QT Interval Variability and Adaptation to Heart Rate Changes in Patients with Long QT Syndrome

Background: Increased QT variability (QTV) has been reported in conditions associated with ventricular arrhythmias. Data on QTV in patients with congenital long QT syndrome (LQTS) are limited.
Methods: Ambulatory electrocardiogram recordings were analyzed in 23 genotyped LQTS patients and in 16 healthy subjects (C). Short-term QTV was compared between C and LQTS. The dependence of QT duration on heart rate was evaluated with three different linear models, based either on the RR interval preceding the QT interval (RR₀), the RR interval preceding RR₀ (RR_-1), or the average RR interval in the 60-second period before QT interval (mRR).
Results: Short-term QTV was significantly higher in LQTS than in C subjects (14.94 ± 9.33 vs 7.31 ± 1.29 ms; P < 0.001). It was also higher in the non-LQT1 than in LQT1 patients (23.00 ± 9.05 vs 8.74 ± 1.56 ms; P < 0.001) and correlated positively with QTc in LQTS (r = 0.623, P < 0.002). In the C subjects, the linear model based on mRR predicted QT duration significantly better than models based on RR₀ and RR_-1. It also provided better fit than any nonlinear model based on RR₀. This was also true for LQT1 patients. For non-LQT1 patients, all models provided poor prediction of QT interval.
Conclusions: QTV is elevated in LQTS patients and is correlated with QTc in LQTS. Significant differences with respect to QTV exist among different genotypes. QT interval duration is strongly affected by noninstantaneous heart rate in both C and LQT1 subjects. These findings could improve formulas for QT interval correction and provide insight on cellular mechanisms of QT adaptation.     

Heart Rate Variability and Sudden Infant Death Syndrome

PERTICONE, F., ET AL.: Heart Rate Variability and Sudden Infant Death Syndrome. The sudden infant death syndrome (SIDS) is the most common cause of death in infancy. The pathophysiological mechanism leading to SIDS is still obscure. In the QT hypothesis, the mechanism must be an arrhythmogenic sympathetic imbalance: the infants die suddenly of cardiac arrhythmia. Recently, it has been suggested that analysis of heart rate variability (HRV), expressed as standard deviation or variance analysis, can provide adequate information on sympathovagal interaction. We studied 150 newborns enrolled in a previous prospective electrocardiographic study to evaluate the predictive value of QT interval for SIDS. We analyzed the ECGs recorded with infants alert on the fourth day of life and after 2 months. For each ECG, the HRV was calculated using the first standard deviation of of RR intervals (ms) measured for 1 minute. The average RR interval was 441 ± 71 ms at the fourth day and 420 ± 39 ms at the second month. The QT_c and HRV mean values were 396 ± 23 and 23 ± 12 ms at the fourth day, 412 ± 19 and 15 ± 7 msec at the second month. Therefore, the SD values of heart rate were correlated with QT_cin order to assess a possible relationship between the two variables. The correlation coefficient and regression equation were: -0.639 and y = 423.67 - 2.18*× (P < 0.002) at the fourth day, -0.146 and y = 418.09 - 0.37*× (NS) at the second month. In conclusion, our data seems to confirm a delayed maturation or impaired fuctioning of the autonomic nervous system in the first weeks of life, reflecting a direct correlation with QT prolongation.     

Multiparametric Analysis of Heart Rate Variability Used for Risk Stratification Among Survivors of Acute Myocardial Infarction

A multiparametric heart rate variability analysis was performed to prove if combined heart rate variability (HRV) measures of different domains improve the result of risk stratification in patients after myocardial infarction. In this study, standard time domain, frequency domain and non-linear dynamics measures of HRV assessment were applied to 572 survivors of acute myocardial infarction. Three parameter sets each consisting of 4 parameters were applied and compared with the standard measurement of global heart rate variability HRVi. Discriminant analysis technique and t-test were performed to separate the high risk groups from the survivors. The predictive value of this approach was evaluated with receiver operator (ROC) and positive predictive accuracy (PPA) curves. Results - The discriminant analysis shows a separation of patients suffered by all cause mortality in 80% (best single parameter 74%) and sudden arrhythmic death in 86% (73%). All parameters of set I show a high significant difference (p<0.001) between survivors and non-survivors based on two-tailed t-test. The specificity level of the multivariate parameter sets is at the 70% sensitivity level (ROC) about 85–90%, whereas HRVi shows maximum levels of 70%. The PPA in the all cause mortality group is at the 70% sensitivity level twice as high as the univarihate HRV measure and increases to more than fourfold as high within the VT/VF group. In conclusion, in this population, the multiparametric approach with the combination of four parameters from all domains especially from NLD seems to be a better predictor of high arrhythmia risk than the standard measurement of global heart rate variability.     

