Epidemiological evidence of increased waist circumference,but not body mass index,associated with impaired baroreflex sensitivity

Although an inverse relationship between body mass index (BMI) and baroreflex sensitivity (BRS) was found, the effect of waist circumference (WC) on BRS is still inconclusive. The contradictory results of previous studies may be related to the heterogeneity and relatively small sample size of the subjects examined. The aim of this population-based study was to investigate whether the influence of increased WC is more detrimental to BRS than BMI. A total of 760 community dwellers were recruited and they were classified into Q1 (n = 189), Q2 (n = 183), Q3 (n = 192) and Q4 (n = 196) groups, based on WC quartiles. Spontaneous BRS was determined by spectral α coefficient method. Valsalva ratio was the longest RR interval after release of Valsalva maneuver divided by the shortest RR interval during maneuver. Cardiac autonomic function was calculated by power spectrum of heart rate in low and high frequency (LF, 0.04–0.15 Hz; HF, 0.15–0.40 Hz), and LF/HF ratio in supine position for five minutes. There were significant differences in spontaneous BRS and Valsalva ratio among different WC groups. In multivariate analysis, obesity was inversely associated with spontaneous BRS and Valsalva ratio. However, these inverse relationships became insignificant after further adjustment for WC quartiles. In contrast, Q4 vs. Q1, Q3 vs. Q1 and Q2 vs. Q1 of WC were inversely related to spontaneous BRS. Q4 vs. Q1 and Q3 vs. Q1 of WC were negatively associated with the Valsalva ratio. In conclusion, increased and even high-normal WC had a stronger adverse effect on BRS than BMI, independent of cardio-metabolic risk factors.     

Early signs of cardiovascular dysregulation in young adult binge drinkers

Binge drinking is widespread on American college campuses, but its effects on the cardiovascular system are poorly understood. This study sought evidence of preclinical cardiovascular changes in binge drinking young adults (n = 24) compared to nondrinking (n = 24) and social drinking (n = 23) peers during baseline, paced sighing (0.033 Hz), and paced breathing (0.1 Hz) tasks. Binge drinkers showed consistent but often statistically nonsignificant evidence of greater sympathetic activation and reduced baroreflex sensitivity. Interestingly, the structure of group‐averaged baseline heart rate spectra was considerably different between groups in the low frequency range (0.05–0.15 Hz). In particular, the binge drinking group–averaged spectra showed several spectral peaks not evident in the other groups, possibly indicating two functionally distinct subranges (0.05–0.08 and 0.08–0.15 Hz) that reflect vascular tone baroreflex activity and heart rate baroreflex activity, respectively. Vascular tone baroreflex gain and power in two peaks in the 0.05–0.08 Hz range were associated with years of drinking in the binge drinking group. Vascular dysfunction may be an early indicator of drinking‐related change in the cardiovascular system.     

Variant autonomic regulation during active standing in Swedish and Japanese junior high school children

The present investigation is about cardiovascular responses and relevant autonomic function in Swedish and Japanese pubertal children on active standing using non-invasive continuous beat-to-beat finger arterial pressure (FAP) monitoring and power spectral analysis. Examined were 54 Swedish and 57 Japanese children (13-15 years). FAP and heart rate (HR) was continuously recorded in the supine position and during standing. Supine FAP was significantly higher in Swedish compared with Japanese children (121/62 versus 103/53 mmHg, P < 0.001). Swedish children showed a higher increase in arterial pressure and HR upon uprising, resulting in a higher vasoconstrictor index (5.04 +/- 0.22 versus 2.31 +/- 0.11 mmHg s(-1), P < 0.001, respectively). There were also higher increases in arterial pressure and HR in the following steady state period (1-7 min) between the two groups. These differences were also found after adjustment of body weight and height. Frequency domain analysis of HR and arterial pressure variability indicated significantly higher low/high frequency power of HR and low frequency power of arterial pressure. These results suggest that Swedish pubertal children have higher basal blood pressure and enhanced cardiovascular sympathetic responses. These differences in the two cohorts might be caused by genetic factors.     

