Heart Rate Variability Triangular Index Research Articles

Whole and Particle-Free Diesel Exhausts Differentially Affect Cardiac Electrophysiology, Blood Pressure, and Autonomic Balance in Heart Failure–Prone Rats

Epidemiological studies strongly link short-term exposures to vehicular traffic and particulate matter (PM) air pollution with adverse cardiovascular (CV) events, especially in those with preexisting CV disease. Diesel engine exhaust is a key contributor to urban ambient PM and gaseous pollutants. To determine the role of gaseous and particulate components in diesel exhaust (DE) cardiotoxicity, we examined the effects of a 4-h inhalation of whole DE (wDE) (target PM concentration: 500 µg/m(3)) or particle-free filtered DE (fDE) on CV physiology and a range of markers of cardiopulmonary injury in hypertensive heart failure-prone rats. Arterial blood pressure (BP), electrocardiography, and heart rate variability (HRV), an index of autonomic balance, were monitored. Both fDE and wDE decreased BP and prolonged PR interval during exposure, with more effects from fDE, which additionally increased HRV triangular index and decreased T-wave amplitude. fDE increased QTc interval immediately after exposure, increased atrioventricular (AV) block Mobitz II arrhythmias shortly thereafter, and increased serum high-density lipoprotein 1 day later. wDE increased BP and decreased HRV root mean square of successive differences immediately postexposure. fDE and wDE decreased heart rate during the 4th hour of postexposure. Thus, DE gases slowed AV conduction and ventricular repolarization, decreased BP, increased HRV, and subsequently provoked arrhythmias, collectively suggesting parasympathetic activation; conversely, brief BP and HRV changes after exposure to particle-containing DE indicated a transient sympathetic excitation. Our findings suggest that whole- and particle-free DE differentially alter CV and autonomic physiology and may potentially increase risk through divergent pathways.

Preserved heart rate variability during therapeutic hypothermia correlated to 96 hrs neurological outcomes and survival in a pig model of cardiac arrest*

Therapeutic hypothermia initiated with cardiopulmonary resuscitation improves neurologic outcomes and survival after prolonged cardiac arrest. However, the potential mechanism by which hypothermia improves neurologic outcomes remains unclear. In the current study, we investigated the effect of rapid head cooling on 96-hr neurologic outcomes and survival by heart rate variability analysis in a pig model of prolonged cardiac arrest. Prospective randomized controlled animal study. University-affiliated research laboratory. Yorkshire-X domestic pigs (Sus scrofa). A protocol of 10 mins of untreated ventricular fibrillation followed by 5 mins of cardiopulmonary resuscitation in a pig model of cardiac arrest was used in this study. Sixteen male domestic pigs weighing between 39 and 45 kg were randomized into two groups, hypothermia (n = 8) and control (n = 8). For the hypothermia group, intranasal-induced head cooling was initiated with cardiopulmonary resuscitation and persisted for 4 hrs after resuscitation. For the control group, cardiopulmonary resuscitation was started with normothermia. Time and frequency domain heart rate variability was calculated in 5-min sections of electrocardiographic recordings at baseline and 4 hrs after resuscitation. Neurologic outcomes were evaluated every 24 hrs during the 96-hr postresuscitation observation period. No differences in the baseline measurement and resuscitation outcome were observed between the groups. However, the 96-hr cerebral performance categories of the hypothermic group were significantly lower than control (1.0 ± 0.0 vs. 4.0 ± 1.9, p = .003). Four hrs after resuscitation, mean RR interval, heart rate variability triangular index, and normalized very-low-frequency power were restored to baseline in the hypothermia group. Square root of the mean squared differences of successive RR intervals and SD of instantaneous RR intervals were significantly improved in the cooled animals compared with controls. A significant correlation between 4-hr heart rate variability and 96-hr cerebral performance category was observed in this study. Selective head cooling maintains a certain level of autonomic nervous system function in this pig model of cardiac arrest. The preserved heart rate variability during postresuscitation hypothermia was associated with favorable 96-hr neurologic recovery and survival.

