24-h Heart Rate Variability Research Articles

Soluble urokinase plasminogen activator receptor, C‐reactive protein and triglyceride are associated with heart rate variability in non‐diabetic Danes

Heart rate variability (HRV) is associated with an increased risk of cardiovascular morbidity and mortality. HRV is in part a function of the activity of the autonomic nervous system and has been associated with low-grade inflammation. In patients with type 2 diabetes, HRV is decreased and is a predictor of poor outcome. As HRV and its determinants in non-diabetic individuals have not been studied properly, the aim of this observational study was to evaluate possible associations between HRV vs. impaired fasting glucose, insulin resistance, lipidaemia and markers of inflammation and immune activation in these individuals. Healthy individuals (n = 596, 55-75 years) from the community were evaluated with ambulant 48-h continuous electrocardiogram monitoring and fasting markers of lipidaemia, inflammation and immune activation, respectively. Insulin resistance was estimated by HOMA-IR. Time domain components of HRV were calculated. Heart rate and HRV were not associated with glucose metabolic parameters but were inversely associated with soluble urokinase plasminogen activator receptor (suPAR), high-sensitive CRP and leucocyte number (P < 0·001), respectively. Both 24-h and night-time HRV were inversely associated with plasma triglyceride, whereas HDL, LDL and total cholesterol were not. A model including suPAR, CRP, gender, triglyceride, age, systolic blood pressure, physical activity and smoking status explained 12·2% (P < 0·0001) of the 24-h HRV and 7·3% (P < 0·0001) of the night-time HRV. The single strongest factor to explain 24-h and night-time HRV appeared to be suPAR (P = 0·001 and P = 0·0067, respectively). A low HRV is not related to prediabetes, that is, insulin resistance and impaired fasting glucose, but is related to the immune and inflammatory markers suPAR and CRP and plasma triglyceride.

Autonomic nervous system balance in children and adolescents with craniopharyngioma and hypothalamic obesity

Dysregulation of the autonomic nervous system is thought to be involved in craniopharyngioma-related hypothalamic obesity (CRHO). Increased parasympathetic activity and decreased sympathetic activity have been suggested. We aimed to study autonomic activity using heart rate variability (HRV) and biochemical measures in youth with CRHO compared with controls and to explore relationships between obesity and autonomic indices. A cross-sectional study of 16 youth with CRHO and 16 controls matched for sex, age, and BMI. Anthropometrics, fasting blood-work, resting energy expenditure (REE), 24-h HRV, and 24-h urine catecholamines were assessed. Quality of life, sleepiness, and autonomic symptoms were evaluated. Power spectral analysis of the HRV was performed. HRV power spectral analysis parameters of both parasympathetic activity (mean high frequency (HF (ms(2))) 611±504 vs 459±336, P=0.325) and sympathetic activity (median low frequency/HF 1.62 (1.37, 2.41) vs 1.89 (1.44, 2.99), P=0.650) did not differ between the groups. Parasympathetic activity negatively correlated with central adiposity in both groups (r=-0.53, P=0.034 and r=-0.54, P=0.029) and sympathetic activity positively correlated with central adiposity in CRHO (r=0.51, P=0.043). Youth with CRHO had significantly lower REE; lower health and activity scores in the quality of life questionnaires, and higher sleepiness scores. Autonomic activity was similar in CRHO and control subjects. The degree of central adiposity correlated negatively with parasympathetic activity and positively with sympathetic activity in children with CRHO. These results provide a new perspective regarding autonomic balance in this unique patient population.

