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RR Interval (rr + interval)

Distribution by Scientific Domains
Medical Sciences96%
Life Sciences3%
Distribution within Medical Sciences
Cardiovascular Disease77%
Neurology5%
Anesthesia & Pain Management3%
3 Other Subdomains15%

Kinds of RR Interval

  • mean rr interval
    		•

    Selected Abstracts

    The Measurement of the QT and QTc on the Neonatal and Infant Electrocardiogram: A Comprehensive Reliability Assessment

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009
    B.S., Robert M. Gow M.B.
    Background: An electrocardiogram has been proposed to screen for prolonged QT interval that may predispose infants to sudden death in the first year of life. Understanding the reliability of QT interval measurement will inform the design of a screening program. Methods: Three pediatric cardiologists measured the QT/RR intervals on 60 infant electrocardiograms (median age 46 days), from leads II, V5 and V6 on three separate occasions, 7 days apart, according to a standard protocol. The QTc was corrected by Bazett's (QTcB), Fridericia's (QTCFrid), and Hodges' (QTcH) formulae. Intraobserver and interobserver reliability were assessed by intraclass correlation coefficients (ICC), limits of agreement and repeatability coefficients for single, average of two and average of three measures. Agreement for QTc prolongation (> 440 msec) was assessed by kappa coefficients. Results: QT interval intraobserver ICC was 0.86 and repeatability coefficient was 25.9 msec; interobserver ICC increased from 0.88 for single observations to 0.94 for the average of 3 measurements and repeatability coefficients decreased from 22.5 to 16.7 msec. For QTcB, intraobserver ICC was 0.67, and repeatability was 39.6 msec. Best interobserver reliability for QTcB was for the average of three measurements (ICC 0.83, reproducibility coefficient 25.8 msec), with further improvement for QTcH (ICC 0.92, reproducibility coefficient 16.69 msec). Maximum interobserver kappa for prolonged QTc was 0.77. Misclassification around specific cut points occurs because of the repeatability coefficients. Conclusions: Uncorrected QT measures are more reliable than QTcB and QTCFrid. An average of three independent measures provides the most reliable QT and QTc measurements, with QTcH better than QTcB. [source]

    Clustering of RR Intervals Predicts Effective Electrical Cardioversion for Atrial Fibrillation

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2004
    MAARTEN P. VAN DEN BERG M.D.
    Introduction: Atrial fibrillation (AF) is characterized by an irregularly irregular ("random") heart beat. However, controversy exists whether the ventricular rhythm in AF is truly random. We investigated randomness by constructing three-dimensional RR interval plots (3D plots), allowing identification of "clustering" of RR intervals. It was hypothesized that electrical cardioversion (ECV) would be more effective in AF patients with clustering, because clustering might reflect a higher degree of organization of atrial fibrillatory activity. Methods and Results: The study group consisted of 66 patients (44 men and 22 women; mean age 68 ± 11 years,) who were referred for ECV because of persistent AF. Twenty-four-hour Holter recordings were used to construct 3D plots by plotting each RR interval (x axis) against the previous RR interval (y axis) and the number of occurrences of each of these x,y combinations (z axis). A clustering index was calculated as the percentage of beats within the peaks in the 3D plot. Based on the 3D plots, clustering of RR intervals was present in 31 (47%) of the 66 patients. ECV was effective in restoring sinus rhythm in 29 (94%) of these 31 patients, whereas sinus rhythm was restored in only 25 (71%) of the remaining 35 patients without clustering (P = 0.020). The clustering index ranged from <2% in the 12 patients with failed ECV to >8% in the 32 patients with sinus rhythm at the end of the study (4 weeks after the ECV); the clustering index in the 22 patients with a relapse of AF after effective ECV was intermediate (P = 0.034 and P = 0.042, respectively). Conclusion: This study indicates that ECV is more effective in restoring sinus rhythm in AF patients with clustering compared to patients in whom no clustering is apparent on 3D plots. In addition, the degree of clustering appears to be predictive of the overall outcome of ECV; the higher the degree of clustering, the higher the likelihood of sinus rhythm at follow-up. [source]

    Cardiac Autonomic Control in Patients with Refractory Epilepsy before and during Vagus Nerve Stimulation Treatment: A One-Year Follow-up Study

    EPILEPSIA, Issue 3 2006
    Eija Ronkainen
    Summary:,Purpose: To elucidate possible effect of vagus nerve stimulation (VNS) therapy on interictal heart rate (HR) variability in patients with refractory epilepsy before and after 1-year VNS treatment. Methods: A 24-hour electrocardiogram (ECG) was recorded at the baseline and after 12 months of VNS treatment in 14 patients with refractory epilepsy, and once in 28 healthy age- and sex-matched control subjects. Time and frequency domain measures, along with fractal and complexity measures of HR variability, were analyzed from the ECG recordings. Results: The mean value of the RR interval (p = 0.008), standard deviation of N-N intervals (SDNN) (p < 0.001), very-low frequency (VLF) (p < 0.001), low-frequency (LF) (p = 0.001), and high-frequency (HF) (p = 0.002) spectral components of HR variability, and the Poincaré components SD1 (p = 0.005) and SD2 (p < 0.001) of the patients with refractory epilepsy were significantly lower than those of the control subjects before VNS implantation. The nocturnal increase in HR variability usually seen in the normal population was absent in patients with refractory epilepsy. VNS had no significant effects on any of the HR-variability indexes despite a significant reduction in the frequency of seizures. Conclusions: HR variability was reduced, and the nocturnal increase in HR variability was not present in patients with refractory epilepsy. One-year treatment with VNS did not have a marked effect on HR variability, suggesting that impaired cardiovascular autonomic regulation is associated with the epileptic process itself rather than with recurrent seizures. [source]

