Short-term spectral analysis of heart rate variability during supine-standing-supine test in patients with paroxysmal atrial fibrillation

The aim of the study was to assess the sympathovagal balance in group of 27 patients without significant structural heart disease after an attack of atrial fibrillation. The investigation was performed using spectral analysis of heart rate variability during examination under conditions of different orthostatic loads in single phases, called the supine-standing- supine test. The findings were compared with a group of healthy persons. These revealed a significantly decreased total spectral power (430.7 vs 1558.0 ms(2) supine1; 477.6 vs 1042,5 ms(2) standing; 567.5 vs 1948.5 ms(2) supine2), and spectral power of the high frequency spectral component (140.8 vs 619.3 ms(2) supine1; 96.2 vs 203.3 ms(2) standing; 186.3 vs 739.4 ms(2) supine2) in the studied group of patients in comparison with the control group.     

Short-term and long-term blood pressure and heart rate variability in the mouse

Knowledge on murine blood pressure and heart rate control mechanisms is limited. With the use of a tethering system, mean arterial pressure (MAP) and pulse interval (PI) were continuously recorded for periods up to 3 wk in Swiss mice. The day-to-day variation of MAP and PI was stable from 5 days after surgery. Within each mouse (n = 9), MAP and PI varied by 21+/-6 mm Hg and 17+/-4 ms around their respective 24-h averages (97+/-3 mm Hg and 89+/-3 ms). Over 24-h periods, MAP and PI were bimodally distributed and clustered around two preferential states. Short-term variability of MAP and PI was compared between the resting (control) and active states using spectral analysis. In resting conditions, variability of MAP was mainly confined to frequencies <1 Hz, whereas variability of PI was predominantly linked to the respiration cycle (3-6 Hz). In the active state, MAP power increased in the 0.08- to 3-Hz range, whereas PI power fell in the 0.08- to 0.4-Hz range. In both conditions, coherence between MAP and PI was high at 0.4 Hz with MAP leading the PI fluctuations by 0.3-0.4 s, suggesting that reflex coupling between MAP and PI occurred at the same frequency range as in rats. Short-term variability of MAP and PI was studied after intravenous injection of autonomic blockers. Compared with the resting control state, MAP fell and PI increased after ganglionic blockade with hexamethonium. Comparable responses of MAP were obtained with the alpha-blocker prazosin, whereas the beta-blocker metoprolol increased PI similarly. Muscarinic blockade with atropine did not significantly alter steady-state levels of MAP and PI. Both hexamethonium and prazosin decreased MAP variability in the 0.08- to 1-Hz range. In contrast, after hexamethonium and metoprolol, PI variability increased in the 0.4- to 3-Hz range. Atropine had no effect on MAP fluctuations but decreased those of PI in the 0.08- to 1-Hz range. These data indicate that, in mice, blood pressure and its variability are predominantly under sympathetic control, whereas both vagal and sympathetic nerves control PI variability. Blockade of endogenous nitric oxide formation by N(G)-nitro-L-arginine methyl ester increased MAP variability specifically in the 0.08- to 0.4-Hz range, suggesting a role of nitric oxide in buffering blood pressure fluctuations.     

Modified interaction of blood pressure and heart rate in idiopathic dilated cardiomyopathy]

BACKGROUND: Neurovegetative and haemodynamic changes impact on the regulation pattern of blood pressure and heart rate in patients with heart failure. We studied these patterns and their interactions in patients with idiopathic dilated cardiomyopathy (IDC) and in healthy subjects (REF). METHODS: We continually measured the heart rate and blood pressure (Portapres device) in twenty-five supine IDC patients (age: 51 +/- 13 y; left ventricular end-diastolic diameter 67 +/- 11 mm; ejection fraction 30 +/- 11%) and in twenty-seven REF (age: 50 +/- 11 y) Recording time was 30 minutes. The heart rate (HR) of each beat and the systolic blood pressure (SYS) of the subsequent beat were measured. Code numbers (symbols) were assigned to the beat-to-beat changes in HR and SYS (increase: 1; decrease: 0). The frequencies of the symbols sequences of three successive beats were counted. In this way we obtained a matrix consisting of eight (two to the power of three) HR and SYS combinations: 000, 100, 010, 001, 111, 110, 011 and 101. We then counted the frequencies of the different combinations of the symbol sequences in HR and SYS (2(3) x 2(3) = 64 combinations). The relative frequencies of symbol patterns appearing in HR, SYS and in the combined analysis of HR and SYS, were compared for IDC and REF using the T-test for independent samples. RESULTS: Significant differences were seen between IDC and REF. The HR patterns 101 and 010 were more frequent in IDC than in REF patients (11.1 +/- 4.7 vs. 7.7 +/- 2.9%, p = 0.003, and 16.1 +/- 6.3 vs. 11.7 +/- 4.9%, p = 0.008). This finding was even more marked in the analysis of the SYS patterns 101 and 010 (11.0 +/- 7.4 vs. 8.2 +/- 2.9%, p < 0.001, and 11.6 +/- 7.4 vs. 5.4 +/- 2.7%, p < 0.001). Non-alternating patterns were more frequent in REF (e.g. 000HR & 111SYS: 4.6 +/- 3.3 vs. 2.9 +/- 2.4%, p = 0.03). CONCLUSIONS: We demonstrated significant interaction of the regulation patterns of blood pressure and heart rate, as also their interactions in IDC. Opposed changes in HR and SYS mediated by the baroreflex, became superimposed by alternans phenomena in IDC. The pattern analysis of changes in HR and SYS detects these disturbances of neurovegetative short-term control.     

