Standard Deviation Of RR Intervals Research Articles

Acute cardiac autonomic responses after a bout of resistance exercise

Summary Objective The aim of this study was to analyze the heart rate variability (HRV) after a session of resistance exercise and compare the responses to those obtained in a series of maximal and submaximal aerobic exercises. Methods Ten male volunteers with previous experience with resistance training were recruited. The participants underwent three exercise protocols, including a session of resistance exercise composed of 10 exercises. In different days, participants performed a progressive maximal intermittent test (30-15IFT) and a continuous submaximal test at an intensity of 45% of the final velocity attained in the maximal test (45%VIFT). The autonomic responses were analyzed during the 10 min following exercise, by HRV analysis and vagal reactivation indices. Results The time domain indices were lower for maximal aerobic exercise, followed by resistance exercise and by the submaximal aerobic exercise (standard deviation of RR intervals (SDNN): 32 ± 15.4, 11 ± 3.7, 45.5 ± 15.3, P 0.05), and they were both slower than submaximal exercise (P Conclusion We may conclude that autonomic responses after resistance exercise remained higher than after maximal aerobic exercise.

Influence of mercury exposure on blood pressure, resting heart rate and heart rate variability in French Polynesians: a cross-sectional study

BackgroundPopulations which diet is rich in seafood are highly exposed to contaminants such as mercury, which could affect cardiovascular risk factorsObjectiveTo assess the associations between mercury and blood pressure (BP), resting heart rate (HR) and HR variability (HRV) among French PolynesiansMethodsData were collected among 180 adults (≥ 18 years) and 101 teenagers (12-17 years). HRV was measured using a two-hour ambulatory electrocardiogram (Holter) and BP was measured using a standardized protocol. The association between mercury and HRV and BP parameters was studied using analysis of variance (ANOVA) and analysis of covariance (ANCOVA)ResultsAmong teenagers, the high frequency (HF) decreased between the 2nd and 3rd tertile (380 vs. 204 ms2, p = 0.03) and a similar pattern was observed for the square root of the mean squared differences of successive R-R intervals (rMSSD) (43 vs. 30 ms, p = 0.005) after adjusting for confounders. In addition, the ratio low/high frequency (LF/HF) increased between the 2nd and 3rd tertile (2.3 vs. 3.0, p = 0.04). Among adults, the standard deviation of R-R intervals (SDNN) tended to decrease between the 1st and 2nd tertile (84 vs. 75 ms, p = 0.069) after adjusting for confounders. Furthermore, diastolic BP tended to increase between the 2nd and 3rd tertile (86 vs. 91 mm Hg, p = 0.09). No significant difference was observed in resting HR or pulse pressure (PP)ConclusionsMercury was associated with decreased HRV among French Polynesian teenagers while no significant association was observed with resting HR, BP, or PP among teenagers or adults

Heart rate and heart rate variability in pregnant warmblood and Shetland mares as well as their fetuses

Heart rate (HR) is an important parameter of fetal well-being. In horses, HR and heart rate variability (HRV) can be determined by fetomaternal electrocardiography (ECG) from mid-pregnancy to foaling. Normal values for physiological parameters in larger breeds are often used as reference values in ponies. However, HR increases with decreasing size of the animal and in ponies is higher than in warmblood horses. It is not known if fetal HR is affected by breed and if values obtained in larger breeds can be used to assess Shetland fetuses. We have determined fetomaternal beat-to-beat (RR) interval (inversely correlated to HR) and HRV in warmblood ( n = 6) and Shetland pregnancies ( n = 7) at days 280 and 300 of gestation by ECG. Maternal RR interval was lower in pony than in warmblood mares (day 280: Shetland: 958 ± 110, warmblood: 1489 ± 126 ms, p < 0.01) The SDRR (standard deviation of RR interval) and the RMSSD (root mean square of successive RR differences) did not differ between breeds at any time. Also RR interval as well as HRV did not differ between warmblood and pony fetuses (RR interval day 280: Shetland: 606 ± 39, warmblood: 589 ± 38 ms). In conclusion, although maternal RR interval is clearly higher in Shetland than in warmblood mares, fetal RR interval in the two breeds is on the same level.