    Effects of age on the cardiac and vascular limbs of the arterial baroreflex

    EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2003
    C. M. Brown
    Abstract Background Healthy ageing has several effects on the autonomic control of the circulation. Several studies have shown that baroreflex-mediated vagal control of the heart deteriorates with age, but so far there is little information regarding the effect of ageing on sympathetically mediated baroreflex responses. The aim of this study was to assess the effects of ageing on baroreflex control of the heart and blood vessels. Materials and Methods In 40 healthy volunteers, aged 20,87 years, we applied oscillatory neck suction at 0·1 Hz to assess the sympathetic modulation of the heart and blood vessels and at 0·2 Hz to assess the effect of parasympathetic stimulation on the heart. Breathing was maintained at 0·25 Hz. Blood pressure, electrocardiographic RR intervals and respiration were recorded continuously. Spectral analysis was used to evaluate the magnitude of the low-frequency (0·03,0·14 Hz) and high-frequency (0·15,0·50 Hz) oscillations in the RR interval and blood pressure. Responses to neck suction were assessed as the change in power of the RR interval and blood pressure fluctuations at the stimulation frequency from baseline values. Results Resting low- and high-frequency powers of the RR interval decreased significantly with age (P < 0·01). However, the low-frequency power of systolic blood pressure did not correlate with age. Spontaneous baroreflex sensitivity (alpha-index) showed a significant inverse correlation with age (r = ,0·46, P < 0·05). Responses of the RR interval and systolic blood pressure to 0·1 Hz neck suction stimulation were not related to age, however, the RR interval response to 0·2 Hz neck suction declined significantly with age (r = ,0·61, P < 0·01). Conclusions These results confirm an age-related decrease in cardiovagal baroreflex responses. However, sympathetically mediated baroreflex control of the blood vessels is preserved with age. [source]

    Instant centre frequency at anaesthetic induction , a new way to analyse sympathovagal balance,

    FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2003
    Edmundo Pereira De Souza Neto
    Abstract The instant centre frequency (ICF) of RR interval has been proposed as a global index to analyse the sympathovagal interaction in the heart. The aim of this study was to assess the ICF during anaesthesia to test if it can reliably capture the neural control of the cardiovascular system. Twenty-four ASA II or III patients scheduled for cardiac surgery were included in the study. They were allocated in two groups: control, no treatment (group 1, n = 12), and beta-adrenergic blockade by atenolol (group 2, n = 12). Spectra of pulse interval series were computed with a time,frequency method and they were divided into: very low frequency (VLF, 0.000,0.040 Hz), low frequency (LF, 0.050,0.150 Hz) and high frequency (HF, 0.160,0.500 Hz). Normalized power was obtained by dividing the cumulative power within each frequency band (LF or HF) by the sum of LF and HF; the ratio of LF/HF was also calculated. Instant centre frequency is a time-varying parameter that the evolution along time of the gravity centrum of a local spectrum. All spectral indexes were recorded at the following time points: before induction, after induction and before intubation, during intubation, and after intubation. The atenolol group had lower normalized LF and the LF/HF ratio (P < 0.05) higher HF before induction; and lower LF/HF ratio after induction and before intubation (P < 0.05). The ICF was higher in atenolol group at all times. The ICF shifted towards HF frequency after induction and before intubation and shifted towards LF during intubation in both groups. The autonomic nervous system control on the heart through the interaction of sympathetic and parasympathetic reflex mechanisms could be studied by the ICF. The ICF may assess the autonomic cardiac modulation and may provide useful information for anaesthetic management. [source]

    Odor processing in multiple chemical sensitivity

    HUMAN BRAIN MAPPING, Issue 3 2007
    Lena Hillert
    Abstract Multiple chemical sensitivity (MCS) is characterized by somatic distress upon exposure to odors. As in other idiopathic environmental intolerances, the mechanisms behind the reported hypersensitivity are unknown. Using the advantage of the well-defined trigger (odor), we investigated whether subjects with MCS could have an increased odor-signal response in the odor-processing neuronal circuits. Positron emission tomography (PET) activation studies with several different odorants were carried out in 12 MCS females and 12 female controls. Activation was defined as a significant increase in regional cerebral blood flow (rCBF) during smelling of the respective odorant compared to smelling of odorless air. The study also included online measurements of respiratory frequency and amplitude and heart rate variations by recording of R wave intervals (RR) on the surface electrocardiogram. The MCS subjects activated odor-processing brain regions less than controls, despite the reported, and physiologically indicated (decreased RR interval) distress. In parallel, they showed an odorant-related increase in activation of the anterior cingulate cortex and cuneus-precuneus. Notably, the baseline rCBF was normal. Thus, the abnormal patterns were observed only in response to odor signals. Subjects with MCS process odors differently from controls, however, without signs of neuronal sensitization. One possible explanation for the observed pattern of activation in MCS is a top-down regulation of odor-response via cingulate cortex. Hum. Brain Mapp, 2007. © 2006 Wiley-Liss, Inc. [source]

    QT Interval Correction in Patients with Cirrhosis

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2007
    ANDREA ZAMBRUNI M.D.
    Introduction: QT interval prolongation is a common electrophysiological abnormality in patients with cirrhosis. As QT interval varies with the heart rate, many QT correction formulas have been proposed, the Bazett's one being the most criticized because it overcorrects the QT interval and may be misleading. This study focused on the QT-RR relationship in patients with cirrhosis to derive a population-specific QT correction formula. Methods: One hundred cirrhotic patients of different etiology and severity and 53 healthy controls comparable for age and sex were enrolled. The QT-RR relationship was analyzed in patients by five regression analysis models to derive the population-specific QT-RR equation. The QTc was calculated and compared with those calculated by four common QT correction formulas (Bazett, Fridericia, Framingham, and Hodges). The correlation coefficient QTc-RR was calculated as a measure of the independence of QTc from the original RR interval. Results: In patients the QT-RR relationship was best described by the power equation "QT = 453.65 × RR1/3.02" (R2= 0.41), similar to the Fridericia's formula. Bazett's formula led to the longest QTc (P < 0.0001), which was still significantly influenced by the RR interval (R =,0.39; P < 0.0001), while the estimated equation led to a QTc value not influenced by RR (R =,0.014). Conclusion: Bazett's correction should be avoided in patients with cirrhosis because it still provides a rate-dependent QTc value and might be misleading, particularly when assessing the overall preoperative cardiac risk and the effect of drugs affecting the QT interval. In its place, our formula or that of Fridericia can be confidently employed. [source]

    Clustering of RR Intervals Predicts Effective Electrical Cardioversion for Atrial Fibrillation