Abnormal heart rate variability in AA amyloidosis of familial mediterranean fever

Background: A scarcity of data exists relating to the effect of amyloidosis of Familial Mediterranean fever (FMF) on the autonomic nervous system. Our aim was to further investigate the presence of dysautonomia in FMF-AA amyloidosis, using a comparative case series design. Material and methods: The study group consisted of 40 patients with FMF: 20 without co-morbidities or amyloidosis and 20 in various stages of renal amyloidosis. Time domain and power spectral analyses of heart rate dynamics were performed according to accepted procedures. Findings were compared with 20 healthy control subjects. Results: No statistically significant differences were found in any of the studied heart rate variability (HRV) parameters between patients with uncomplicated FMF and controls. In contrast, patients with progressive amyloidosis (post renal transplantation or on dialysis) had significantly lower HRV parameters compared to control subjects (i.e. mean low frequency power spectral components 104.30 ms2 vs. 172.09 ms2, p <0.05, mean standard deviation of all normal RR intervals 32.27 ms vs. 51.51 ms, p <0.05, mean HRV triangular index 9.08 vs. 15.82, p <0.05). The adjusted odds ratio was 14.5 (95%CI 1.21–165.03, p = 0.04) for HRV triangular index lower than 12.2 in the progressive amyloidosis group, 41.24 (95%CI 1.81–938.68, p = 0.02) for low frequency power spectral components values lower than 142.35 ms2, and 12.67 (95%CI 1.04–153.96, p = 0.04) for standard deviation of all normal RR intervals values lower than 40.15 ms. Conclusion: Amyloidosis of FMF, particularly at a progressive stage, is associated with HRV abnormalities suggestive of the presence of autonomic nervous system dysfunction.

The effects of inflammation on heart rate and rhythm in a canine model of cardiac surgery

Heart rate (HR) and rhythm disturbances are common after cardiac surgery. This study tests the hypothesis that the inflammation caused by cardiac surgery is an underlying mechanism for postoperative changes in HR, rhythm, and HR variability (HRV). Normal canines (n = 6 per group) were divided into 4 groups: (1) anesthesia, (2) sternotomy and pericardiotomy, (3) atriotomy, and (4) corticosteroids combined with an atriotomy. Continuous electrocardiographic recordings were done preoperatively and for 3 postoperative days. Electrophysiologic testing was done at the initial and terminal surgeries. C-reactive protein level was assessed at each study day, and tissue myeloperoxidase activity was assessed at the terminal study. Measurements of HRV were determined daily to detect changes in autonomic tone. Postoperatively, the HR increased in the pericardiotomy (P = .0005) and atriotomy (P = .001) groups and HRV decreased in both the groups. No significant change occurred in either the HR or HRV in the anesthesia (P = .52) and steroid (P = .16) groups. HRV (triangular index) on postoperative day 3 was correlated with the tissue myeloperoxidase levels (r = -.83; P = .0004). Autonomic blockade with atropine and esmolol resulted in an HR and HRV that were not significantly different between groups. Atrial premature beats occurred postoperatively in the all the groups except the anesthesia group and were independent of the degree of inflammation. Cardiac surgery increases the postoperative HR by reducing HRV, mostly because of a reduction in vagal tone. Furthermore, the magnitude of these changes is dependent on the degree of inflammation and is normalized by corticosteroids.

Incremental effects of serum uric acid levels, autonomic dysfunction, and low-grade inflammation on nocturnal blood pressure in untreated hypertensive patients and normotensive individuals

We aimed to evaluate the associations between nocturnal blood pressure (BP) and serum uric acid (SUA) level, low-grade inflammation, and cardiac autonomic function in untreated dipper and nondipper hypertensive patients and normotensive individuals. The study included 92 consecutive patients (44 men, 48 women; mean age 51.6 ± 9.7 years) who presented for initial evaluation of hypertension. All patients underwent 24-hour Holter monitoring to assess heart rate variability (HRV) and ambulatory BP. Serum high-sensitivity C-reactive protein (hs-CRP) and SUA levels were measured. Due to the non-normal distribution of hs-CRP and microalbuminuria (MAU), they were normalized by logarithmic transformation. Of the study group, 60 patients (65.2%) were diagnosed as hypertensive (50% nondippers). In univariate correlation analysis, log(MAU) showed a significant correlation with nocturnal BP (r=0.560, p<0.001). Among HRV parameters, SDNN, SDANN, and triangular index were inversely correlated with log(hs-CRP) (r=-0.356, p=0.001; r=-0.350, p=0.001; r=-0.314, p=0.002, respectively) and nighttime BP (r=-0.286, p=0.006; r=-0.251, p=0.02; r=-0.294, p=0.004, respectively). Log(hs-CRP) was positively correlated with nighttime BP (r=0.302, p=0.003). Serum UA levels were correlated with only nocturnal BP; i.e., nocturnal mean (r=0.260, p=0.01), systolic (r=0.249, p=0.016), and diastolic BP (r=0.249, p=0.017). In multiple linear regression analysis, log(hs-CRP) and age were independent predictors of cardiac autonomic dysfunction, and log(hs-CRP), SUA, and HRV parameters were independent predictors of nocturnal BP measurements. Our findings suggest the role of low-grade inflammation, uric acid levels, and autonomic dysfunction even in the early stages of hypertension.

