Autonomic Modulation of Sinus and Atrioventricular Nodes in Premature Low-Birth-Weight Infants

Respiratory vagal activity is expressed by heart rate variability (HRV) at approximately 1 month of age in premature low-birth-weight infants (PLBWI). However, the autonomic inputs into the sinus node (SAN) and atrioventricular node (AVN) in PLBWI are unclear. We evaluated the variability in PP and PR intervals at day zero (day 0) and 1 month (1 month) after birth in 16 PLBWI (gestation 32.3 ± 1.3 weeks, birth weight 1.578 ± 257 g). The polygraph was recorded during sleep on day 0 and at 1 month. PP and PR intervals and the number of respiratory cycles were measured, and frequency analysis was performed by auto-correlation fast Fourier transforms. Power spectral density (PSD: ms²) was calculated for the low frequency domain (LF: 0.036∼0.146 Hz), high frequency domain (HF: 0.146∼0.390 Hz), total frequency (TF: 0.036∼2.000 Hz), and respiratory sinus arrhythmia (RSA: frequency bandwidth of 0.3 Hz with peak respiratory frequency as median), and the PSD ratio in the PP and PR intervals (LF/HF, RSA/TF) were compared. Compared with day 0, a decrease in the LF/HF ratio and an increase in the RSA/TF ratio in PP intervals were observed at 1 month, consistent with expression of respiratory vagal activity. For PR intervals, on the other hand, the LF/HF ratio increased, indicative of accentuated sympathetic activity. However, the respiratory vagal input was weak, and the RSA/TF ratio remained unchanged. These observations suggest that, in PLBWI at 1 month, AVN conduction was not predominatly influenced by respiratory-related vagal activity, but was controlled by autonomic regulation, independent of the SAN.     

Changes in Heart Rate, Heart Rate Variability, and Heart Rate Turbulence during Evolving Reperfused Myocardial Infarction

Depressed cardiac parasympathetic activity is associated with electrical instability and adverse outcomes after myocardial infarction (MI). Heart rate turbulence (HRT), reflecting reflex vagal activity, and heart rate variability (HRV), reflecting tonic autonomic variations are both reduced in the subacute phase of MI. However, the evolution of these components of cardiac autonomic control between subacute and chronic phase of MI has not been defined. We prospectively studied 100 consecutive patients with a recent first MI with ST-segment elevation, who underwent successful direct percutaneous coronary interventions. Beta-adrenergic blockers and angiotensin-converting enzyme (ACE) inhibitors were administered according to the state-of-the-art medical practice guidelines. HRT and HRV were measured from 24-hour ambulatory electrocardiographic recordings 10 days and 12 months after the index MI. There was no significant difference in mean RR interval between the subacute and chronic phase of MI (875 ± 145 versus 859 ± 122 ms). Indices of HRV increased significantly during the observation period (SDNN: from 88.8 ± 26.8 to 116.0 ± 35.7 ms, P < 0.001; SDNNi: from 37.9 ± 15.9 to 46.0 ± 16.3 ms, P < 0.001; SDANN: from 79.6 ± 34.7 to 105.6 ± 35.4 ms, P < 0.001). In contrast, there were no significant changes in indices of HRT (turbulence onset: from −0.008 ± 0.022 to −0.012 ± 0.025%; turbulence slope: from 7.78 ± 5.9 to 8.06 ± 6.8 ms/beat). In contrast to reflex autonomic activity, there was a significant recovery of tonic autonomic activity within 12 months after MI. These different patterns of recovery of reflex versus tonic cardiac autonomic control after MI need to be considered when risk stratifying post-MI patients.     

