Effect of obstructive sleep apnea on the response to hypertension therapy

Obstructive sleep apnea (OSA) often precedes cardiovascular disease, partly due to treatment resistant hypertension. The nocturnal apneas of OSA trigger increased sympathetic nervous discharge during both sleep and wakefulness. Apneas also trigger cardiac release of the endogenous diuretic atrial natriuretic peptide. We hypothesized that treatment of the excess sympathetic nervous activity of OSA with a β₁ blocker would lower 24 h blood pressure (BP) more than diuretic therapy. Subjects with OSA associated hypertension received 2 weeks of placebo followed by the β₁ blocker nebivolol or hydrochlorothiazide (HCTZ) for 6 weeks in a blinded crossover study. BP, baroreflex sensitivity (BRS), heart rate variability (HRV), arterial reactivity, and stiffness were measured after placebo and each treatment. The β₁ blocker lowered clinic BP by ?11/?8 mmHg, more than the ?3/?1 effect of HCTZ (P < 0.01). The β₁ blocker lowered 24 h diastolic blood pressure (DBP) more than HCTZ. Although given at bedtime, neither drug increased BP dipping. Nebivolol increased HRV in the high-frequency band. Nebivolol did not alter BRS while HCTZ significantly diminished BRS compared to nebivolol (P < 0.01). Nebivolol increased flow-mediated brachial artery dilation when compared to HCTZ and slowed pulse wave velocity, indicating a decrease in arterial stiffness.

Diuretic therapy failed to lower BP in OSA subjects and this might account for the frequent association of OSA with treatment resistant hypertension. However, blockade of the excess sympathetic nervous activity of OSA with a β₁ blocker lowered both clinic and 24 h DBP.     

骶神经刺激对慢性功能性便秘自主神经功能影响观察

目的评价骶神经刺激治疗（SNS）对慢性功能性便秘患者自主神经功能的影响。 方法搜集西京消化病医院和西安马应龙肛肠医院2016年9月至2017年11月收治的86例慢性功能性便秘患者,随机分为治疗组与对照组,治疗组42例,对照组44例。治疗组采用非植入性骶神经刺激治疗,对照组采用电针八髎穴治疗。比较两组间及各组内治疗前后便秘症状评分和心率变异性（HRV）测定值。 结果组内比较症状评分均降低（P<0.05）;治疗组内HRV各指标的变化差异具有统计学意义（HF：u=-2.269,P=0.023;LF：u=-5.183,P=0.000;LF/HF：u=-4.359,P=0.000）,对照组无影响。组间比较,治疗前后的症状评分和HRV各指标差异无统计学意义（P>0.05）,伴随症状差值（t=4.040,P=0.000）和HRV各值差值（ΔHF：u=-2.583,P=0.010;ΔLF：u=-5.089,P=0.000;ΔLF/HF：u=-3.299,P=0.001）差异具有统计学意义。 结论SNS可能具有通过影响自主神经功能改善慢性功能性便秘的作用。     

Effects of nocturnal noninvasive mechanical ventilation on heart rate variability of patients with advanced COPD

BACKGROUND: Cardiovascular comorbidities have a negative impact on the health status and prognosis of patients with COPD. We determined whether nocturnal noninvasive (positive) mechanical ventilation (NIMV) can improve heart rate variability (HRV), decrease circulating natriuretic peptide levels, and improve functional performance of patients with very advanced COPD. METHODS: A randomized, double-blind, parallel controlled trial was conducted in 23 participants with stable but advanced COPD. Participants received standard medical therapy plus nocturnal NIMV or standard medical therapy plus sham NIMV for 3 months. RESULTS: After 3 months of NIMV therapy, the 24-h triangular interpolation of N-N intervals increased from 322 to 473 ms (p = 0.034), the 24-h HRV index (HRVI) increased from 21.8 to 29.9 ms (p = 0.035), nocturnal HRVI increased from 6.1 to 8.0 ms (p = 0.026), and the SD of the average N-N interval increased from 37 to 41 ms (p = 0.020). None of these indexes changed significantly in the control group. Additionally, compared with the control group, the pro-atrial natriuretic peptide levels declined significantly in the NIMV group (p = 0.013). CONCLUSIONS: NIMV applied nocturnally over 3 months may improve HRV, reduce circulating natriuretic peptide levels, and enhance the functional performance of patients with advanced but stable COPD. While not definitive due to small sample size, these data suggest that nocturnal NIMV may reduce the impact of cardiac comorbidities in COPD patients.     

