Impact of chronic DDD pacing on time-domain indexes of heart rate variability in patients with hypertrophic obstructive cardiomyopathy

The aim of this study was to examine whether DDD pacing affects time-domain indexes of heart rate variability (HRV) in patients with hypertrophic obstructive cardiomyopathy (HOCM). We studied 11 patients (7 men, age 52 +/- 8 years) with HOCM refractory to drugs. In all patients a DDD pacemaker was implanted and the atrioventricular delay was programmed to ensure a full ventricular activation sequence. Time-domain indexes of HRV (mean NN, SDANN, SDNN, SD, rMSSD, pNN50) were determined from 24-hour Holter recordings 3 days before and 1 year after pacemaker implantation. The pacemaker was turned off during the second recordings. The same indexes were determined in ten healthy controls at the same time points. The controls showed no significant differences in any of the measured parameters between the two time points. The HOCM patients showed an increase in SD (from 27 +/- 13 to 41 +/- 13 ms, P < 0.001), rMSSD (from 18 +/- 5 to 32 +/- 8 ms, P < 0.001), and pNN50 (from 1.03 +/- 1.06 to 8.52 +/- 4.84%, P < 0.0001). As a result, the values of these three parameters, which were lower in the HOCM patients than in the controls before pacing, were restored to normal levels by the end of the study. In conclusion, our findings indicate that long-term pacing in HOCM patients restores the sympathovagal balance in the heart by increasing vagal activity.     

Taichiquan acutely increases heart rate variability

A group of 15 elderly men and 14 young male students of physical education made twice a series of Taichiquan (TCQ) practices. Their electrocardiograms were recorded on tape-recorder and heart rates and heart rate variability (HRV) were calculated from digitized data. Here we report the results of recordings in supine positions before and after the first and second series of TCQ. Intervals between heart beats (RRIs) and their standard deviation (SDNN) increased in older men from recordings before the exercise to postexercise. In young subjects the SDNN and total variance (TV) of RRIs increased. HRV increases immediately after TCQ-exercise in young and old male healthy subjects. Whether these practices have permanent effects and effects in patients need controlled and prospective studies.     

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.     

Autonomic dysfunction in HIV patients on antiretroviral therapy: studies of heart rate variability

BACKGROUND: The presence of autonomic dysfunction in HIV patients is largely unknown. Early studies found autonomic dysfunction in patients with AIDS. Introduction of highly active antiretroviral combination therapy (ART) has dramatically changed the course of the disease and improved prognosis and decreased morbidity. At present it is not known whether introduction of ART also has decreased autonomic dysfunction. AIM: To evaluate whether autonomic dysfunction is present in an ART-treated HIV population. METHODS: HIV patients receiving ART for at least 3 years (n = 16) and an age-matched control group of healthy volunteers (n = 12) were included. All were non-smokers, non-diabetic and had never received medication for dyslipidaemia or hypertension. Following a 10 min resting period a 5 min ECG recording was performed. Heart rate variability (HRV) analysis was performed in accordance with current guidelines and data reported as median (interquartile range). RESULTS: The resting heart rate was higher in HIV patients compared with controls [69 (62-74) versus 57 (52-60); P<0.001]. Total HRV measured as standard deviation of normal-to-normal (SONN) was lower in the HIV group compared with the controls [36 (25-55) versus 74 (57-84) ms; P<0.01] as was parasympathetic activity measured as square root of the mean squared difference of successive normal-to-normal intervals (RMSSD) [22 (9-30) versus 35 (24-62) ms; P<0.05]. Low frequency power was lower in the HIV group compared with the control group [294 (161-602) versus 946 (711-1668) ms(2); P<0.01]. High frequency power as well as systolic and diastolic blood pressure did not differ between the groups. CONCLUSIONS: The HIV patients in ART have increased resting heart rate and decreased short-term heart rate variability indicating parasympathetic dysfunction.     

Derangement of heart rate variability during a catastrophic earthquake: a possible mechanism for increased heart attacks