Varied Walking Dose In Women With Type 2 Diabetes: Heart Rate Variability And Hemorheology Responses

Type 2 diabetes accelerates and exacerbates the age-related decline in heart rate variability (HRV) and impairment of hemorheology. While exercise training is one of the cornerstone therapies for managing type 2 diabetes, little is known about the optimum dose of exercise training for the improvement of HRV and/or hemorheology. PURPOSE: To investigate HRV and hemorheology adaptations to 12 wk of varied-dose treadmill walking in women aged 65-74 yr with type 2 diabetes. METHODS: Fifteen subjects with uncomplicated type 2 diabetes (Age: 69 ± 2 yr; BMI: 30 ± 5 kg·m-2; VO2peak: 20.3 ± 3.1 ml·kg-1·min-1) were randomly allocated into two exercise training groups (Group 1: 2 x 60 min·wk-1 or Group 2: 4 x 30 min·wk-1). The exercise program was 12 wk and the exercise intensity was set and adjusted every 6 wk to equal 100% of each individual’s gas-exchange threshold. Time domain indices of HRV included i. the standard deviation of RR intervals (SDNN) ii. the square root of the mean of squared differences between successive intervals (RMSSD). Frequency domain indices of HRV included: log-transformed low and high frequency (lnLF and lnHF, respectively) power. Red blood cell (RBC) aggregation was measured in plasma and a standard aggregating solution (3% dextran 70 kDa), and RBC deformability was determined via ektacytometry. Dependent variables were measured before (wk -6 and 0), during (wk 6) and after (wk 12) the walking program. RESULTS: Twelve weeks of exercise training significantly improved VO2peak, time to exhaustion, and the gas-exchange threshold (p < 0.05), independent of exercise group. While exercise training did not improve glycemic control, high-density lipoprotein concentration increased by 7.5% for both groups (p = 0.01). Exercise training reduced RBC aggregation in plasma by -6.6% and in dextran-70 by -12.2% (p < 0.05), and improved RBC deformability by 3.4% (p < 0.05) for both groups. No change in HRV was observed for Group 1, whereas SDNN, RMSSD and lnHF power were improved in Group 2 (p < 0.05). CONCLUSIONS: These results suggest that the accumulated weekly exercise duration may be the most important training component for the prescription of exercise in older women with type 2 diabetes. Exercise frequency should be considered, however, when prescribing exercise to improve HRV.

Correlates of Cardiac Autonomic Control in High-Fit Endurance Athletes

PURPOSE: To examine the correlates of cardiac autonomic control, assessed by heart rate variability (HRV) and heart rate recovery (HRR), in a group of high-fit endurance athletes. METHODS: Nineteen endurance athletes participated in this study (age: 29.8±6 yrs; 8 males) and had maximal oxygen consumptions (VO2max) that placed them above the 99th percentile based on American College of Sports Medicine normative values (VO2max: 67.1±2 ml/kg/min). Participants were assessed for VO2max via a graded exercise test (GXT), percent body fat (BF), weekly physical activity (PA), resting HRV, and HRR. HRV indices were obtained from a 5-minute EKG collected during supine rest and were reported in the time domain as the standard deviation of RR intervals (SDNN) and percentage of adjacent RR interval differences >50 ms (pNN50). Spectral power in the total (TP; 0.00-0.4 Hz), low- (LF; 0.04-0.15 Hz), and high- (HF; 0.15-0.40 Hz) frequency power ranges was derived via an FFT and were transformed using the natural log (ln). Nonlinear indices of HRV were reported as Poincare plots (SD1 and SD2) and sample entropy (SampEn). HRR, a marker of vagal reactivation, was reported as the reduction in HR from peak exercise to the HR one minute after the cessation of the GXT. Pearson's correlation coefficients were reported between autonomic and physiological variables and were considered significant at the 0.05 level. RESULTS: Participants exhibited a maximal HR of 186.9±3 bpm, a resting HR of 49.7±2 bpm, a BF of 11.2±1%, and reported a PA of 6558.1±658 kcals/week. Means of the autonomic variables were as follows: SDNN (89.2±11ms), pNN50 (46.0±6%), lnTP (8.7±0.2ms2), lnLF (7.2±0.2 ms2), lnHF (7.3±0.3 ms2), LF/HF (1.4±0.3), SD1 (60.9±10ms), SD2 (108.8±13ms), SampEn (1.6±0.1), and HRR (30.8±3bpm). There were significant correlations between age and lnHF (r= -0.46), LF/HF (r= 0.53), SampEn (r= -0.49), and maximal heart rate (r= -0.65). VO2max was only significantly correlated with PA (r= 0.54) and HRR (r= 0.50). CONCLUSION: These data suggest that the relationship between age and HRV is evident in high-fit endurance athletes, whereas the relationship between fitness and HRV is not. The maintained relationship between HRR and VO2max suggests that HRR may be a better marker of fitness-related differences in autonomic control in this population.