Effect of weight loss on sympatho-vagal balance in subjects with grade-3 obesity: restrictive surgery versus hypocaloric diet

Few and mostly uncontrolled studies indicate that weight loss improves heart rate variability (HRV) in grade-3 obesity. The aim of this study was to compare in grade-3 obesity surgery and hypocaloric diet on clinical and metabolic variables and on autonomic indices of HRV. Twenty-four subjects (body mass index, BMI 45.5 ± 9.13 kg/m(2)) underwent surgery (n = 12, gastric banding, LAGB) or received hypocaloric diet (n = 12, 1,000-1,200 kg/day). Clinical [BMI, systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate] and metabolic variables [glucose, cholesterol, HDL- and LDL-cholesterol, triglycerides, AST and ALT transaminases] and 24-h Holter electrocardiographic-derived HRV parameters [R-R interval, standard deviation of R-R intervals (SDNN); low/high-frequency (LF/HF) ratio, and QT interval] were measured at baseline and after 6 months. The two groups were identical at baseline. BMI (-7.5 ± 3.57 kg/m(2), mean ± SD), glucose (-24.1 ± 26.77 mg/dL), SBP (-16.7 ± 22.19 mmHg) and DBP (-6.2 ± 8.56 mmHg) decreased in LAGB subjects (p < 0.05) and remained unchanged in controls. At 6 months, SDNN increased in LAGB subjects (+25.0 ± 37.19 ms, p < 0.05) and LF/HF ratio diminished (2.9 ± 1.84 vs. 4.9 ± 2.78; p = 0.01), with no change in controls; LF (daytime) and HF (24 h and daytime) increased in LAGB subjects, with no change in controls. Decrease in BMI correlated with SBP and DBP decrease (p < 0.05), and DBP decrease correlated with HR decrease (p < 0.05) and QT shortening (p < 0.05). Weight loss is associated with improvement of glucose metabolism, of blood pressure, and with changes in time and frequency domain parameters of HRV; all these changes indicate recovery of a more physiological autonomic control, with increase in parasympathetic and reduction in sympathetic indices of HRV.

Reduced capacity of heart rate regulation in response to mild hypoglycemia induced by glibenclamide and physical exercise in type 2 diabetes

ObjectiveDecreased heart rate variability (HRV) is associated with enhanced mortality due to abnormal cardiac rhythm. While hypoglycemic events are increasingly common in the treatment of type 2 diabetes, HRV is part of the counter-regulation against low blood glucose levels. We hypothesized that HRV was impaired in mild hypoglycemia in diabetic individuals. Materials/MethodsHyperinsulinemic–hypoglycemic clamps were performed in twelve type 2 diabetic patients without cardiovascular disease and in non-diabetic subjects matched for age, sex, and weight. In an additional study, hypoglycemic events, induced by either a single morning dose of glibenclamide or physical exercise, were recorded for the subsequent 24h. Blood glucose concentrations and electrocardiograms were continuously monitored. Serum hormone levels, hypoglycemic symptoms, and forearm blood flow were measured at defined time points. ResultsOccurrence of a symptomatic hypoglycemic episode (mean blood glucose 3.1±0.4mmol/l) attenuated most of the time and frequency domain measurements in both healthy and diabetic individuals. The magnitude of reduction of HRV parameters was significantly lower in diabetic compared to healthy subjects. Glibenclamide taken in the morning enhanced the daily number of mild hypoglycemic events compared with placebo or moderate exercise. Concordantly, 24-h mean HRV measurements were decreased. ConclusionHRV response to hypoglycemia is impaired in type 2 diabetic subjects resulting in a higher than expected risk for sudden arrhythmia following mild hypoglycemic episodes.

Detecting Congestive Heart Rate Variability Failure Using Pointcaré Trend Analysis Plot

The function of heart rate variability (HRV) has been studied over the years, but less is known about the factors predicting recovery from work stress during sleep. The availability to register reliable data for short-time HRV has raised the interest to find the congestive HRV signal. The objective of this study was to identify individual-level factors related to work and leisure-time predicting the recovery of autonomic nervous system (ANS) during congestion measured by 24-h HRV. 15 subjects (11 men, aged 22 to 71, and 4 women, aged 54 to 63) with severe congestive heart failure (NYHA class 3-4). This group of subjects was part of a larger study group receiving conventional medical therapy prior to receiving the oral inotropic agent, milrinone. Questionnaire data was gathered with a self-administered questionnaire of individual characteristics, perceived work ability, stress and psychological resources. The individual recordings are each about 20 hours in duration, and contain two ECG signals each sampled at 250 samples per second with 12-bit resolution over a range of ±10 millivolts. In this study, we only calculate first 15 minus of each subject.

