transverse aortic constriction (TAC). The rats in the two groups were further divided into the 7-day subgroup (n=10), 14-day subgroup (n=10) and 28-day subgroup (n=10), respectively according to their survival time after TAC. The blood pressure values of the rats in each group were measured through intubation of carotid artery to calculate the mean arterial pressure (MAP). The conditions of cardiomyocyte apoptosis were detected using terminal dexynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Enzyme-linked immunosorbent assay (ELISA) was applied to measure the expression of caspase-3 in the myocardial tissues, and correlation analysis was performed. The MAPs in 7-, 14- and 28-day subgroups of the observation group were significantly higher than those in the corresponding subgroups of the control group (P<0.05). The 7-, 14- and 28-day subgroups of the observation group had remarkably elevated myocardial caspase-3 expression levels compared with the subgroups of the control group (P<0.05). The apoptosis rates of myocardial cells in the three subgroups of the observation group were obviously higher than those in the corresponding subgroups of the control group (P<0.05). Pearson's correlation analysis indicated that the cardiomyocyte apoptosis rate of hypertensive rats was positively correlated with the duration of hypertension, severity of hypertension and caspase-3 expression (P<0.05). Hypertension can induce apoptosis of myocardial cells, and the apoptosis becomes more serious with the constantly elevated level and prolonged duration of hypertension. In addition, the activity of caspase-3 has a close correlation with cardiomyocyte apoptosis.

β-Blockers and ivabradine differentially affect cardiopulmonary function and left ventricular filling index

OBJECTIVE

Patients with left ventricular (LV) diastolic dysfunction are characterized by exertional dyspnoea. Heart rate (HR) reduction by β-blockers can improve exercise tolerance by prolonging LV filling, but their negative inotropic and lusitropic properties can be detrimental in this disease. We tested the effects of administering ivabradine, a HR-lowering drug without impact on cardiac kinetics that may favorably affect diastolic function.

METHODS

Twenty-four patients with coronary artery disease (CAD) and normal LV ejection fraction on chronic β-blocker therapy were included. NT-proBNP serum levels were determined prior to and after cardiopulmonary exercise. β-Blockers were then replaced by ivabradine and patients were re-tested after 6 weeks. Patients were initially classified as having a low (E/e' ≤ 8; n = 11) or high (E/e' > 8; n = 13) LV filling index.

RESULTS

E/e' significantly decreased during ivabradine therapy in patients with high E/e' (10.7 ± 2.9 vs. 8.9 ± 1.7; p < 0.01), whereas no difference occurred in patients with low E/e' (6.4 ± 0.7 vs. 6.5 ± 1.1; p = ns). With ivabradine, patients with high E/e' had an increased oxygen uptake at the anaerobic threshold (from 10.8 ± 1.4 to 11.8 ± 1.9 ml/min/kg; p < 0.05) and a steeper slope of the initial oxygen pulse curve (from 293 ± 109 to 359 ± 117 µl/beat/kg/W; p < 0.05). Moreover, patients with high E/e' had lower NT-proBNP serum levels at rest (169 ± 207 vs. 126 ± 146 pg/ml; p < 0.05) and after exercise (190 ± 256 vs. 136 ± 162 pg/ml; p < 0.05) during ivabradine therapy.

CONCLUSIONS

In patients with CAD and elevated E/e', switching therapy from β-blockers to ivabradine may cause a reduction in LV filling pressures and an improved stroke volume response to exercise.

Taurine prevents hypertension and increases exercise capacity in rats with fructose-induced hypertension

BACKGROUND

Fructose-induced hypertension was used to test the hypothesis that taurine supplementation and/or exercise can prevent hypertension and increase exercise capacity.

METHODS

Five groups of 15 Sprague-Dawley rats were allocated and designated as control, high fructose-fed (fructose), high fructose-fed plus exercise (FE), high fructose-fed plus 2% taurine supplement (FT) and high fructose-fed plus 2% taurine supplement and exercise (FET) groups. Noninvasive systolic blood pressure (SBP) was recorded weekly and invasive arterial blood pressure (ABP) was recorded at the end of the 4-week trial. Three consecutive swimming tests were performed in the selected rats from each group and the plasma biomarkers were measured in the remaining rats.