Heart Rate Variability in Patients with Familial Amyloid Polyneuropathy

The purpose of this study was to evaluate heart rate variability (HRV) in patients with familial amyloid polyneuropathy (FAP) using the time- and frequency-domain analysis. The study population consisted of 19 patients with FAP, and 19 age and sex matched normal volunteers. The 24-hour Holter recordings of all subjects in sinus rhythm and off medication were analyzed. Five time-domain indices of HRV were computed. The frequency component of HRV was calculated by fast Fourier transform analysis of the RR intervals. The power spectrum of the low frequency (LF) between 0.04–0.15 Hz and high frequency (HF) between 0.15–0.40 Hz and the LF/HF ratio was calculated. Global measures of HRV including the standard deviation of the mean of RR intervals (SDNN) and the standard deviation of 5-minute mean RR intervals (SDANN) were decreased in patients with FAP. Specific vagal influences on HRV including the proportion of RR intervals more than 50 milliseconds different (pNN50) and the HF power on spectral analysis were less in patients with FAP. LF power and LF/HF ratio were more decreased in patients with FAP at the advanced stage than at the early stage. In conclusion, HRV was significantly decreased in patients with FAP at the early stage, and sympathetic activity was more decreased in patients at the advanced stage. These findings suggest that the decrease of the HRV is an indicator of this disease and the power spectral analysis of the HRV is beneficial in assessing the severity of the autonomic dysfunction.     

Changes in Heart Rate Variability with Age

Depressed heart rate variability (HRV) after a myocardial infarction is associated with increased mortality. This is thought to be due to reduced parasympathetic activity and heightened sympathetic activity. Aging is associated with depressed HRV, but little is known of the affect of aging on parasympathetic activity. This study examined 56 healthy subjects (age range 40–102 years; 39 women). None had a history of heart disease or were on medication that would affect cardiac function. All had normal resting ECGs, normal heart size on chest X ray, and normal electrolytes. In all subjects, 24-hour Holter recordings were performed and used to measure HRV. In particular, the study examined the affect of age on HRV triangular index, which gives an estimate of overall HRV, and on RMSSD (square root of the mean squared differences of successive normal-to-normal RR intervals), which gives an estimate of short-term components of HRV and is thought to reflect the overall extent of vagal modulations of heart rates. Both these parameters were compared in patients younger and older than 70 years. Each recording lasted at least 17 hours; the majority of recordings were longer than 20 hours. There was a significant decrease in HRV triangular index with age (r =?0.4, P < 0.05) and no significant change in RMSSD with age(r =?0.08, P = NS). There was a significant difference in HRV index in those > 70 years compared with those < 70 years (38.0 ± 9.3 vs 31.0 ± 11, respectively, P <0.02). There was no significant difference in RMSSD between the two age groups (26.7 ± 8.2 ms vs 28.4 ± 11.3 ms, respectively, P = NS). Thus, the study concludes that aging reduces the global measure of HRV and may reflect reduced responsiveness of autonomic activity to external environmental stimuli with age. However, the time-domain short-term components of HRV are not affected by age and, therefore, the fast and presumably vagal modulations of heart rate appear to be maintained.     

Alteration of QT Rate Dependence Reflects Cardiac Autonomic Imbalance in Patients with Obstructive Sleep Apnea Syndrome

QT rate dependence is one of the major properties of ventricular repolarization with its circadian and autonomic modulations. The authors postulated that dynamic alterations in QT interval adaptation could help characterize patients with cardiac autonomic alterations, like those with obstructive sleep apnea syndrome (OSAS). To assess ventricular repolarization features in patients with OSAS, QT parameters and their dynamicity along RR intervals were compared from 24-hour ECG data of patients with and without this syndrome, assessing cardiac autonomic nervous system equilibrium by means of time-domain and frequency-domain analyses of heart rate variability (HRV). The study group consisted of 74 consecutive patients referred to the Sleep Laboratory for clinically suspected OSAS. The syndrome was confirmed in 30 (40.5%) patients according to standard polysomnographic criteria. QT length related to heart rate (HR) was found significantly shorter for HR < 70 beats/min in patients with OSAS   (−1.32 ± 0.35)   compared with patients without OSAS   (−1.99 ± 0.40; P < 0.01)   . This flattened relationship was correlated with the severity of the sleep related disorder. Using multiple linear regression analysis, the apnea/hypopnea index and nocturnal normalized high frequencies (HFnu) were the most significant predictors of the QT/RR slope   (R = 0.61; P < 0.0001)   . OSAS is significantly associated with a flattened relationship between QT duration and RR interval at low HRs. The alteration of cardiac parasympathetic tone occuring in severe OSAS patients may explain this altered rate dependent adaptation of myocardial repolarization. (PACE 2003; 26[Pt. I]:1446–1453)     