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2004
    MAARTEN P. VAN DEN BERG M.D.
    Introduction: Atrial fibrillation (AF) is characterized by an irregularly irregular ("random") heart beat. However, controversy exists whether the ventricular rhythm in AF is truly random. We investigated randomness by constructing three-dimensional RR interval plots (3D plots), allowing identification of "clustering" of RR intervals. It was hypothesized that electrical cardioversion (ECV) would be more effective in AF patients with clustering, because clustering might reflect a higher degree of organization of atrial fibrillatory activity. Methods and Results: The study group consisted of 66 patients (44 men and 22 women; mean age 68 ± 11 years,) who were referred for ECV because of persistent AF. Twenty-four-hour Holter recordings were used to construct 3D plots by plotting each RR interval (x axis) against the previous RR interval (y axis) and the number of occurrences of each of these x,y combinations (z axis). A clustering index was calculated as the percentage of beats within the peaks in the 3D plot. Based on the 3D plots, clustering of RR intervals was present in 31 (47%) of the 66 patients. ECV was effective in restoring sinus rhythm in 29 (94%) of these 31 patients, whereas sinus rhythm was restored in only 25 (71%) of the remaining 35 patients without clustering (P = 0.020). The clustering index ranged from <2% in the 12 patients with failed ECV to >8% in the 32 patients with sinus rhythm at the end of the study (4 weeks after the ECV); the clustering index in the 22 patients with a relapse of AF after effective ECV was intermediate (P = 0.034 and P = 0.042, respectively). Conclusion: This study indicates that ECV is more effective in restoring sinus rhythm in AF patients with clustering compared to patients in whom no clustering is apparent on 3D plots. In addition, the degree of clustering appears to be predictive of the overall outcome of ECV; the higher the degree of clustering, the higher the likelihood of sinus rhythm at follow-up. [source]

    Relationship Between Heart Rate Turbulence and Heart Rate, Heart Rate Variability, and Number of Ventricular Premature Beats in Coronary Patients

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2004
    IWONA CYGANKIEWICZ M.D., Ph.D.
    Introduction: Heart rate variability (HRV) illustrates regulation of the heart by the autonomic nervous system whereas heart rate turbulence (HRT) is believed to reflect baroreflex sensitivity. The aim of this study was to determine the association between HRT and HRV parameters and the relationship between HRT parameters and heart rate and number of ventricular premature beats (VPBs) used to calculate HRT parameters. Methods and Results: In 146 patients (117 males and 29 females; mean age 62 years) with coronary artery disease, a 24-hour ECG Holter monitoring was performed to calculate mean heart rate (RR interval), number of VPBs, time- and frequency-domain HRV parameters and two HRT parameters: turbulence onset (TO) and turbulence slope (TS). Univariate and multivariate regression analyses were performed to evaluate the association between tested parameters. Significant correlation between TS and mean RR interval was observed (r = 0.42; p < 0.001), while no association for TO vs. RR interval was found. TS values were significantly higher in patients with less than 10 VPBs/24 hours than in patients with more frequent VPBs. Significant associations between HRT and HRV parameters were found with TS showing stronger correlation with HRV parameters than TO (r value ranging from 0.35 to 0.62 for TS vs. ,0.16 to ,0.38 for TO). Conclusion: HRT parameters correlate strongly with HRV parameters indicating that HRT should be considered as a reflection of both baroreceptors response and overall autonomic tone. Heart rate dependence of turbulence slope indicates the need to adjust this parameter for heart rate. (J Cardiovasc Electrophysiol, Vol. 15, pp. 731-737, July 2004) [source]

    Repolarization Abnormality in Idiopathic Ventricular Fibrillation:

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2004
    Assessment Using 24-Hour QT-RR, QaT-RR Relationships
    Introduction: We evaluated the characteristics of QT-RR and QaT (apex of T wave)-RR relationships in patients with idiopathic ventricular fibrillation (IVF) compared with control subjects. We hypothesized that IVF patients have unique repolarization dynamics related to a reduced fast Na current and a prominent transient outward current. Methods and Results: The study group consisted of 9 men (age 47 ± 10 years) with IVF (6 with Brugada type and 3 with non-Brugada type) who had experienced nocturnal episodes of VF. The control group consisted of 28 healthy age-matched men (age 44 ± 12 years). The relationships between QT and RR intervals and between QaT and RR intervals were analyzed from 24-hour Holter ECG data using an automatic measurement system. Both QT and QaT at RR intervals of 0.6, 1.0, and 1.2 seconds were determined from QT-RR and QaT-RR linear regression lines. Both QT-RR and QaT-RR slopes were lower in the IVF group than in the control group (QT-RR: 0.092 ± 0.023 vs 0.137 ± 0.031, P < 0.001; QaT-RR: 0.109 ± 0.025 vs 0.153 ± 0.028, P < 0.001). QT at an RR interval of 0.6 second did not differ between two groups, but QT at RR intervals of either 1.0 or 1.2 seconds was significantly shorter in the IVF group than in the control group (RR 1.0 s: 0.384 ± 0.018 vs 0.399 ± 0.017, P < 0.05; RR 1.2 s: 0.402 ± 0.019 vs 0.426 ± 0.020, P < 0.01). QaT at RR intervals of either 1.0 or 1.2 seconds also was shorter in the IVF group (RR 1.0 s: 0.289 ± 0.022 vs 0.312 ± 0.021, P < 0.01; RR 1.2 s: 0.311 ± 0.024 vs 0.343 ± 0.024, P < 0.01). In four patients, oral administration of disopyramide (300 mg/day) was effective in suppressing VF episodes and increased slopes of QT-RR and QaT-RR relationships. Conclusion: IVF patients had lower slopes of QT-RR and QaT-RR regression lines and impaired prolongation of QT and QaT at longer RR intervals compared with control subjects. These unique repolarization dynamics may be related to the frequent occurrence of VF episodes at night. (J Cardiovasc Electrophysiol, Vol. 15, pp. 59-63, January 2004) [source]

    Circadian Profile of Cardiac Autonomic Nervous Modulation in Healthy Subjects:

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2003
    Differing Effects of Aging, Gender on Heart Rate Variability
    Introduction: Although heart rate variability (HRV) has been established as a tool to study cardiac autonomic activity, almost no data are available on the circadian patterns of HRV in healthy subjects aged 20 to 70 years. Methods and Results: We investigated 166 healthy volunteers (81 women and 85 men; age 42 ± 15 years, range 20,70) without evidence of cardiac disease. Time-domain HRV parameters were determined from 24-hour Holter monitoring and calculated as hourly mean values and mean 24-hour values. All volunteers were fully mobile, awoke around 7 A.M., and had 6 to 8 hours of sleep. Circadian profiles of vagus-associated HRV parameters revealed a marked day-night pattern, with a peak at nighttime and a plateau at daytime. The characteristic nocturnal peak and the day-night amplitude diminished with aging by decade. Estimates of overall HRV (geometric triangular index [TI], SD of NN intervals [SDNN]) and long-term components of HRV (SD of the averages of NN intervals for all 5-min segments [SDANN]) were low at nighttime and increased in the morning hours. There was a significant decline of 24-hour values of all HRV parameters (P < 0.001) and a strong negative correlation (P < 0.001) with increasing age. Mean 24-hour RR interval (P < 0.001), SDNN, mean SD of NN intervals for all 5-minute intervals (SDNNi), and SDANN (all P < 0.01) were significantly higher in men. Younger men also exhibited significantly higher values for vagus-associated parameters (root mean square successive difference [rMSSD], P < 0.05; SDNNi, P < 0.01); however, gender differences diminished with increasing age. Conclusion: Normal aging is associated with a constant decline of cardiac vagal modulation due to a significant decrease of nocturnal parasympathetic activity. The significant gender-related difference of HRV decreases with aging. These findings emphasize the need to determine age-, gender-, and nycthemeral-dependent normal ranges for HRV assessment. (J Cardiovasc Electrophysiol, Vol. 14, pp. 791-799, August 2003) [source]