RESULTS

Noninvasive SBP differed significantly (P < 0.001) from week 3, both noninvasive and invasive ABP increased significantly (P < 0.001), and exercise capacity significantly decreased (P < 0.001) in the fructose group compared with the control group. The individual effects of swimming and taurine supplementation were incapable of preventing the development of hypertension and SBP significantly (P < 0.001) increased in the FE and FT groups; exercise capacity in those groups remained similar to control. The combined effects of exercise and taurine alleviated hypertension and significantly increased exercise capacity in the FET group. Insulin resistance increased significantly and plasma nitric oxide (NO) decreased significantly in the F, FE, and FT groups. Both parameters remained similar to control values in the FET group with an increasing antioxidant activity.

CONCLUSION

Taurine supplementation in combination with exercise prevents hypertension and increases exercise capacity by possibly antioxidation and maintaining NO concentrations.

Candesartan improves maximal exercise capacity in hypertensives: results of a randomized placebo-controlled crossover trial

Cardiac hypertrophy and remodelling in hypertension has been associated with impaired exercise capacity. The authors tested whether an angiotensin receptor blocker, candesartan, improved exercise peak oxygen volume (VO2) in this population. A total of 154 untreated hypertensive patients, aged 40 to 66 years, with World Health Organization stage I or II hypertension and left ventricular hypertrophy, were randomized to receive placebo, candesartan (32 mg), each of these plus aspirin (300 mg/d), or the same preparations in a reverse order, for 3 weeks, with a 3-week washout period between treatments. The authors measured maximal workload and oxygen reserve with an exercise test, 24 hour-ambulatory blood pressure, and echocardiography at the end of each treatment. Hypertensive patients did not achieve the maximal workload (116 [99-133] W vs 132 (AMA style = no period on vs) [116-149] W; P=.01). This impaired exercise capacity was in a multiple regression analysis related to lower oxygen reserve (r=0.49, P<.001), and the lower oxygen reserve to higher left ventricular hypertrophy by echocardiography (beta=-0.34), respectively. The use of candesartan alone or with aspirin resulted in an improvement of peak VO2 and exercise tolerance, when compared with controls. Patients with hypertension and cardiac hypertrophy cannot achieve a predicted maximal workload. The use of an angiotensin receptor blocker in therapy may represent a useful treatment in these patients for its effect on exercise peak VO2 and exercise tolerance. The use of aspirin did not affect outcome.

Exercise performance during losartan- or atenolol-based treatment in hypertensive patients with electrocardiographic left ventricular hypertrophy (a LIFE substudy)

The objective of the study was to assess the influence of left ventricular (LV) hypertrophy regression on exercise capacity in hypertensive patients. Doppler echocardiography was performed at rest and during exercise in 51 patients with electrocardiographic LV hypertrophy before and after 1 year of randomized blinded losartan- or atenolol-based antihypertensive treatment. After 1 year, blood pressure was comparably reduced by 32/14 and 27/13 mmHg, respectively, in the losartan and atenolol groups, but the atenolol group had higher mean LV mass index (118 vs 103 g/m2) and lower LV ejection fraction (61% vs 67%) and midwall shortening (15.8% vs 16.8%) (all p<0.05). Resting diastolic Doppler indices remained unchanged and did not differ between the groups. Peak oxygen uptake during exercise was virtually unchanged after 1 year and did not differ between the groups in spite of a lower peak exercise heart rate in atenolol-treated patients. In multivariate analysis, higher peak oxygen uptake at 1 year was associated with lower body mass index, and higher systolic blood pressure and shorter isovolumic relaxation time at peak exercise (multiple R2 = 0.51, p<0.01), while age, gender, heart rate increase during exercise, reduction in LV mass and study treatment did not enter. In conclusion, reduction in blood pressure and LV mass induced by losartan or atenolol treatment was not accompanied by improved exercise capacity after 1 year. The results may be explained by persistent impairment of myocardial relaxation influencing exercise capacity.