Autonomic mechanisms and sudden death after abrupt coronary occlusion

In spite of recent advances in secondary prevention, sudden cardiac death has remained a major public health problem as the majority of fatalities occur in subjects without a history of severe heart disease. Abrupt rupture of a vulnerable plaque resulting in thrombotic occlusion of a coronary artery is a common cause of sudden death in this population. Coronary occlusion does not, however, invariably lead to sudden death but may cause acute myocardial infarction or exacerbation of chest pain. Extensive studies in experimental animals and increasing clinical evidence indicate that autonomic nervous activity has a significant role in modifying the clinical outcome. Sympathetic hyperactivity favours the genesis of life-threatening ventricular tachyarrhythmias while vagal activation exerts an antifibrillatory effect. Strong afferent stimuli from the ischaemic myocardium impair arterial baroreflex and may lead to dangerous haemodynamic instability. Studies with a human angioplasty model have shown that there is wide interindividual variation in the type and severity of autonomic reactions during the early phase of abrupt coronary occlusion, a critical period for out-of-hospital cardiac arrest. The site of the occlusion is not a significant determinant of the reactions, whereas the severity of a coronary stenosis, adaptation or ischaemic preconditioning, beta-blockade and gender seem to affect the autonomic reactions and occurrence of complex ventricular arrhythmias. Clinical and angiographic factors are, however, poor predictors of autonomic reactions in an individual patient. Recent studies have documented a hereditary component for autonomic function, and genetic factors may also modify the clinical manifestations of acute coronary occlusion.     

Atorvastatin Improves the Impaired Baroreflex Sensitivity via Anti-Oxidant Effect in the Rostral Ventrolateral Medulla of SHRSP

We have demonstrated that oxidative stress in the rostral ventrolateral medulla (RVLM), a vasomotor center in brainstem, increases sympathetic nerve activity (SNA) and that oral administration of atorvastatin inhibited SNA via anti-oxidant effect in the RVLM of stroke-prone spontaneously hypertensive rats (SHRSPs). The impairment of baroreflex sensitivity (BRS) is known as the predictive factor of mortality in the hypertension and BRS is impaired in SHRSP. The aim of the present study was to determine whether oral administration of atorvastatin improved the impaired BRS via anti-oxidant effect in the RVLM in SHRSP. Atorvastatin (20 mg/kg/day) or vehicle was orally administered for 28 days in SHRSPs. Systolic blood pressure (SBP), heart rate, and 24-h urinary norepinephrine excretion as an indicator of SNA were comparable between atorvastatin- and control-SHRSP. Thiobarbituric acid-reactive substance (TBARS) levels as a marker of oxidative stress was significantly lower in atorvastatin-SHRSP than in control-SHRSP. Baroreflex sensitivity measured by the spontaneous sequence method was significantly higher in atorvastatin-SHRSP than in control-SHRSP. These results suggest that atorvastatin improves the impaired BRS in SHRSP via its anti-oxidant effect in the RVLM of SHRSP.     

Treatment of Resistant Hypertension With Endovascular Baroreflex Amplification: 3-Year Results From the CALM-FIM Study

ObjectivesThe aim of this study was to evaluate the long-term (3-year) safety and effectiveness of endovascular baroreflex amplification (EVBA) from both the European and American CALM-FIM cohorts.BackgroundThe CALM-FIM study demonstrated that EVBA in patients with resistant hypertension significantly lowered blood pressure (BP) with an acceptable safety profile during 6-month follow-up.MethodsThe CALM-FIM studies were prospective, nonrandomized, first-in-human studies that enrolled patients with resistant hypertension (office systolic BP ≥160 mm Hg and mean 24-hour ambulatory BP ≥130/80 mm Hg despite a stable regimen of ≥3 antihypertensive medications, including a diuretic agent). The incidence of (serious) adverse events and changes in BP, heart rate, and prescribed antihypertensive medication up to 3 years after implantation were determined.ResultsThe Mobius device was implanted in 47 patients (30 in Europe, 17 in the United States; mean age 54 years, 23 women). Five serious adverse events (hypotension, n = 2; hypertension, n = 1; vascular access complications, n = 2) and 2 transient ischemic attacks occurred within 30 days postprocedure. Two strokes and 1 transient ischemic attack occurred more than 2 years postimplantation. Mean office BP at baseline was 181 ± 17/107 ± 16 mm Hg and decreased by 25/12 mm Hg (95% CI: 17-33/8-17 mm Hg) at 6 months and 30/12 mm Hg (95% CI: 21-38/8-17 mm Hg) at 3 years. Mean 24-hour ambulatory BP at baseline was 166 ± 16/98 ± 15 mm Hg and decreased by 20/11 mm Hg (95% CI: 14-25/8-15 mm Hg) at 6 months.ConclusionsEVBA with the MobiusHD was effective in reducing BP at 3-year follow-up and appears to have an acceptable safety profile in patients with uncomplicated implantation, although data from randomized sham-controlled trials are needed to further evaluate the risk-benefit profile. (Controlling and Lowering Blood Pressure With the MobiusHD? [CALM-FIM_EUR], NCT01911897; Controlling and Lowering Blood Pressure With the MobiusHD? [CALM-FIM_US], NCT01831895)     