At 1:47 AM on September 21, 1999, the middle part of Taiwan was struck by a major earthquake measuring 7.3 on the Richter scale. It has been shown that the mental stress caused by an earthquake could lead to a short- or long-term increase in frequency of cardiac death probably through activation of the sympathetic nervous system. The aim of this study was to investigate the effects of emotional stress on the autonomic system during an actual earthquake. Fifteen patients receiving a 24-hour Holter ECG study starting from 10+/-4 hours before the onset of the earthquake were included for the analysis of time- and frequency-domains of heart rate variability (HRV) at several time periods. A 24-hour Holter study recorded 2-6 months before the earthquake in 30 age- and sex-matched subjects served as the control group. Heart rate and the low frequency (LF) to high frequency (HF) ratio increased significantly after the earthquake and were attributed mainly to the withdrawal of the high frequency component (parasympathetic activity) of HRV. Sympathetic activation was blunted in elderly subjects > 60 years old. The concomitant ST-T depression observed in the Holter study correlated with a higher increment of LF as compared to HF components. The changes observed in HRV recovered completely 40 minutes following the earthquake. The derangement of HRV results from the withdrawal of the parasympathetic component and the arousal of sympathetic activity by the stressful earthquake. However, this autonomic derangement returned towards normal 40 minutes following the earthquake.     

扩张型心肌病患儿室性早搏与心率变异性相关性研究

目的探讨扩张型心肌病（DCM）患儿室性早搏与心率变异性的关系。方法采用TLC3000A十二导动态心电仪,对30例正常儿童和65例DCM患儿进行动态心电分析。DCM组分为室早组和非室早组,室性早搏组按室早发生频率不同分为A组（偶发）、B组（频发）、C组（联律.多形.成对.室速）,对各组进行心率变异（HRV）分析。结果DCM患儿室早各组和非室早组HRV与对照组比较差异有显著性（P〈0.01）;非室早组和室早A组HRV值差异无显著性（P〉0.05）;室早B组及C组与非室早组比较HRV明显下降,差异有显著性,且室早各组HRV依次下降,各指标组间均有显著性差异（P〈0.05）。结论DCM患儿HRV值与室性早搏的严重程度有一定相关性,HRV值对DCM患儿并发室性心律失常的诊断有一定价值,也可作为预测DCM预后的一项指标。     

On- and off-responses of heart rate to exercise - relations to heart rate variability

During physical exercise, heart rate (HR) increases by parasympathetic withdrawal and increase of sympathetic activity to the heart. HR variability (HRV) in time and frequency domains provides information about autonomic control of the cardiovascular system. Non-linear analysis using the Poincaré plot method is able to reveal supplementary information about cardiac autonomic control. The aim of this study was to determine the association between HRV parameters, the initial increase of HR at the onset of exercise (on-response) and HR decrease in the recovery phase after acute exercise (off-response). HR was continuously monitored in 17 healthy male subjects (mean age: 20.3 +/- 0.2 (SEM) years) at rest (25 min supine; 5 min standing), during exercise (8 min of step test at 70% of maximal power output) and in the recovery phase (30 min supine). HRV analysis in time and frequency domains and evaluation of the Poincaré plot measures (length, widths) were performed on selected segments of HR time series. HR on- and off-responses were quantified using an exponential curve fitting technique. The time constants T(on) and T(off), representing the rate of on- and off-responses to exercise, were computed. Postexercise HRV indices and time constant of on-response - T(on) - to exercise were negatively correlated. From preexercise HRV indices, only Poincaré plot parameters were correlated with T(on). No correlation between HRV indices and parameters of off-response was found. In conclusion, preexercise HRV parameters are not closely correlated with the rate of cardioacceleration at the onset of exercise and cannot predict the rate of HR recovery. On the other hand, postexercise HRV parameters are related to the rate of initial adjustment of HR to exercise referring to the importance of rapid HR on-response for a faster recovery after exercise.     

Effect of diabetes mellitus on heart rate variability in patients with congestive heart failure

This study sought to determine if the severity of autonomic perturbations in patients with heart failure are affected by the presence of diabetes. Decreased HRV is frequent in diabetic patients free of clinically apparent heart disease and has been invoked as a risk factor for sudden cardiac death. However, reduced HRV is also commonly present in patients with left ventricular dysfunction. The effect of diabetes on autonomic dysfunction in this setting is not known. Holter ECGs from 69 diabetic patients and 85 nondiabetic control subjects with heart failure were analyzed. The severity of autonomic dysfunction was assessed using 24-hour time- and frequency-domain HRV analysis. Prognostically important time- and frequency-domain HRV measures (SDNN, SDANN5, total power, and ultra-low frequency power) were not different between the two groups. Time- and frequency-domain parameters modulated by parasympathetic tone (pNN50, RMSSD, and HF power) were depressed to a similar degree in the diabetic and the nondiabetic groups. The low frequency power was significantly lower in diabetic patients (5.8 +/- 0.7 vs 5.3 +/- 1.0, P = 0.02). The ratio of low to high frequency power was substantially lower in the diabetic group (2.2 +/- 0.2 vs 1.4 +/- 0.2, P < 0.0001). These differences were more apparent in insulin-treated diabetics. In the presence of heart failure, HRV parameters that are most predictive of adverse outcome are similar in diabetic and nondiabetic patients. Furthermore, during increased sympathetic stimulation in the setting of heart failure, diabetes does not worsen parasympathetic withdrawal but may mitigate sympathetic activation.     