Heart rate variability and diastolic heart failure

Diastolic heart failure accounts for up to 40% of patients with congestive heart failure (CHF), and is associated with a better prognosis as compared to patients with systolic dysfunction. Nevertheless, patients with diastolic dysfunction have a significantly higher mortality as compared to the normal population. Reduced heart rate variability (HRV), a marker of autonomic dysfunction, is associated with increased mortality in patients with systolic heart failure. We therefore sought to determine to what extent HRV is altered in a population of patients with diastolic heart failure. Twenty-four hour ambulatory (Holter) recordings were performed in 19 consecutive patients with diastolic heart failure, in 9 patients with systolic heart failure, as well as in 9 healthy volunteers (normal controls). Time and frequency domain HRV variables were obtained for all three groups of patients. Both Time and Frequency domain variables were found to be reduced in both heart failure groups compared to normal controls. When compared with each other, patients with diastolic function had relatively higher values of HRV variables, compared to those with systolic dysfunction (SDNN, Total power, ULF power, all P 相似文献   

Breathing pattern recordings using respiratory inductive plethysmography,before and after a physiotherapy breathing retraining program for asthma: A case report

Breathing retraining (BR) improves symptoms, psychological well-being and quality of life in adults with asthma; but there remains uncertainty as to mechanism of effect. One of the intuitively logical theories is that BR works through altering breathing pattern. There is currently no evidence, however, that BR does result in measurable changes in breathing pattern. In this case report we describe the effects of physiotherapy BR on a 57-year-old female with a 10-year history of asthma. Data were collected before and after a physiotherapy BR program comprising three sessions over 18 weeks: breathing pattern (respiratory inductive plethysmography (RIP); physiology (end tidal carbon dioxide (ETCO₂), heart rate, oxygen saturations, spirometric lung function); questionnaires (Asthma Control Questionnaire (ACQ), Hospital Anxiety and Depression Score, Nijmegen Questionnaire); and medication usage. After BR, the patient’s symptoms improved. Her physiology was largely unchanged, although her FEV₁ increased by 0.12L, peak flow by 21L/min. The patient reported using less Salbutamol, yet her asthma control improved (ACQ down 1.5). Her Nijmegen score dropped from positive to negative for hyperventilation (from 39 to 7). Her anxiety-depression levels both reduced into ‘normal’ ranges. The patient’s expiratory time increased, with longer respiratory cycles and slower respiratory rate. No changes were seen in relative contributions of ribcage and abdomen. Controlled trials are now needed to determine the generalizability of these findings.     

Influencing the Heart Rate of Rats with Weak External Mechanical Stimulation

HSIU, H., et al. : Influencing the Heart Rate of Rats with Weak External Mechanical Stimulation. The ventricular-arterial coupling is assumed to minimize the expenditure of cardiac energy. From the conjecture of the resonance theory, the arterial system transmits pressure waves and resonates with the heartbeat, therefore, the arterial system is similar to a mechanical resonator. Theoretically, the heart rate can be paced with weak external mechanical stimulation and corresponding blood pressure changes can be observed. A waterbed was activated to generate 0.5-mmHg pressure vibrations as a stimulus and the rate was set to deviate 5% from the control heart rate. Among 13 studies on seven rats, the linear regression between X (stimulation frequency − control heart rate) and Y (actual changes of the heart rate) is Y = 0.992X = 0.062 (Hz) with a correlation coefficient of 0.97 (Y = X implies complete steering). The intercorrelation coefficient between the change in mean blood pressure and the heart rate was 0.79. The study showed that this weak mechanical stimulation influences the heart rate, and the blood pressure changes according to the heart rate. Cardiovascular optimization and the resonance theory may explain the way one may regulate the heart rate and the blood pressure of humans noninvasively in the future. (PACE 2003; 26[Pt. I]:36–43)     

Heart rate variability in arrhythmogenic right ventricular cardiomyopathy correlation with clinical and prognostic features