Low dose of methyltestosterone in ovariectomised rats improves baroreflex sensitivity without geno‐ and cytotoxicity

This study evaluated the effects of the isolated use of a low dose of methyltestosterone (MT) on cardiovascular reflexes and hormonal levels and its geno‐ and cytotoxic safety in ovariectomized rats. Female Wistar rats were divided into four groups (n = 6), respectively: SHAM (received vehicle methylcellulose 0.5%), SHAM + MT (received MT 0.05 mg/kg), OVX (received vehicle), and OVX + MT (received MT). Twenty‐one days after ovariectomy, treatment was given orally daily for 28 days. The Bezold–Jarisch reflex (BJR) was analyzed by measuring the bradycardic and hypotensive responses elicited by phenylbiguanide (PBG) administration. The baroreflex sensitivity (BRS) was evaluated by phenylephrine and sodium nitroprussite. Myocyte hypertrophy was determined by morphometric analysis of H&E stained slides. Biochemical data were analyzed, as well as micronucleus assay. MT improved BRS and increased testosterone values, but did not change estradiol in the OVX group. MT did not promote changes in mean arterial pressure, heart rate, BJR, serum concentrations of troponin I, weight and histopathology of the heart. MT was able to restore the BRS in OVX rats. The geno‐ and cytotoxic safety of the MT was demonstrated by the absence of an increase in the micronucleus (PCEMN) or change in the ratio between normochromatic erythrocytes and polychromatic erythrocytes (NCE/PCE).     

Effects of glucose-insulin-potassium on baroreflex sensitivity,left ventricular function and ventricular arrhythmia in the subacute phase of myocardial infarction in rats

Glucose-insulin-potassium (GIK) is clinically used for reducing mortality in acute myocardial infarction (MI). It is known that ventricular arrhythmia, left ventricular dysfunction and impaired baroreflex sensitivity (BRS) are the three major determinants for predicting the mortality after acute MI. The present work was designed to study the effects of GIK on BRS, ventricular arrhythmia, and left ventricular function in rats with coronary artery ligature. Sprague-Dawley rats were used and the myocardial infarction was produced by ligature of the left anterior descending artery. Five weeks after coronary artery ligation, BRS was measured in conscious state with a computerized blood pressure monitoring system and left ventricular function and electrocardiogram were determined in the anaesthetized state in the subacute phase of myocardial infarction. It was found that GIK did not affect the blood pressure and heart period in both conscious and anaesthetized rats. GIK did not enhance BRS, but reduced ventricular arrhythmia and improved left ventricular function by reducing left ventricular end diastolic pressure in anaesthetized rats with MI. It is proposed that reducing ventricular arrhythmia and improving left ventricular function contribute to the effect of GIK on reducing the mortality after MI.     

Resistance exercise training improves heart rate variability in women with fibromyalgia

Fibromyalgia (FM) is characterized by generalized muscle pain, low muscle strength and autonomic dysfunction. Heart rate (HR) variability (HRV) is reduced in individuals with FM increasing their risk for cardiovascular morbidity and mortality. We tested the hypothesis that resistance exercise training (RET) improves HRV, baroreflex sensitivity (BRS) and muscle strength in women with FM. Women with FM (n = 10) and healthy controls (n = 9), aged 27-60 years, were compared at baseline. Only women with FM underwent supervised RET 2 days per week for 16 weeks. Baseline and post-training measurements included HRV and spontaneous baroreflex sensitivity (BRS, alpha index) from continuous electrocardiogram and blood pressure (BP) recorded with finger plethysmography during 5 min in the supine position. RR interval, total power, log transformed (Ln) squared root of the standard deviation of RR interval (RMSSD), low-frequency power and BRS were lower (P<0.05), and HR and pulse pressure were higher (P<0.05) in women with FM than in healthy controls. After RET, mean (SEM) total power increased (387 +/- 170 ms(2), P<0.05), RMSSD increased (0.18 +/- 0.08 Ln ms, P<0.05) and Ln of high-frequency power increased (0.54 +/- 0.27 Ln ms(2), P = 0.08) in women with FM. Upper and lower body muscle strength increased by 63% and 49% (P<0.001), and pain perception decreased by 39% in women with FM. There were no changes in BRS, HR and BP after RET. Our study demonstrates that RET improves total power, cardiac parasympathetic tone, pain perception and muscle strength in women with FM who had autonomic dysfunction before the exercise programme.