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Successive Differences (successive + difference)
Selected AbstractsPrior pallidotomy reduces and modifies neuronal activity in the subthalamic nucleus of Parkinson's disease patientsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2008A. Zaidel Abstract Parkinson's disease (PD) patients with prior radio-frequency lesions in the internal segment of the globus pallidus (GPi, pallidotomy), whose symptoms have deteriorated, may be candidates for further invasive treatment such as subthalamic deep brain stimulation (STN DBS). Six patients with prior pallidotomy (five unilaterally; one bilaterally) underwent bilateral STN DBS. The microelectrode recordings (MERs, used intraoperatively for STN verification), ipsilateral and contralateral to pallidotomy, and MERs from 11 matched PD patients who underwent bilateral STN DBS without prior pallidotomy were compared. For each trajectory, average, variance and mean successive difference (MSD, a measure of irregularity) of the root mean square (RMS) of the STN MER were calculated. The RMS in trajectories ipsilateral to pallidotomy showed significant reduction of the mean average and MSD of STN activity when compared with trajectories from patients without prior pallidotomy. The RMS parameters contralateral to pallidotomy tend to lie between those ipsilateral to pallidotomy and those without prior pallidotomy. The average STN power spectral density of oscillatory activity was notably lower ipsilateral to pallidotomy than contralateral, or without prior pallidotomy. The finding that pallidotomy reduces STN activity and changes firing characteristics, in conjunction with the effectiveness of STN DBS despite prior pallidotomy, calls for reappraisal and modification of the current model of the basal ganglia (BG) cortical network. It highlights the critical role of direct projections from the BG to brain-stem structures and suggests a possible GPi,STN reciprocal positive-feedback mechanism. [source] Circadian Profile of Cardiac Autonomic Nervous Modulation in Healthy Subjects:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2003Differing 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] The impact of menstrual cycle phase on cardiac autonomic regulationPSYCHOPHYSIOLOGY, Issue 4 2009Paula S. Mckinley Abstract This study investigated menstrual cycle phase differences in heart rate (HR) and RR interval variability (RRV) in 49 healthy, premenopausal, eumenorrheic women (age 30.2±6.2 years). HR and RRV were computed from ambulatory 24-h electrocardiogram, collected for up to 6 days, with at least 1 day each during early to midfollicular and midluteal menstrual phases. Phase effects on HR and RRV were assessed using linear mixed effects models with a random intercept to account for the correlation of observations within each subject as well as intrasubject variation. During follicular phase monitoring, women had significantly lower average HR (,2.33 bpm), and higher standard deviation, the root mean squared successive difference, and high frequency (0.04,0.15 Hz) and low frequency (0.15,0.40 Hz) RRV than during the luteal phase. These results provide strong support for the influence of menstrual phase on cardiac autonomic regulation in premenopausal women. [source] Characteristics of Heart Rate Variability Can Predict Impending Septic Shock in Emergency Department Patients with SepsisACADEMIC EMERGENCY MEDICINE, Issue 5 2007Wei-Lung Chen MD ObjectivesTo determine whether heart rate variability (HRV) measures can be used to predict which septic patients in the emergency department (ED) will progress to septic shock. MethodsThe authors prospectively enrolled consecutive patients who met the 2001 International Sepsis Definitions Conference criteria of sepsis and visited the ED of a university teaching hospital over a six-month period. In addition to the septic workup, a continuous 10-minute electrocardiogram recording was performed at the same time. The HRV measures were calculated off-line and correlated with the outcome of the patients. ResultsEighty-one patients aged 30,84 years who met the inclusion criteria were enrolled. The patients were classified as those with no septic shock (n= 60) and those with septic shock (n= 21), according to their outcome within six hours. The baseline root mean square successive difference, high-frequency power, and normalized high-frequency power of the septic shock group were significantly higher than those of the no septic shock group. The low-frequency power, normalized low-frequency power, and low-/high-frequency power ratio of the septic shock group were significantly lower than those of the no septic shock group. Multiple logistic