Heart rate and heart rate variability in subjectively reported insomnia

According to epidemiological studies, insomnia is associated with cardiovascular mortality. However, it is yet to be determined whether this link is mediated by known cardiovascular risk factors. The current study aimed at investigating the association between primary insomnia, defined as subjectively reported sleep disturbance in the absence of any other pathology or substance intake, and alterations in polysomnographically determined nocturnal heart rate (HR) and heart rate variability (HRV). A total of 4,581 nocturnal short-term electrocardiographic recordings (5 min each) from 104 participants (58 with primary insomnia, 46 healthy controls) were evaluated for HR as well as for time and frequency domain measures of HRV. In the primary insomnia group, we found a lower wake-to-sleep HR reduction and a lower standard deviation of RR intervals (SDNN) compared to healthy controls. However, between-group differences in resting HR were not found, and previous results of an increase in sympathovagal balance and a decrease in parasympathetic nocturnal activity in objectively determined insomnia could not be confirmed in our sample of self-report insomnia patients. When restricting our analyses to insomnia patients with objectively determined short sleep duration, we found reduced parasympathetic activity as indicated by decreased high frequency power of HRV, as well as decreased root mean square of successive RRI differences (RMSSD) and percentage of successive RRIs that differ by more than 50 ms (pNN50) values. A lower wake-to-sleep HR reduction and alterations in HRV variables might, at least partially, mediate the increased rates of cardiovascular morbidity and mortality observed in insomnia patients.

Effects of altitude in high-rise building on the autonomic nervous modulation in healthy subjects

This study intended to study the effects of altitude in the high-rise building on the automatic nervous modulation in healthy subjects. Heart rate variability (HRV) analysis was performed to assess the automatic nervous modulation of the subjects at three different altitudes in the air-conditioned high-rise building, i.e., the first basement (4 m beneath sea level), the 31st floor (133 m above sea level), and the 46th floor (200 m above sea level). We found that the heart rate was significantly decreased, whereas the standard deviation of RR intervals (SD RR), total power and high frequency power were significantly increased when the subject was elevated to a higher altitude. The normalized low frequency power and low-/high-frequency power ratio on the 31st and 46th floors were significantly different between genders; however, no such difference was found on the first basement. The age correlated significantly and positively with the percentage change in the SD RR and coefficient of variation of RR intervals when the subjects were elevated from the first basement to the 46th floor. In conclusion, higher altitude in an air-conditioned high-rise building can lead to an increase in HRV/vagal modulation. The stay at a higher altitude in a high-rise building may lead to increased overall HRV and vagal modulation of a subject, especially for the elder people and the people who had a small HRV at ground level.

The circadian pattern of cardiac autonomic modulation in a middle-aged population

ObjectivesTo examine the circadian pattern of cardiac autonomic modulation (CAM) and its attributes in general population.MethodsWe obtained 24-h beat-to-beat RR data using a high resolution 12-lead Holter ECG in a community-dwelling sample of 115 non-smokers. We performed heart rate variability (HRV) analysis on the normal RRs from each 5-min segment to obtain time-specific HRV indices: high (HF; 0.15–0.40 Hz) and low (LF; 0.04–0.15 Hz) frequency powers, standard deviation of RR intervals (SDNN), and the square root of the mean of the sum of the squared differences of the adjacent RR intervals (RMSSD). For each individual, we fit the segment-specific HRV data to a cosine periodic function, and estimated 3 individual-level cosine function parameters to quantify the circadian variation: the mean (M), amplitude (A), and acrophase (θ). We then used a random-effects meta-analysis to summarize the M, A, and θ, and their 95% confidence intervals (CI).ResultsThe mean age was 56 (SD 8) years, with 63% female and 76% white. The averages of M, A and θ (95%CI) of log HF were 3.59 (3.43–3.76) ms2, 0.61 (0.54–0.68) ms2, and 3:10 (2:25–3:55) AM, respectively, and that of RMSSD were 22.3 (20.5–24.1) ms, 6.5 (5.4–7.5) ms, 3:45 (2:55–4:35) AM, respectively. Older age is associated with lower mean of HRV. Males have higher oscillation amplitude than females. The acrophase of LF/HF was earlier in females than in males, and in younger individuals than in older individuals.ConclusionsThe circadian pattern of CAM can be quantified by 3 cosine parameters of HRV, which are correlated with age and gender.