Heart Rate Variability in Patients with Systemic Sarcoidosis

Purpose: The identification of subjects with systemic sarcoidosis at higher risk for sudden death is an unresolved issue. An influence of the autonomic activity on the genesis of ventricular arrhythmias was postulated. Heart rate variability (HRV) analysis provides a useful method to measure autonomic activity, and is a predictor of increased risk of death in various conditions. Therefore, the aim of the study was to evaluate HRV in patients with systemic sarcoidosis. Methods : The study included 35 patients with biopsy proven systemic sarcoidosis who were not taking antiarrhythmic medications. Thallium scintigraphy was performed to all patients with systemic sarcoidosis. The cardiac sarcoidosis was accepted in 16 patients as abnormal thallium scintigraphy and normal coronary arteriography. The time‐domain analysis of HRV was expressed as the standard deviation of all normal to normal NN intervals (SDNN) detected during 24‐hour Holter monitoring. Twenty‐four healthy subjects represented a control group for HRV analysis. Results: There were no differences in age (44 ± 13 years for cardiac sarcoidosis, 42 ± 15 years for noncardiac sarcoidosis, and 40 ± 10 years for control group; P = NS), sex (the ratio of female; 63%, 68%, and 55%, respectively; P = NS), and echocardiographic ejection fraction (63 ± 10%, 67 ± 8%, and 69 ± 6%, respectively; P = NS) among study groups. The mean SDNN value of the group with cardiac sarcoidosis was significantly lower than both the group with noncardiac sarcoidosis and the control group (72 ± 32 ms vs 110 ± 46 ms and 152 ± 36 ms; P < 0.05, respectively). Conclusion: HRV is decreased in patients with systemic sarcoidosis compared to the control group. This decreasing is more obvious in patients with cardiac sarcoidosis.     

高血压患者心率变异性及心率减速力变化

目的探讨高血压患者心率变异性(heart rate variability,HRV)及心率减速力(deceleration capacity of heart rate,DC)变化。方法选取80例健康体检和64例高血压患者进行24 h动态心电图监测,分析比较2组的HRV时域指标:全部窦性心搏R-R间期标准差(standard deviation of normal-to-normal intervals,SDNN)、R-R间期平均值的标准差(standard deviation of the average normal-to-normal intervals,SDANN)、相邻R-R间期差值的均方根(root mean square of successive differece,RMSSD)、相邻R-R间期差值>50 ms的百分比(proportion of number of pairs ofadjacent normal-to-normal intervals by more than 50 ms,PNN50)、三角指数和DC,探讨高血压患者HRV与DC的相关性,以及较健康体检者差异是否有统计学意义。结果高血压患者的SDNN、SDANN、三角指数、DC均较健康体检者减低,差异有统计学意义(P<0.01),RMSSD、PNN50差异无统计学意义。高血压组DC与SDNN、SDANN、RMSSD、PNN50均呈正相关,差异有统计学意义(P<0.01)。结论高血压患者HRV和DC减低,自主神经功能受损;高血压组DC与HRV时域指标呈正相关。     

Aerobic physical training has little effect on cardiovascular autonomic control in aging rats subjected to early menopause

We investigated and compared the effects of physiological menopause (PM) and early menopause (EM) and the adaptations promoted by physical training on the cardiovascular autonomic control of aged rats. Female Wistar rats (N = 72) were assigned to 3 groups: control (22 weeks old rats, undergoing sham surgery in the 10th week of life), PM (82 weeks old rats, undergoing sham surgery in the 10th week of life) and EM (82 weeks old rats, undergoing ovariectomy in the 10th week of life). In each group, half of the rats were subjected to swimming training over a period of 10 weeks. Sedentary PM and EM groups had higher basal mean arterial pressure (MAP) and heart rate (HR) and lower intrinsic HR compared to the sedentary control group. Physical training reduced MAP in PM group. All trained groups had lower basal HR; however, only control and PM-trained groups showed decreased intrinsic HR. The assessment of cardiac autonomic balance showed that PM and EM sedentary groups exhibited sympathetic predominance compared to control group. After physical training, only EM group presented sympathetic predominance. HR variability (pulse interval) was similar among all sedentary groups. However, control and PM-trained groups showed lower power in low frequency band (LF; 0.2–0.75 Hz) and higher power in high frequency band (HF; 0.75–3.0 Hz). The analysis of systolic arterial pressure variability revealed that PM and EM sedentary groups had higher LF power. However, PM group showed lower LF power following physical training. Finally, PM and EM groups had a reduction in spontaneous baroreflex sensitivity, that was attenuated by physical training. The overall results suggest that PM or EM promotes similar negative effects on MAP, HR and cardiovascular autonomic control. However, unlike the PM group, physical training was not able to mitigate all negative effects of EM on cardiovascular autonomic control.     

