Reproducibility patterns of plasma norepinephrine and muscle sympathetic nerve traffic in human obesity

BACKGROUND AND AIMS

The present study was designed to assess the reproducibility of the two markers of adrenergic drive, venous plasma norepinephrine and efferent postganglionic muscle sympathetic nerve traffic (MSNA) in reflecting the sympathetic activation characterizing the obese state in human beings.

METHODS AND RESULTS

In 15 male obese normotensive subjects (age: 40.1+/-2.2, mean+/-SEM) we measured, in two experimental sessions three weeks apart, blood pressure (BP, Finapres), heart rate (EKG), plasma norepinephrine (HPLC assay) and MSNA (microneurography, peroneal nerve). In each session three norepinephrine samples were obtained and norepinephrine reproducibility between sessions was assessed by considering a single norepinephrine sample or by averaging 2-3 samples. Reproducibility data were compared to the ones displayed by the MSNA technique. While MSNA values showed a highly significant correlation between sessions (r=0.89, p<0.001), norepinephrine values based on a single blood sample evaluation did not correlate with each other (r=0.44, p=NS). Norepinephrine correlation coefficient values increased and achieved statistical significance when average data from 3 blood samples were examined (r=0.56, p<0.03).

CONCLUSIONS

In human obesity MSNA displays a reproducibility pattern higher than plasma norepinephrine. The reproducibility of the norepinephrine approach can be improved by increasing the number of blood samples on which norepinephrine assay is performed. To obtain such a goal, and to make reproducibility closer to the MSNA one, three norepinephrine samples are needed.

Indexation of left ventricular mass to body surface area and height to allometric power of 2.7: is the difference limited to obese hypertensives?

Whether left ventricular mass (LVM) should be normalized to different indexes in relation to body size is still debated. We sought to evaluate the prevalence of left ventricular hypertrophy (LVH) defined by different indexation criteria in a cohort of hypertensive subjects categorized according to body mass index (BMI). A total of 2213 essential hypertensive subjects included in the Evaluation of Target Organ Damage in Hypertension (ETODH) were divided in three groups according to BMI thresholds (<25, 25-29.9 and >or=30 kg m(-2)). All patients underwent extensive investigations including quantitative echocardiography. LVH was defined as an LVM index equal to or higher than (1) 125 g m(-2) in men and 110 g m(-2) in women, (2) 51 g m(-2.7) in men and 47 g m(-2.7) in women. Overall, 687 out of 2213 patients (31.0%) were found to have LVH when LVM was indexed to body surface area (BSA) and 1030 (46.5%) when indexed to height(2.7). A total of 845 patients (38.2%) had normal BMI, 954 patients (43.1%) were overweight and 414 (18.7%) were obese. Prevalence rates of LVH in the three groups were 25.1, 31.6, 41.2% by indexation to BSA and 29.9, 50.5, 71.8% by indexation to height(2.7), respectively. LVM indexed to BSA markedly underestimates LVH prevalence in obese as well as overweight hypertensive patients. To avoid a systematic misclassification of cardiovascular risk, LVM should be routinely indexed to height(2.7) in overweight and obese patients representing a large percentage of the hypertensive population.

Dynamic adaptation of cardiac baroreflex sensitivity to prolonged exposure to microgravity: data from a 16-day spaceflight

This study explored the process of arterial baroreflex adaptation to microgravity, starting from the first day of flight, during the 16-day STS-107 Columbia Space Shuttle mission. Continuous blood pressure (BP), ECG, and respiratory frequency were collected in four astronauts on ground (baseline) and during flight at days 0–1, 6–7, and 12–13, both at rest and during moderate exercise (75 W) on a cycle ergometer. Sensitivity of the baroreflex heart rate control (BRS) was assessed by sequence and spectral alpha methods. Baroreflex effectiveness index (BEI); low-frequency (LF) power and high-frequency (HF) power of systolic BP (SBP), diastolic BP (DBP), and R-R interval (RRI); the RRI LF/HF ratio; and the RRI root mean square of successive differences (RMSSD) index were also estimated. We found that, at rest, BRS increased in early flight phase, compared with baseline (means ± SE: 18.3 ± 3.4 vs. 10.4 ± 1.2 ms/mmHg; P < 0.05), and it tended to return to baseline in subsequent days. During exercise, BRS was lower than at rest, without differences between preflight and in-flight values. At rest, in the early flight phase, RMSSD and RRI HF power increased ( P < 0.05) compared with baseline, whereas LF powers of SBP and DBP decreased. No statistical difference was found in these parameters during exercise before vs. during flight. These findings demonstrate that heart rate baroreflex sensitivity and markers of cardiac vagal modulation are enhanced during early exposure to microgravity, likely because of the blood centralization, and return to baseline values in subsequent flight phases, possibly because of the fluid loss. No deconditioning seems to occur in the baroreflex control of the heart.

