Standard Deviation Of Normal RR Intervals Research Articles

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

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

Twenty Years Experience of Home TPN in Crohn's Disease: A Focus on Complications

conditions in patients with new onset of ulcerative colitis and compare the ANS activity with healthy controls (HC). The participants had nomedication ormedical condition affecting the heart rate or the ANS activity. The UC patients were assessed in remission, 3-6 months after the onset of the disease. The ANS function was assessed with HRV by analysis of 24hour Holter monitoring. These were started with controlled respirations in supine and standing position and then the patients were discharged for 24-hours of continuing Holter monitoring. The HRV analysis was performed in both time (RR-intervals, standard deviation of normal RR intervals (SDNN), the root-mean square of difference of successive normal RR intervals (RMSSD)) and frequency domains (low frequency (LF), high frequency (HF), LF/HF ratio). The RR intervals measure the heart rate and SDNN the total variability. RMSSD mainly reflect the parasympathetic tone and the LF/HF ratio in standing position mainly reflects the sympathetic tone. Subjects with UC were compared with HC using the nonparametric Mann Whitney U test. Differences were considered to be significant at the 5% level. Results: Forty-one UC patients and 31 HC were analyzed. There was no significant difference in age between UC patients and HC (34(26-45) vs. 35(28-44) years, NS). The UC patients had a lower LF/HF ratio in standing position compared with HC (3.52(1.60-5.28) vs. 5.51(3.74-8.47), p=0.03). Patients with left-sided colitis including proctitis had a lower LF/ HF ratio in standing position than patients with extensive colitis (2.49(0.86-4.45) vs. 4.59(2.29-7.70), p=0.03).There was no difference in LF/HF ratio in supine position. There was no difference in heart rate (RR intervals) (821(786-874) vs. 864(807-929) ms, NS), total variability (SDNN) 160(140-187) vs. 166(140-182) ms, NS) or parasympathetic tone (RMSSD) (40.5(32.6-61.8) vs. 44.8(34.4-62.1), NS) between the UC patients and the HC. Conclusion: The present study demonstrates an attenuated sympathetic ANS response in patients with new onset of UC and this was correlated to the extension of the disease. Whether this is a preexisting condition in the UC patients or an effect of the inflammation is unclear. An ongoing study will assess the role of ANS activity at onset for the disease course in UC patients.

Systemic inflammation, heart rate variability and air pollution in a cohort of senior adults

ObjectivesShort-term elevation of ambient particulate air pollution has been associated with autonomic dysfunction and increased systemic inflammation, but the interconnections between these pathways are not well understood. We examined the...

Effects of Exercise Training on Noninvasive Cardiac Measures in Patients Undergoing Long-term Hemodialysis: A Randomized Controlled Trial

Noninvasive screening studies may identify hemodialysis (HD) patients at increased risk of sudden cardiac death. Interventions that improve the findings of such screening studies may reduce sudden cardiac death. Randomized and controlled clinical trial. 59 HD patients were randomly assigned to an exercise training group (group A; 30 patients) or control group (group B; 29 patients). Group A participated in a 10-month supervised exercise training program during the HD sessions (3 times weekly). Each risk factor separately and the composite risk score. Patients were considered high risk according to the criteria (aerobic capacity: peak oxygen consumption [Vo(2)peak] < or = 14 mL/kg/min, left ventricular ejection fraction < or = 30%, SD of normal RR intervals [SDNN] < or = 70 milliseconds, positive T-wave alternans, or positive late potentials). Statistical analysis included a 2-group comparison of change scores and analysis of covariance adjusting for baseline. At entry and end of the study, Vo(2)peak and left ventricular ejection fraction were estimated, heart rate variability was calculated (measurement of SDNN, mean RR intervals), and the ratio between low- (LF) to high-frequency (HF) components (LF/HF) and late potentials and T-wave alternans were detected. Baseline measurements were similar between the 2 groups. At follow-up, 9 patients from group A and 20 from group B (P = 0.003) were considered high risk. The change in number of risk markers over time was significantly different between groups (-0.5 +/- 0.7 in group A versus 0.07 +/- 0.3 in group B; P < 0.001). Additionally, the change in Vo(2)peak over time was 3.5 +/- 3.2 in group A and -0.2 +/- 3.5 mL/kg/min in group B (P < 0.001), left ventricular ejection fractions were 3.4% +/- 3.9% and 0.2% +/- 7.7% (P < 0.05), SDNNs were 12.6 +/- 16.3 and -1.1 +/- 10.2 milliseconds (P < 0.001), and LF/HF ratios were 0.3 +/- 0.4 and -0.1 +/- 0.3 (P < 0.001), respectively. Change in numerical score of the signal-averaged electrocardiogram also was found to be statistically different (P < 0.05) between groups. Clinical outcomes, including survival, were not assessed. Exercise training improves aerobic capacity and ameliorates some indicators of risk of sudden cardiac death in HD patients.