Sex differences in baroreflex sensitivity, heart rate variability, and end organ damage in the TGR(mRen2)27 rat

The aim of this investigation was to evaluate sex differences in baroreflex and heart rate variability (HRV) dysfunction and indexes of end-organ damage in the TG(mRen2)27 (Ren2) rat, a model of renin overexpression and tissue renin-angiotensin-aldosterone system overactivation. Blood pressure (via telemetric monitoring), blood pressure variability [BPV; SD of systolic blood pressure (SBP)], spontaneous baroreflex sensitivity, HRV [HRV Triangular Index (HRV-TI), standard deviation of the average NN interval (SDNN), low and high frequency power (LF and HF, respectively), and Poincaré plot analysis (SD1, SD2)], and cardiovascular function (pressure-volume loop analysis and proteinuria) were evaluated in male and female 10-wk-old Ren2 and Sprague Dawley rats. The severity of hypertension was greater in Ren2 males (R2-M) than in Ren2 females (R2-F). Increased BPV, suppression of baroreflex gain, decreased HRV, and associated end-organ damage manifested as cardiac dysfunction, myocardial remodeling, elevated proteinuria, and tissue oxidative stress were more pronounced in R2-M compared with R2-F. During the dark cycle, HRV-TI and SDNN were negatively correlated with SBP within R2-M and positively correlated within R2-F; within R2-M, these indexes were also negatively correlated with end-organ damage [left ventricular hypertrophy (LVH)]. Furthermore, within R2-M only, LVH was strongly correlated with indexes of HRV representing predominantly vagal (HF, SD1), but not sympathetic (LF, SD2), variability. These data demonstrated relative protection in females from autonomic dysfunction and end-organ damage associated with elevated blood pressure in the Ren2 model of hypertension.

The Efficiency of 10‐Second Resting Heart Rate for the Evaluation of Short‐Term Heart Rate Variability Indices

High values of resting heart rate were found to be correlated with adverse outcomes in various patient groups. Heart rate variability (HRV) is a reliable technique in determining autonomic nervous system function. Our aim was to evaluate whether a 10-second resting heart rate obtained from a resting electrocardiogram (ECG), could be used as a reliable evaluation of short-term HRV. Seventy-nine healthy volunteers were included in the study. All participants underwent a 10-second ECG, and 5-minute HRV measurement under strict criteria. A significantly negative correlation was found between resting heart rate and 5-minute max-RR, min-RR, standard deviation of normal RR intervals (SDNN), root mean square of successive differences of RR intervals (RMSSD), HRV triangular index, number of intervals differing by 50 milliseconds from the preceding interval (NN50), pNN50, standard deviation of the points perpendicular to the line of identity (SD1), standard deviation along the line of identity (SD2), and high frequency spectral component (HF). A significant positive correlation was found between resting heart rate and a 5-minute low frequency spectral component (LF) and LF/HF ratio. Specifically, max-RR and min-RR were found to have the best correlation with resting heart rate. Resting heart rate obtained from a 10-second ECG can be used for crude estimation of all HRV results in healthy individuals who do not take medications, with variable efficacy depending on the measured parameter. Resting heart rate was especially efficient in predicting max-RR and min-RR. Further research should focus on assessing the reliability of a resting heart rate for HRV evaluation, in patients with autonomic dysfunction and high-risk cardiac patients.