    Noninvasive Assessment of Cardiac Resynchronization Therapy for Congestive Heart Failure Using Myocardial Strain and Left Ventricular Peak Power as Parameters of Myocardial Synchrony and Function

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2002
    Ph.D., ZORAN B. POPOVI
    Resynchronization Therapy for Heart Failure.Introduction: Although invasive studies have shown that cardiac resynchronization therapy by biventricular pacing improves left ventricular (LV) function in selected heart failure patients, it is impractical to apply such techniques in the clinical setting. The aim of this study was to assess the acute effects of cardiac resynchronization therapy by noninvasive techniques. Methods and Results: Twenty-two patients enrolled in the InSync trial (age 64 ± 9 years, 18 men and 4 women; all with ejection fraction <35% and QRS >130 msec) were studied 1 to 12 months after pacemaker implantation during pacing, and while ventricular pacing was inhibited. Regional myocardial strains of the interventricular septum, LV free wall, and right ventricular free wall were derived from color Doppler tissue echocardiography. Peak power index was calculated as a product of simultaneously recorded noninvasive blood pressure and pulse-wave (PW) Doppler velocity of the LV outflow tract. The Z ratio (sum of LV ejection and filling times divided by RR interval) and tei index were calculated from PW Doppler data. During pacing, overall regional strain improved (P = 0.01), while the LV strain coefficient of variation decreased from 2.7 ± 2.4 to 1.3 ± 0.7 (P = 0.009). Additionally, peak power index improved from 84 ± 24 to 94 ± 27 cm· mmHg/sec (P = 0.004). The Z ratio increased from 0.71 ± 0.08 to 0.78 ± 0.07 (P = 0.0005), while the tei index decreased from 0.86 ± 0.33 to 0.59 ± 0.16 (P = 0.0002). Conclusion: Using novel noninvasive indices, we demonstrated that cardiac resynchronization therapy improves LV performance. [source]

    Post-operative pressure lability and cardiac baroreflex in normotensive patients as a function of age

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2008
    A. CIVIDJIAN
    Background: Pressure lability may be linked to the loss of the cardiac baroreflex. The reduction of the sensitivity of the cardiac baroreflex has not been delineated in the post-operative period according to age in normotensive patients. This study addresses pressure lability and slope of the cardiac baroreflex as a function of age. Methods: Patients were allocated to the following three groups: young (20,39 years, n=7), middle aged (40,59 years, n=7) and elderly (60,79 years, n=6), and studied before minor intra-abdominal surgery under CO2 peritoneal insufflation and nitrous oxide,isoflurane,sufentanil anesthesia, up to 24 h after extubation. An electrocardiogram and non-invasive beat-by-beat pressure monitoring (Finapres®) allowed offline calculation of the sensitivity of the cardiac baroreflex (,sequence' technique) and standard deviation (SD) of heart rate (HR; HR variability) and systolic blood pressure (SBP; pressure lability). Results: Before anesthesia, (a) an inverse relationship was observed between the slope of the cardiac baroreflex and age and (b) a trend (P<0.09) existed between the slope of the cardiac baroreflex and pressure lability, irrespective of age. During the early post-operative period, young patients returned to their baseline slope of the cardiac baroreflex; no inverse relationship between increased SD of SBP and decreased SD of RR interval was observed. Middle-aged and elderly patients displayed a depressed slope of the cardiac baroreflex both before and after anesthesia. Conclusion: At variance with the pre-operative period, no simple inverse relationship was observed between increased pressure lability and depressed HR variability in young patients during the early post-operative period. [source]

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

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2009
    JAN N, MEC M.D.
    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. [source]

    Relationship Between Global Myocardial Index and Automatic Left Ventricular Border Detection Pattern to Identify Biventricular Pacing Candidates

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2007
    DRAGOS COZMA M.D., Ph.D.
    Objective of the Study: to evaluate the relation between global myocardial index (GMI) and the pattern of left ventricular (LV) volume curves variation, using automatic border detection (ABD), and their role in assessing LV asynchrony. Methods: We studied 52 patients (mean age = 55 ± 17 years) with dilated cardiomyopathy. QRS duration (QRSd) and GMI were measured. Currently accepted TDI and M-mode parameters were used to indicate LV dyssynchrony. On-line continuous LV volume changes were recorded using ABD. Ejection time (ET ABD) was measured from the ABD wave-forms as time interval between maximal and minimal volume variation during LV electromechanical systole. We derived the ejection time index (ETiABD) as the ratio between ET ABD and RR interval (ETiABD = ET/RR). Results: 31 patients had a QRSd >120 ms and 21 patients had a QRSd <120 ms. Ventricular dyssynchrony was observed in 39 patients (29 patients had a QRSd > 120 ms). GMI was significantly higher in patients with, than in patients without ventricular dyssynchrony (1.06 ± 0.18 vs 0.73 ± 0.13, P = 0.0001), while ETABD was significantly smaller (233 ± 39 ms vs 321 ± 28 ms, P = 0.0001). The corresponding difference for ETiABD was 26.9 ± 6.8% vs 6.3 ± 4%, P < 0.0001. By simple regression analysis an inverse linear correlation was observed between GMI and ETiABD (r2=,0.51, P < 0.0001). The pattern of ABD waveforms showed increased isovolumic contraction and relaxation times in patients with LV asynchrony, similar to the GMI pattern. Conclusions: Regional delays in ventricular activation cause uncoordinated and prolonged ventricular contractions, with lengthening of the isovolumic contraction and relaxation times and shortening of the time available for filling and ejection. GMI explores these parameters and together with ABD might be useful to identify patients with ventricular asynchrony. [source]