Prognostic value of heart rate variability after acute myocardial infarction in the era of immediate reperfusion

The incidence and significance of impaired heart rate variability (HRV) after acute myocardial infarction (AMI) have not yet been evaluated in cohorts of patients in whom early reperfusion was systematically attempted. Therefore, HRV was evaluated in 412 unselected patients with AMI (311 men, mean age: 60+/-12 years, anterior AMI in 172 patients) treated with direct coronary angioplasty (PTCA) within 12 hours of symptom onset (mean 3.5+/-2.0 h). Standard deviation of normal RR intervals (SDNN), square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD) and left ventricular ejection fraction (LVEF, mean: 55+/-15%) were measured 11+/-9 days after AMI before discharge. Angiotensin-converting enzyme (ACE) inhibitors and beta-blockers were prescribed at discharge in 81.1% and 70.1% of patients, respectively. Mean SDNN was 94+/-30 ms (range 14-155). SDNN was <50 ms in 7% of patients. Mean RMSSD was 34+/-32 ms (range 2-234). RMSSD was <15 ms in 21% of patients. Low SDNN (<50 ms) was unrelated to gender, age, infarct location or extension of CHD but was related to low LVEF (p<0.001, logistic regression analysis). During mean follow-up of 4.3+/-3 years, there were 31 deaths; 24 were cardiac. SDNN was higher in long-term survivors (102+/-39 ms) as compared to nonsurvivors (81+/-33 ms, p=0.02) but RMSSD was unrelated to the long-term vital status. Four-year survival of patients with a SDNN <50 ms vs >50 ms was 80% vs 92%, respectively (p<0.001, Kaplan Meier analysis). Low SDNN (odds ratio OR=2.0, p<0.05) but not RMSSD was an independent denominator for long-term mortality as were low LVEF (OR=1.0 decrease in LVEF, p<0.01, proportional hazards model) and age (OR=1.1, p<0.001). Only 3/31 fatalities and 1/24 cardiac deaths were predicted by a SDNN <50 ms and only 5/31 fatalities by a RMSSD <15 ms. The incidence of severely depressed HRV in patients after AMI is low (<10%) in the era of early reperfusion of the infarct vessel using direct PTCA. Mortality in patients with a very low HRV when assessed by SDNN is substantial but the positive predictive value of this parameter is low.

The relationships between self-assessed habitual physical activity and non-invasive measures of cardiac autonomic modulation in young healthy volunteers