Oxidative stress and autonomic nervous system functions in restless legs syndrome

Oxidative stress has been implicated in over 100 disorders in recent years; however, the situation in restless legs syndrome (RLS) has not been studied yet. Fifty patients with RLS not medicated for RLS and 50 sex- and age-matched, healthy controls and controls with no pathology except mild iron deficiency or iron deficiency anaemia were enrolled. Patients with secondary RLS other than iron deficiency were excluded. Total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), arylesterase (ARE), paraoxonase (PON), stimulated paraoxonase (stim-PON), lipid hydroperoxides (LOOHs), acetyl cholinesterase (AChE) and butyryl cholinesterase (BuChE) were measured. Heart rate variability (HRV) analysis was performed. TOS, ARE and AChE were increased (P = 0·018, P < 0·001 and P < 0·001, respectively), whereas LOOHs were decreased (P < 0·001) in RLS group. TAS, OSI, PON and stim-PON were comparable. Erythrocyte sedimentation rate (ESR) and mean platelet volume (MPV) were increased (P = 0·021 and P = 0·037, respectively) in RLS group. HRV triangular index (HRVi) was lower (P = 0·012) in RLS group. Other HRV parameters were similar. Increased AChE and decreased LOOHs, which were influenced by increased PON1, were considered as indicators of efforts towards the protection of dopaminergic activity in central nervous system in RLS group. Increased ESR, MPV and low HRVi indicate elevated sympathetic activity in RLS group. Elevated sympathetic activity might be beneficial in relieving RLS symptoms, also causing increases in TOS. The evidence we found regarding oxidative stress and autonomic nervous system might be seminal in RLS treatment.

Analysis of 24-hour heart rate variations in patients with epilepsy receiving antiepileptic drugs

ObjectiveThe goal of the study described here was to evaluate interictal heart rate variability (HRV) in young patients with epilepsy, a patient population in whom sudden unexpected death in epilepsy (SUDEP) is known to be more common. MethodsTwenty-four-hour ambulatory ECG Holter recordings of 37 patients (15–40years old) and 32 healthy controls were compared. ResultsAll of the time domain indices (SDNN, SDANN, RMSSD, and HRV triangular index) were significantly suppressed (P<0.001), and there was a marked reduction in parasympathetic tone (reduced HFnu,P<0.001) and an increase in sympathetic tone (increased LFnu and LF/HF ratio, P<0.001) in the patient group. Stepwise linear regression analysis revealed that polytherapy and epilepsy duration >10years were independent variables associated with a reduction in SDNN. ConclusionOur data suggest that the major determinants of suppressed SDNN are polytherapy and epilepsy duration >10years. Analysis of spectral measures of frequency domain indices suggests that an increased sympathetic tone in association with a decreased parasympathetic tone may constitute the mechanism underlying SUDEP in young people with epilepsy.

Electrocardiogram analysis using a combination of statistical, geometric, and nonlinear heart rate variability features

The paper addresses a common and recurring problem of electrocardiogram (ECG) classification based on heart rate variability (HRV) analysis. Current understanding of the limits of HRV analysis in diagnosing different cardiac conditions is not complete. Existing research suggests that a combination of carefully selected linear and nonlinear HRV features should significantly improve the accuracy for both binary and multiclass classification problems. The primary goal of this work is to evaluate a proposed combination of HRV features. Other explored objectives are the comparison of different machine learning algorithms in the HRV analysis and the inspection of the most suitable period T between two consecutively analyzed R-R intervals for nonlinear features. We extracted 11 features from 5min of R-R interval recordings: SDNN, RMSSD, pNN20, HRV triangular index (HTI), spatial filling index (SFI), correlation dimension, central tendency measure (CTM), and four approximate entropy features (ApEn1-ApEn4). Analyzed heart conditions included normal heart rhythm, arrhythmia (any), supraventricular arrhythmia, and congestive heart failure. One hundred patient records from six online databases were analyzed, 25 for each condition. Feature vectors were extracted by a platform designed for this purpose, named ECG Chaos Extractor. The vectors were then analyzed by seven clustering and classification algorithms in the Weka system: K-means, expectation maximization (EM), C4.5 decision tree, Bayesian network, artificial neural network (ANN), support vector machines (SVM) and random forest (RF). Four-class and two-class (normal vs. abnormal) classification was performed. Relevance of particular features was evaluated using 1-Rule and C4.5 decision tree in the cases of individual features classification and classification with features' pairs. Average total classification accuracy obtained for top three classification methods in the two classes' case was: RF 99.7%, ANN 99.1%, SVM 98.9%. In the four classes' case the best results were: RF 99.6%, Bayesian network 99.4%, SVM 98.4%. The best overall method was RF. C4.5 decision tree was successful in the construction of useful classification rules for the two classes' case. EM and K-means showed comparable clustering results: around 50% for the four classes' case and around 75% for the two classes' case. HTI, pNN20, RMSSD, ApEn3, ApEn4 and SFI were shown to be the most relevant features. HTI in particular appears in most of the top-ranked pairs of features and is the best analyzed feature. The choice of the period T for nonlinear features was shown to be arbitrary. However, a combination of five different periods significantly improved classification accuracy, from 70% for a single period up to 99% for five periods. Analysis shows that the proposed combination of 11 linear and nonlinear HRV features gives high classification accuracy when nonlinear features are extracted for five periods. The features' combination was thoroughly analyzed using several machine learning algorithms. In particular, RF algorithm proved to be highly efficient and accurate in both binary and multiclass classification of HRV records. Interpretable and useful rules were obtained with C4.5 decision tree. Further work in this area should elucidate which features should be extracted for the best classification results for specific types of cardiac disorders.