Quantitative analysis of heart rate variability in patients with absence epilepsy

There are no studies quantifying the nature of autonomic changes in absence epilepsy. Aims : We characterized the heart rate variability (HRV) during pre-interictal epileptiform discharges (IED), IED and post-IED states in absence epilepsy. Electroencephalogram (EEG) records with generalized 3-Hz spike-wave discharges in 8 patients (M: F: 3 : 5; mean age: 13.0 ± 2.5 years) with absence epilepsy were identified and corresponding electrocardiogram (ECG) time series were obtained. The time domain HRV measures were applied to pre-IED, IED and post-IED simultaneous ECG tracing. There was slight tachycardia during the IED phase (pre-IED: 90.15 ± 3.45 bpm, IED: 94.82 ± 4.63 bpm, P = 0.09) which returned to baseline during the post-IED phase (post-IED: 89.65 ± 3.78 bpm). There was significant decrease in the standard deviation of RR interval (pre-IED: 40.0 ± 4.15 ms, IED: 30.4 ± 4.19 ms, P = 0.032) and trend in reduction of triangular index (pre-IED: 0.05 ± 0.01, IED: 0.04 ± 0.004, P = 0.08) during the IED phase when compared to pre-IED phase. The percentage of RR intervals >50 ms was lower during the IED phase and achieved significance when compared to post-IED phase (IED: 10.08 ± 4.89, post-IED: 18.74 ± 6.17, P = 0.050). While mean HR and RR interval significantly correlated with the duration of IEDs, there was no significant correlation between its duration with change in HRV parameters between the groups. There was no significant difference in HRV parameters between patients with long (>10s) and short (<10s) duration of IED. Transient increase in heart rate during IED phase was noted in patients with absence epilepsy. Longer duration of IED seems to be linked with significant tachycardia. While most HRV parameters did not reach statistical significance, standard deviation of RR intervals and triangular index was noted to be decreased during the IED phase and returns to pre-IED levels after the episode.

Is childhood abuse or neglect associated with symptom reports and physiological measures in women with irritable bowel syndrome?

Early childhood traumatic experiences (e.g., abuse or neglect) may contribute to sleep disturbances as well as to other indicators of arousal in patients with irritable bowel syndrome (IBS). This study compared women with IBS positive for a history of childhood abuse and/or neglect to women with IBS without this history on daily gastrointestinal (GI), sleep, somatic, and psychological symptom distress, polysomnographic sleep, urine catecholamines (CAs) and cortisol, and nocturnal heart rate variability (HRV). Adult women with IBS recruited from the community were divided into two groups: 21 with abuse/neglect and 19 without abuse/neglect based on responses to the Childhood Trauma Questionnaire (CTQ; physical, emotional, sexual abuse, or neglect). Women were interviewed, maintained a 30-day symptom diary, and slept in a sleep laboratory. Polysomnographic and nocturnal HRV data were obtained. First-voided urine samples were assayed for cortisol and CA levels. Women with IBS positive for abuse/neglect history were older than women without this history. Among GI symptoms, only heartburn and nausea were significantly higher in women with abuse/neglect. Sleep, somatic, and psychological symptoms were significantly higher in women in the abuse/neglect group. With the exception of percentage of time in rapid eye movement (REM) sleep, there were few differences in sleep-stage variables and urine hormone levels. Mean heart rate interval and the natural log of the standard deviation of RR intervals for the entire sleep interval (Ln SDNN) values were lower in those who experienced childhood abuse/neglect. Women with IBS who self-report childhood abuse/neglect are more likely to report disturbed sleep, somatic symptoms, and psychological distress. Women with IBS should be screened for adverse childhood events including abuse/neglect.