Blood pressure lowering effects of rimonabant in obesity-related hypertension

Obesity-related hypertension represents a common clinical condition characterised by complex pathophysiological and therapeutic features. From a pathophysiological view point, results of experimental and animal studies have led to the hypothesis that neurogenic mechanisms participate in the development and progression of the disease. The hypothesis is based on the evidence that metabolic (i.e. insulin-resistance) and neural (sympathetic activation) alterations frequently co-exist in the obese hypertensive patient and that they reciprocally potentiate each other. From a therapeutic view point, the 2007 European Society of Hypertension/European Society of Cardiology emphasised the importance in this clinical condition of treatment not only through antihypertensive drugs but also via lifestyle changes and drug-induced interventions that reduce body weight. The four Rimonabant In Obesity (RIO) studies have shown that rimonabant can decrease body weight. A recent meta-analysis, based on the RIO results, showed that rimonabant, particularly in obese hypertensive patients, can also decrease - although modestly (2.8 mmHg for systolic and 2.2 mmHg for diastolic) - blood pressure. These effects, which appear to be triggered by the weight reduction induced by the drug, are clinically relevant because they contribute favourably to lower the elevated cardiovascular risk profile of the obese hypertensive patient.

Effects of a fixed combination of perindopril and indapamide on macrovascular and microvascular outcomes in patients with type 2 diabetes mellitus (the ADVANCE trial): a randomised controlled trial

BACKGROUND

Blood pressure is an important determinant of the risks of macrovascular and microvascular complications of type 2 diabetes, and guidelines recommend intensive lowering of blood pressure for diabetic patients with hypertension. We assessed the effects of the routine administration of an angiotensin converting enzyme (ACE) inhibitor-diuretic combination on serious vascular events in patients with diabetes, irrespective of initial blood pressure levels or the use of other blood pressure lowering drugs.

METHODS

The trial was done by 215 collaborating centres in 20 countries. After a 6-week active run-in period, 11 140 patients with type 2 diabetes were randomised to treatment with a fixed combination of perindopril and indapamide or matching placebo, in addition to current therapy. The primary endpoints were composites of major macrovascular and microvascular events, defined as death from cardiovascular disease, non-fatal stroke or non-fatal myocardial infarction, and new or worsening renal or diabetic eye disease, and analysis was by intention-to-treat. The macrovascular and microvascular composites were analysed jointly and separately. This trial is registered with ClinicalTrials.gov, number NCT00145925.

FINDINGS

After a mean of 4.3 years of follow-up, 73% of those assigned active treatment and 74% of those assigned control remained on randomised treatment. Compared with patients assigned placebo, those assigned active therapy had a mean reduction in systolic blood pressure of 5.6 mm Hg and diastolic blood pressure of 2.2 mm Hg. The relative risk of a major macrovascular or microvascular event was reduced by 9% (861 [15.5%] active vs 938 [16.8%] placebo; hazard ratio 0.91, 95% CI 0.83-1.00, p=0.04). The separate reductions in macrovascular and microvascular events were similar but were not independently significant (macrovascular 0.92; 0.81-1.04, p=0.16; microvascular 0.91; 0.80-1.04, p=0.16). The relative risk of death from cardiovascular disease was reduced by 18% (211 [3.8%] active vs 257 [4.6%] placebo; 0.82, 0.68-0.98, p=0.03) and death from any cause was reduced by 14% (408 [7.3%] active vs 471 [8.5%] placebo; 0.86, 0.75-0.98, p=0.03). There was no evidence that the effects of the study treatment differed by initial blood pressure level or concomitant use of other treatments at baseline.

INTERPRETATION

Routine administration of a fixed combination of perindopril and indapamide to patients with type 2 diabetes was well tolerated and reduced the risks of major vascular events, including death. Although the confidence limits were wide, the results suggest that over 5 years, one death due to any cause would be averted among every 79 patients assigned active therapy.