regression analysis identified root mean square successive difference as the best predictor of impending septic shock for septic ED patients. ConclusionsHRV measures may be used to identify septic ED patients with impending septic shock. Among those HRV measures, root mean square successive difference seems to be the best indicator to predict the occurrence of septic shock. [source] Assessment of Noise in Digital ElectrocardiogramsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2002VELISLAV BATCHVAROV BATCHVAROV, V., et al.: Assessment of Noise in Digital Electrocardiograms. Technically related noise in 12-lead ECGs recorded with ambulatory recorders has never been systematically compared with that in ECGs recorded with conventional ECGs. This study compared serial 10-second ECGs obtained in ten healthy men, age 22,45 years, who were recorded in the supine resting position using a (1) MAC VU recorder, (2) digital ambulatory SEER MC recorder with a Multi-Link detachable ECG cable, and (3) digital ambulatory SEER MC recorder with a light ambulatory ECG cable. In each ECG, averaged sinus rhythm cycles of the entire recording were realigned with the native signal and subtracted. The resulting "residuum" was quantified by computing its standard deviation and root mean square of successive differences (RMSSD). While the RMSSD residuum values were significantly lower with the MAC VU recorder (6.27 ± 0.98 ,V) than with the SEER MC recorder with either ECG cables (7.29 ± 1.31 and 7.17 ± 1.31 ,V, P < 0.003 and p < 0.02), the difference was practically negligible and there was no detectable difference in the standard deviation residuum values. The study concludes that valid ECG investigations of serial ECG testing may be conducted using the ambulatory SEER MC recorders providing the biological sources of ECG noise are controlled. The available technology for noise assessment suggests that studies involving advanced analysis of serial ECGs (e.g., of drug related changes), should incorporate objective characterisation of ECG quality. [source] Genetic influences on heart rate variability at rest and during stressPSYCHOPHYSIOLOGY, Issue 3 2009Xiaoling Wang Abstract We tested whether the heritability of heart rate variability (HRV) under stress is different from rest and its dependency on ethnicity or gender. HRV indexed by root mean square of successive differences (RMSSD) and high-frequency (HF) power was measured at rest and during 3 stressors in 427 European and 308 African American twins. No ethnic or gender differences were found for any measures. There was a nonsignificant increase in heritability of RMSSD (from 0.48 to 0.58) and HF (from 0.50 to 0.58) under stress. Up to 81% and 60% of the heritabilities of RMSSD and HF under stress could be attributed to genes influencing rest levels. The heritabilities due to genes expressed under stress were 0.11 for RMSSD and 0.23 for HF. The findings suggest that, independent of ethnicity and gender, HRV regulation at rest and under stress is largely influenced by the same genes with a small but significant contribution of stress-specific genetic effects. [source] Influence of Heavy Cigarette Smoking on Heart Rate Variability and Heart Rate Turbulence ParametersANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2009Goksel Cagirci M.D. Background: Cigarette smoking increases the risk of cardiovascular events related with several mechanisms. The most suggested mechanism is increased activity of sympathetic nervous system. Heart rate variability (HRV) and heart rate turbulence (HRT) has been shown to be independent and powerful predictors of mortality in a specific group of cardiac patients. The goal of this study was to assess the effect of heavy cigarette smoking on cardiac autonomic function using HRV and HRT analyses. Methods: Heavy cigarette smoking was defined as more than 20 cigarettes smoked per day. Heavy cigarette smokers, 69 subjects and nonsmokers 74 subjects (control group) were enrolled in this study. HRV and HRT analyses [turbulence onset (TO) and turbulence slope (TS)] were assessed from 24-hour Holter recordings. Results: The values of TO were significantly higher in heavy cigarette smokers than control group (,1.150 ± 4.007 vs ,2.454 ± 2.796, P = 0.025, respectively), but values of TS were not statistically different between two groups (10.352 ± 7.670 vs 9.613 ± 7.245, P = 0.555, respectively). Also, the number of patients who had abnormal TO was significantly higher in heavy cigarette smokers than control group (23 vs 10, P = 0.006). TO was correlated with the number of cigarettes smoked per day (r = 0.235, P = 0.004). While LF and LF/HF ratio were significantly higher, standard deviation of all NN intervals (SDNN), standard deviation of the 5-minute mean RR intervals (SDANN), root mean square of successive differences (RMSSD), and high-frequency (HF) values were significantly lower in heavy smokers. While, there was significant correlation between TO and SDNN, SDANN, RMSSD, LF, and high frequency (HF), only HF was correlated with TS. Conclusion: Heavy cigarette smoking has negative effect on autonomic function. HRT is an appropriate noninvasive method to evaluate the effect of cigarette on autonomic function. Simultaneous abnormal HRT and HRV values may explain increased cardiovascular event risk in heavy cigarette smokers. [source] Nighttime Vagal Cardiac Control and Plasma Fibrinogen Levels in a Population of Working Men and WomenANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009Roland Von Känel M.D. Background: Elevated plasma fibrinogen levels have prospectively been associated with an increased risk of coronary artery disease in different populations. Plasma fibrinogen is a measure of systemic inflammation crucially involved in atherosclerosis. The vagus nerve curtails inflammation via a cholinergic antiinflammatory pathway. We hypothesized that lower vagal control of the heart relates to higher plasma fibrinogen levels. Methods: Study participants were 559 employees (age 17,63 years; 89% men) of an airplane manufacturing plant in southern Germany. All subjects underwent medical examination, blood sampling, and 24-hour ambulatory heart rate recording while kept on their work routine. The root mean square of successive differences in RR intervals during the night period (nighttime RMSSD) was computed as the heart rate variability index of vagal function. Results: After controlling for demographic, lifestyle, and medical factors, nighttime RMSSD explained 1.7% (P = 0.001), 0.8% (P = 0.033), and 7.8% (P = 0.007), respectively, of the variance in fibrinogen levels in all subjects, men, and women. Nighttime RMSSD and fibrinogen levels were stronger correlated in women than in men. In all workers, men, and women, respectively, there was a mean ± SEM increase of 0.41 ± 0.13 mg/dL, 0.28 ± 0.13 mg/dL, and 1.16 ± 0.41 mg/dL fibrinogen for each millisecond decrease in nighttime RMSSD. Conclusions: Reduced vagal outflow to the heart correlated with elevated plasma fibrinogen levels independent of the established cardiovascular risk factors. This relationship seemed comparably stronger in women than men. Such an autonomic mechanism might contribute to the atherosclerotic process and its thrombotic complications. [source] Ethnic (Black-White) Contrasts in 24-Hour Heart Rate Variability in Male Adolescents with High and Low Blood Pressure: The Bogalusa Heart StudyANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2000Elaine M. Urbina M.D. Background: Heart rate variability (HRV) has been used to study autonomic effects on the heart. The time-domain measure RMSSD (root mean square of successive differences) represents high frequency (HF) changes in HRV reflecting parasympathetic nervous system activity (PS). The frequency-domain ratio of low to high power (LF/HF) represents sympathetic (SYMP) to PS balance. In adults, increased SYMP tone has been found in hypertensive as compared to normals. The present study was performed to look for differences in HRV by race and between young subjects with high and low levels of diastolic blood pressure (DBP). Methods: Subjects included 34 healthy males age 13,17 years (53% white). Half were selected with K4 DBP < 85th% for height (HT) measured twice, 3,5 years apart. Half had DBP < 15th% for HT. Subjects underwent a physical examination including BP, HT, WT, and ECG prior to Holter monitor application. HRV data was analyzed from 24-hour Holter recordings obtained during normal activity. Results: The RMSSD was lower in whites compared to blacks for day, night, and 24-hour average (P , 0.05) with day-time measurements showing the largest racial difference. This suggests increased PS tone in blacks especially with activity. The LF/HF ratio was higher in whites for all times, reaching significance during the day (all P , 0.05) suggesting SYMP predominance in whites during activity. Subjects with higher levels of DBP had lower RMSSD and higher LF/HF ratio for all times, but these did not reach statistical significance. Conclusions: There is a trend towards SYMP predominance in children with higher DBP. Healthy white adolescents exhibit increased SYMP tone compared to blacks when measured during normal daytime activity. [source] Respiratory effects on the reproducibility of cardiovascular autonomic parametersCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2007Éva 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] | ||||||||||