Dimensional analysis of heart rate variability in heart transplant recipients

Periodicities in the heart rate have been known for some time. We discuss these periodicities in normal and transplanted hearts. We then consider the possibility of dimensional analysis of these periodicities in transplanted hearts and problems associated with the record.     

Short-term secondhand smoke exposure decreases heart rate variability and increases arrhythmia susceptibility in mice

Exposure to secondhand smoke (SHS), a major indoor air pollutant, is linked to increased cardiovascular morbidity and mortality, including cardiac arrhythmias. However, the mechanisms underlying the epidemiological findings are not well understood. Impaired cardiac autonomic function, indexed by reduced heart rate variability (HRV), may represent an underlying cause. The present study takes advantage of well-defined short-term SHS exposure (3 days, 6 h/day) on HRV and the susceptibility to arrhythmia in mice. With the use of electrocardiograph telemetry recordings in conscious mice, HRV parameters in the time domain were measured during the night after each day of exposure and 24 h after 3 days of exposure to either SHS or filtered air. The susceptibility to arrhythmia was determined after 3 days of exposure. Exposure to a low concentration of SHS [total suspended particle (TSP), 2.4 +/- 3.2; and nicotine, 0.3 +/- 0.1 mg/m(3)] had no significant effect on HRV parameters. In contrast, the exposure to a higher but still environmentally relevant concentration of SHS (TSP, 30 +/- 1; and nicotine, 5 +/- 1 mg/m(3)) significantly reduced HRV starting after the first day of exposure and continuing 24 h after the last day of exposure. Moreover, the exposed mice showed a significant increase in ventricular arrhythmia susceptibility and atrioventricular block. The data suggest that SHS exposure decreased HRV beyond the exposure period and was associated with an increase in arrhythmia susceptibility. The data provide insights into possible mechanisms underlying documented increases in cardiovascular morbidity and mortality in humans exposed to SHS.     

Age dependency and correlation of heart rate variability,blood pressure variability and baroreflex sensitivity

Simultaneous analysis of heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) with different types of measures may provide non-duplicative information about autonomic cardiovascular regulation. Therefore, a multiple signal analysis of cardiovascular time series will enhance the physiological understanding of neuro cardiovascular regulation with deconditioning in bedrest or related gravitational physiological studies. It has been shown that age is an important determinant of HRV and BRS in healthy subjects. Whereas in the case of BPV, the effect of aging seems to depend upon the activity status of the subjects. In view of the facts that most of the previous works were dealing with only the variability of one kind of cardiovascular parameters in one study with conventional time-domain and/or frequency-domain analysis, we therefore designed the present work to compare the HRV, BPV and BRS between young and middle-aged male healthy subjects in one study with the same subjects using various techniques, including the approximate entropy (ApEn) measurement, a statistic quantifying HRV "complexity" derived from non-linear dynamics.     

Content of myosin-activating protein kinases in myocardium of patients with dilated cardiomyopathy and in the animal heart

The skeletal myosin light chain kinase (skMLCK) was identified in human and chicken embryo myocardium but not in embryo and adult rat heart using western blotting. The content of skMLCK and myosin-activating protein kinases: RhaA-activated protein kinase (ROCK), integrin-linked protein kinase (ILK), and zipper-interacting protein kinase (ZIPK) was compared in normal human myocardium and the hearts of patients with dilated cardiomyopathy (DCM). It was demonstrated that the content of skMLCK, ROCK and ILK increases in DCM whereas the content of ZIPK decreases. The results obtained may reflect compensatory processes in cardiomyocytes in DMC, which are aimed at increasing their viability and contractility.     