Heart rate variability estimates cardiac autonomic modulation, but the relationship between habitual physical activity and heart rate variability remains unclear. The aims of this study were to compare RR-interval and heart rate variability indices in individuals of different habitual physical activity levels, and examine the relationship between habitual physical activity and heart rate variability. Ninety-two healthy volunteers (47 men, 45 women; mean age 23.1 years, s = 2.1) were divided into tertiles according to the Baecke Questionnaire score. Standard heart rate variability indices were derived from 5-min resting RR-interval recordings with paced respiration (0.25 Hz). Between-group differences and the relationship between habitual physical activity and heart rate variability were assessed. More active participants (tertiles 2–3) had longer RR-intervals than those in tertile 1 (P < 0.05). Participants in tertile 2 had higher root mean squared differences of successive normal RR-intervals than those in tertile 1 and a higher standard deviation of normal RR-intervals than those in tertiles 1 and 3. There was a positive linear relationship between habitual activity and RR-interval. Differing RR-interval lengths were found in subgroups of young individuals according to level of habitual physical activity. More active individuals showed resting bradycardia without evidence of enhanced cardiac parasympathetic modulation. The mechanism linking habitual physical activity and RR-interval length appears to be independent of physiological mechanisms that can be measured by heart rate variability.

Time domain parameters can be estimated with less statistical error than frequency domain parameters in the analysis of heart rate variability

Introduction Measures of heart rate variability (HRV) can be divided in time domain and frequency domain parameters. It is frequently ignored that estimation of frequency-domain parameters is a 2-step procedure where statistical error from the first step (spectral estimation) is neglected in subsequent analyses. Methods We performed a simulation study to quantify the statistical error by using frequency domain instead of time domain parameters. We generated tachograms from a stationary AR(1) process for a wide range of parameters and compared the resulting estimation error (in terms of precision and variability) for the standard deviation of normal RR intervals (SDNN) and low frequency (LF), high frequency (HF), and LF/HF power. Results Estimation of frequency domain parameters is associated with (up to 10-fold) increased variability, as compared with the SDNN. Moreover, the SDNN has higher precision. Conclusion Frequency domain parameters should be applied in HRV analysis only if important physiological reasons suggest their use. If used, frequency domain parameters should be interpreted with caution, taking into account the statistical weaknesses of spectral estimation.

Genome-wide association study of electrocardiographic and heart rate variability traits: the Framingham Heart Study.

BackgroundHeritable electrocardiographic (ECG) and heart rate variability (HRV) measures, reflecting pacemaking, conduction, repolarization and autonomic function in the heart have been associated with risks for cardiac arrhythmias. Whereas several rare monogenic conditions with extreme phenotypes have been noted, few common genetic factors contributing to interindividual variability in ECG and HRV measures have been identified. We report the results of a community-based genomewide association study of six ECG and HRV intermediate traits.MethodsGenotyping using Affymetrix 100K GeneChip was conducted on 1345 related Framingham Heart Study Original and Offspring cohort participants. We analyzed 1175 Original and Offspring participants with ECG data (mean age 52 years, 52% women) and 548 Offspring participants with HRV data (mean age 48 years, 51% women), in relation to 70,987 SNPs with minor allele frequency ≥ 0.10, call rate ≥ 80%, Hardy-Weinberg p-value ≥ 0.001. We used generalized estimating equations to test association of SNP alleles with multivariable-adjusted residuals for QT, RR, and PR intervals, the ratio of low frequency to high frequency power (LF/HFP), total power (TP) and the standard deviation of normal RR intervals (SDNN).ResultsAssociations at p < 10-3 were found for 117 (QT), 105 (RR), 111 (PR), 102 (LF/HF), 121 (TP), and 102 (SDNN) SNPs. Several common variants in NOS1AP (4 SNPs with p-values < 10-3; lowest p-value, rs6683968, p = 1 × 10-4) were associated with adjusted QT residuals, consistent with our previously reported finding for NOS1AP in an unrelated sample of FHS Offspring and other cohorts. All results are publicly available at NCBI's dbGaP at .ConclusionIn the community-based Framingham Heart Study none of the ECG and HRV results individually attained genomewide significance. However, the presence of bona fide QT-associated SNPs among the top 117 results for QT duration supports the importance of efforts to validate top results from the reported scans. Finding genetic variants associated with ECG and HRV quantitative traits may identify novel genes and pathways implicated in arrhythmogenesis and allow for improved recognition of individuals at high risk for arrhythmias in the general population.