Heart Rate Variability in Children with Congenital Heart Disease Before and After Open Heart Surgery

Background: Spectrum analysis of heart rate variability (HRV) is a noninvasive procedure that provides information on sympathetic and parasympathetic controls. Reduced HRV may indicate cardiac autonomic dysfunction and susceptibility to hemodynamic instability during anesthesia, after myocardial infarction or cardiac operations. Aim: This study was designed to investigate the effects of cardiopulmonary bypass on HRV variability in children with congenital heart disease and if HRV is turning to the normal in postoperative period and when, as well as the duration of the process. Methods: HRV data were obtained from 29 pediatric patients with congenital heart disease, who underwent elective cardiac surgery. Electrocardiographic data were collected with PC-based ECG acquisition system (PC-ECG 1200). ECG results were obtained by assessing 200 heart beats that recorded in supine position. Clinical data including age, type of cardiac lesion, type of surgical procedure, cardiopulmonary bypass (CPB) time, cross clamp time were recorded. Results: 16 male and 13 female patients mean aged 8.08±3.8 (1-15), 27 had an acyanotic heart disease, 2 of them had a cyanotic heart disease. Standard deviation of all normal RR intervals (SDNN) (p=0.048) and HRV triangular index (p=0.017) were significantly lower in the postoperative first month than preoperatively. There were no significant preoperative differences in other time or frequency domain measures of HRV between the preoperative recordings and postoperative for the first month. SDNN, low and high frequency were found significantly low when compared between the postoperative first and third month, although HF was decreased in the first postoperative month, but did not reach statistical significance. Conclusion: Our findings showed that decreased HRV is a nonspecific marker of cardiovascular stress just after the cardiac operations, reflecting an alteration in autonomic nervous system input to the heart and turning to the normal in the third month.

Independent Evolution of Heart Autonomic Function and Insulin Sensitivity During Weight Loss

In order to investigate the improvement of insulin resistance and cardiac autonomic function along massive weight loss, 12 obese women were evaluated before, and 3 and 12 months after Roux-en-Y gastric bypass. The 12-month values were compared to those of BMI-matched controls. Insulin sensitivity was assessed by euglycemic clamp and the cardiac autonomic function by the analysis of the Heart Rate Variability (HRV). After surgery, glucose uptake progressively increased from 4.3 +/- 0.5 mg/kg lean body mass (LBM)/min preoperative (pre-op) to 4.9 +/- 0.5 and 7.0 +/- 0.5, 3- and 12-month postoperative (post-op) (P = 0.04 and P = 0.006 vs. pre-op), whereas the cardiac autonomic function showed a biphasic pattern. HRV values increased 3 months post-op, and decreased at 12 months, thus indicating an early sympathetic withdrawal followed by a later reactivation (e.g., the standard deviation of the normal-to-normal intervals was 116 +/- 7 ms in pre-op, 161 +/- 10 at 3 months, P = 0.008 vs. pre-op, and 146 +/- 15 at 12 months, P = 0.03 vs. pre-op and P = 0.02 vs. 3 m). Insulin sensitivity was significantly related to body weight (P = 0.02), whereas the cardiac indexes were significantly linked to the profile of energy intake (e.g., HRV triangular index vs. energy intake P = 0.003). No significant relationship linked insulin sensitivity to the cardiac autonomic indexes. Insulin sensitivity and cardiac parameters of the 12-month post-op patients were similar to their matched controls. During massive weight loss, the cardiac autonomic deregulation and insulin resistance improved concomitantly but independently from each other. Our results suggest that the extent of the improvement is associated with the final body weight.