    Effects of Head-Up Tilt-Table Test on the QT Interval

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2010
    Michael Findler M.D.
    Background. The QT interval shortens in response to sympathetic stimulation and its response to epinephrine infusion (in healthy individuals and patients with long QT syndrome) has been thoroughly studied. Head-up tilt-table (HUT) testing is an easy way to achieve brisk sympathetic stimulation. Yet, little is known about the response of the QT interval to HUT. Methods. We reviewed the electrocardiograms of HUT tests performed at our institution and compare the heart rate, QT, and QTc obtained immediately after HUT with the rest values. Results. The study group consisted of 41 patients (27 females and 14 males) aged 23.9 ± 8.4 years. Head-up tilting led to a significant shortening of the RR interval (from 825 ± 128 msec at rest phase to 712 ± 130 msec in the upward tilt phase, P < 0.001) but only to a moderate shortening of the QT interval (from 363.7 ± 27.9 msec during rest to 355 ± 30.3 msec during upward tilt, P = 0.001). Since the RR interval shortened more than the QT interval, the QTc actually increased (from 403 ± 21.5 msec during rest phase to 423.2 ± 27.4 msec during upward tilt, P < 0.001). The QTc value measured for the upward tilt position was longer than the resting QTc value in 33 of 41 patients. Of those, 4 male patients and 2 female patients developed upward-tilt QTc values above what would be considered abnormal at rest. Conclusions. During HUT the QT shortens less than the RR interval. Consequently, the QTc increases during head-up tilt. Ann Noninvasive Electrocardiol 2010;15(3):245,249 [source]

    Assessment of Physiological Amplitude, Duration, and Magnitude of ECG T-Wave Alternans

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2009
    Laura Burattini Ph.D.
    Background: An association between T-wave alternans (TWA) and malignant ventricular arrhythmias is generally recognized. Because relatively low levels of TWA have also been observed in healthy (H) subjects, the question arises as to whether these are ascribable to noise and artifacts, or can be given the relevance of a physiological phenomenon characterizing a preclinical condition. Methods: To answer this question, in the present study 20-minute not noisy, sinus ECG recordings, from 138 H-subjects and 148 coronary artery diseased (CAD) patients, were submitted to our adaptive match filter (AMF) procedure to identify and parameterize TWA in terms of duration (TWAD), amplitude (TWAA), and magnitude (TWAM, defined as the product of TWAD times TWAA). The 99.5th percentiles of mean values of TWAA, TWAD, and TWAM over 20-minute ECGs were used to define three threshold levels (THRD, THRA, and THRM), which allow discrimination of abnormal TWA levels. Results: Nonstationary TWA was found in all our H-subjects and CAD-patients. TWAD, TWAA, and TWAM levels were classified as being physiological in 99% of H-subjects and 87% of CAD-patients. A linear correlation (r =,0.52, P < 0.001) was found between TWAA and RR interval in the H-population. Conclusions: Our results support the hypothesis of the existence of physiological TWA levels, which are to be considered in the effort to improve reliability of nonphysiological TWA levels discrimination. [source]

    ECG Evaluation of Ventricular Properties: The Importance of Cardiac Cycle Length

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009
    Fabrice Extramiana M.D., Ph.D.
    Ventricular repolarization properties are dependent on cardiac cycle length. The aim of this article is to emphasize the importance of taking into account heart rate influences on QT duration but also on current and future T-wave morphology parameters. The relationship between QT interval duration and RR interval is a fundamental property of the myocardium that is impaired by the presence of channelopathies such as the LQTS or SQTS, but also by the presence of a cardiomyopathy. Assessing this property is also important when the individual QT/RR relationship is used for individual QT correction in the setting of evaluation of drugs' effect on QT duration. T-wave descriptors such as the relative weight of the terminal part of the T-wave, the amplitude of T-wave apex and Principal Component Analysis parameters are also dependent on heart rate. Assessing ventricular repolarisation ECG parameters at different heart rates avoids the need for difficult rate-correction and helps to better understand and characterize ventricular repolarisation properties. [source]

    Beat-to-Beat QT Interval Variability Is Primarily Affected by the Autonomic Nervous System

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2008
    Ph.D., Takanao Mine M.D.
    Background: Beat-to-beat QT interval variability is associated with life-threatening arrhythmias and sudden death, however, its precious mechanism and the autonomic modulation on it remains unclear. The purpose of this study was to determine the effect of drugs that modulate the autonomic nervous system on beat-to-beat QT interval. Method: RR and QT intervals were determined for 512 consecutive beats during fixed atrial pacing with and without propranolol and automatic blockade (propranolol plus atropine) in 11 patients without structural heart disease. Studied parameters included: RR, QTpeak (QRS onset to the peak of T wave), QTend (QRS onset to the end of T wave) interval, standard deviation (SD) of the RR, QTpeak, and QTend (RR-SD, QTpeak-SD, and QTend-SD), coefficients of variation (RR- CV, QTpeak-CV, and QTend-CV) from time domain analysis, total power (TP; RR-TP, QTpeak-TP, and QTend-TP), and power spectral density of the low-frequency band (LF; RR-LF, QTpeak-LF, and QTend-LF) and the high-frequency band (HF; RR-HF, QTpeak-HF and QTend-HF). Results: Administration of propranolol and infusion of atropine resulted in the reduction of SD, CV, TP, and HF of the QTend interval when compared to controlled atrial pacing (3.7 ± 0.6 and 3.5 ± 0.5 vs 4.8 ± 1.4 ms, 0.9 ± 0.1 and 0.9 ± 0.1 vs 1.2 ± 0.3%, 7.0 ± 2.2 and 7.0 ± 2.2 vs 13.4 ± 8.1 ms2, 4.2 ± 1.4 and 4.2 ± 1.2 vs 8.4 ± 4.9 ms2, respectively). Administration of propranolol and atropine did not affect RR interval or QTpeak interval indices during controlled atrial pacing. Conclusions: Beat-to-beat QT interval variability is affected by drugs that modulate the autonomic nervous system. [source]