Role of exercise training on cardiovascular disease in persons who have type 2 diabetes and hypertension

Exercise training is an essential component in the medical management of patients who have type 2 diabetes and hypertension. Regular exercise improves the cardiovascular health of individuals who have these conditions through multiple mechanisms (Fig. 1). These mechanisms include improvements in endothelial vasodilator function,left ventricular diastolic function, arterial stiffness.systematic inflammation, and reducing left ventricular mass. Exercise training also reduces total and abdominal fat, which mediate improvements in insulin sensitivity and blood pressure, and possibly, endothelial function. Persons who are in a prediabetic stage or those who have the metabolic syndrome may be able to prevent or delay the progression to overt diabetes by adopting a healthier lifestyle, of which increasing habitual levels of physical activity isa vital component. Most persons who have diabetes and hypertension or are at risk for these conditions should be able to initiate an exercise program safely after appropriate medical screen-ing and the establishment of an individualized exercise prescription. Despite the increasing amount of evidence that shows the benefits of exercise training, this modality of prevention and treatment continues to be underused. Although patients' lack of knowledge of the benefits of exercise or lack of motivation contributes to this underuse, a lack of clear and specific guidelines from health care professionals also is an important factor. Clinicians need to educate patients about the benefits of exercise for managing their type 2 diabetes and assist in formulating specific advice for increasing physical activity. Specific instructions should be given to patients, rather than general advice, such as "you should exercise more often." Many cardiac re-habilitation and clinical exercise programs can accommodate patients who have type 2 diabetes and hypertension. Such programs can establish individualized exercise prescriptions and provide an environment that is conducive for "lifestyle change" that underlies long-term compliance to exercise and risk factor modification.

Association between exercise capacity and left ventricular geometry in overweight patients with mild systemic hypertension

The purpose of this study was to determine the relation between left ventricular (LV) geometry and exercise capacity in unmedicated, hypertensive patients. Analysis of the data revealed peak oxygen consumption (ml kg(-1) min(-1)) for concentric hypertrophy (corrected mean +/- SE 23.5 +/- 1.2) was significantly less (F = 3.68, p <0.02) than the concentric remodeling (28.1 +/- 1.2) and normal (27.3 +/- 0.6) geometries. The LV geometric pattern was found to be associated with exercise capacity in unmedicated, hypertensive patients, such that patients with concentric hypertrophy showed reduced capacity.

Relationship between exercise systolic blood pressure and left ventricular geometry in overweight, mildly hypertensive patients

OBJECTIVE

To examine the association between the graded exercise systolic blood pressure (SBP) response and left ventricular (LV) geometric structure in patients with untreated mild hypertension.

PARTICIPANTS

The study included 80 sedentary, overweight patients (43 female and 37 male) with unmedicated high normal blood pressure or stage 1-2 hypertension.

METHODS

An echocardiogram was used to determine LV mass and the relative wall thickness (RWT) in relation to the chamber dimension. Participants performed a maximal graded exercise test, and the SBP was recorded at workloads of 2, 4 and 6 metabolic equivalents and at peak exercise. Separate statistical models were used to determine the influence of LV mass indexed for height(2.7) (LVMIh) and RWT on submaximal exercise SBP and peak exercise SBP, controlling for resting SBP, age, gender, ethnicity and body mass index.

RESULTS

A greater RWT was associated with a higher submaximal SBP level (P = 0.038). Neither LVMIh (P = 0.989) nor the interaction of RWT and LVMIh (P = 0.787) were related to the submaximal SBP. None of the main or interaction effects of RWT and LVMIh were associated with the peak exercise SBP level.

CONCLUSION

Increases in RWT were associated with higher submaximal exercise SBP responses in a sample of overweight, unmedicated hypertensives. These results suggest that RWT is an important determinant of the association between cardiac mass and exercise SBP response.

Impact of diastolic Doppler indices on exercise capacity in hypertensive patients with electrocardiographic left ventricular hypertrophy (a LIFE substudy)

OBJECTIVE

To assess whether Doppler evidence of impaired early diastolic relaxation during exercise is associated with lesser exercise capacity in hypertensive patients.

DESIGN

Single center addition to the echocardiographic substudy in the Losartan Intervention For Endpoint (LIFE) reduction in hypertension study.

SETTING

University hospital out-patient clinic.