Correlation of Heart Rate Variability Parameters and QT Interval in Patients After PTCA of Infarct Related Coronary Artery as an Indicator of Improved Autonomic Regulation

The purpose of this study was to determine if PTCA of the infarct related coronary artery (IRA) in the late phase of myocardial infarction (MI) can improve autonomic regulation of sinus rhythm and electrical stability of the myocardium measured by heart rate variability (HRV), QT, QTc, and its dispersion (QTd) and if any correlation exists among these measures. The study was performed in 25 patients (21 male, age: 50 ± 9 years, EF: 52%± 11%) in the late phase of MI (2.5 ± 1.5 months). HRV parameters were calculated automatically. QT, QTc, and QTd were measured manually from a 12-lead surface ECG (50 mm/s). All measurements were made before and 3–5 days after PTCA. Day and night parameters of HRV were sampled over two periods: 2 pm to 10 pm (day) and 10 pm to 6 am (night). Parameters of HRV measured from whole recordings were significantly higher after successful PTCA: SDRR (116 31 vs 128 ± 38 ms), SD (55 ± 17 vs 62 ± 22 ms), rMSSD (30 ± 13 vs 36 ± 14 ms) and HF (246 ± 103 vs 417 ± 224 ms2). Significant differences were found during daytime for SD, rMSSD, and HF, and during nighttime for SDRR, SDANN. QT interval duration, QT corrected to the heart rate, and QT dispersion were significantly lower after PTCA (QTd: 54 ± 15 vs 39 ± 12 ms). There was no correlation between HRV and QT values before PTCA. High correlations were found after the procedure, particularly between QTd and nighttime HRV. Conclusions: PTCA of IRA in the late phase of MI enhances sympathovagal regulation of the cardiac rhythm and the electrical stability of the heart, which may be prognostically important.     

Heart Rate Variability in Emergency Department Patients with Sepsis

OBJECTIVE: To test the hypothesis that heart rate variability (HRV) can provide an early indication of illness severity among patients presenting to the emergency department (ED) with sepsis. METHODS: The authors enrolled a convenience sample of 15 ED patients meeting the American College of Chest Physicians/Society of Critical Care Medicine criteria for sepsis. Each patient had continuous Holter monitoring performed in the ED. Acute Physiology and Chronic Health II (APACHE II) and Sequential Organ Failure (SOFA) scores were calculated for the day of presentation. Holter tapes obtained in the ED were analyzed off-line to calculate HRV variables for the 5-minute segment with the least artifact and non-sinus beats. These variables were correlated with APACHE II and SOFA scores. RESULTS: LFnu (normalized low-frequency power), an assessment of the relative sympathetic contribution to overall HRV, was correlated with increased illness severity as calculated using APACHE II (r = -0.67, r(2) = 0.43) and SOFA (r = -0.80, r(2) = 0.64) scores. LF/HF ratio (low-frequency/high-frequency ratio), a measure of sympathovagal balance, was correlated with the SOFA score [r = -0.54 (95% CI = -0.83 to -0.01), r(2) = 0.29]. All five patients who required critical care monitoring or ventilatory support or who died during the first 5 days of their hospitalization had LFnu values below 0.5 and LF/HF ratios less than 1.0. None of the patients with measurements greater than these threshold values died or required these interventions during the five days following admission. CONCLUSIONS: A single variable, LFnu, which reflects sympathetic modulation of heart rate, accounted for 40-60% of the variance in illness severity scores among patients presenting to the ED with sepsis. HRV, as reflected in LFnu and the LF/HF ratio and measured with a single brief (5-minute) period of monitoring while in the ED, may provide the emergency physician with a readily available, noninvasive, early marker of illness severity. The threshold effect of LFnu and LF/HF in the prediction of early clinical deterioration was an unexpected finding and should be regarded as hypothesis-generating, pending further study.     