The identification of subjects with arrhythmogenic right ventricular cardiomyopathy (ARVC) 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 after myocardial infarction. For these reasons, the aim of the study was to evaluate HRV and its correlations with ventricular arrhythmias, heart function, and prognostic outcome in patients with ARVC. The study included 46 patients with ARVC who were not taking antiarrhythmic medications. The diagnosis was made by ECG, echocardiography, angiography, and endomyocardial biopsy. Exercise stress test and Holter monitoring were obtained in all patients. 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. Thirty healthy subjects represented a control group for HRV analysis. The mean follow-up was 10.8 +/- 1.86 years. SDNN was reduced in patients with ARVC in comparison with the control group (151 +/- 36 vs 176 +/- 34, P = 0.00042). Moreover, there was a significant correlation of this index with the age of the patients (r = - 0.59, P < 0.001), with the left (r = 0.44, P = 0.002) and right (r = 0.47, P = 0.001) ventricle ejection fraction, with the right ventricular end diastolic volume (r = - 0.62, P < 0.001), and with the ventricular arrhythmias, detected during the same Holter record used for HRV analysis (patients with isolated ventricular ectopic beats < 1,000/24 hours, 184 +/- 34; patients with isolated ventricular ectopic beats > 1,000/24 hours and/or couplets, 156 +/- 25; patients with repetitive ventricular ectopic beats (> or = 3) and/or ventricular tachycardia, 129 +/- 25; P < 0.001). During follow-up two patients showed a transient but significant reduction of SDNN and a concomitant increase of the arrhythmic events. In eight patients an episode of sustained ventricular tachycardia occurred, but the mean SDNN of this subgroup did not differ from the mean value of the remaining patients (152 +/- 15 vs 150 +/- 39; P = NS). Only one subject died after heart transplantation during follow-up (case censored). Time-domain analysis of HRV seems to be a useful method to assess the autonomic influences in ARVC. A reduction of vagal influences correlates with the extent of the disease. The significant correlation between SDNN and ventricular arrhythmias confirmed the influences of autonomic activity in the modulation of the electrical instability in ARVC patients. However, SDNN was not predictive of spontaneous episodes of sustained ventricular tachycardia.     

Mobile biofeedback of heart rate variability in patients with diabetic polyneuropathy: a preliminary study

Biofeedback of heart rate variability (HRV) was applied to patients with diabetic polyneuropathy using a new mobile device allowing regularly scheduled self‐measurements without the need of visits to a special autonomic laboratory. Prolonged generation of data over an eight‐week period facilitated more precise investigation of cardiac autonomic function and assessment of positive and negative trends of HRV parameters over time. Statistical regression analyses revealed significant trends in 11 of 17 patients, while no significant differences were observed when comparing autonomic screening by short‐term HRV and respiratory sinus arrhythmia at baseline and after the 8 weeks training period. Four patients showed positive trends of HRV parameters despite the expected progression of cardiac autonomic dysfunction over time. Patient compliance was above 50% in all but two patients. The results of this preliminary study indicate a good practicality of the handheld device and suggest a potential positive effect on cardiac autonomic neuropathy in patients with type 2 diabetes.     

Sympathetic control of short-term heart rate variability and its pharmacological modulation

The static relationship between heart rate (HR) and the activity of either vagal or sympathetic nerves is roughly linear within the physiological range of HR variations. The dynamic control of HR by autonomic nerves is characterized by a fixed time delay between the onset of changes in nerve activity and the onset of changes in HR. This delay is much longer for sympathetically than for vagally mediated changes in HR. In addition, the kinetics of the HR responses shows the properties of a low-pass filter with short (vagal) and long (sympathetic) time constants. These differences might be secondary to differences in nervous conduction times, width of synaptic cleft, kinetics of receptor activation and post-receptor events. Because of the accentuated low-pass filter characteristics of the HR response to sympathetic modulation, sympathetic influences are almost restricted to the very-low-frequency component of HR variability, but the chronotropic effects of vagal stimulation usually predominate over those of sympathetic stimulation in this frequency band. Oscillations in cardiac sympathetic nerve activity are not involved in respiratory sinus arrhythmia (high-frequency component) and make a minor contribution to HR oscillations of approximately 10-s period (low-frequency component of approximately 0.1 Hz), at least in the supine position. In the latter case, HR oscillations are derived mainly from a baroreflex, vagally mediated response to blood pressure Mayer waves. Beta-blockers and centrally acting sympathoinhibitory drugs share the ability to improve the baroreflex control of HR, possibly through vagal facilitation, which might be beneficial in several cardiovascular diseases.     

Respiratory sinus arrhythmia as a predictor of sudden cardiac death after myocardial infarction

Background. Measurement of high-frequency (HF) spectral power of heart rate (HR) variability has not been able to identify the patients at risk of sudden cardiac death (SCD) despite the experimental evidence of protective role of vagal activity for fatal arrhythmias.

Aim. We developed a novel respiratory sinus arrhythmia (RSA) analysis method and tested its ability to predict SCD after an acute myocardial infarction.

