The interplay between sympathetic overactivity, hypertension and heart rate variability (review, invited)

Role of the autonomic nervous system in young, middle-aged, and older individuals with essential hypertension and sleep-related changes in neurocardiac regulation

Essential hypertension involves complex cardiovascular regulation. The autonomic nervous system function fluctuates throughout the sleep-wake cycle and changes with advancing age. However, the precise role of the autonomic nervous system in the development of hypertension during aging remains unclear. In this study, we characterized autonomic function during the sleep-wake cycle in different age groups with essential hypertension. This study included 97 men (53 with and 44 without hypertension) aged 30-79 years. They were stratified by age into young (< 40 years), middle-aged (40-59 years), and older (60-79 years) groups. Polysomnography and blood pressure data were recorded for 2 min before and during an hour-long nap. Autonomic function was assessed by measuring heart rate variability and blood pressure variability. Data were analyzed using t tests, correlation analyses, and two-way analysis of variance. During nonrapid eye movement (nREM), a main effect of age was observed on cardiac parasympathetic measures and baroreflex sensitivity (BRS), with the highest and lowest levels noted in the younger and older groups, respectively. The coefficients of the correlations between these measures and age were lower in patients with hypertension than in normotensive controls. The BRS of young patients with hypertension was similar to that of their middle-aged and older counterparts. However, cardiac sympathetic activity was significantly higher (p = 0.023) and BRS was significantly lower (p = 0.022) in the hypertension group than in the control group. During wakefulness, the results were similar although some of the above findings were absent. Autonomic imbalance, particularly impaired baroreflex, plays a more significant role in younger patients with hypertension. The nREM stage may be suitable for gaining insights into the relevant mechanisms.

Mat Pilates training reduces blood pressure in both well-controlled hypertensive and normotensive postmenopausal women: a controlled clinical trial study

AIM

The aim of this study was to compare the Mat Pilates training-induced responses in resting and ambulatory blood pressure monitoring (ABPM), blood pressure variability (BPV), and heart rate variability (HRV) in well-controlled hypertensive and normotensive postmenopausal women.

METHODS

Forty-seven postmenopausal women were allocated in well-controlled hypertensive (HT) and normotensive (NT) groups. The exercise program was performed three times a week for 12 weeks. Before and after the intervention resting, blood pressure (BP), ABPM, HRV, and BPV were analyzed.

RESULTS

Student's t-test showed no difference in baseline anthropometric and resting BP values between groups. The generalized estimation equation (GEE) showed no interactions (group*time), but time (p < .05) reductions in resting systolic, diastolic and mean BP after training in both groups. Sleep ambulatory systolic, diastolic and mean BP were higher overall in the HT group (p < .05 in group effect). We also found a time effect (p < .05) with significant increases in BPV in the mean diurnal and nocturnal deviations weighted for the duration of the daytime and nighttime interval (SDdn) in systolic, diastolic and mean BP, and in the average real variability (ARV) in diastolic and mean in both groups. In addition, HRV increases (p < .05 in time effect) through the percentage of pairs of adjacent RR intervals with a difference of at least 50 ms (pNN50) after training in both groups.

CONCLUSION

Both normotensive and well-controlled hypertensive postmenopausal women may have similar Mat Pilates exercise training-induced responses in ambulatory BP, BPV and HRV.

Is There Association between Altered Adrenergic System Activity and Microvascular Endothelial Dysfunction Induced by a 7-Day High Salt Intake in Young Healthy Individuals

This study aimed to test the effect of a 7-day high-salt (HS) diet on autonomic nervous system (ANS) activity in young healthy individuals and modulation of ANS on microvascular endothelial function impairment. 47 young healthy individuals took 7-day low-salt (LS) diet (3.5 g salt/day) followed by 7-day high-salt (HS) diet (~14.7 g salt/day). ANS activity was assessed by 24-h urine catecholamine excretion and 5-min heart rate variability (HRV). Skin post-occlusive reactive hyperemia (PORH) and acetylcholine-induced dilation (AChID) were assessed by laser Doppler flowmetry (LDF). Separately, mental stress test (MST) at LS and HS condition was conducted, followed by immediate measurement of plasma metanephrines’ level, 5-min HRV and LDF microvascular reactivity. Noradrenaline, metanephrine and normetanephrine level, low-frequency (LF) HRV and PORH and AChID significantly decreased following HS compared to LS. MST at HS condition tended to increase HRV LF/HF ratio. Spectral analysis of PORH signal, and AChID measurement showed that MST did not significantly affect impaired endothelium-dependent vasodilation due to HS loading. In this case, 7-day HS diet suppressed sympathetic nervous system (SNS) activity, and attenuated microvascular reactivity in salt-resistant normotensive individuals. Suppression of SNS during HS loading represents a physiological response, rather than direct pathophysiological mechanism by which HS diet affects microvascular endothelial function in young healthy individuals.