Ambulatory heart rate and target organ damage in never-treated essential hypertensives

Limited evidence is available about the relationship between ambulatory heart rate (HR) and target organ damage (TOD) in uncomplicated hypertension. We sought to investigate the association between ambulatory HR and subclinical cardiac, vascular and renal markers of TOD in never-treated essential hypertensives. A total of 580 subjects with recently diagnosed (<or= 1 year) grade 1 and 2 hypertension, categorized by tertiles of HR levels, assessed by two 24-h ambulatory blood pressure monitoring at 1- to 4-week interval, sex and the presence or absence of TOD were considered for this analysis. All subjects also underwent laboratory and ultrasonographic investigations searching for microalbuminuria (MA), left ventricular hypertrophy (LVH) and carotid atherosclerosis (carotid thickening/plaque). In the whole population, as well as in both genders, LVH, carotid atherosclerosis and MA prevalence rates did not significantly increase with 48-h HR tertiles. When patients were categorized according to the presence or absence of TOD (that is, LVH, carotid atherosclerosis or MA) no significant intergroup differences in 48-h HR were found. Furthermore, average 48-h HR was similar in patients without organ involvement as in those with one, two or three TOD signs. Finally, in a multivariate analysis age, 48-h systolic blood pressure and metabolic syndrome assessed by ATP III criteria, but not HR were independently associated with TOD. Our findings showing that 48-h ambulatory HR is not associated with markers of TOD do not support the view that a faster HR may have an additive value in predicting organ damage in the early phases of essential hypertension.

The need for combination antihypertensive therapy to reach target blood pressures: what has been learned from clinical practice and morbidity-mortality trials?

Pharmacological treatment of hypertension represents a cost-effective way for preventing cardiovascular and renal complications. To benefit maximally from antihypertensive treatment blood pressure (BP) should be brought to below 140/90 mmHg in every hypertensive patient, and even lower (< 130/80 mmHg) if diabetes or renal disease co-exists. Most of the time such targets cannot be reached using monotherapies. This is especially true in patients who exhibit a high cardiovascular risk. The co-administration of two agents acting by different mechanisms considerably increases BP control. Such preparations are not only efficacious, but also well tolerated, and some fixed low-dose combinations have a tolerability profile similar to placebo. This is for instance the case for the preparation containing the angiotensin-converting enzyme inhibitor perindopril (2 mg) and the diuretic indapamide (0.625 mg), a fixed low-dose combination that has recently been shown in controlled interventional trials to be more effective than monotherapies in reducing albuminuria, regressing cardiac hypertrophy and improving macrovascular stiffness. Fixed-dose combinations are becoming more and more popular and are even proposed by current hypertension guidelines as a first-line option to treat hypertensive patients.

Achieving blood pressure goals globally: five core actions for health-care professionals. A worldwide call to action

The prevalence of hypertension continues to rise across the world, and most patients who receive medical intervention are not adequately treated to goal. A Working Group including representatives of nine international health-care organizations was convened to review the barriers to more effective blood pressure control and propose actions to address them. The group concluded that tackling the global challenge of hypertension will require partnerships among multiple constituencies, including patients, health-care professionals, industry, media, health-care educators, health planners and governments. Additionally, health-care professionals will need to act locally with renewed impetus to improve blood pressure goal rates. The Working Group identified five core actions, which should be rigorously implemented by practitioners and targeted by health systems throughout the world: (1) detect and prevent high blood pressure; (2) assess total cardiovascular risk; (3) form an active partnership with the patient; (4) treat hypertension to goal and (5) create a supportive environment. These actions should be pursued with vigour in accordance with current clinical guidelines, with the details of implementation adapted to the economic and cultural setting.

Ambulatory blood pressure, target organ damage and aortic root size in never-treated essential hypertensive patients

The relationship between ambulatory blood pressure (ABP), target organ damage (TOD) and aortic root (AR) size in human hypertension has not been fully explored to date. We investigated the relationship between ABP, different markers of TOD and AR size in never-treated essential hypertensive patients. A total of 519 grade 1 and 2 hypertensive patients (mean age 46+/-12 years) referred for the first time to our outpatient clinic underwent the following procedures: (1) routine examination, (2) 24 h urine collection for microalbuminuria (MA), (3) ambulatory blood pressure monitoring over two 24 h periods within 4 weeks, (4) echocardiography and (5) carotid ultrasonography. AR dilatation was defined by sex-specific criteria (> or =40 mm in men and > or =37 mm in women). AR diameter was increased in 3.7% of patients. Demographic variables (body mass index, age and male gender), average night-time diastolic blood pressure (BP) (but not clinic or average 48 h BP), left ventricular mass index and carotid intima-media (IM) thickness showed an independent association with AR size in both univariate and multivariate analyses. When TOD data were analysed in a categorical way, a stepwise increase in the prevalence of left ventricular hypertrophy (LVH) (I=17.5%, II=27.6%, III=35.8%) and carotid IM thickening (I=20.9%, II=28.8%, III=34.4%), but not in MA (I=6.8%, II=9.1%, III=8.7%) was found with the progression of AR size tertiles. Our results show that (1) AR enlargement in uncomplicated never-treated hypertensive patients has a markedly lower prevalence than traditional markers of cardiac and extracardiac TOD; (2) night-time BP, LVH and carotid IM thickening are independent predictors of AR dimension.