Relationship of Blood Pressure Variability and Heart Rate with Plasma hsCRP in Patients with Recently Diagnosed Hypertension

ëª©ì : 혈압의 변동성과 심장박동수는 í‘œì  장기 손상과 심장 혈관 합병증과 ê´€ë ¨ì´ 있다. 하지만 ê·¸ ì •í™•í•œ ê¸°ì „ì€ ë°í˜€ì ¸ 있지 않다. 이에 ì €ìžë“¤ì€ 혈압의 변동성 및 심장박동수와 염증 인자가 관계가 있는지 í™•ì¸í•˜ê³ ìž 본 연구를 시행하였다. 방법: 최근 진단되거나 새로이 진단된 151ëª ì˜ ê³ í˜ˆì•• 환자의 24시간 활동성 혈압을 분석하였다. 혈압의 변동성은 ì¸¡ì •ëœ 혈압의 표준편차로 표시하였다. 24시간 활동성 혈압 검사 중 동시에 ì¸¡ì •ëœ í‰ê· ì‹¬ìž¥ë°•ë™ìˆ˜ 및 표준편차를 ì¸¡ì •í•˜ì˜€ë‹¤. 혈중 high-sensitivity C-reactive protein (hsCRP)를 염증 인자로 사용하였다. ê²°ê³¼: 대상 환자의 í‰ê· ë‚˜ì´ëŠ” 44 ± 11.3세로 이 중 남자는 74.2%이었다. hsCRP는 남자 환자(0.131 ± 0.014 vs. 0.06 ± 0.023, p= 0.001) 및 í¡ì—°ë ¥ì´ 있는 환자(0.136 ± 0.017 vs. 0.101 ± 0.017, p= 0.003)에서 높게 나타났다. 상관 분석에서 24시간 동안의 이완기 혈압의 변동성은 hsCRP와 양의 상관관계를 보였다(p= 0.002, r = 0.258). 또한 24시간 동안(p= 0.004, r = 0.236), 활동시간 동안(p= 0.003, r = 0.239), 수면시간 동안의 (p= 0.020, r = 0.190) í‰ê· ì‹¬ìž¥ë°•ë™ìˆ˜ ê·¸ë¦¬ê³ 24시간 동안의 심장박동수의 변동성은(p= 0.025, r = 0.182) hsCRP와 양의 상관관계를 보였다. ë‹¤ì¤‘ì„ í˜•íšŒê·€ë¶„ì„ì—ì„œ 24시간 동안의 이완기 혈압의 변동성과(β = 0.286, p= 0.011) 활동시간 동안의 í‰ê· ì‹¬ìž¥ë°•ë™ìˆ˜ê°€(β = 0.169, p= 0.049) hsCRP와 ìœ ì˜í•œ 관계가 있었다. ê²°ë¡ : 24시간 활동성 혈압을 통하여 ì¸¡ì •ëœ 이완기 혈압의 변동성 및 심장박동수는 염증 인자인 hsCRP와 연관성이 있었다. 혈압의 변동성과 심장박동수는 염증반응과 연관하여 심장혈관 합병증에 영향을 주는 것으로 생각한다. 중심 단어: 혈압의 변동성; 심장박동수; C 반응단백; ê³ í˜ˆì••

Depressive symptoms and autonomic nervous system dysfunction in an elderly population-based study: The PROOF study