    Baroreflex Sensitivity: Measurement and Clinical Implications

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2008
    Maria Teresa La Rovere M.D.
    Alterations of the baroreceptor-heart rate reflex (baroreflex sensitivity, BRS) contribute to the reciprocal reduction of parasympathetic activity and increase of sympathetic activity that accompany the development and progression of cardiovascular diseases. Therefore, the measurement of the baroreflex is a source of valuable information in the clinical management of cardiac disease patients, particularly in risk stratification. This article briefly recalls the pathophysiological background of baroreflex control, and reviews the most relevant methods that have been developed so far for the measurement of BRS. They include three "classic" methods: (i) the use of vasoactive drugs, particularly the ,-adrenoreceptor agonist phenylephrine, (ii) the Valsalva maneuver, which produces a natural challenge for the baroreceptors by voluntarily increasing intrathoracic and abdominal pressure through straining, and (iii) the neck chamber technique, which allows a selective activation/deactivation of carotid baroreceptors by application of a negative/positive pressure to the neck region. Two more recent methods based on the analysis of spontaneous oscillations of systolic arterial pressure and RR interval are also reviewed: (i) the sequence method, which analyzes the relationship between increasing/decreasing ramps of blood pressure and related increasing/decreasing changes in RR interval through linear regression, and (ii) spectral methods, which assess the relationship (in terms of gain) between specific oscillatory components of the two signals. The limitations of the coherence criterion for the computation of spectral BRS are discussed, and recent proposals for overcoming them are presented. Most relevant clinical applications of BRS measurement are finally reviewed with particular reference to patients with myocardial infarction and heart failure. [source]

    Heart Rate Variability in Patients with Essential Hyperhidrosis: Dynamic Influence of Sympathetic and Parasympathetic Maneuvers

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2005
    Dayimi Kaya M.D.
    Background: Essential hyperhidrosis has been associated with an increased activity of the sympathetic system. In this study, we investigated cardiac autonomic function in patients with essential hyperhidrosis and healthy controls by time and frequency domain analysis of heart rate variability (HRV). Method: In this study, 12 subjects with essential hyperhidrosis and 20 healthy subjects were included. Time and frequency domain parameters of HRV were obtained from all of the participants after a 15-minute resting period in supine position, during controlled respiration (CR) and handgrip exercise (HGE) in sitting position over 5-minute periods in each stage. Results: Baseline values of HRV parameters including RR interval, SDNN and root mean square of successive R-R interval differences, low frequency (LF), high frequency (HF), normalized unit of high frequency (HFnu), normalized unit of low frequency (LFnu), and LF/HF ratio were identical in two groups. During CR, no difference was detected between the two groups with respect to HRV parameters. However, the expected increase in mean heart rate (mean R-R interval) did not occur in hyperhidrotic group, whereas it did occur in the control group (Friedman's P = 0.000). Handgrip exercise induced significant decrease in mean R-R interval in both groups and no difference was detected between the two groups with respect to the other HRV parameters. When repeated measurements were compared with two-way ANOVA, there was statistically significant difference only regarding mean heart rate in two groups (F = 6.5; P = 0.01). Conclusion: Our overall findings suggest that essential hyperhidrosis is a complex autonomic dysfunction rather than sympathetic overactivity, and parasympathetic system seems to be involved in pathogenesis of this disorder. [source]

    Abnormalities of the Repolarization Characteristics of Patients with Heart Failure Progress with Symptom Severity

    ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2004
    Ch.B., Christopher C. E. Lang B.Sc. (Hons)
    Background:,Congestive heart failure is a common condition with high mortality. Many of these deaths are sudden and unexpected. Ventricular action potential, surface repolarization (QT interval), and dispersion of repolarization are prolonged in the failing heart, contributing to arrhythmogenesis and sudden death. We studied the relationship between QT and heart rate (RR interval) from ambulatory recordings using a novel method in patients with ischemic heart disease and varying degrees of left-ventricular impairment (IHD) and compared them to healthy subjects (HS). We compare the degree of abnormality with the functional impairment and ejection fraction. Methods:,Using a previously described automated method for continuous estimation of the QT/RR characteristic that incorporates a correction formula for compensation of QT adaptation lag (VERDA, Del Mar Reynolds Medical Ltd., Hertford, UK), we compared recordings from 41 IHD patients with age-matched HS. Results:,IHD Patients have prolonged 24-hour mean QTo (461 ms vs 426 ms, P < 0.01), and abnormal rate dependence relative to controls (24-hour mean slope: 0.20 vs 0.14, P < 0.001; J: 0.38 vs 0.28, P < 0.001). There is increased temporal variation in J with respect to HS. These abnormalities of repolarization increase with worsening NYHA class, but do not correlate with ejection fraction. Conclusions:,The use of a universal correction formula to compare dynamic QT data in IHD patients is inappropriate. The observed progressive abnormalities may be responsible for the high incidence of sudden death through promotion of arrhythmias. [source]

    Respiratory effects on the reproducibility of cardiovascular autonomic parameters

    CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2007
    Éva Zöllei
    Summary The aim of this study was to assess the influence of breathing pattern on the reproducibility of the most commonly used heart rate and blood pressure variability parameters and baroreflex indices. 5,5 min ECG and blood pressure recordings were made and repeated for 10 healthy volunteers in supine rest on 10 consecutive days during spontaneous and 6 min,1 patterned breathing. We investigated the following parameters: mean RR interval (RRI); the standard deviation of RR intervals (SDRR); the root mean square of successive differences in RRI (RMSSD); the percentage of RRIs which differed by 50% from the proceeding RRI (PNN50); mean systolic arterial pressure (SAP); the standard deviation of SAP (SAP SD); mean mean arterial pressure (MAP); mean diastolic blood pressure (DAP) and baroreflex indices from spontaneous sequence method (upBRS and downBRS) and from cross spectral analysis (LF alpha, HF alpha). To assess reproducibility for each parameter within- and between-subject variability values were calculated and the ratio of within- and between-subject variability was assessed. In addition, we calculated intraclass correlation coefficient (ICC). Compared to spontaneous respiration during 6 min,1 patterned breathing the heart rate and blood pressure variability increased; upBRS, LF alpha and HF alpha increased, downBRS did not change. However, ICC showed good reproducibility for most parameters, which did not improve further with controlled breathing. In conclusion, respiration had a strong influence on the most widely used cardiovascular autonomic parameters. The controlling of breathing did not result in consistent improvement in their reproducibility. [source]

    Differences in sino-atrial and atrio-ventricular function with age and sex attributable to the Scn5a+/, mutation in a murine cardiac model