Continuous multiorgan variability analysis to track severity of organ failure in critically ill patients

Purpose

The purpose of this study is to evaluate the utility of using continuous heart rate variability (HRV) and respiratory rate variability (RRV) monitoring for (a) tracking daily organ dysfunction in critically ill patients and (b) identifying patterns of variability changes during onset of shock and resolution of respiratory failure.

Materials and Methods

Thirty-three critically ill patients experiencing respiratory and/or cardiac failure underwent continuous recording of their electrocardiogram and capnogram (CO₂) waveforms from admission or intubation until discharge (maximum 14 days). HRV and RRV were computed in 5-minute overlapping windows, using Continuous Individualized Multi-organ Variability Analysis software. Multiple organ dysfunction scores were recorded daily. HRV and RRV trajectories were characterized during onset of shock and resolution of respiratory failure.

Results

Both HRV and RRV decreased with increasing severity of multiple organ dysfunction scores for a variety of variability metrics. A decline in several measures of HRV and no decline in RRV were observed before onset of shock (n = 6). In contrast, during resolution of respiratory failure, an increase in RRV was observed in patients who successfully passed extubation (n = 12), with no change in RRV in those who subsequently failed extubation (n = 2).

Conclusions

There is an association between reduced HRV and RRV and increasing organ dysfunction in critically ill patients. The significance of observing trends of decreasing HRV (with onset of shock) and increasing RRV (with resolution of respiratory failure) merits further investigation.     

射频消融治疗房室折返性心动过速对心率变异的影响

对30例(22例左侧旁道、8例右侧旁道)房室折返性心动过速患者在射频消融前后进行心率变异分析,旨在了解射频消融房室旁道前后心脏植物神经张力的改变.结果显示左侧旁道患者消融后 LFP/HFP显著性增高,提示副交感神经张力相对减低,交感神经张力相对增高.但右侧旁道患者消融后心率变异无变化.关于射频消融左侧旁道心率变异的机理及左、右侧旁道消融后心率变异变化存在差异的原因有待阐明.     

Effects of sevoflurane on QT dispersion and heart rate variability

The purpose of this study was to use estimates of corrected QT dispersion (QTcd) and heart rate variability (HRV) to assess the effects of sevoflurane, an inhalation agent used frequently in clinical practice, on autonomic cardiac function. This study was conducted prospectively and in a blind manner on 20 women between 38 and 51 y of age who were classified as American Society of Anesthesiologists stage I–II and whose treatment required total abdominal hysterectomy. Electrocardiograms were recorded by 12-lead Holter monitor for 5 min before sevoflurane induction and again for 5 min at 10 min after tracheal intubation. Data on the first recording were considered as baseline; those on the second recording were viewed as final data. The study was terminated at this point, and surgery was allowed to proceed. QTcd and HRV values were assessed by a cardiologist, who was blinded to all data. All parameters were expressed as a mean value ± standard deviation. Wilcoxon’s test was used to compare baseline and final data. Statistical significance was considered asP< .05. No significant changes were observed between baseline and final QTcd values and between low and high-frequency components (LF and HF) of HRV; nor were changes seen in the LF/HF ratio. With the patient under sevoflurane/nitrous oxide anesthesia, no significant changes were detected in QTcd, LF, and HF values, and in the LF/HF ratio, whereas a significant increase (P=.001) was seen in standard deviation of the R-R interval, which was used as a measure of cardiac autonomic tone.     

Investigation of gender difference in thermal comfort for Chinese people

Gender difference in thermal comfort for Chinese people was investigated through two laboratory experiments. Both subjective assessment and objective measurement were taken during the experiment. Skin temperature (17 points) and heart rate variability (HRV) were measured in one of the experiment. Our results show that there are gender differences in thermal comfort for Chinese people. Correlation of thermal sensation votes and air temperature and vapor pressure shows that females are more sensitive to temperature and less sensitive to humidity than males. Subjective assessment, skin temperature and HRV analysis suggest that females prefer neutral or slightly warmer condition, due to their constantly lower skin temperature and the fact that mean skin temperature is a good predictor of sensation and discomfort below neutrality. Female comfortable operative temperature (26.3°C) is higher than male comfortable operative temperature (25.3°C), although males and females have almost the same neutral temperature and that there is no gender difference in thermal sensation near neutral conditions.