Association of Low Heart Rate Variability with Atherosclerotic Cardiovascular Disease in Hemodialysis Patients

Objective: The aim of this study was to investigate the left-ventricular (LV) mass-adjusted association between low heart rate variability (HRV) and atherosclerotic cardiovascular disease (ASCVD) among hemodialysis patients in Kuwait. Subjects and Methods: One hundred and eight patients were enrolled in the study. HRV time domain measures were obtained by 48-hour Holter monitoring, including the standard deviation of all R-wave-to-R-wave (RR) intervals (SDNN), standard deviation of all 5-min averaged intervals (SDANN), HRV triangular index (HRV-TI), percent of adjacent RR intervals differing by >50 ms (pNN50), and root mean square of sums of squares of all differences (rMSSD). Left ventricular ejection fraction (LVEF) and LV mass index (LVMI) were measured by M-mode echocardiography. Comorbidity was assessed using medical record review. Prevalent ASCVD was defined as coronary artery, cerebrovascular, or peripheral vascular disease. Results: Prevalence of ASCVD, LV hypertrophy, and LVEF <40% were 56, 59, and 10%, respectively. The SDANN was negatively associated with ASCVD (–20 ms; p = 0.003), LV systolic dysfunction (–20 ms; p = 0.001), elevated LVMI (–20 ms; p = 0.002), hypertension (–34 ms; p = 0.01), and diabetes (–20 ms; p = 0.001). After adjustment for hypertension and LVMI using logistic regression, ASCVD was associated with the lowest quartile of SDANN (OR = 4.3, p = 0.009), HRV-TI (OR = 3.3, p = 0.03), and SDNN (OR = 2.3, p = 0.10). These associations persisted after adjusting for LVEF. Conclusion: In dialysis patients, low HRV indices were strongly associated with prevalent ASCVD, independent of LVMI and LVEF. The interrelationships among HRV, diabetes, hypertension, and LVMI should be addressed in studies of HRV and ASCVD.

Correlation between the Severity of Obstructive Sleep Apnea and Heart Rate Variability Indices

The risk of cardiovascular disease is known to be increased in obstructive sleep apnea syndrome (OSAS). Its mechanism can be explained by the observation that the sympathetic tone increases due to repetitive apneas accompanied by hypoxias and arousals during sleep. Heart rate variability (HRV) representing cardiac autonomic function is mediated by respiratory sinus arrhythmia, baroreflex-related fluctuation, and thermoregulation-related fluctuation. We evaluated the heart rate variability of OSAS patients during night to assess their relationship with the severity of the symptoms. We studied overnight polysomnographies of 59 male untreated OSAS patients with moderate to severe symptoms (mean age 45.4± 11.7 yr, apnea-hypopnea index [AHI]=43.2±23.4 events per hour, and AHI >15). Moderate (mean age 47.1±9.4 yr, AHI=15-30, n=22) and severe (mean age 44.5±12.9 yr, AHI >30, n=37) OSAS patients were compared for the indices derived from time and frequency domain analysis of HRV, AHI, oxygen desaturation event index (ODI), arousal index (ArI), and sleep parameters. As a result, the severe OSAS group showed higher mean powers of total frequency (TF) (p=0.012), very low frequency (VLF) (p= 0.038), and low frequency (LF) (p=0.002) than the moderate OSAS group. The LF/HF ratio (p=0.005) was higher in the severe group compared to that of the moderate group. On the time domain analysis, the HRV triangular index (p=0.026) of severe OSAS group was significantly higher. AHI was correlated best with the LF/HF ratio (rp=0.610, p<0.001) of all the HRV indices. According to the results, the frequency domain indices tended to reveal the difference between the groups better than time domain indices. Especially the LF/HF ratio was thought to be the most useful parameter to estimate the degree of AHI in OSAS patients.

Analysis of heart rate variability as an index of noncardiac surgical stress

Measurement of heart rate variability (HRV) is useful in assessing the function of the autonomic nervous system and in staging of clinical diseases. The purpose of this study is to assess a feasibility of HRV for evaluating surgical stress during the noncardiac perioperative period. Standard deviation of normal-to-normal RR intervals (SDNN) and HRV triangular index derived from 24-h Holter ECC were measured in 24 patients undergoing digestive surgery. Holter ECG was performed at 1 day before operation, the first day (postoperative day 1: POD1), and the 7th day (POD7) after operation. Indices of HRV were compared with factors influencing surgical stress, such as duration of the operation and amount of blood loss during the operation, and postoperative complications. The SDNN and HRV triangular index decreased significantly on POD1 and recovered on POD7 (P < 0.05). Heart rate variability indices correlated significantly to duration and blood loss of operation (both P < 0.05). In 7 patients with postoperative complications, HRV indices were statistically lower than those in patients without complications on POD1 (P < 0.05). Our results indicate that HRV may provide useful information with respect to surgical stress.