Arrhythmia Risk Prediction in Idiopathic Dilated Cardiomyopathy Based on Heart Rate Variability and Baroreflex Sensitivity

This study examined the relation between heart rate variability (HRV) and baroreflex sensitivity (BRS) and subsequent major arrhythmic events (MAE), defined as sustained VT, VF or sudden death, in 263 patients with idiopathic dilated cardiomyopathy (IDC) in sinus rhythm. The predefined measure of HRV was the standard deviation of all normal-to-normal RR intervals (SDNN) on baseline 24-hour ambulatory ECG. BRS was determined by the phenylephrine method. Over 52 ± 21 months of follow-up, MAE occurred in 38 patients (14%). SDNN at baseline 24-hour ambulatory ECG (106 ± 46 vs 109 ± 45, ns) and BRS (7.9 ± 5.5 vs 7.7 ± 5.3 ms/mmHg, ns) were both similar in patients with versus without MAE during follow-up. In contrast, left ventricular ejection fraction was significantly lower in patients with versus without MAE (24%± 7% vs 31%± 10%, P < 0.019. Conclusions: Neither HRV nor BRS predicted MAE in patients with IDC.     

慢性肺心病患者的心率变异性

目的：观察慢性肺心病患者心率变异性，了解其自主神经功能的变化。方法：对25例慢性肺心病，25例健康对照者（对照组）作前瞻性对照研究，记录24h动态心电图，作时域和频域分析，结果：与对照组比较，肺心病组相邻心搏的R－R间期之差＞50ms的心搏数占R－R间期数的百分(pNN50)，每5min正常R－R间期标准差的平均值（SDANN），频域指标的高频（HF）明显降低，低频与高频的比值（LF／HF），明显升高，差异均有非常显著意义（P均＜0．01），而频域指标的低频（LF）无明显变化（P＞0．05），经过治疗后，肺心病组处于缓解期，与治疗前比较，HF，PNN50，SDANN等指标明显增加，而LF／HF明显降低，差异均有非常显著意义（P均＜0．01），肺心病组病人治疗后HF，pNN50,SDANN等指标均低于对照组，而LF／HF明显高于对照组，差异均有非常显著意义（P均＜0．01），肺心病组治疗后LF与治疗前及对照组比较，差异不具显著意义（P＞0．05）。结论：肺心中层得不仅交感神经活动占优势，同时并存迷走神经功能受损，自主神经功能可能存在连续性障碍。     

慢性充血性心力衰竭患者的心率变异性分析

目的：评价心率变异性在慢性充血性心力衰竭患者中的变化。方法：用24h动态心电图研究慢性充血性心力衰竭患者与对照组的心率变异性及比较其他心脏结构及功能参数。结果：慢性充血性心力衰竭组的SDNN，SDANN，LF，HF，LF／HF均较对照组显著降低（P＜0．05），且随心衰严重程度增加，心率变异性呈递减，并与LVEF，LVEDD及LVSF改变相关（P＜0．05或P＜0．01）。结论：心率变异性可作为了解心衰程度、指导治疗和判定预后的参考指标之一。     

Decreased Heart Rate Variability in Patients with Congestive Heart Failure and Chronotropic Incompetence

Heart rate variability was studied in 41 patients (aged 48 ± 12 years) with congestive heart failure secondary to idiopathic dilated cardiomyopathy. All patients underwent a treadmill exercise test and 24-hour Holter ECC monitoring. Chronotropic incompetence was defined as the failure to achieve > 80% of the predicted maximal heart rate response given by 220 – age (years) at peak exercise. Spectral heart rate variability was analyzed from 24-hour Holter ECCs and was expressed as total (0.01–1.00 Hz), low (0.04–0.15 Hz), and high (0.15–0.40 Hz) frequency components. The standard deviation of all normal RR intervals (SDNN) was also computed. Chronotropic incompetence was observed in ten patients. Peak oxygen consumption was significantly lower in patients witb chronotropic incompetence compared with those without chronotropic incompetence. The total (5.11 ± 1.26 In [ms²] vs 6.41 ± 0.92 In [ms²]; P = 0.009) and low (3.38 ± 1.65 In [ms²] vs 5.45 ± 1.34 In [ms²];P = 0.003), but not the high (3.42 ± 1.04 In [ms²] vs 4.00 ± 1.12 in [ms²]; P = 0.249) frequency components of heart rate variability were significantly lower in patients with chronotropic incompetence, although there was no significant difference in mean heart rate (88 ± 20 beats/min vs 86 ± 15 beats/min; P = 0.831) or left ventricular ejection fraction (22%± 10% vs 24%± 10%; P = 0.619). SDNN was also significantly lower in patients with chronotropic incompetence compared witb those without chronotropic incompetence (64 ± 34 ms vs 102 ± 37 ms; P = 0.030). Conclusions: The observation that heart rate variability is significantly decreased in patients with congestive heart failure who have chronotropic incompetence suggests that chronotropic incompetence may relate to an abnormal autonomic influence on the heart in these patients.     