Relationship between cardiac autonomic function and sustained ventricular tachyarrhythmias in patients with an implantable cardioverter defibrillators

Low left ventricular ejection fraction (LVEF) is the main indication of implantable cardioverter defibrillators (ICD) in patients with dilated cardiomyopathy (DCM) for the primary prevention of sudden cardiac death, but ICD therapy at follow-up occurs in a minority of patients. We investigated whether heart rate variability (HRV) may improve risk stratification in DCM patients. We studied 42 patients (age 67.3 ± 3.5; 37 males) who had undergone ICD implant for either idiopathic or ischaemic DCM (LVEF <40%) 34.6 ± 19.7 months prior to the study (range 6-84). Patients underwent 24 h electrocardiographic Holter monitoring, and HRV was assessed over 2 hours in the afternoon showing stable sinus rhythm. Left ventricular ejection fraction was measured by two-dimensional echocardiography. The serum levels of C-reactive protein and N-terminal pro-B-type natriuretic peptide (NT-proBNP) were also obtained. The primary endpoint was the occurrence of appropriate ICD shocks in the 6 months preceding the study. The occurrence of appropriate ICD discharge from ICD implant was considered as a secondary endpoint. In the last 6 months, appropriate ICD shocks had occurred in seven patients (17%). There were no differences between patients with and without ICD shocks in clinical variables, as well as in LVEF and in C-reactive protein and NT-proBNP serum levels. In contrast, most HRV parameters were significantly depressed in patients with, compared with those without, ICD shocks; the most significant difference was shown for the average of the standard deviations of RR intervals in all consecutive 5 min segments (n ¼ 12) within the 2 h (26.7 ± 9 vs. 39.7 ± 14 ms; P = 0.02) in the time domain and for LF amplitude (8.4 ± 3 vs. 14.8 ± 7 ms; P = 0.02) in the frequency domain. Implantable cardioverter defibrillator discharge had occurred in 11 patients (26%) since ICD implant (average 35 months). No clinical or laboratory variable showed significant differences between patients with or without ICD discharge, except very low-frequency (VLF) amplitude (23.8 ± 7 vs. 30.8 ± 10.6 ms, respectively; P = 0.049). In ICD patients with reduced LVEF, several depressed HRV indices were significantly associated with appropriate ICD shocks in the previous 6 months, and VLF amplitude was the only variable significantly associated with ICD shocks recorded since ICD implant. These data suggest that full HRV analysis might be helpful for improving risk stratification for life-threatening ventricular arrhythmias and ICD indication in patients with DCM.

Inspiratory muscle weakness is associated with autonomic cardiovascular dysfunction in patients with type 2 diabetes mellitus

Diabetic autonomic neuropathy is a complication of diabetes mellitus (DM) that can cause cardiovascular and respiratory abnormalities. The association between respiratory muscle weakness and autonomic cardiovascular neuropathy has not yet been studied. The aims of the present study were to assess respiratory muscle strength, pulmonary function, and heart rate (HR) variability in diabetic patients with and without diabetic autonomic neuropathy. Twenty-four patients with type 2 DM were divided into two groups: those without diabetic autonomic neuropathy (C group, n=12); and those with diabetic autonomic neuropathy (DAN group, n=12). We evaluated pulmonary function, maximum static inspiratory pressure (PImax), maximum static expiratory pressure (PEmax), and HR variability. The results of the pulmonary function tests were similar in both the groups. PImax was lower in the DAN group (80±24 vs. 102±24cmH(2)O, p=0.03), but PEmax was similar in both the groups. RR intervals (878±122 vs. 743±88ms; p<0.01), standard deviation of RR intervals (28±11 vs. 14±4ms; p<0.01) and squared root of the sum of successive differences of squared RR intervals (15±6 vs. 8±5ms; p<0.01) were higher in the C group. In the DAN group, resting HR was higher (82±10 vs. 69±9bpm; p=0.01) than in the C group. There was a positive correlation between PImax and RR intervals (r=0.452, p=0.02) and a negative correlation between PImax and resting HR (r=-0.482, p=0.01), and PImax and DM duration (r=-0.463, p=0.02). Patients with type 2 DM and autonomic neuropathy showed reduced respiratory muscle strength and less HR variability. Respiratory muscle weakness may be associated with autonomic dysfunction in these patients.