Heart Rate Variability in Patients with Allergic Rhinitis

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

Effects of Different Size Particulate Matters on Heart Rate Variability in the Elderly People

P-399 Introduction: Environmental epidemiologic studies have shown that the elderly people are susceptible for particulate air pollution. The decreases in heart rate variability (HRV) are important indices of health effect caused by particulate matter (PM). The objective of this study was to investigate the short-term effects of submicron particle (PM1), PM1–2.5, and coarse particle (PM2.5–10) on HRV parameters in the elderly. Method: The study population consisted of 15 non-smoking volunteers aged from 53 to 75 yrs, all of whom resided in the metropolitan Taipei area, Taiwan. Personal PM exposures were measured using a direct-reading portable dust monitor (GRIMM Model 1.108, Germany) in 1-minute interval, while each subject’s 24-hour electrocardiographics were recorded by a PacerCorder® holter recorder (DELMAR™ Medical LLC., model 461A, USA) in 5-minute interval. For each subject, health status and environmental factors were assessed by questionnaire and activity diary. The mass concentrations of PM1, PM1–2.5, and PM2.5–10 were measured and recorded as 1-hour, 2-hour, 3-hour, 4-hour, 5-hour, 6-hour, 7-hour, and 8-hour moving averages. Linear mixed-effects models were applied to estimate the effects of PM on time domain indices and frequency domain indices of HRV, using interquartile range (IQR) increase in PM concentrations. Time domain HRV parameters included the standard deviation of normal RR intervals (SDNN) and the square root of the mean of the squared differences between adjacent normal RR intervals (r-MSSD). Frequency domain HRV parameters included low frequency (LF) and high frequency (HF). Results: After adjusting for gender, age, body mass index, sleeping hours, β-block medicine, disease type, temperature, and relative humidity, the 3-hour moving averages of PM1 concentrations were found to have the strongest impact on HRV parameters. The strongest effects of PM1–2.5 on the decreases in SDNN, LF, and HF were shown for the 3-hour moving average, while the effect on r-MSSD decrease was the strongest for the 4-hour moving average. The largest decreases in SDNN, LF, r-MSSD, and HF for the effects of PM2.5–10 were found for 8 hours, 8 hours, 7 hours, and 4 hours moving averages, respectively. In addition, the impact of 3-hour PM moving average on the HRV decrease displayed the order of PM2.5–10 > PM1 > PM1–2.5, while only PM2.5–10 showed a significant impact on the HRV decrease after 5 hours. Conclusions: Results of our study indicated that PM may have both of the short-term effects and the delayed effects on HRV reduction in the elderly, with stronger delayed effect found for coarse particles in comparison with particles of other size ranges. Compared to the IQR concentrations of PM1 and PM1–2.5, coarse particles demonstrated a larger impact on the decrease in HRV for the elderly people.

Particulate Exposures and Heart Rate Variability During Sleep in Boilermaker Construction Workers