    ACTA PHYSIOLOGICA, Issue 1 2010
    K. Jeevaratnam
    Abstract Aim:, To investigate the interacting effects of age and sex on electrocardiographic (ECG) features of Scn5a+/, mice modelling Brugada syndrome. Methods:, Recordings were performed on anaesthetized wild-type (WT) and Scn5a+/, mice and differences attributable to these risk factors statistically stratified. Results:,Scn5a+/, exerted sex-dependent effects upon sino-atrial function that only became apparent with age. RR intervals were greater in old male than in old female Scn5a+/,. Atrio-ventricular (AV) conduction was slower in young female mice, whether WT and Scn5a+/,, than the corresponding young male WT and Scn5a+/,. However, PR intervals lengthened with age in male but not in female Scn5a+/, giving the greatest PR intervals in old male Scn5a+/, compared with either old male WT or young male Scn5a+/, mice. In contrast, PR intervals were similar in old female Scn5a+/, and in old female WT. QTc was prolonged in Scn5a+/, compared with WT, and female Scn5a+/, compared with female WT. Age-dependent alterations in durations of ventricular repolarization relative to WT affected male but not female Scn5a+/,. Thus, T-wave durations were greater in old male Scn5a+/, compared with old male WT, but indistinguishable between old female Scn5a+/, and old female WT. Finally, analysis for combined interactions of genotype, age and sex demonstrated no effects on P wave and QRS durations and QTc intervals. Conclusion:, We demonstrate for the first time that age, sex and genotype exert both independent and interacting ECG effects. The latter suggest alterations in cardiac pacemaker function, atrio-ventricular conduction and ventricular repolarization greatest in ageing male Scn5a+/,. [source]

    Circadian Variation in Heart-Rate Variability in Localization-related Epilepsy

    EPILEPSIA, Issue 5 2007
    Hĺkan Persson
    Summary:,Purpose: Case,control studies of sudden unexpected death in epilepsy (SUDEP) have reported that SUDEP is more likely to occur during sleep and thus presumably during night hours. The circadian variation of heart-rate variability (HRV) might be of relevance to this risk. We examined night versus daytime HRV in patients with newly diagnosed and refractory localization-related epilepsy, assessing the effects of drug treatment and epilepsy surgery on the night/daytime HRV ratio. Methods: We used spectral analysis to assess HRV and calculated the night-time (00.00,05.00)/daytime (07.30,21.30) ratio of HRV in 14 patients with newly diagnosed localization-related epilepsy before and during carbamazepine (CBZ) treatment and in 21 patients with temporal lobe epilepsy before and after epilepsy surgery. Both groups were compared with age- and sex-matched controls. Results: No significant differences were found from controls in the night/daytime ratios of HRV whether compared before or after initiation of treatment with CBZ in newly diagnosed epilepsy patients. When patients were used as their own controls, night/daytime ratios of standard deviation of RR intervals (p = 0.04) and total power (p = 0.04) were significantly lower during treatment than before. Compared with those of controls, the night/daytime ratios were lower in epilepsy surgery patients before surgery [low-frequency power (p = 0.04); high-frequency power (p = 0.04)]. Night/daytime ratios did not change significantly after surgery. Conclusions: The HRV of the patients was more affected during night-time when the risk of SUDEP seems to be highest in such patients. [source]

    Effects of age on the cardiac and vascular limbs of the arterial baroreflex

    EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2003
    C. M. Brown
    Abstract Background Healthy ageing has several effects on the autonomic control of the circulation. Several studies have shown that baroreflex-mediated vagal control of the heart deteriorates with age, but so far there is little information regarding the effect of ageing on sympathetically mediated baroreflex responses. The aim of this study was to assess the effects of ageing on baroreflex control of the heart and blood vessels. Materials and Methods In 40 healthy volunteers, aged 20,87 years, we applied oscillatory neck suction at 0·1 Hz to assess the sympathetic modulation of the heart and blood vessels and at 0·2 Hz to assess the effect of parasympathetic stimulation on the heart. Breathing was maintained at 0·25 Hz. Blood pressure, electrocardiographic RR intervals and respiration were recorded continuously. Spectral analysis was used to evaluate the magnitude of the low-frequency (0·03,0·14 Hz) and high-frequency (0·15,0·50 Hz) oscillations in the RR interval and blood pressure. Responses to neck suction were assessed as the change in power of the RR interval and blood pressure fluctuations at the stimulation frequency from baseline values. Results Resting low- and high-frequency powers of the RR interval decreased significantly with age (P < 0·01). However, the low-frequency power of systolic blood pressure did not correlate with age. Spontaneous baroreflex sensitivity (alpha-index) showed a significant inverse correlation with age (r = ,0·46, P < 0·05). Responses of the RR interval and systolic blood pressure to 0·1 Hz neck suction stimulation were not related to age, however, the RR interval response to 0·2 Hz neck suction declined significantly with age (r = ,0·61, P < 0·01). Conclusions These results confirm an age-related decrease in cardiovagal baroreflex responses. However, sympathetically mediated baroreflex control of the blood vessels is preserved with age. [source]

    Clustering of RR Intervals Predicts Effective Electrical Cardioversion for Atrial Fibrillation

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2004
    MAARTEN P. VAN DEN BERG M.D.
    Introduction: Atrial fibrillation (AF) is characterized by an irregularly irregular ("random") heart beat. However, controversy exists whether the ventricular rhythm in AF is truly random. We investigated randomness by constructing three-dimensional RR interval plots (3D plots), allowing identification of "clustering" of RR intervals. It was hypothesized that electrical cardioversion (ECV) would be more effective in AF patients with clustering, because clustering might reflect a higher degree of organization of atrial fibrillatory activity. Methods and Results: The study group consisted of 66 patients (44 men and 22 women; mean age 68 ± 11 years,) who were referred for ECV because of persistent AF. Twenty-four-hour Holter recordings were used to construct 3D plots by plotting each RR interval (x axis) against the previous RR interval (y axis) and the number of occurrences of each of these x,y combinations (z axis). A clustering index was calculated as the percentage of beats within the peaks in the 3D plot. Based on the 3D plots, clustering of RR intervals was present in 31 (47%) of the 66 patients. ECV was effective in restoring sinus rhythm in 29 (94%) of these 31 patients, whereas sinus rhythm was restored in only 25 (71%) of the remaining 35 patients without clustering (P = 0.020). The clustering index ranged from <2% in the 12 patients with failed ECV to >8% in the 32 patients with sinus rhythm at the end of the study (4 weeks after the ECV); the clustering index in the 22 patients with a relapse of AF after effective ECV was intermediate (P = 0.034 and P = 0.042, respectively). Conclusion: This study indicates that ECV is more effective in restoring sinus rhythm in AF patients with clustering compared to patients in whom no clustering is apparent on 3D plots. In addition, the degree of clustering appears to be predictive of the overall outcome of ECV; the higher the degree of clustering, the higher the likelihood of sinus rhythm at follow-up. [source]