Method. The RSA analysis method was developed in 13 subjects from simultaneous recordings of respiration and R-R intervals. An adaptive threshold was computed based on the zero-phase forward and reverse digital filtering in the analysis of RSA. With this method, only respiration-related R-R interval fluctuations are included. The prognostic power of RSA, analyzed from 24-hour electrocardiographic recordings, was subsequently assessed in a large postinfarction population including 1631 patients with mean follow-up of 40±17 months.

Results. Depressed RSA was a strong predictor of SCD (hazard ratio 7.4; 95% CI 3.6–15.1; P <0.0001) but only a weak predictor of non-SCD. The RSA index remained an independent predictor of SCD after adjustments for ejection fraction and other clinical risk variables (RR 4.7; 95% CI 2.28–9.85).

Conclusions. Reduced respiratory-related HR dynamics, detected by RSA index, are a specific marker of an increased risk of SCD among postinfarction patients.     

Heart Rate Variability in Myocardial Infarction With and Without Malignant Arrhythmias: Comparison with Heart Transplant Recipients and Normal Subjects

Myocardial autonomic denervation occurs after acute MI. This process is followed by a reduction of heart rate variability (HRV) and an increase of malignant ventricular arrhythmias and sudden death. This study investigated whether there are any significant differences in HRV among the population of MI who did and did not have malignant ventricular arrhythmias (MVAs), normal subjects and heart transplant recipients, the paradigm of the denervated heart. We studied 25 subjects aged 42 ± 17 years, with normal clinical and cardiac noninvasive evaluation (group A); 70 patients aged 57 ± 14 years, who had MI hut no arrhythmic event in 36 months of follow-up (group B); 13 patients with MI aged 65 ± 9 years, who had had sustained VT, VF, or sudden death (group C); and 16 cardiac transplant recipients aged 35 ± 14 years (group D). The ECG was sampled for 256 seconds. We calculated, in time and frequency domain, the standard deviation of the RR cycle length and the spectral component's very low frequency (< 0.05 Hz), low frequency (0.05–0.15 Hz), and high frequency (0.15–0.35 Hz). The values of HRV in group A were significantly greater than in groups B, C, and D (P < 0.001) and greater in group B than in groups C and D (P < 0.001). Groups C and D did not differ (P = 0.610). These data indicate that HRV of patients who have had an MI and MVAs is very similar to that of heart transplant recipients. This is an indirect evidence that myocardial autonomic denervation may play an important role in the genesis of malignant arrhythmic events.     

Heart rate turbulence and heart rate variability in patients with atrial synchronous ventricular pacing

Background: Heart rate turbulence (HRT) and heart rate variability (HRV) have been shown to be independent and powerful predictors of mortality in a specific group of cardiac patients. Pacing has unfavorable effects on autonomic function. Our aim is to investigate autonomic responses to atrial synchronous ventricular pacing (VDD) by evaluating HRT and HRV parameters.
Methods and Results: The study groups comprised 12 control and 12 patients without organic heart disease and with normal sinus function who were implanted with a permanent VDD pacing system for high-degree atrioventricular block. The HRV and HRT analysis were assessed from a 24-hour Holter recording. There was no statistically significant difference between the two groups for HRV parameters. When HRT parameters were compared, turbulence onset was significantly higher in the cardiac paced group than the controls group (2.729 ± 8.818 vs –1.565 ± 8.301, P = 0.006), but no statistically significant difference was found between the two groups for turbulence slope (11.166 ± 10.034 vs 31.675 ± 28.107, P = 0.68). The number of patients who had abnormal HRT onset was significantly higher in the paced group than controls (9 vs 2, P = 0.004).
Conclusion: Atrial synchronous pacing has unfavorable effects on autonomic function. Altered ventricular depolarization sequence may lead to changes in autonomic response. Although we found no difference in HRV parameters between the control and VDD patient groups, the HRT onset and number of patients with abnormal HRT onset was significantly higher in VDD patients. HRT onset can be a better way of noninvasive autonomic response predictor in VDD patients.     