Concentrations of myosin-activating protein kinases in the myocardium of patients with dilated cardiomyopathy and in animal heart

Skeletal myosin light chain kinase in the myocardia of various animal species was identified by immunoblotting. The myocardial concentrations of this protein and myosin-activating protein kinases (RhoA-activated kinase, integrin-linked kinase, and zipper-interacting kinase) were compared in healthy humans and patients with dilated cardiomyopathy. Skeletal myosin light chain kinase was detected in the human and chicken embryo hearts, rather than in the embryonic and adult rat hearts. In the myocardium of patients with dilated cardiomyopathy, the concentrations of myosin light chain kinase, RhoA-activated kinase, and integrin-linked kinase increase and the concentration of zipper-interacting kinase decreases. The results obtained are likely to characterize compensatory processes in cardiomyocytes in dilated cardiomyopathy that are aimed at increasing their viability and contractility.     

Spectral analysis of the heart rate variability in sleep

Spectral analysis of heart rate variability (HRV) during overnight polygraphic recording was performed in 11 healthy subjects. The total spectrum power, power of the VLF, LF and HF spectral bands and the mean R-R were evaluated. Compared to Stage 2 and Stage 4 non-REM sleep, the total spectrum power was significantly higher in REM sleep and its value gradually increased in the course of each REM cycle. The value of the VLF component (reflects slow regulatory mechanisms, e.g. the renin-angiotensin system, thermoregulation) was significantly higher in REM sleep than in Stage 2 and Stage 4 of non-REM sleep. The LF spectral component (linked to the sympathetic modulation) was significantly higher in REM sleep than in Stage 2 and Stage 4 non-REM sleep. On the contrary, a power of the HF spectral band (related to parasympathetic activity) was significantly higher in Stage 2 and Stage 4 non-REM than in REM sleep. The LF/HF ratio, which reflects the sympathovagal balance, had its maximal value during REM sleep and a minimal value in synchronous sleep. The LF/HF ratio significantly increased during 5-min segments of Stage 2 non-REM sleep immediately preceding REM sleep compared to 5-min segments of Stage 2 non-REM sleep preceding the slow-wave sleep. This expresses the sympathovagal shift to sympathetic predominance occurring before the onset of REM sleep. A significant lengthening of the R-R interval during subsequent cycles of Stage 2 non-REM sleep was documented, which is probably related to the shift of sympathovagal balance to a prevailing parasympathetic influence in the course of sleep. This finding corresponds to a trend of a gradual decrease of the LF/HF ratio in subsequent cycles of Stage 2 non-REM sleep.     

ACE I/D polymorphism in Indian patients with hypertrophic cardiomyopathy and dilated cardiomyopathy

Aim The study was carried to determine the association of angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism with the risk of hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and restrictive cardiomyopathy (RCM). Methods and results A total of 174 patients diagnosed with cardiomyopathy (118 with HCM, 51 with DCM, and 5 with RCM) and 164 ethnically, age- and gender-matched controls were included in the study. ACE I/D genotyping was performed by PCR. In total, 25.86% of the patients were in New York Heart Association (NYHA) class III and IV at presentation. A total of 67.24% patients had dyspnea, 56.89% had angina pectoris, and 25.28% of the patients had at least one event of syncope. Frequency of occurrence of the disease was more in male patients compared to female patients (P < 0.05). After adjustment for age, sex, body mass index (BMI), and smoking habit, the prevalence of ACE DD genotype, and ACE ‘D’ allele was significantly higher in patients as compared to controls and was associated with increased risk (DD: OR 2.11, 95% CI 1.27–3.52, P < 0.05; ‘D’: OR 1.91, 95% CI 1.08–3.35, P < 0.05). The mean septal thickness was higher for DD and ID genotypes (20.40 ± 3.73 mm and 21.82 ± 5.35 mm, respectively) when compared with II genotype (18.63 ± 6.69 mm) in HCM patients, however, the differences were not significant statistically (P > 0.05). The DCM patients with ID genotype showed significantly decreased left ventricular ejection fraction (LVEF) at enrolment (26.50 ± 8.04%) (P = 0.04). Conclusion Our results suggest that D allele of ACE I/D polymorphism significantly influences the HCM and DCM phenotypes.     