    Repolarization Abnormality in Idiopathic Ventricular Fibrillation:

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2004
    Assessment Using 24-Hour QT-RR, QaT-RR Relationships
    Introduction: We evaluated the characteristics of QT-RR and QaT (apex of T wave)-RR relationships in patients with idiopathic ventricular fibrillation (IVF) compared with control subjects. We hypothesized that IVF patients have unique repolarization dynamics related to a reduced fast Na current and a prominent transient outward current. Methods and Results: The study group consisted of 9 men (age 47 ± 10 years) with IVF (6 with Brugada type and 3 with non-Brugada type) who had experienced nocturnal episodes of VF. The control group consisted of 28 healthy age-matched men (age 44 ± 12 years). The relationships between QT and RR intervals and between QaT and RR intervals were analyzed from 24-hour Holter ECG data using an automatic measurement system. Both QT and QaT at RR intervals of 0.6, 1.0, and 1.2 seconds were determined from QT-RR and QaT-RR linear regression lines. Both QT-RR and QaT-RR slopes were lower in the IVF group than in the control group (QT-RR: 0.092 ± 0.023 vs 0.137 ± 0.031, P < 0.001; QaT-RR: 0.109 ± 0.025 vs 0.153 ± 0.028, P < 0.001). QT at an RR interval of 0.6 second did not differ between two groups, but QT at RR intervals of either 1.0 or 1.2 seconds was significantly shorter in the IVF group than in the control group (RR 1.0 s: 0.384 ± 0.018 vs 0.399 ± 0.017, P < 0.05; RR 1.2 s: 0.402 ± 0.019 vs 0.426 ± 0.020, P < 0.01). QaT at RR intervals of either 1.0 or 1.2 seconds also was shorter in the IVF group (RR 1.0 s: 0.289 ± 0.022 vs 0.312 ± 0.021, P < 0.01; RR 1.2 s: 0.311 ± 0.024 vs 0.343 ± 0.024, P < 0.01). In four patients, oral administration of disopyramide (300 mg/day) was effective in suppressing VF episodes and increased slopes of QT-RR and QaT-RR relationships. Conclusion: IVF patients had lower slopes of QT-RR and QaT-RR regression lines and impaired prolongation of QT and QaT at longer RR intervals compared with control subjects. These unique repolarization dynamics may be related to the frequent occurrence of VF episodes at night. (J Cardiovasc Electrophysiol, Vol. 15, pp. 59-63, January 2004) [source]

    Interleukin-6 Levels are Inversely Correlated with Heart Rate Variability in Patients with Decompensated Heart Failure

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2001
    DORON ARONSON M.D.
    Interleukin-6 and Heart Rate Variability.Introduction: Increased local and systemic elaboration of cytokines have an important role in the pathogenesis of congestive heart failure (CHF) through diverse mechanisms. Because cytokines are known to act at the neuronal level in both the peripheral and central nervous system, we sought to determine whether increased cytokine levels are associated with the autonomic dysfunction that characterizes CHF. Methods and Results: We studied 64 patients admitted for decompensated CHF (mean age 59 ± 12 years). Autonomic function was assessed using time, and frequency-domain heart rate variability (HRV) measures, obtained from 24-hour Holter recordings. In addition, norepinephrine, tumor necrosis factor-, (TNF-,), and interleukin-6 (IL-6) were measured in all patients. TNF-, levels did not correlate with any of the HRV measures. IL-6 inversely correlated with the time-domain parameters of standard deviation of RR intervals (SDNN) (r =,0.36, P = 0.004) and standard deviation of all 5,minute mean RR intervals (SDANN) (r =,0.39, P = 0.001), and with the frequency-domain parameters of total power (TP) (r =,0.37, P = 0.003) and ultralow-frequency (ULF) power (r =,0.43, P = 0.001). No correlation was found between IL-6 and indices of parasympathetic modulation. Using multiple linear regression models, adjusting for clinical variables and drug therapies, the strong inverse relationship between IL-6 and SDNN (P = 0.006), SDANN (P = 0.001), TP (P = 0.04), and ULF power (P = 0.0007) persisted. Conclusion: Reduction of long-term HRV indices is associated with increased levels of IL-6 in patients with decompensated heart failure. The ability of long-term HRV parameters to better reflect activation of diverse hormonal systems may explain their greater prognostic power for risk stratification in patients with CHF. [source]

    Gender-Related Differences in Modulation of Heart Rate in Patients with Congestive Heart Failure

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000
    DORON ARONSON M.D.
    Gender and HRV in Heart Failure Introduction. The prognosis of women with congestive heart failure (CHF) is better than that for men, but the mechanisms underlying the female survival advantage are not well understood. CHF is characterized by profound abnormalities in cardiac autonomic control that contribute to progressive circulatory failure and influence survival. Methods and Results. Time- and frequency-domain heart rate variability (HRV) indexes were obtained from 24-hour Holter recordings and compared to assess the role of gender in 131 men and 68 women with CHF (mean age 60 ± 13.6 years, range 21 to 87; New York Heart Association Functional Class III [66%] and IV [34%]). Gender-related differences in HRV were observed only in the subset of patients with nonischemic heart failure (55 men and 39 women). Among the time-domain indexes, the SD of the RR intervals (76 ± 5.3 msec vs 55.3 ± 3.2 msec, P < 0.0001) and indexes denoting parasympathetic modulation, the percentage of RR intervals with >50 msec variation (4.0%± 1.0% vs 6.5%± 1.3%, P = 0.02), and the square root of mean squared differences of successive RR intervals (19.1 ± 3.3 vs 28.4 ± 3.8, P = 0.004) were higher in women. Among the frequency-domain indexes, the total power (7.5 ± 0.13 In-msec2 vs 8.3 ± 0.14 In-msec2, P = 0.0002), the ultralow-frequency power (7.2 ± 0.11 In-msec2 vs 8.0 ± 0.14 In-msec2, P < 0.0001), the low-frequency power (3.8 ± 0.25 In-msec2 vs 4.8 ± 0.28 In-msec2, P = 0.006), and the high-frequency power (3.8 ± 0.24 In-msec2, vs 4.6 ± 0.26 In-msec2, P = 0.003) were greater in women than in men. Conclusion. Women with nonischemic CHF have an attenuated sympathetic activation and parasympathetic withdrawal compared with men. Gender-based differences in autonomic responses in the setting of CHF may be related to the female survival advantage. (J Cardiovasc Electrophysiol, Vol. 11, pp. 1071-1077, October 2000) [source]