冠心病患者心率变异性与室性心律失常的关系

目的　探讨冠心病患者心律变异性 (HRV )与室性心率失常之间的关系。方法　对 88例冠心病患者 ,根据动态心电图上室性早搏 (室早 )频次分为冠心病频发室早组 ( 4 2例 )和冠心病无室早组 ( 4 6例 )进行比较 ,并分别与正常对照组( 3 0例 )进行比较 ,观察HRV的时域指标和室性心律失常。结果　冠心病患者HRV时域指标SDNN、SDANN、SDNNin dex、rMSSD和PNN50 均明显低于正常对照组 (P <0 .0 5～ 0 .0 1) ,而冠心病频发室早组除rMSSD外 ,余各项指标也明显低于冠心病无室早组 (P <0 .0 5～ 0 .0 1) ;SDNN与冠心病室性早搏频次存在明显的相关性。结论　冠心病患者HRV减低 ,反映了冠心病患者心脏自主神经调节功能失衡 ,尤其在伴有频发室早的患者中更为明显 ;冠心病室早的发生与交感神经活性增强有关 ,通过长时HRV分析 ,能对此作出客观评价     

Prognostic Value of Heart Rate Variability in Patients Awaiting Cardiac Transplantation

Time and frequency domain parameters of heart rate variability (HRV) were determined in patients with severe end stage heart failure awaiting cardiac transplantation (HTX). These parameters were then correlated with mortality to investigate the performance of HRV in discriminating between groups with high and low risk of death. The standard deviation of five consecutive RR intervals (SDANN) was found to be the parameter with the greatest sensitivity (90%) and specificity (91%). Patients with SDANN values of < 55 msec had a twenty-fold increased risk of death (90% confidence limits: 4–118, P < 0.001). The results furthermore suggest that measurements of HRV are superior to other prognostic markers such as left ventricular ejection fraction, pulmonary artery wedge pressure, cardiac index, and serum sodium levels. We conclude that HRV is a powerful, noninvasive tool to assess the risk of death in candidates for HTX. HRV measurements can therefore be used as a supplement to other markers of risk to determine the optimal therapeutic strategy in patients with severe congestive heart failure.     

针灸并用对卒中后抑郁患者心率变异性的影响

目的观察针灸并用对卒中后抑郁患者心率变异性(HRV)的影响。方法将120例患者分为对照组(n=60)和治疗组(n=60)。两组均给予口服百忧解及针刺治疗,治疗组配合艾灸疗法,比较两组治疗前后汉密尔顿抑郁量表(HAMD)17项评分及HRV改变。结果治疗后,治疗组HAMD评分低于对照组,减分率高于对照组(P0.05);两组24 h正常R-R间期标准差(SDNN)、24 h每5分钟平均正常R-R间期标准差(SDANN)均较治疗前增加(P0.05),治疗组大于对照组(P0.05);24 h相邻R-R间期差值的均方根(RMSSD)、24 h相邻R-R间期差值50 ms的百分数(PNN50)较治疗前降低(P0.05),治疗组小于对照组(P0.05);两组低频功率(LF)、高频功率(HF)及LF/HF均大于治疗前(P0.05),治疗组大于对照组(P0.05)。结论针灸结合较单纯针刺能更好地调整卒中后抑郁患者自主神经功能,改善其抑郁状态。     

Concomitant-acquired Long QT and Brugada syndromes associated with indapamide-induced hypokalemia and hyponatremia

Electrolyte disturbances are known to cause acquired Long QT syndrome (LQTS) and Brugada syndrome. While a reduction in INa due to SCN5A mutation is implicated as the underlying mechanism in Brugada syndrome, hyponatremia, which can give rise to a reduced INa, has never been reported in literature as a cause or precipitating factor in this syndrome. We detailed a case in which concomitant-acquired LQTS and Brugada syndrome were associated with severe hypokalemia and hyponatremia following indapamide use for treatment of hypertension and highlighted the potential role of hyponatremia in the pathogenesis of the acquired form of Brugada syndrome.     