Vagal modulation of heart rate variability during atrial fibrillation in pigs

Atrial fibrillation (AF) is the most common sustained cardiac dysrhythmia and is associated with an increased risk for sudden cardiac death. The ventricular rhythm is irregular and displays both non-linear and linear patterns; however, it has not been determined whether vagally derived patterns are manifest within the irregular rhythm. Moreover, indices of increased vagal control are associated with reduced risk of sudden cardiac death. In this study, we sought to determine whether the ventricular rhythm pattern during AF is, in part, modulated by vagal activity. Vagal oscillations were forced at 0.15 Hz by neck suction in 12 pigs with sustained AF with and without glycopyrrolate (0.15 microg/kg, intravenously) vagal blockade. Vagal activity was evaluated using time- and frequency-domain heart rate variability measures. The standard deviation of RR intervals (SDRRI) was significantly increased during vagal activation compared with baseline (P = 0.006). Moreover, SDRRI correlated significantly with spectral power at 0.15 Hz during baseline (r = 0.90, P < .001) and vagal activation (r = 0.86, P < 0.05). Glycopyrrolate blocked the increase in SDRRI (P < 0.001) and blunted spectral power at 0.15 Hz (P < 0.05). These results indicate that: (1) power spectral analysis may be used to assess parasympathetic regulation during AF, and (2) vagal oscillations produce an entrainment of the ventricular rhythm during AF in pigs.

The effect of ice water ingestion on autonomic modulation in healthy subjects

Drinking ice water is a common daily activity. The safety of ice water ingestion has been questioned due to its possible deleterious effect on heart rate or cardiac rhythm, especially in patients with acute myocardial infarction. Thus, we investigated the heart rate variability (HRV) before and after ice water ingestion in normal subjects to delineate the possible effect of ice water ingestion on autonomic nervous modulation. Subjects were volunteers who came to the hospital to receive routine health examination. They were randomly assigned to drinking 250ml of ice water or room temperature water. Twenty-eight subjects in the room temperature water ingestion group and 25 subjects in the ice water ingestion group were studied. The relationships between the change in HRV measures before and after water ingestion and clinical parameters were assessed by correlation analysis. After ice water ingestion, the percentage change in mean RR intervals (RRIs) (4±4 vs. -1±4, P<0.001), standard deviation of RRIs (19±35 vs. 0±21, P=0.018), high-frequency power (64±90 vs. -3±41, P<0.001), and normalized high-frequency power (39±99 vs. -5±31, P=0.038) were higher, while the percentage change in low-/high-frequency power ratio (3±92 vs. 44±97, P=0.017) was lower, when compared with those after the room temperature water ingestion. Ice water ingestion can decrease heart rate through temperature stimulus-mediated vagal enhancement in healthy subjects.

Left Atrial Ablation at the Anatomic Areas of Ganglionated Plexi for Paroxysmal Atrial Fibrillation

Modification of left atrial ganglionated plexi (GP) is a promising technique for the treatment of paroxysmal atrial fibrillation (AF) but its therapeutic efficacy is not established. This study aimed at evaluating the effectiveness of anatomic GP modification by means of an implantable arrhythmia monitoring device. In 56 patients with paroxysmal AF, radiofrequency ablation at anatomic sites, where the main clusters of GP have been identified in the left atrium, was performed. In all patients, an electrocardiogram monitor (Reveal XT, Medtronic Inc., Minneapolis, MN, USA) was implanted before (n = 7) or immediately after (n = 49) AF ablation. Average duration of the procedure was 142 ± 18 min and average fluoroscopy time 20 ± 7 min. In total, 53-81 applications of RF energy were delivered (mean of 18.2 ± 3.8 at each of the four areas of GP ablation). Heart rate variability was assessed in 31 patients. Standard deviation of RR intervals over the entire analyzed period, the root mean square of differences between successive RR intervals, and high frequencies decreased, while HRmin, HRmean, and LF to HF ratio increased immediately postablation; these values returned to baseline 6 months after the procedure. At end of 12-month follow-up, 40 (71%) patients were free of arrhythmia recurrence. Ten patients had AF recurrence, two patients had left atrial flutter, and four patients had episodes of flutter as well as AF recurrence. Duration of episodes of AF after ablation gradually decreased over the follow-up period. Regional ablation at the anatomic sites of the left atrial GP can be safely performed and enables maintenance of sinus rhythm in 71% of patients with paroxysmal AF for a 12-month period.