深慢腹式阻力呼吸改善COPD患者肺功能的研究

用深慢腹式呼吸配合阻力呼吸的方法，对慢性阻塞性肺疾病患者进行呼吸训练，以提高患者呼吸肌的肌力和耐力，从而改善患者的肺功能。将５５例ＣＯＰＤ患者分为两组，治疗组３０例进行深慢腹式阻力呼吸锻炼，对照组２５例进行深慢腹式呼吸锻炼。６周后测定并对比锻炼前后肺功能指标（ＶＣ，ＴＶ，ＴＬＣ，ＦＥＶ_１％，ＦＶＣ％，ＰＥＦＲ，ＲＶ，ＦＲＣ，ＲＶ／了ＬＣ％，Ｖ_（５０）／ＨＴ，Ｖ_（２５）／ＨＴ，Ｖ_（５０）／Ｖ_（２５）），治疗组的ＶＣ，ＦＶＣ％，ＰＥＦＲ，ＲＶ，ＲＶ／ＴＬＣ％有显著改善（Ｐ＞０．０５）。运动耐力亦有提高（可多上一层楼）。对照组无显著改善。     

A Theoretical Right Atrial Pressure Feedback Heart Rate Control System to Restore Physiologic Control to the Rate-limited Heart

Physiologic control of heart rate may be limited by sinus node injury or congenital conduction defects. Control theory may be applied to restore physiologic rate control. Mean right atrial pressure is a likely candidate for incorporation into an artificial control system because of its: (1) stability at rest; (2) tendency to increase during exertion in the rate-limited heart; (3) ability to decrease with increasing heart rate in the rate-limited heart; and (4) accessibility for measurement via the transvenous route. A theoretical right atrial pressure feedback heart rate control system is presented; applications to physiologic pacing of patients with sick sinus syndrome, rate control of the transplanted heart, and pump frequency control of the total artificial heart are discussed.     

反馈式呼吸刺激联合主动循环呼吸训练对肺癌术后患者的影响

目的探讨肺癌患者术后实施反馈式呼吸刺激联合主动循环呼吸训练对其肺功能和肺部并发症的影响。方法选取2018年1月—2019年12月医院收治的80例肺癌患者为研究对象,按照组间基线资料可比的原则分为对照组和观察组,各40例。术后对照组实施常规护理,观察组在对照组基础上增加反馈式呼吸刺激联合主动循环呼吸训练,比较两组患者干预前后肺功能、生活质量和肺部并发症发生情况。结果干预前两组肺功能比较,差异无统计学意义(P>0.05);干预后观察组肺功能指标优于对照组,差异有统计学意义(P<0.05)。观察组术后肺部并发症总发生率低于对照组,差异具有统计学意义(P<0.05)。干预前两组生活质量评分比较,差异无统计学意义(P>0.05);干预后观察组生活质量评分高于对照组,差异有统计学意义(P<0.05)。结论肺癌患者术后实施反馈式呼吸刺激联合主动循环呼吸训练可有效改善其肺功能,减少肺部并发症的发生率,改善患者预后,提升患者生活质量。     

Effect of standing on short term heart rate variability across age

This study examined the response of heart rate variability measures to standing in three age groups of male subjects: Children (6-11 years), young adults (20-30 years) and elderly (60-70 years). Supine and standing heart rate variability indices were measured in all the subjects using power spectral analysis. The effect of posture on heart rate variability was assessed using the change in heart rate variability measures over resting values during the first 2 min following active standing. There was an attenuated response in normalized low frequency (LF) and high frequency (HF) power to standing in the elderly as compared with young adults and children. Heart rate variability responses to standing were highest in the young adults, followed by the children and the elderly, although the differences between the young adults and children were not significant. More studies are needed to characterize HRV responses to posture in children.     

病毒性心肌炎的室性心律失常与窦性心率震荡的关系及药物干预研究

目的:探讨病毒性心肌炎患者24小时动态心电图(DCG)中室性心律失常与心率震荡(HRT)的关系。方法:56例临床诊断室性心律失常患者分为病毒性心肌炎组(A组)和无器质性病变者组(B组),均行DCG监测,计算心率震荡的初始值(TO)、斜率(TS)。A组患者口服美托洛尔(25mg/次,每天二次)1月后复查24hDCG。结果:A组TO、TS分别较B两明显升高和降低,且A组口服美托洛尔1月后明显改善。结论:自主神经调节功能受损是病毒性心肌炎发生室性心律失常的重要原因,HRT可作为病毒性心肌炎判断预后的重要指标,口服美托洛尔可改善HRT。