Heart Rate Variability and Major Arrhythmic Events in Patients with Idiopathic Dilated Cardiomyopathy

This prospective study of 71 patients with idiopathic dilated cardiomyopathy (IDC) and preserved sinus rhythm was designed to evaluate the relation between heart rate variability (HRV) and subsequent major arrhythmic events. Standard time- and frequency-domain HRV parameters were obtained from analysis of 24-hour Holter ECG recordings. During a mean follow-up of 15 ± 5 months, major arrhythmic events including sustained ventricular tachycardia, ventricular fibrillation, and sudden cardiac death occurred in 10 of the 71 study patients (14%). Neither time- nor frequency-domain indices of HRV differed significantly between patients with and patients without subsequent major arrhythmic events. However, there was a trend toward a lower standard deviation of the average normal RR interval for all 5-minute segments of the 24-hour recording (68 ± 17 ms vs 80 ± 31 ms; P = 0.06) in patients with major arrhythmic events. In addition, the percentage of adjacent normal RR intervals differing > 50 ms over the recording period tended to be lower in patients with major arrhythmic events (6%± 3% vs 9%± 6%; P = 0.08). Our results indicate a tendency toward attenuated parasympathetic activity in IDC patients with subsequent major arrhythmic events compared to arrhythmia-free patients. Larger studies with longer follow-up periods are necessary to clarify the role of HRV measurements for arrhythmia risk prediction in patients with IDC.     

204例无症状性心肌缺血患者心率变异生的分析

目的：探讨老年冠心病患无症状肌缺血心率变异生的变化情况,方法：204例冠心病患在日常生活状态下进行24h三通道动态心电图监测,并详细记录日常活动和相关症状,同时对无症状心肌缺血进行心率变异性分析。结果：无症状心肌缺血与心绞痛均可引起心率变异性多个参数的减低,204例患出现823次心肌缺血,其中624次为无症状心肌缺血,无症状心肌缺血组心率变异性及多个参数均低于有症状心肌缺血和正常对照组比后降低幅度更大,P均＜0．05,结论：三通道动态心电图是检测无症状心肌缺血心率变异性的有效方法,老年冠心病患无症状心肌缺血心率变异性多个参数均低于心绞痛和正常对照组,提示无症状心肌缺血更易引起心血管事件的发生,应引起临床的重视。     

Heart Rate Variability Used as an Arrhythmia Risk Stratifier After Myocardial Infarction

Heart rate variability (HRV) is considered to represent a noninvasive tool to assess cardiac autonomic tone at the level of the sinus node. It has been shown to have predictive power for risk assessment in patients surviving acute myocardial infarction. For this purpose, HRV should be assessed from 24-hour Holter recordings obtained 7–10 days following the infarction. Although there is some recovery of HRV during the first 3 months after infarction, HRV remains reduced in postinfarction patients compared to values obtained in healthy individuals. Compared to assessment of left ventricular function as a risk marker, HRV is superior with respect to prediction of arrhythmic events and sudden death whereas both parameters yield comparative power for prediction of total cardiac mortality. Since the predictive power of HRV analysis alone is relatively low, the combined use of HRV measurements together with traditional risk markers (such as ventricular ectopic beats, signal-averaged ECG, or left ventricular function) results in improved risk prediction with positive predictive accuracy in the range of 30%–50%.     

Heart Rate Variability in Patients with Vasovagal Syndrome

The aim of this study was to assess the heart rate variability in patients with vasovagal syndrome (WS). Heart rate variability was expressed as: (1) the standard deviation (SD) of the mean RR interval; and (2) the SD as a percentage of the mean RR interval (%SD). Heart rate variability was measured in VVS patients and compared with control individuals. Eighteen patients (mean age 50 ± 14 years) with a history of recurrent syncope and positive tilt testing were included in the study. Fifteen asymptomatic individuals (mean age 53 ± 13 years) with no history of syncope and negative tilt testing were used as a control group. The SD and %SD (39 ± 38 and 5 ± 4 msec) in the WS group were statistically higher at the tenth minute of tilt testing than in the control group (20 ± 14 and 2.5 ±1.8 msec, P = 0.03 and P < 0.05, respectively). The mean RR interval (mean heart rate) was shorter after the 15th minute of tilt testing in the WS group than in the control group (RR-WS 687 ± 136 msec, RR-control 801 ± 131 msec, P < 0.05). It is concluded that heart rate variability, as expressed by the SD of the mean RR interval, and the SD as a percentage of the mean RR interval (%SD) are significantly higher in VVS patients than in control asymptomatic individuals.