The Role of the Selective Serotonin Re-Uptake Inhibitor Sertraline in Nondepressive Patients with Chronic Ischemic Heart Failure: A Preliminary Study

Selective serotonin re-uptake inhibitors (SSRIs) have been associated with better psychiatric status, functional capacity, and fewer arrhythmias in depressive patients with heart failure (HF). In this study, we tested the impact of sertraline (an SSRI) on patients with HF, but not clinical depression. We studied 62 clinically stable, nondepressive patients with ischemic HF (New York Heart Association class: I-II), and implantable cardioverter-defibrillator (ICD). Following psychiatric evaluation and quality of life (QoL) assessment, 24-hour electrocardiogram recordings including heart rate variability (HRV) and ICD interrogation were performed every 4 months for 1 year. Ventricular effective refractory period (ERP) at 600-, 500-, and 400-ms cycle length and the inducibility of ventricular tachycardia (VT) were assessed via the ICD. After that, sertraline 50 mg/day was administered for 12 months and the whole evaluation was repeated. Sertraline was associated with fewer ventricular extrasystoles per 24 hours and a significant change in HRV (increase in mean R-R, 5-minute standard deviation of RR intervals, and root mean-square difference of successive RR intervals, and reduction in ultra and very low frequency). It was also followed by an improvement in patients' QoL. A trend toward a decrease was observed in the number of recalled nonsustained VTs. The episodes of sustained VT were not significantly reduced. Ventricular ERPs and VT inducibility remained unaltered. In clinically stable, nondepressive patients with ischemic HF and ICD, sertraline is associated with reduced ventricular extrasystoles, better QoL, and a possible improvement in some HRV indexes. This suggests that SSRIs may have a favorable clinical impact on these patients, independent of the improvement in depressive symptoms.

Depression, heart rate variability, and exercise training in dialysis patients

Functional limitations, altered cardiac autonomic activity, and psychological distress are known disorders in chronic hemodialysis (HD) patients, relating to increased morbidity and mortality. The aim of this study was to examine the influence of an exercise training program on emotional parameters and heart rate variability (HRV) indices, as well as to determine whether emotional stress contributes to autonomic dysfunction in these patients. Forty-four HD patients were randomly assigned into group A (24 patients, aged 46.3+/-11.2 years), who participated in a 1-year intradialytic exercise training program and group B (20 patients, aged 45.8+/-10.8 years), who were used as controls. At baseline and a year after, measures of HRV were obtained for the estimation of standard deviation of RR intervals, the mean square successive differences, percentage of RR intervals differing by more than 50 ms from the preceding RR interval (pNN50), and low to high frequency components. Emotional parameters (Beck Depression Inventory - BDI and Hospital Anxiety and Depression Scale - HADS) were also assessed by validated questionnaires. Moreover, all patients performed a spiroergometric study for the estimation of VO2peak. At baseline, all measurements were similar in the two groups and remained almost unchanged after a year in group B. After a year of training, VO2peak increased from 16.79+/-5.24 to 22.33+/-4.90 ml/kg per min (P<0.001) in group A. Trained patients also showed an increase in standard deviation of RR intervals by 58.8% (P<0.001), the mean square successive differences by 68.1% (P<0.001), pNN50 by 23.5% (P<0.001), and a low to high frequency ratio by 17.3% (P<0.001). Finally, at the end of the study, group A showed a decrease in BDI score by 34.5% (P<0.001) and HADS by 23.9% (P<0.001). Canonical correlation revealed significant inverse correlation among depression (in BDI and HADS) and HRV indices before and after exercise training. Cardiac autonomic modulation seemed to be sensitive to the experience of persistent depression in HD patients. Significantly, exercise training reduced emotional distress and concomitantly improved HRV.