METHODS

A total of 60 patients (29 women and 31 men) with essential hypertension and electrocardiographic LV hypertrophy.

INTERVENTIONS

Assessment of Doppler echocardiography and ergospirometry during semi-upright bicycling.

MAIN OUTCOME MEASURE

Exercise capacity and its relation to diastolic Doppler indices at rest and during exercise.

RESULTS

Average resting blood pressure was 181/97 +/- 18/9 mmHg, LV mass/body surface area 127 +/- 26 g/m2, midwall shortening 16 +/- 2%, and isovolumic relaxation time (IVRT) and transmitral early to atrial filling velocity (E/A) ratio 121 ms and 0.80, respectively. Exercise capacity, assessed as peak oxygen uptake and exercise load at exhaustion in all patients, were 20 and 25% higher, respectively, in men than women (both P < 0.01). In multivariate analysis, higher peak exercise load was related to male gender, higher E/A ratio at rest, greater reduction in IVRT during exercise and higher peak exercise heart rate (multiple R2 = 0.59, P < 0.01). Younger age, greater reduction in IVRT during exercise, higher midwall shortening and peak exercise heart rate were associated with higher peak oxygen uptake (multiple R2 = 0.47, P < 0.01).

CONCLUSION

Diastolic LV performance significantly influences exercise capacity in hypertensive patients with LV hypertrophy. Impaired exercise capacity is more strongly associated with blunted reduction in IVRT during exercise than with lower E/A ratio at rest.

Divergent cardiac response to exercise in essential hypertension vs. normotension and the effect of enalapril

The aims of this study were to examine (1) the cardiac response to exercise in essential hypertension and (2) the effect of long-term enalapril treatment on cardiac reserve. Ten normotensive control subjects and 15 patients with moderate, essential hypertension underwent radionuclide ventriculography during graded, supine exercise (0 W-50 W-100 W). The hypertensive patients were studied during monotherapy using hydrochlorothiazide and 3 and 12 months after supplementation with enalapril 10-40 mg o.d. During exercise, the control subjects demonstrated a 17% increase in left ventricular ejection fraction (LVEF) mediated by a 30% decrease in end-systolic volume, a small increase in stroke volume and a minor biphasic (increase-decrease) change in end-diastolic volume. In the hypertensive patients, both the end-diastolic and the end-systolic volume increased substantially with no increase in LVEF, although stroke volume increased by 33%. Long-term therapy with enalapril induced only a minor change towards a more normal pattern of cardiac response to exercise. The hypertensive patients increased their stroke volume during exercise by recruiting preload reserve instead of increasing contractility. Long-term treatment with enalapril had little, if any, effect on this abnormal cardiac response.

Physical performance is preserved after regression of left ventricular hypertrophy

Reversal of left ventricular hypertrophy has been shown to improve left ventricular diastolic function in elderly patients with hypertension, but little is known about whether this affects physical performance. Left ventricular mass, cardiac function at rest and during submaximal exercise, and physical performance were assessed in 38 elderly patients with hypertension with left ventricular hypertrophy and normal systolic function before and after 8 and 14 months of therapy with amlodipine or hydrochlorothiazide or both. Blood pressure control was achieved with amlodipine in 18 patients, with hydrochlorothiazide in seven, and with the combination of these drugs in 13. Left ventricular mass index was similarly reduced from approximately 150 to approximately 100 g/m2 at 14 months' in each treatment group. Systolic function was maintained with the three treatment regimens, whereas similar decreases in time to peak filling rate and increases in first-third filling fraction occurred both at rest and during submaximal exercise after 8 months and further after 14 months of therapy. Exercise capacity did not significantly change in the group as a whole, but individual changes in peak oxygen uptake at the end of treatment correlated significantly with the decrease in time to peak filling rate during submaximal exercise (r = -0.49; p < 0.01). It is concluded that long-term blood pressure control with amlodipine or hydrochlorothiazide or both is associated with significant reductions in left ventricular mass and improved diastolic function in elderly patients with hypertension with left ventricular hypertrophy. Despite this reduction in left ventricular mass, left ventricular systolic function and physical performance are well preserved during submaximal exercise.