冠心病患者心率变异性分析

目的了解冠心病（CHD）患者的心率变异性（HRV）特点,探讨CHD患者自主神经变化的临床意义。方法测定93例CHD患者和49例健康对照者24h心率变异性的时域指标,并进行比较分析。结果CHD组24hHRV指标水平明显低于健康对照组（P〈0．01）,差异有统计学意义。结论CHD患者HRV降低提示心血管自主神经系统功能受损害。     

Heart rate and blood pressure variability in cardiac diseases: pharmacological implications

Summary— Even at rest, blood pressure and heart rate fluctuate continuously around their mean values. Considerable interest has recently focused on the assessment of spontaneous fluctuations in heart rate and blood pressure, ie, heart rate and blood pressure variability, using time or frequency domain indexes. Heart rate variability has been extensively studied in cardiovascular disease and has emerged as a valuable parameter for detecting abnormalities in autonomic cardiovascular control, evaluating the prognosis and assessing the impact of drug therapy on the autonomic nervous system in patients with myocardial infarction, congestive heart failure or a heart transplant. In contrast, until the recent development of noninvasive methods for continuous blood pressure recording, blood pressure variability received little attention, and this parameter remains to be evaluated in cardiovascular disease.     

Attenuated Valsalva heart rate response in subjects with smoking history: possible role of autonomic dysfunction

Summary. The effects of smoking habits on aotnomic cardiovascular heart rate reflexes were studied in 143 healthy subjects by using the Valsalva manoeuvre and deep breathing tests. Smoking seemed to cause attenuation of the Valsalva heart rate response. This attenuation was present also after adjustment for possible confounding factors including alcohol consumption. Our findings show that in subjects with smoking history there may occur dysfunction in some part of the autonomic reflex arch mediating the Valsalva heart rate response.     

原发性扩张型心肌病心率变异性与心功能和预后关系的初探

目的 :探讨心率变异性 (HRV)与原发性扩张型心肌病 (DCM)心功能和预后的关系。方法 :对 60例DCM病人进行心率变异性检测 ,并追踪观察 18个月。将患者分为非心力衰竭组 (A组 )、心力衰竭组 (B组 )、死亡组 (C组 ) ,回顾分析HRV与心功能和预后的关系。结果 :①C组、B组与A组相比SDNN、SDANN、RMSSD、PNN50 均减小 (P <0 0 5 )。②B组、C组较A组TP减少 (P <0 0 5 ) ,C组LF/HF比值增大。结论 :HRV可反映DCM患者的心功能 ,对预测DCM预后亦有较高的价值 ,是一种预测DCM预后的简单方法。     

Alternans of blood pressure and heart rate in dilated cardiomyopathy

Impaired myocardial performance is known to be associated with electrical and mechanical beat-to-beat alternans phenomena. The alternans in blood pressure and heart rate and their interdependency in idiopathic dilated cardiomyopathy (IDC) were studied. The arterial blood pressure and the electrocardiograph (ECG) were continuously recorded in 22 patients suffering from IDC (age 49 +/- 13 years, ejection fraction 0.33 +/- 0.13, left ventricular diameter of 67 +/- 8 mm) and in 21 healthy controls (age 52 +/- 15 years). The beat-to-beat variations of the interbeat intervals (IBI) and of the blood pressure amplitudes (AMP) were measured. An alternans beat was defined as a beat preceded and followed by beats that had higher or lower values in the respective modality. The percentages of singular and repetitive alternans patterns, and the interdependency of the alternans patterns in AMP and IBI were assessed. The study found significantly more singular and repetitive alternans patterns in the IDC group compared to the control group both in the analysis of AMP and IBI (singular alternans in IBI: 55 +/- 11 vs 47 +/- 7%, P < 0.01; singular alternans in AMP: 61 +/- 15 vs 45 +/- 6%, P < 0.01; triple alternans in IBI: 29 +/- 18 vs 16 +/- 9%, P < 0.01; triple alternans in AMP: 34 +/- 24 vs 12 +/- 7%, P < 0.01). The amplitudes of the AMP alternans patterns were higher in IDC compared to controls (9 +/- 7 vs 4 +/- 2% of AMP, P = 0.01) whereas they did not differ in IBI. The correlation analysis revealed a significant interdependency of the alternans pattern in IBI and AMP in 18 of 22 IDC patients and in 12 of 21 controls (r = 0.50 +/- 0.21 [IDC]; r = 0.26 +/- 0.05 [controls]). The slope of the linear regression (delta AMP vs delta IBI) was steeper in the IDC group compared to the control group (62 +/- 50 vs 20 +/- 22 mmHg/s, P < 0.01). The percentages of alternans patterns appearing in IBI and AMP were positively correlated to the left ventricular diameter (r = 0.70 in the IBI, and r = 0.30 in the AMP). The blood pressure amplitude and the heart rate did not differ between the two groups. Patients suffering from IDC have a higher prevalence, stability, amplitude, and interdependency of alternans patterns in IBI and AMP compared to the control group. The amount of alternans patterns indicates the stage of disease. The alternans analysis may have impact on the functional assessment of patients suffering from heart failure.     