SAB4-PD-04 Introduction: Studies have shown associations between PM2.5 exposure and decreased heart rate variability (HRV), a marker of cardiac autonomic control. Limited data exists on the cardiac effects of PM2.5 exposure during sleep, a period free of cardiac influences from extraneous activities. We investigated the association between HRV during sleep and daytime PM2.5 exposures in a group of boilermaker construction workers exposed to welding fumes. Methods: Thirty male workers participated in a short-term prospective study with a repeated measures design. Participants were continuously monitored over 2 24-hour periods, including a nonworkday (baseline) and a workday, for personal PM2.5 exposure and by ambulatory ECG. Health status and physical activities were assessed by questionnaire. Three time domain measures of HRV were computed over an 8-hour sleep period: root-mean-square of differences between adjacent RR intervals (rMSSD), standard deviation of normal RR intervals (SDNN), and the mean of the standard deviation of normal 5-minute RR intervals (SDNNi). Personal PM2.5 exposures were averaged over the workday and evaluated in relation to HRV parameters during sleep in linear regression models. Results: The mean PM2.5 concentration at work was 0.88 ± 0.15 mg/m3 and ranged from 0.13 mg/m3 to 3.73 mg/m3. With increasing PM2.5 exposure, there was a decline in all 3 HRV parameters during sleep. Among smokers (n = 14), for each 1 mg/m3 increase in 8-hour daytime average PM2.5, there was a change of −9.7 ms (95% CI, −15.5 to −3.8) for rMSSD, −11.1 ms (95% CI, −25.0 to 2.9) for SDNN, and −9.2 ms (95% CI, −14.8 to −3.5) for SDNNi after adjustment for baseline sleep HRV. Among non-smokers (n = 16), for each 1 mg/m3 increase in 8-hour daytime average PM2.5, there was a change of −4.1 ms (95% CI, −12.9 to 4.7) for rMSSD, −28.1 ms (95% CI, −58.2 to 1.9) for SDNN, and −5.4 ms (95% CI, −16.4 to 5.6) for SDNNi after adjustment for baseline sleep HRV. Conclusions: Preliminary results suggest that high levels of daytime PM2.5 exposures may cause changes in HRV during the subsequent night's sleep in healthy, working men. Findings further suggest that smokers may be more susceptible to the cardiac alterations. Supported by NIEHS ES09860 and ES00002.

Short-Term Effects of Air Pollution on Heart Rate Variability in Senior Adults in Steubenville, Ohio

We examined the association between ambient air pollution levels and heart rate variability (HRV) in a panel study of 32 subjects. We used linear mixed models to analyze the effects of fine particles (PM2.5), sulfate (SO4), elemental carbon (EC), and gases on log-transformed standard deviation of normal RR intervals (SDNN), mean square of differences between adjacent RR intervals (r-MSSD), and high- and low-frequency power (HF, LF). An interquartile range (IQR) increase of 5.1 mug/m in SO4 on the previous day was associated with a decrease of -3.3% SDNN (95% confidence = -6.0% to -0.5%), -5.6% r-MSSD (-10.7% to -0.2%), and -10.3% HF (-19.5% to -0.1%). Associations with total PM2.5 were similar. HRV was not associated with EC, NO2, SO2, or O3. In addition to traffic-related particles, elevated levels of sulfate particles may also adversely affect autonomic function.

Cardiac Autonomic Modulation Following High-Intensity Static Muscle Contractions

The purpose of this investigation was to examine cardiac autonomic modulation, as measured by wavelet analysis of heart rate variability, following a series of high-intensity static muscle contractions. After 10 minutes of rest, electrocardiograms (ECGs) were collected in 17 participants (age, 24.5 +/- 1 yr) 2.5 minutes before (REST) and 10 minutes after a series of static contractions of the knee extensors. Participants performed contractions with the nondominant leg (knee fixed at 90 degrees) at either 70% or 85% (randomized order) of their maximal voluntary contraction (MVC) on two separate visits. The postexercise ECGs were further divided into four consecutive 2.5-minute segments (POST 1-POST 4) to evaluate the time course of any possible autonomic changes after exercise. Each 2.5-minute segment was evaluated for the standard deviation of normal RR intervals (SDNN) and the percentage of successive RR intervals that differed by more than 50 ms (pNN50). Frequency-domain indices were obtained via wavelet transformation giving coefficients that reflected high- and low-frequency fluctuations in heart period (HFw and LFw). SDNN was elevated during POST-1 and pNN50 was reduced during POST-3 and POST-4 (P < 0.05) compared to REST for both intensities. Furthermore, HFw and LFw were increased during POST-1 and reduced during POST-3 and POST-4 compared to REST for both intensities (P < 0.05). These data suggest that complex alterations cardiac autonomic modulation exist for at least 10 minutes following a series of high-intensity static contractions performed at either 70% or 85% of MVC.