To assess the relationship between depressive symptoms, evaluated through self-reported history as well as current depressive symptoms, and impaired autonomic nervous system activity, evaluated by long-term heart rate variability and baroreflex sensitivity among elderly community residents, aged 65 years. Subjects from the Proof cohort Study were evaluated for depressive symptoms and self-reported history of depression at inclusion. Autonomic nervous system activity was assessed through 24-h heart rate variability and baroreflex sensitivity. Cross-sectional analyses were performed to study the relationship between the different status of depression and autonomic nervous system activity. Among the 1011 Proof study participants, 823 subjects were included in the analyses. Current depressive symptoms were present among 67 subjects; history of depression was reported by 228 subjects. Psychoactive drugs were used by 59 subjects. Low frequency (p=0.02), very low frequency (p<0.01) and Low/High frequency ratio (p<0.001) were lower among subjects with depressive symptoms and history of depression, independently of antidepressant treatment. The association remained significant for Low/High frequency ratio after adjustment for gender and physical activity (p=0.004). Current depressive symptoms may be linked to autonomic nervous system lower performances. A possible long-term effect of depressive symptoms at middle-age may influence later-life autonomic nervous system activity. Our results highlight the importance of taking into account the depressive symptoms in the cardiovascular risk, even in the elderly.

Caloric restriction may reverse age‐related autonomic decline in humans

Caloric restriction (CR) retards aging in laboratory rodents. No information is available on the effects of long-term CR on physiologic markers of aging and longevity in humans. Heart rate variability (HRV) is a marker for cardiac autonomic functioning. The progressive decline in HRV with aging and the association of higher HRV with better health outcomes are well established. Heart rate variability assessment is a reliable tool by which the effects of CR on autonomic function can be assessed. Time- and frequency-domain analyses compared 24-h HRV in 22 CR individuals aged 35-82 years and 20 age-matched controls eating Western diets (WD). The CR group was significantly leaner than the WD group. Heart rate was significantly lower, and virtually, all HRV values were significantly higher in the CR group than in the WD group (P < 0.002). Heart rate variability in the CR individuals was comparable with published norms for healthy individuals 20 years younger. In addition, when differences in heart rate (HR) and HRV between CR and WD were compared with previously published changes in HRV induced in healthy adults given atenolol, percent differences in each measure were generally similar in direction and magnitude and suggested declines in sympathetic and increases in parasympathetic modulation of HR and increased circadian variability associated with CR. These findings provide evidence that CR has direct systemic effects that counter the expected age-associated changes in autonomic function so that HRV indexes in CR individuals are similar to those of individuals 20 years younger eating WDs.

Simple function tests for autonomic neuropathy have a higher predictive value on all-cause mortality in diabetes compared to 24-h heart rate variability

AimTo compare the long-term predictive power of heart rate variability (HRV) based on 24 h ECG recordings with a battery of simple autonomic function tests with regard to all-cause mortality in diabetic individuals. Methods240 diabetic persons were randomly selected from the diabetic population. A 24-h ECG was obtained and analysed on the Pathfinder 700. In the RR Tools Program time domain and frequency domain parameters were computed. Five function tests were conducted: Valsalva ratio, heart rate response to standing (30:15 ratio), expiration/inspiration ratio (E/I ratio), orthostatic blood pressure response (Ortho BP), and increase in diastolic blood pressure during sustained handgrip. Results178 patients agreed to participate and 136 patients who completed all 5 function tests and had an acceptable ECG recording were included in the analyses. 64 individuals (47%) died during the 15½ year follow-up. Using Cox proportional hazard analyses correcting for age and gender we found that among the HRV parameters only the power in the low frequency band (LF) had an independent predictive value on all-cause mortality (p=0.0002). Multivariate analysis of the five function tests showed that Valsalva (p=0.002), 30:15 ratio (p=0.037), and handgrip (p=0.037) were independent predictors of death. When finally the independent predictors among the function tests and the HRV parameters were assessed in the same model, no significant value could be shown for LF power (p=0.44). ConclusionThe study indicates that simple autonomic function tests are superior to HRV based on 24-h ECG recordings in predicting all-cause mortality in the diabetic population.

Hypertensive response to exercise: a marker of altered metabolism in endurance athletes?

BackgroundInappropriate high blood pressure response to exercise in non athletes is known to be a predictor for future resting systemic hypertension. However, the relevance of exercise hypertension in endurance athletes...