Theoretical and clinical assessment of the sensitivity of heart rate variability indices

The application of modern methods of mathematical processing of non-stationary quasi-periodic data to the analysis of heart-rate variability is considered. Methods for the assessment of new parameters in non-linear variability analysis are described in detail. Mathematical models of heart rhythm are developed with the presence of various noise processes taken into account. A model of the state of the cardiovascular system based on the analysis of heart-rate variability has been developed. A theoretical estimate of the sensitivity of heart-rate variability indices to changes in the state of the cardiovascular system has been obtained for model data. Clinical studies of the parameters of heart-rate variability included in the analysis have been performed within the framework of cardiological screening for coronary heart disease.     

Sample entropy analysis of neonatal heart rate variability

Abnormal heart rate characteristics of reduced variability and transient decelerations are present early in the course of neonatal sepsis. To investigate the dynamics, we calculated sample entropy, a similar but less biased measure than the popular approximate entropy. Both calculate the probability that epochs of window length m that are similar within a tolerance r remain similar at the next point. We studied 89 consecutive admissions to a tertiary care neonatal intensive care unit, among whom there were 21 episodes of sepsis, and we performed numerical simulations. We addressed the fundamental issues of optimal selection of m and r and the impact of missing data. The major findings are that entropy falls before clinical signs of neonatal sepsis and that missing points are well tolerated. The major mechanism, surprisingly, is unrelated to the regularity of the data: entropy estimates inevitably fall in any record with spikes. We propose more informed selection of parameters and reexamination of studies where approximate entropy was interpreted solely as a regularity measure.     

Plasma and urinary selenium in Saudi Arabian patients with dilated cardiomyopathy

We measured selenium (Se) levels in the urine and blood plasma samples of 72 Saudi Arabian patients with dilated cardiomyopathy (DCM) and 70 control subjects of the same origin. To correct for differences in the hydration state of the subjects, the selenium concentration for each urine sample was normalized by dividing it by the concentration of creatinine (CREAT) in the same sample. The median (and range) of the values found for the concentration of Se in plasma, urine, and normalized concentration in urine for the control subjects was 1.306 (0.66–2.50) μM, 0.478 (0.05–2.00) μM, and 56.7 (10.6–426.5) μM Se/M CREAT, respectively, whereas, for the patients, it was 1.246 (0.53–2.45) μM, 0.39 (0.05–1.90) μM, and 75.1 (4.9–656.2) μM Se/M CREAT, respectively. Additionally, the patients were separated into three subgroups according to the severity of their disease state as judged by NYHA procedure, and were then compared to the control group. Only group 4 (the most severe state of the disease) had a significantly lower concentration of urinary Se than the control group. However, the difference became nonsignificant when normalized for CREAT levels. There was no significant difference in the plasma Se levels between the controls and any of the patient groups. As the plasma Se in the control group and in the DCM patients both fell on the low end of the “normal” range, with the patients being marginally lower than the controls, there is no firm evidence from this study to suggest that Se is related to the high incidence rate of DCM found in Saudi Arabia.     

Baroreflex sensitivity determined by spectral method and heart rate variability, and two-years mortality in patients after myocardial infarction

Sympathetic overactivity and low parasympathetic activity is an autonomic dysfunction (AD) which enhances cardiac mortality. In the present study, the impact of AD on the mortality in patients after myocardial infarction was evaluated. We examined 162 patients 7-21 days after myocardial infarction, 20 patients of whom died in the course of two years. Baroreflex sensitivity (BRS) was estimated by spectral analysis of spontaneous fluctuations of systolic blood pressure and cardiac intervals (Finapres, 5 min recording, controlled breathing 20/min). The heart rate variability was determined as SDNN index (mean of standard deviations of RR intervals for all 5-min segments of 24-hour ECG recordings). BRS < 3 ms/mm Hg and/or SDNN index < 30 ms were taken as markers of AD. The risk stratification was performed according to the number of the following standard risk factors of increased risk of cardiac mortality (SRF): ejection fraction < 40%, positive late potentials and the presence of ventricular extrasystoles > 10/h. No difference in mortality between patients with AD (4%) and without AD (4.5%) was found in 92 patients without SRF, the mortality in 6 patients with three SRF was 66.6%. Five of these patients had AD. Out of 64 patients with one or two SRF, 32 had AD. The mortality of patients without AD was 6.25% and 31.2% of those with AD (p<0.025). It is concluded that AD enhanced two-years mortality five fold in our patients with moderate risks.     