Preserved heart rate variability identifies low-risk patients with nonischemic dilated cardiomyopathy: Results from the DEFINITE trial

The recent expansion of indications for prophylactic implantable cardioverter-defibrillator (ICD) placement in subjects with nonischemic dilated cardiomyopathy has raised concerns about the cost-effectiveness of this therapy. The purpose of this study was to identify low-risk patients with nonischemic dilated cardiomyopathy who may not require prophylactic ICD placement. This was a prospective study of 274 participants in the Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial, a randomized controlled trial that evaluated the role of prophylactic ICD placement in patients with nonischemic dilated cardiomyopathy. The patients underwent 24-hour Holter recording for analysis of heart rate variability (HRV). The primary HRV variable was the standard deviation of normal R-R intervals (SDNN). Patients with atrial fibrillation and frequent ventricular ectopy (>25% of beats) were excluded from HRV analysis (23% of patients). SDNN was categorized in tertiles, and Kaplan-Meier analysis was performed to compare survival in the three tertiles and excluded patients. The study population was 73% male, with a mean age of 59 +/- 12 years and mean left ventricular ejection fraction of 21% +/- 6%. After 3-year follow-up, significant differences in mortality rates were observed: SDNN >113 ms: 0 (0%), SDNN 81-113 ms: 5 (7%), SDNN <81 ms: 7 (10%), excluded patients: 11 (17%) (P = .03). There were no deaths in the tertile with SDNN >113 ms regardless of treatment assignment (ICD vs control). Patients with nonischemic dilated cardiomyopathy and preserved HRV have an excellent prognosis and may not benefit from prophylactic ICD placement. Patients with severely depressed HRV and patients who are excluded from HRV analysis because of atrial fibrillation and frequent ventricular ectopy have the highest mortality.

The Relationship between Ambient Air Pollution and Heart Rate Variability Differs for Individuals with Heart and Pulmonary Disease

Associations between concentrations of ambient fine particles [particulate matter < 2.5 μ m aerodynamic diameter (PM2.5)] and heart rate variability (HRV) have differed by study population. We examined the effects of ambient pollution on HRV for 18 individuals with chronic obstructive pulmonary disease (COPD) and 12 individuals with recent myocardial infarction (MI) living in Atlanta, Georgia. HRV, baseline pulmonary function, and medication data were collected for each participant on 7 days in fall 1999 and/or spring 2000. Hourly ambient pollution concentrations were obtained from monitoring sites in Atlanta. The association between ambient pollution and HRV was examined using linear mixed-effect models. Ambient pollution had opposing effects on HRV in our COPD and MI participants, resulting in no significant effect of ambient pollution on HRV in the entire population for 1-, 4-, or 24-hr moving averages. For individuals with COPD, interquartile range (IQR) increases in 4-hr ambient PM2.5 (11.65 μ g/m3) and nitrogen dioxide (11.97 ppb) were associated with 8.3% [95% confidence interval (CI), 1.7–15.3%] and 7.7% (95% CI, 0.1–15.9%) increase in the SD of normal R-R intervals (SDNN), respectively. For individuals with MI, IQR increases in 4-hr PM2.5 (8.54 μ g/m3) and NO2 (9.25 ppb) were associated with a nonsignificant 2.9% (95% CI, –7.8 to 2.3) and significant 12.1 (95% CI, –19.5 to –4.0) decrease in SDNN. Beta-blocker and bronchodilator intake and baseline forced expiratory volume in 1 sec modified the PM–SDNN association significantly, with effects consistent with those by disease group. Results indicate heterogeneity in the autonomic response to air pollution due to differences in baseline health, with significant associations for ambient NO2 suggesting an important role for traffic-related pollution.