Abnormal heart rate regulation in murine hearts with familial hypertrophic cardiomyopathy-related cardiac troponin T mutations

Mutations in cardiac troponin T (cTnT), Δ160E and R92Q, have been linked to familial hypertrophic cardiomyopathy (FHC), and some studies have indicated that these mutations can lead to a high incidence of sudden cardiac death in the relative absence of significant ventricular hypertrophy. Alterations in autonomic function have been documented in patients with hypertrophic cardiomyopathy. We hypothesize that alterations in autonomic function may contribute to mutation-specific clinical phenotypes in cTnT-related FHC. Heart rate (HR) variability (HRV) has been used to assess autonomic function from an electrocardiograph. Nontransgenic, Δ160E, or R92Q mice were implanted with radiofrequency transmitters to obtain continuous electrocardiograph recordings during 24-h baseline and 30-min recordings after β-adrenergic receptor drug injections. Although Δ160E mice did not differ from nontransgenic mice for any 24-h HRV measurements, R92Q mice had impaired HR regulation, as measured by a decrease in the SD of the R-R interval, a decrease in the low frequency-to-high frequency ratio, a decrease in normalized low frequency, and an increase in normalized high frequency. β-Adrenergic receptor density measurements and HRV analysis after drug injections did not reveal any significant differences for Δ160E or R92Q mice versus nontransgenic mice. Arrhythmia analysis revealed both an increased incidence of heart block in R92Q mice at baseline and frequency of premature ventricular contractions after isoproterenol injections in Δ160E and R92Q mice. In addition, Δ160E and R92Q mice exhibited a prolonged P duration after drug injections. Therefore, between two independent and clinically severe cTnT mutations within the same functional domain, only R92Q mice exhibited altered autonomic function, whereas both mutations demonstrated abnormalities in conduction and ventricular ectopy.

Modulation of peripheral chemoreflex by neurohumoral adaptations after kidney transplantation

BackgroundPeripheral chemoreceptors residing predominantly in the carotid body monitor changes in arterial blood oxygen and are mechanistically linked to the cardiorespiratory control by the autonomic nervous system. Enhanced sympathetic activation is common in end-stage renal disease and kidney transplantation has been shown to improve cardiorespiratory reflex measures of autonomic function.ObjectiveThe aim of the present study was to test whether improvement in renal function following kidney transplantation is related to an improvement in chemosensory function.Methods and ResultsWe compared hyperoxic chemoreflex sensitivity (CHRS) in patients after renal transplantation (RTX) to that in patients on maintenance hemodialysis (HD), and that of age- and gender-matched healthy controls. In addition, we investigated the impact of common confounding factors including pharmacological neurohumoral modulation and diabetes mellitus. The difference in the R-R intervals divided by the difference in the oxygen pressures before and after deactivation of the chemoreceptors by 5-min inhalation of 7 L oxygen was calculated as the hyperoxic CHRS. Autonomic activity was characterized by 24-h time-domain heart rate variability (HRV) parameters. CHRS was improved in RTX patients as compared to HD patients being related to HRV. CHRS was related to the concomitant presence of diabetes and medication with cyclosporine.ConclusionOur findings indicate that chemosensory activity following kidney transplantation is related to cardiac autonomic control, but functional testing might only be useful to characterize the time course and extent of sympathetic activation in selected patients due to existing co-morbidities and immunosuppressive medication in this population.

Metabolic Syndrome and Short-Term and Long-Term Heart Rate Variability in Elderly Free of Clinical Cardiovascular Disease: The PROOF Study