Heart Rate Variability for Evaluating Surgical Stress and Development of Postoperative Complications

Heart rate variability (HRV) has recently been used to detect autonomic nerve tone, which is affected by various stresses. To test out hypothesis that HRV can determine surgical stress, we examined perioperative HRV in 30 patients with surgical treatment. Relations between HRV and factors of surgical stresses, such as duration of the operation, amount of blood loss at the operation, and developments of complications, were evaluated. Mean heart rate (HR) increased and other HRV indices decreased postoperatively. Most indices correlated significantly to the duration of the operation and amount of blood loss at the operation on postoperative day 1. Only the standard deviation of normal to normal RR intervals (SDNN) and HRV triangular index showed significantly low values in complicated patients. HRV measurement in the perioperative period showed a significant relation to surgical stress. The present results indicated that HRV may provide useful information with respect to surgical stress.

Heart Rate Variability in Patients with Allergic Rhinitis

Considering the role of autonomic imbalance in the pathogenesis of hypersensitivity reactions, we evaluated the autonomic system through time-domain analysis of heart rate variability (HRV) in patients with allergic rhinitis. Twenty-four patients with allergic rhinitis and 22 healthy subjects (mean age, 41 +/- 8 years and 37 +/- 9 years, respectively) were enrolled in the study. The diagnosis of allergic rhinitis was based on the history, symptoms, and skin prick tests results. Twenty-four-hour ambulatory electrocardiographic recordings were obtained, and the time-domain indices were analyzed. Analysis of HRV revealed that the SD of normal RR intervals, SD of successive differences in normal cycles, and HRV triangular index were not significantly different between the groups, but the root mean square successive difference, number of RR intervals exceeding 50 milliseconds, and percentage difference between adjacent normal RR intervals exceeding >50 milliseconds were significantly greater in the study group, compared with the control group. Our findings showed that HRV indices, which predict parasympathetic predominance, were increased in patients with allergic rhinitis. This finding shows that vagal activation is present not only in the nose but also in other systems, including the cardiovascular system.

Time and frequency domain analyses of heart rate variability in patients with epilepsy

Heart rate variability (HRV) is a useful tool for the detection of sympathetic–parasympathetic balance of autonomic nervous system in patients at risk of sudden death (SD). SD is more common in patients with epilepsy and the exact mechanisms of SD are unknown. Autonomic nervous system involvement in patients with epilepsy has rarely been studied and has shown conflicting results. Our purpose was to determine if HRV showed any changes in patients with epilepsy in comparison with normal population. A short period analysis of HRV was performed for both the frequency and time domain in 43 epilepsy patients who had generalized tonic-clonic seizures (GTCS) and who were not taking any medications and also in 43 age and sex matched controls. In the time domain analysis, patients displayed higher SDNN (standard deviation of all R–R intervals), SDANN (standard deviation of mean NN intervals in 5 min recordings) and HRV triangular index than did healthy subjects ( p < 0.0001). Patients tended to display higher pNN50 (number of R–R intervals differed by >50 ms from adjacent interval divided by the total number of all R–R intervals) and RMSSD (root-mean-square of successive differences) values than did healthy subjects, but the differences were not statistically significant ( p > 0.05). In the frequency domain analysis, the spectral measures of HRV showed a reduction of high frequency (HF) values (is a marker of parasympathetic activity) and an increase of low frequency (LF) values (is a measure of sympathetic activity); as a result, the ratio between low and high frequencies (LF/HF) was significantly increased ( p < 0.0001, p < 0.0001 and p < 0.001, respectively). Our data suggests an increase in the sympathetic control of the heart rate in epilepsy patients who have GTCS. This increased sympathetic activity could play a key role in the development of ventricular tachyarrhythmias in patients with epilepsy and may be related to the higher incidence of sudden death in this disorder as compared to controls.