Effects of one-lung ventilation on cardiac autonomic nervous activity as evaluated by power spectral analysis of heart rate variability

The purpose of this prospective study was to evaluate the effects ofone-lung ventilation on the activity of the cardiac autonomic nervous system.Ten adult patients who underwent thoracotomy were endotracheally intubatedwith a double-lumen tube under general anesthesia using isoflurane. Afterinduction of anesthesia, a continuous, 256-sec electrocardiogram (ECG) wasobtained during bilateral lung ventilation (control) followed by recordingsduring one-lung ventilation of each side. Using the R–R intervaltachograms obtained for the 256-sec ECGs, low frequency (LF: 0.04–0.15Hz) and high frequency (HF: 0.15–0.40 Hz) bands of the spectral densityof the heart rate variability and the HF/LF ratio were analyzed using the fastFourier transform algorithm. Log(HF), which indicates parasympatheticactivity, increased during one-lung ventilation on each side, but did notdiffer between ventilated sides. Log(LF), which represents sympathetic andparasympathetic activity, increased similarly to log(HF) on both sides.Log(HF/LF), the balance of the sympathetic and parasympathetic activity, didnot change during one-lung ventilation. We suggest that one-lung ventilationalone does not substantially affect the cardiac autonomic nervous system.     

腹腔镜手术对小儿心率变异性的影响

目的观察腹腔镜手术下小儿心率变异性（Heart rate variability，HRV）的变化，为小儿术中及术后心血管的康复提供依据。方法选择ASAⅠ或Ⅱ级择期行腹腔镜手术的患儿20例，全部采用静吸复合全麻，气管内插管，呼吸机行间歇正压通气。分别于麻醉前、气腹前、气腹5min、气腹20min、气腹30min和放气腹5min观察心率变异性指标总功率（TP）、高频功率（HF）、低频功率（LF）、低频标准化值（LFNU）、高频标准化值（HFNU）和低频高频功率比（LF／HF）的变化。结果与气腹前比较，TP、LF、LFNU和LF／HF显著升高（P〈0．01），Hk，无明显变化（P〉0．05）。结论腹腔镜手术气腹后小儿交感神经占优势。HRV可作为麻醉循环监测的敏感指标，动态反映小儿自主神经的变化。     

Reproducibility of abnormal heart rate variability indices: the case of hypertensive sleep apnoea syndrome

Before heart rate variability can be used as an investigational tool in the clinical setting, its reproducibility must be known. We studied heart rate variability four times during 44 weeks in 15 hypertensive patients with sleep apnoea syndrome. Time and frequency domain analytical approaches were used during the spontaneous and controlled breathing tests, orthostatic manoeuvre and the cold pressor test. Alterations in resting heart rate were taken into account using the coefficient of component variance. In general, the response of heart rate variability was abnormal and variability was reduced in the hypertensive patients with sleep apnoea syndrome compared with reference data. Time domain measures of heart rate variability demonstrated generally better reproducibility over four recordings than frequency domain measures in these hypertensive patients with sleep apnoea syndrome. On the other hand, the reproducibility of frequency domain measures depended on the specific conditions: during orthostatic manoeuvre and cold pressor test the best reproducibility was found using normalized units. In the reference data set, there were no significant differences between the two heart rate variability recordings during any of the autonomic nervous function tests. In this follow-up study we found that simple procedures such as the controlled breathing test show good reproducibility. More complex tests such as the orthostatic manoeuvre require special attention in order to obtain acceptable reproducibility of heart rate variability measurements. Quantitatively minor changes in the variability indices when the overall variability is reduced exert major effects on the results. Therefore we suggest that reproducibility data obtained in healthy volunteers are not valid for the interpretation of data in patients with damaged cardiovascular autonomic control.