Autonomic nervous system (ANS) activity decrease has been associated with a higher risk of sudden cardiovascular and cerebrovascular disease. Thus, we explored the relationship between ANS control of the cardiovascular system and metabolic syndrome. We analyzed the relationship with both short-term and long-term heart rate variability (HRV) and metabolic syndrome in the cross-sectional PROgnostic indicator OF cardiovascular and cerebrovascular events (PROOF) cohort study of 1,011 elderly subjects recruited amongst the inhabitants of the city of Saint Etienne, France, aged 65.6 ± 0.8 years at the inclusion date. Physical examination included measurements of height, weight, systolic and diastolic blood pressure, waist circumference, and biological parameters. HRV variables were measured over 5-min, nighttime, and 24-h periods using Holter monitoring. After adjustment for current type 2 diabetes, depression, and smoking, we found that metabolic syndrome status, high-density lipoprotein cholesterol (HDL-C), and waist circumference were significantly (p < 0.05) associated with total power, very-low frequency, low-frequency/high-frequency (LF/HF) ratio, and normalized LF. HDL-C and metabolic syndrome status were significantly associated with decreased long-term HRV variables. Both nighttime and 24-h HRV showed closer associations with metabolic syndrome than did short-term HRV (5-min). Metabolic syndrome severity was associated with a decrease in both the long-term and short-term HRV variables. ANS control alteration of the cardiovascular system was more pronounced when evaluated by long-term than short-term HRV recordings, particularly in women.

Autonomic nervous system activity is independently associated with the risk of shift in the non-dipper blood pressure pattern

An insufficient decrease in nocturnal blood pressure (BP) is a known factor in cardiovascular mortality. We aimed to determine whether autonomic nervous system (ANS) activity and its change over 2 years were associated with a shift to non-dipper status, independently of initial BP, in a general elderly population. From participants in the PROOF study, 600 subjects untreated for hypertension were selected (age at baseline: 65 years, men: 41.5%). Dipper/non-dipper status was defined using repeated measures of 24-h ambulatory BP at baseline and 2 years later. ANS activity was evaluated on the basis of 24-h heart rate variability at both examinations. Among the 454 dipper subjects at baseline, 26.2% became non-dippers. Multivariate analysis showed that a +1 between-subject s.d. increase in the very low frequency at baseline was associated with a decreased odds ratio for the shift to non-dipper status 2 years later (OR=0.61 [0.41-0.91], P=0.02). The within-subject change between the two measurements of day and night systolic BP and day diastolic BP also contributed significantly to the risk of shift to non-dipper status. Our results suggest that impaired ANS activity precedes an insufficient decrease in nocturnal BP independent of hypertension status.

051 Reducing particulate air pollution exposure in patients with coronary heart disease: improved cardiovascular health

Introduction Particulate air pollution is a major public health concern and is associated with cardiovascular disease. In healthy volunteers, reducing particulate air pollution exposure attenuates exercise-induced increases in blood pressure and improves heart rate variability. In this study, we investigated the benefit of reducing exposure in patients with coronary heart disease. Methods In an open-label randomised crossover trial, 98 patients with coronary heart disease walked on a predefined city centre route in Beijing in the presence and absence of a highly efficient facemask. Personal exposure to air pollution and exercise was assessed continuously using portable monitors and GPS tracking respectively. Blood pressure was measured using ambulatory blood pressure monitoring. Continuous 12-lead electrocardiography was carried out using a Holter monitor. Subjects9 symptoms were assessed using a simple questionnaire. Results The mask intervention was well tolerated and reduced general symptoms, perceived effort of work and perception of pollution (p 3 ; PM 2.5 ) and particle number (4.19±1.29 vs 4.39±1.45×10 4 particles/cm 3 ) were slightly lower during the mask visit, but based on efficacy studies, we predict the mask reduced the exposure further to 2 μg/m 3 and 1200 particles/cm 3 respectively. During the 2-h walk, exercise performed was identical on both visits. When subjects wore a facemask, mean arterial pressure was lower (93±10 vs 96±10 mm Hg; p=0.025) and heart rate was similar (p>0.05). During the 2-h walk, heart rate variability was increased (HF-power 54 (27 to 108) vs 40 (20 to 69) ms 2 , p=0.005; HF/LF ratio 0.418 (0.258 to 0.712) vs 0.328 (0.207 to 0.573), p=0.004; RMSSD 16.7 (13.2 to 22.5) vs 14.8 (10.9 to 19.6) ms, p=0.007) when a facemask was worn. There were no differences in overall 24-h blood pressure, heart rate or heart rate variability. Maximal ST segment depression throughout the 24-h period was reduced when subjects wore a mask (−142 (−179 to −110) vs −156 (−202 to −123) μV; p=0.046) although there was no difference in the frequency of ST segment depression (>1 mm) episodes or symptoms of angina. Conclusions In patients with coronary heart disease, wearing a facemask reduces symptoms and is associated with objective improvements in myocardial ischaemia, blood pressure and heart rate variability. This simple well-tolerated intervention has the potential to reduce the incidence of cardiovascular events in patients with coronary heart disease living in industrialised or urban environments.