Change of Heart Rate Variability before and after General Anesthesia

Background: This study assessed the changes in the heart rate variability (HRV) indices, which are used to measure the autonomic nervous system function during general anesthesia (GA), and compared the result of the awake state. Methods: Patients undergoing an explo-laparotomy were anesthetized with either isoflurane (Group I, n = 20) or sevoflurane (Group S, n = 20) added to a mixture of nitrous oxide and oxygen. Frequency-domain analysis of the HRV indices using fast Fourier transformation (FFT) resulted in a power spectrum with a very low (VLF), low (LF), and high frequency (HF) and calculated normalized LF (nuLF), normalized HF (nuHF), and LF/HF ratios before and after GA. Time-domain analysis was performed and the pNN50 (proportion of successive RR intervals [RRI] ＞ 50 ms in relation to the total RRI), RMSSD (root mean square of the successive differences in the RRI), standard deviation 1 (SD1) and standard deviation 2 (SD2) from the Poincare plots, HRV triangular index, and TINN (triangular interpolation of NN interval histogram) were also calculated before and after GA. Results: The VLF, LF, HF, nuLF, and LF/HF ratio during GA decreased by 45.2, 95.1, 83.1, 27.3, and 17.4%, respectively, compared with the awake state. However, the nuHF significantly increased. The RMSSD, pNN50, SD1, SD2, HRV triangular index, and TINN also decreased 62.0, 69.2, 62.0, 61.7, 62.4, and 52.4%, respectively. Groups I and S produced similar alterations in the studied parameters during GA. Conclusions: GA reduced all the HRV indices studied except for the nuHF.

PROGNOSIS OF LIFE IMPROVEMENT AFTER LIVING-RELATED RENAL TRANSPLANTATION BY ANALYSIS OF HEART RATE VARIABILITY IN LONG-TERM ELECTROCARDIOGRAM

P324 Aims: Despite recent advances in hemodialysis techniques and medical management for end-stage renal disease (ESRD), mortality is still high among chronic hemodialysis patients. In such patients, cardiovascular complications are leading cause of death. Analysis of heart rate dynamics (R-R intervals) using a long-term electrocardiogram provides prognostic information for patients under various clinical situations. Decreased heart rate variability (HRV) predicts the risk for cardiac death in patients with ESRD. There is no data on prognosis of life after renal transplantation compared to before, using 24 hours HRV analysis. The purpose of this study is to determine therapeutic value of renal transplantation on prognosis of life, by HRV using 24 hours electrocardiogram in a prospective analysis in ESRD patients. Methods: Between March 2002 and May 2003, out of 36 patients before living-related renal transplantation in our department, 24 were enrolled in this study. We excluded 12 patients because of diabetes mellitus, s-Cre>2mg/dl at 6 months, treatment with βblocker before or after transplantation. 24 patients (15 male, 9 female) were aged 37±11 years. Before transplantation, they had been on hemodialysis for 5.3±6.8 years. 4 patients were preemptive. 24 hours electrocardiogram was performed at before operation which is in a dialysis-free day of the middle week, 1month, 6months, 12months after operation. All recordings were made in hospitalization. We used Nihon Kouden RAS3102 as a 24 hours electrocardiogram, and after distinguishing QRS complex, we analyzed it by using MemCalc®. Results: Standard deviation of all R-R intervals during 24 hours (SDNN) which is a predictor of disease prognosis was improved from 115.5±33.1 ms to 151.3±34.3 ms (p=0.0004) significantly in 6 months after transplantaion, and HRV triangular index (total number of all R-R intervals divided by the height of the histogram of R-R intervals measured on a discrele scale with bins of 7.8125 ms) as a predictor of disease prognosis was significantly improved from 33.4±11.4 to 42.7±10.3 (p=0.0013) in 6 months after transplantaion. Power of high frequency band (HF) as a predictor of parasympathetic function and power of low frequency band (LF)/HF as a predictor of sympathetic function had a tendency to improve from 128.7±115.4 ms2 to 232.7±270.2 ms2 (p=0.07), from 8.0±9.9 to 4.6±2.8 (p=0.07) respectively in 6 months after transplantaion, but not significant. Power of ultra low frequency (ULF) and power of very low frequency (VLF), which are predictors of disease prognosis, were improved from 3065±1370 ms2 to 4861±2033 ms2 (p=0.0008), 1439±825 ms2 to 2150±836 ms2 (p=0.0013) respectively in 6 months after transplantaion. All predictors but SDNN and ULF were not significantly improved in a month after transplantation. Conclusions: Prognosis of life under chronic hemodialysis is dramatically improved from just 6 months after renal transplantation. This improvement is earlier than recovery of autonomic function.