Prevalence and factors associated with fast resting heart rate in hypertensive and normotensive patients

Background: Fast resting heart rate (RHR) is easily neglected in clinical practice of hypertension treatment.Aims: We aimed to investigate the prevalence of fast RHR and associated factors in hypertensive and normotensive individuals.Methods: We retrospectively analyzed data from two cross-sectional studies conducted in China. A total of 6763 hypertensive patients and 2807 age and sex-matched normotensive subjects with complete data on resting electrocardiogram and medical history were included. Fast RHR was defined as RHR > 85 bpm.Results: The prevalence of fast RHR was higher in hypertensive patients as compared with the normotensives (14.4% vs 7.1%, P < 0.01). In both hypertensive and normotensive subjects, fast RHR appeared as a "U-type" distribution as aging and a "inverted J type" trend as body mass index (BMI) increasing. Multivariate regression analysis showed that fast RHR was associated with age >65 or <25 years old (OR = 1.32, 95% CI 1.08-1.61), BMI <18.5 kg/m² (OR = 2.94, 95%CI 1.47-5.87) and hypercholesterolemia (OR = 1.30, 95%CI 1.10-1.53) in hypertensive patients. Fast RHR in the normotensives was associated with female (OR = 1.78, 95%CI 1.27-2.48), pre-hypertensive state (OR = 2.38, 95%CI 1.61-3.52), and rural area origin (OR = 1.50, 95%CI 1.01-2.42). Stroke and diabetes conferred closer relevance to fast RHR in both hypertensive (OR = 1.31, 95%CI 1.02-1.69 and OR 2.26, 95%CI 1.60-3.21) and normotensive individuals (OR = 2.67, 95%CI 1.36-5.21 and OR = 2.77, 95%CI 1.47-5.23).Conclusion: Fast RHR might be common in patients with hypertension. Prior stroke and diabetes history is common associated with fast RHR. Other factors associated with fast RHR seem to be different between hypertensive patients and normotensive subjects.Abbreviations: BMI: body mass index; CI: Confidence Interval; DBP: diastolic blood pressure; ECG: electrocardiogram; OR: odd ratio; RHR: resting heart rate; SBP: systolic blood pressure.

DOES THE ANESTHESIA TECHNIQUE AFFECT ARTERIAL PRESSURE AND REGIONAL CEREBRAL OXYGEN SATURATION DURING SHOULDER ARTHROSCOPY IN THE BEACH CHAIR POSITION?

- This study aimed to investigate the impact of posture and anesthesia techniques on blood pressure changes, heart rate and regional cerebral oxygen saturation during shoulder arthroscopy in the beach chair position (BCP). Sixty patients were included in this prospective cohort study: 30 patients mechanically ventilated and subjected to general anesthesia (GA) and 30 patients subjected to interscalene block (ISB) without mechanical ventilation. Noninvasive blood pressure, heart rate (HR), peripheral blood oxygen saturation and regional oxygen saturation of the brain were measured in twelve predefined points during perioperative period. The GA group patients had significantly lower mean arterial pressure and heart rate values compared to patients in ISB group during BCP (p<0.001). There was a significant difference in regional cerebral saturation between the groups measured only in points of induction and emergence from anesthesia in favor of GA group when receiving 100% oxygen (p<0.001). Changes in the mean arterial pressure and regional cerebral oxygen saturation for both brain hemispheres correlated only at the 10^th minute after setting up BCP in GA patients (right, p=0.004 and left, p=0.003). This correlation did not exist in the ISB group patients at any of the points measured. Cerebral desaturation events recorded in both groups were not statistically significantly different. Results of this study demonstrated that GA preserved regional cerebral oxygenation in a safe range during BCP despite changes in the arterial blood pressure and heart rate in comparison to ISB.

Tetrahydrocurcumin in combination with deferiprone attenuates hypertension, vascular dysfunction, baroreflex dysfunction, and oxidative stress in iron-overloaded mice

Excessive iron can generate reactive oxygen species (ROS), leading to oxidative stress that is closely associated with cardiovascular dysfunction. Iron overload was induced in male ICR mice by injection of iron sucrose (10mg/kg/day) for eight weeks. Iron overload was evidenced by increased serum iron indices. The mice developed increased blood pressure, impaired vascular function and blunted response of the autonomic nervous system. These effects were accompanied by increased malondialdehyde levels in various tissues, increased nitric oxide metabolites in plasma and urine, and decreased blood glutathione. Tetrahydrocurcumin (THU, 50mg/kg/day), deferiprone (or L1, 50mg/kg/day) or both was orally administered throughout the period of iron sucrose injection. The treatments significantly alleviated the deleterious cardiovascular effects of iron overload, and were associated with modulation of nitric oxide levels. An imbalance between endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) expression in response to iron overload was normalized by THU, L1 or the combination treatment. Moreover, the treatment decreased the upregulated expression levels of gp91phox, p47phox and HO-1. The combination of THU and L1 exerted a greater effect than THU or L1 monotherapy. These results suggest beneficial effects of THU and L1 on iron-induced oxidative stress, hypertension, and vascular dysfunction.

Adrenergic System Activation Mediates Changes in Cardiovascular and Psychomotoric Reactions in Young Individuals after Red Bull (©) Energy Drink Consumption

Objectives. To assess the effect of Red Bull(©) on (1) blood glucose and catecholamine levels, (2) cardiovascular and respiratory function changes before, during, and after exercise, (3) reaction time, (4) cognitive functions, and (5) response to mental stress test and emotions in young healthy individuals (N=38). Methods. Heart rate (HR) and arterial blood pressure (ABP), blood glucose, adrenaline, and noradrenalin plasma levels were measured before and after Red Bull(©) intake. Participants were subjected to 4 different study protocols by randomized order, before and 30 minutes after consumption of 500 mL of Red Bull(©). Results. Mean ABP and HR were significantly increased at rest after Red Bull(©) intake. Blood glucose level and plasma catecholamine levels significantly increased after Red Bull(©) consumption. Heart rate, respiration rate, and respiratory flow rate were significantly increased during exercise after Red Bull(©) consumption compared to control condition. Intake of Red Bull(©) significantly improved reaction time, performance in immediate memory test, verbal fluency, and subject's attention as well as performance in mental stress test. Conclusion. This study demonstrated that Red Bull(©) has beneficial effect on some cognitive functions and effect on cardiovascular and respiratory system at rest and during exercise by increasing activity of the sympathetic nervous system.