Ambient fine particles modify heart rate variability in young healthy adults

Particulate air pollution has been related with cardiopulmonary morbidity and mortality. Recent studies have shown that an increase in particulate matter (PM)(2.5) ambient concentrations was associated with a decrease in heart rate variability (HRV) in the elderly with cardiovascular conditions, which could increase the risk of death. In order to assess if this association could also be observed in young adults, we studied 40 young healthy residents of the Mexico City Metropolitan Area (MCMA) who underwent 13 h Holter electrocardiographic and PM(2.5) personal monitoring. HRV was evaluated in time domain: the standard deviation of normal RR intervals (SDNN) and the percentage of differences between adjacent normal RR intervals larger than 50 ms (pNN50). In multivariate analysis with mixed effects models, a significant negative association of pNN50 with PM(2.5) accumulative exposure was found. An increase in 30 microg/m(3) of the average PM(2.5) personal exposure in the previous 2 h decreased the pNN50 in 0.08% (P=0.01). This observation revealed an acute effect related to environmental exposure to PM(2.5) with regard to HRV in normal youngsters. The long-term health consequences of this association in young healthy adults remain to be clarified.

Ethnic Differences and Heritability of Heart Rate Variability in African- and European American Youth

This study investigated whether heart rate variability (HRV) in young African-Americans differed from that in young European Americans. It further examined the genetic and/or environmental sources of HRV variance and to what extent they depend on ethnicity or gender in young twins. Subjects were available from 1 data set including 166 subjects (mean age 16 +/- 2 years; 63 African-Americans) and another including 219 twins (11 singletons [4 African-Americans] and 104 pairs [42 African-Americans]; mean age 15 +/- 2 years). HRV was measured over 256 RR intervals in a supine position. Two time-domain variables, the SD of normal RR intervals (SDNN) and the root-mean-square of successive differences (RMSSD) of normal RR intervals, and 3 frequency-domain variables, high-frequency (HF) power, low-frequency (LF) power, and the LF power/HF power ratio, were used. African-Americans had higher RMSSDs (p <0.01) and HF power (p = 0.047) and lower LF power/HF power ratios (p <0.01) than European Americans. These differences remained significant after adjusting for covariates. All HRV parameters were heritable; estimated heritability ranged from 32% to 71%. Model fitting showed no ethnic or gender differences for any measure. SDNN, RMSSD, and HF power were strongly correlated (r values >0.8). One factor explaining >90% of the variance for all 3 measures was identified. The heritability of this combined HRV score was 70%. In conclusion, this study suggests that ethnic differences in HRV already exist in youth, with African-Americans having greater HRV than European Americans. High heritability estimates for HRV measures were observed, and no differences in HRV heritability estimates were noted for ethnicity or gender.

The effect of anesthesia and surgery on heart rate variability in dogs

Heart rate variability (HRV) may be useful for objective assessment of stress and pain in animals. The objective of this study was to describe the effect of anesthesia and surgery on HRV in dogs. We hypothesized that surgery would decrease HRV to a greater degree and for a longer duration than anesthesia alone. Four healthy male dogs (29 ± 2 kg) were instrumented for ambulatory ECG monitoring. Continuous ECG data was obtained for 1 day prior to, and 6 days following anesthesia alone (ANES) or anesthesia plus unilateral stifle arthrotomy (ANSX). The anesthetic protocol included xylazine (0.5 mg kg–1 IM), morphine (0.5 mg kg–1 IM), atropine (0.04 mg kg–1 IM), thiopental (10 mg kg–1 IV) and isoflurane in oxygen. A single dose of morphine (0.5 mg kg–1 IM) was administered at extubation. Time domain analysis of HRV was performed on 5 minutes epochs of artefact- and arrhythmia-free ECG data obtained at 12 noon and 12 midnight on each of the seven experimental days. Mean RR interval, standard deviation of normal R-R intervals (SDNN), and the standard deviation of successive differences in RR intervals (SDSD) were compared to baseline for ANES and ANSX. Pain scores obtained during the day were also evaluated. Significance was set at p < 0.01. There were no differences between groups for any baseline data. Mean RR interval did not differ from baseline on days 1–6 in ANES or ANSX. SDNN and SDSD values at noon were not different from baseline on days 1–6 in ANES or ANSX. At midnight on days 1 and 2, SDNN was significantly decreased from baseline in ANSX, and on day 1 a significant difference between groups existed. ANSX values of SDSD at midnight were significantly decreased from baseline and ANES on day 1. Pain scores for ANSX were significantly greater than baseline on days 1–3, and different from ANES on days 1–5. These results suggest that HRV is decreased following anesthesia plus surgery, and that changes in HRV may be associated with pain.