Parasympathetic but not sympathetic cardiac dysfunction at early stages of Parkinson’s disease

Autonomic cardiovascular dysfunction is common in Parkinson's disease (PD). Imaging studies suggest loss of cardiac sympathetic nerves even in the absence of clinical signs of autonomic dysfunction. Aim of the study was to investigate the functional significance of autonomic cardiovascular denervation at early stages of PD. Seven PD patients (Hoehn and Yahr class 1 or 1.5) without clinical signs of autonomic dysfunction and seven age-matched healthy control subjects were studied. To evaluate the pre- and post-synaptic components of sympathetic innervation, dose-response curves of isoproterenol (no neuronal uptake) and epinephrine (neuronal uptake) on heart rate, contractility, cardiac output and systemic vascular resistance were determined echocardiographically. Additionally, measurements of baroreflex sensitivity and 24-h heart rate variability were done. The chronotropic and inotropic responses during stimulation with isoproterenol and epinephrine were similar in PD patients and control subjects. Assessment of baroreflex sensitivity yielded no difference. Of the parameters of 24-h heart rate variability, only measures of high-frequency heart rate variation that more purely reflect parasympathetic activity were significantly depressed in PD patients as compared with control subjects. The results of our study using direct determination of catecholamine-mediated chronotropic and contractile responses provide evidence against a functionally relevant sympathetic dysfunction. Possibly, sympathetic denervation is incomplete and the remaining fibers are sufficient for the maintenance of autonomic control. In contrast, the depression of several parameters of heart rate variability supports a significant change of parasympathetic activity at an early stage of PD with subclinical autonomic failure.

Predictive value of cardiac autonomic indexes and MIBG washout in ICD recipients with mild to moderate heart failure

We aimed at evaluating the combined use of heart rate variability (HRV), baroreflex sensitivity (BRS), and MIBG imaging in the risk stratification for sudden cardiac death (SCD) of patients with mild to moderate heart failure. Twenty-five patients (17 male and 8 female, mean age 63 +/- 5 years, mean LVEF 36 +/- 3%) with a recently implanted defibrillator (ICD) and mild (NYHA I-II) heart failure due to either ischemic (n = 15) or dilated (n = 10) cardiomyopathy were studied. One week after ICD implantation they underwent (a) baroreflex sensitivity (BRS) evaluation to bolus phenylephrine by the Oxford method, (b) 24-h heart rate variability (HRV) assessment, and (c) MIBG imaging. The mean patient follow-up was 32 +/- 10 months. Simple correlation and stepwise multiple regression analysis was performed to evaluate (a) if the number of sustained ventricular tachycardia (cycle length <330 ms) or fibrillation episodes per month is related to one or more of MIBG, BRS, and HRV indexes and (b) if MIBG % washout is related to HRV and/or BRS. The frequency of fast ventricular arrhythmic episodes (FVAE) demonstrated an inverse relation to BRS (p < 0.0001), rMSSD (p = 0.001), and pNN50 (p = 0.0034), while it was positively related to LF (p < 0.0001) and MIBG % washout (p = 0.001). BRS, LF, rMSSD, and MIBG washout were also independent predictors of FVAE. MIBG washout was related to only one HRV marker (SDNN-I, p < 0.0001), while no correlation was observed with BRS. In ICD recipients with well-compensated heart failure, autonomic markers derived from BRS, HRV, and MIBG studies are related to FVAE. These markers have limited inter-dependency and constitute useful means for SCD risk stratification in this subgroup of patients.