Cardiac data increase association between self-report and both expert ratings of task load and task performance in flight simulator tasks: An exploratory study

Seven professional airplane pilots participated in a one-session test in a Boeing 737-800 simulator. Mental workload for 18 flight tasks was rated by experienced test pilots (hereinafter called “expert ratings”) and by study participants' self-report on NASA's Task Load Index (TLX) scale. Pilot performance was rated by a check pilot. The standard deviation of R–R intervals (SDNN) significantly added 3.7% improvement over the TLX in distinguishing high from moderate-load tasks and 2.3% improvement in distinguishing high from combined moderate and low-load tasks. Minimum RRI in the task significantly discriminated high- from medium- and low-load tasks, but did not add significant predictive variance to the TLX. The low-frequency/high-frequency (LF:HF) RRI ratio based on spectral analysis of R–R intervals, and ventricular relaxation time were each negatively related to pilot performance ratings independently of TLX values, while minimum and average RRI were positively related, showing added contribution of these cardiac measures for predicting performance. Cardiac results were not affected by controlling either for respiration rate or motor activity assessed by accelerometry. The results suggest that cardiac assessment can be a useful addition to self-report measures for determining flight task mental workload and risk for performance decrements. Replication on a larger sample is needed to confirm and extend the results.

Impact of Acute Respiratory Stress on Cardiac Autonomic Control in Young Healthy Subjects Explored by Time and Frequency Domain Methods

To find the possible utility of analysis of heart rate variability in quantifying transient cardiac autonomic modulation, we assessed the impact of breath holding-induced acute respiratory stress on heart rate variability parameters and blood pressure in young healthy subjects. In ten healthy subjects aged between 22-24 years of either sex, R-R intervals and blood pressure were recorded for one minute under resting state, during breath holding and immediately after withdrawal from breath holding. Heart rate variability was quantified by time and frequency domain methods. Mean differences in values were compared separately between resting and during breath holding, during and following withdrawal from breath holding; resting and following withdrawal from breath holding employing paired 't' test. Blood pressure and standard deviation of R-R intervals (SDNN) significantly increased during breath holding and decreased following withdrawal from it. Low frequency power in normalized units (LF nu) significantly decreased, while the high frequency power in normalized units (HF nu) significantly increased with a resulting decrease of the LF/HF ratio following withdrawal from breath holding compared to during breath holding. During the recovery phase only the LF% power significantly decreased as compared with the resting state. Thus, blood pressure and SDNN appeared to better quantify the ability of the heart to meet changing situational demands. LF nu and HF nu or LF/HF ratio reflected the behavior of sympathetic and parasympathetic limbs in adapting to changing situational demand.

Incongruous Changes in Heart Period and Heart Rate Variability with Vagotonic Atropine: Implications for Rehabilitation Medicine

To describe the relationship between vagally mediated bradycardia and heart rate variability indices in young and older healthy individuals. Cross-sectional, physiologic study. Outpatient cardiovascular research laboratory. A total of 34 young (mean age 24 years) and 27 older (mean age 63 years) healthy adults. Eight bolus injections of atropine sulfate were given intravenously to participants while in a supine position (cumulative doses from 0.4 to 7.2 microg/kg). Each dose was followed by a 3-minute data collection period in which subjects controlled their breathing frequency at a rate of 15 breaths per minute. Chronotropic responses were assessed from average RR interval and blood pressure was assessed by automated brachial cuff. Heart rate variability (HRV) indices were calculated to represent both time domain measures (RR interval standard deviation and root mean squared of successive differences) and frequency domain measures (respiratory sinus arrhythmia and total power). RR interval responses exhibited the expected curvilinear pattern to atropine administration with all subjects exhibiting a bradycardia with at least one dose and RR interval returning to baseline or decreasing in most subjects as atropine dosing progressed. RR interval was closely related to vagotonic atropine dose with an r(2) greater than 0.70 in 89% of subjects. Heart rate variability indices were not consistently correlated with the bradycardic effect of vagotonic atropine and ranged from highly positive to highly negative with almost one-fifth of correlations less than 0.5. The relationship between HRV and vagal tone is likely complex and has a large interindividual variation.