The effect of autonomic manipulation on heart rate variability in dogs

Beat-to-beat variation of heart rate is reflective of autonomic balance and has been used to assess pain and stress in human beings. The purpose of this investigation was to pharmacologically manipulate the autonomic nervous system and to determine the effect of these manipulations on heart rate variability (HRV) in dogs. Four adult male hound dogs (27 ± 1 kg) were used in the investigation. Each dog was given five treatments: Parasympathetic blockade (glycopyrrolate; 0.01 mg kg−1 IV and 0.01 mg kg−1 IM), parasympathetic stimulation (phenylephrine; 0.005 mg kg−1 IV + 0.05 mg kg−1hour−1), sympathetic blockade (propranolol; 0.11 mg kg−1 IV), sympathetic stimulation propranolol; 0.01 μg kg−1 minute−1), and saline control. At least 48 hours were allowed between treatments. ECG recordings were obtained using an ambulatory ECG monitor. A 5-minutes period of continuous recording obtained ~30 minutes after initiation of drug administration was used for data analysis. Changes in HRV were evaluated by time and frequency-domain analysis. The standard deviation of normal R-R intervals (SDNN), as well as the standard deviation of successive differences in RR intervals (SDSD) were assessed for each treatment. Low frequency (LFP; 0.05–0.15 Hz), high frequency (HFP; 0.15–0.35 Hz), and total (TP; 0.017–0.5 Hz) spectral power were also determined. The LFP:HFP ratio was also evaluated. A two-way anovawith a Tukey's test was used to detect differences (p < 0.05). Administration of glycopyrrolate or isoproterenol increased HR and decreased SDNN and SDSD below control levels. Phenylephrine or propranolol administration were without effect. LFP was diminished by glycopyrrolate and isoproterenol, but was unaffected by phenylephrine and propranolol. HFP, TP, and LFP:HFP were unaffected by treatment. Both branches of the autonomic nervous system influence SDNN and LFP. SDSD, in contrast, is altered primarily by parasympathetic activity. Thus, it appears that parasympathetic activity modulates HRV in the resting dog, as either withdrawal of parasympathetic influence or accentuated sympathetic activity led to significant changes in these measures of HRV. Conversely, augmentation of parasympathetic activity or withdrawal of sympathetic tone minimally affected HRV.

795 Electrocardiogram after successful primary angioplasty: does it still matter?

@Background: elevated heart rate preceding the onset of ventricular tachycardia (VT), suggesting an increased sympathetic tone, has been reported to reduce the success of antitachycardia pacing (ATP) therapy in patients with implantable cardioverter defibrillators (ICD). Based on the data of the Variability Learned from Implantable Defibrillators (VALID) study, we aimed to assess the impact of autonomic tone on ATP effectiveness in ICD recipiens. Methods and results: a total of 36 out of 226 VALID-study patients implanted with a Biotronik ICD(Phylax XM or Microphylax+) were considred for the present sub-study. These devices have extended memory capacities (18000 RR intervals) that offerred the ability of analyzing heart rate variability (HRV) before the begening of the arrythmia. All the patients had ischemic heart disease. ATP programming was standardized within VT zones. During follow-up, 106 VTs recurred in these patients, 95 were terminated by ATP (ATP+) and ATP was unseccessful in 11 VTs (ATP-). HRV parameters were analyzed during the 30 minutes preceding VT onset. Two time- and three frequency-domain indices were derived semi-automatically: the standard deviation of normal RR intervals (SDNN), the proportion of adjacent normal RR intervals differing by > 50 ms (pNN50), the low-frequency (LF) power reflecting sympathetic tone, the high-frequency (HF) power reflecting parasympathetic activity, and the LF/HF power ratio. The following table summarizes the main