Circadian cardiac autonomic function in perinatally HIV-infected preschool children

The 24-h heart rate variability and QT-interval adaptation was investigated in perinatally HIV-infected preschool children classified according to immunological status in order to assess autonomic function at early stages of infection. Thirty-five perinatally HIV-infected and clinically stable children (4.8 +/- 0.3 years) were enrolled after approval of the study by the University Hospital Pedro Ernesto Ethics Committee and written informed parental consent was obtained. The children were classified according to peripheral CD4+ count (cells/microL) as follows: group 1, N = 11 (>or=1000); group 2, N = 7 (>or=500 and <1000); group 3, N = 17 (<500). Left ventricular ejection fraction (>55%), 24-h RR interval variability (RRV) indexes (NN, SDANN, SDNN index, r-MSSD) and 24-h QT and Bazett-corrected QT (QTc) were determined, and groups were matched for age, body surface area, and left ventricular ejection fraction, reducing biases in RRV. The peak differences () between the highest and lowest RRV and QT indexes were extracted from nocturnal (1 am-6 am) and daytime (1 pm-6 pm) hourly assessed segments, respectively. Pearsons correlation (r) and Kruskal-Wallis ANOVA were used to compare groups. CD4+ count correlated positively with NN (r = 0.45; P = 0.003). There were no significant differences in daytime NN among groups. Nighttime SDNN index (P = 0.01), nighttime r-MSSD (P = 0.003), NN (P = 0.01), SDNN index (P = 0.03) and r-MSSD (P = 0.004) were significantly lower in group 3 than in the other groups. Expected nighttime QTc-interval lengthening was not observed in all groups. In perinatally HIV-infected preschool children with preserved left ventricular systolic function, parasympathetic-mediated autonomic dysfunction parallels immune status, impairing both RRV and circadian QTc interval adaptation.

Assessment of cardiac autonomic nervous activity in frail elderly people with postural abnormalities and in control subjects

Heart rate variability (HRV), which is considered to reflect the activity of the autonomic nervous system (ANS), has been shown to decline with age. The aim of the present study was to explore cardiac ANS in older patients showing frontal-subcortical dysfunction with “Psychomotor Disadaptation Syndrome” (PDS), through the 24-h HRV. We enrolled 14 patients with PDS (mean age: 84.5 ± 6.9 years), they were compared to 13 frail control subjects (mean age: 80.6 ± 6.7 years). Cardiac ANS activity was assessed by 24-h ECG recordings from three leads with a Holter digital monitor. The decrease in cardiac ANS activity observed in PDS subjects was greater than the alteration found in normally aging subjects. The abnormalities of ANS that aggravate the effects of aging can be seen as a type of physical deconditioning. Such patients could benefit from particular attention in physical training.

Outcome of heart rate variability and ventricular late potentials after liver transplantation for familial amyloidotic polyneuropathy

Reduced heart rate variability (HRV) is common in familial amyloidotic polyneuropathy (FAP), as well as cardiac arrhythmias. We examined the effects of liver transplantation (LTx) on 24-h HRV and ventricular late potentials. Twenty-one liver-transplanted FAP patients underwent Holter-ECG recordings and signal average electrocardiography recordings (SAECG) before and after LTx. Mean follow-up time after LTx was 21.7 months. Three patients had marked increased HRV after LTx, but this was in all cases caused by the development of subtle atrial arrhythmia and did not reflect an improvement in the cardiac autonomic control. In total, ten patients were excluded from analysis of HRV because of arrhythmia. Spectral analysis of HRV showed no significant differences before and after LTx in the remaining 11 patients. Positive late potentials were found in 33% of patients before LTx and this proportion was unchanged after LTx. Reduced HRV and positive late potentials are common in Swedish FAP patients, and remain stable, at least within the short term after transplantation. If an increase of HRV after transplantation is observed, it should raise the suspicion that the patient has developed subtle atrial arrhythmia.