Left ventricular aneurysm in patients with idiopathic dilated cardiomyopathy: clinical analysis of six cases

Background. Left ventricular aneurysm (LVA) in patients with idiopathic dilated cardiomyopathy (IDCM) is rarely reported, and the incidence, pathogenesis and clinical features of LVA in IDCM are poorly understood. Methods. The diagnosis of IDCM with LVA formation was made in six patients between January 2003 and September 2008. Left ventriculography, coronary angiography, echocardiogram and electrocardiogram were performed in all patients. The hospital records of these patients with IDCM in our hospital and related literature were reviewed. Results. LVA was located at the posterobasal wall in five patients and at the anterolateral wall in one patient. Two patients had abnormal Q waves and no patients had sustained ST-segment elevation on electrocardiogram. No significant coronary stenosis or mural thrombi was detected in these patients. All patients had severe ventricular arrhythmia, such as frequent multifocal ventricular premature contractions and ventricular tachycardia. Conclusion. IDCM could be a rare cause of LVA. The LVA in IDCM was mainly located at the posterobasal wall. It was seldom accompanied by abnormal Q waves and sustained ST-segment elevation. The pathogenesis of LVA in IDCM seems to be less likely to be related to coronary emboli. Ventricular arrhythmia occurred frequently in these patients. (Neth Heart J 2009;17:475–80.)     

A new algorithm for wavelet-based heart rate variability analysis

One of the most promising non-invasive markers of the activity of the autonomic nervous system is heart rate variability (HRV). HRV analysis toolkits often provide spectral analysis techniques using the Fourier transform, which assumes that the heart rate series is stationary. To overcome this issue, the Short Time Fourier Transform (STFT) is often used. However, the wavelet transform is thought to be a more suitable tool for analyzing non-stationary signals than the STFT. Given the lack of support for wavelet-based analysis in HRV toolkits, such analysis must be implemented by the researcher. This has made this technique underutilized.This paper presents a new algorithm to perform HRV power spectrum analysis based on the Maximal Overlap Discrete Wavelet Packet Transform (MODWPT). The algorithm calculates the power in any spectral band with a given tolerance for the band's boundaries. The MODWPT decomposition tree is pruned to avoid calculating unnecessary wavelet coefficients, thereby optimizing execution time. The center of energy shift correction is applied to achieve optimum alignment of the wavelet coefficients. This algorithm has been implemented in RHRV, an open-source package for HRV analysis. To the best of our knowledge, RHRV is the first HRV toolkit with support for wavelet-based spectral analysis.     

Normalized correlation dimension for heart rate variability analysis.

In this paper we use the concept of large-scale dimension densities to analyze heart rate variability data. This method uses a normalized Grassberger-Procaccia algorithm and estimates the dimension in the rather large scales of the system. This enables us to analyze very short data. First we re-analyze data from the CIC 2002 challenge and can completely distinguish between real data and computer-generated data using only one parameter. We then analyze unfiltered data for 15 patients with atrial fibrillation (AF), 15 patients with congestive heart failure (CHF), 15 elderly healthy subjects, and 18 young healthy subjects. This method can completely separate the AF group from the other groups and the CHF patients show significant differences compared to the young and elderly healthy volunteers. Furthermore, differences are evident in the dimensionality between day and night for healthy persons, but not for the CHF patients. Finally, the results are compared to standard heart rate variability parameters.     

The prognostic value of non-linear analysis of heart rate variability in patients with congestive heart failure--a pilot study of multiscale entropy

Aims

The influences of nonstationarity and nonlinearity on heart rate time series can be mathematically qualified or quantified by multiscale entropy (MSE). The aim of this study is to investigate the prognostic value of parameters derived from MSE in the patients with systolic heart failure.

Methods and Results

Patients with systolic heart failure were enrolled in this study. One month after clinical condition being stable, 24-hour Holter electrocardiogram was recording. MSE as well as other standard parameters of heart rate variability (HRV) and detrended fluctuation analysis (DFA) were assessed. A total of 40 heart failure patients with a mea age of 56±16 years were enrolled and followed-up for 684±441 days. There were 25 patients receiving β-blockers treatment. During follow-up period, 6 patients died or received urgent heart transplantation. The short-term exponent of DFA and the slope of MSE between scale 1 to 5 were significantly different between patients with or without β-blockers (p = 0.014 and p = 0.028). Only the area under the MSE curve for scale 6 to 20 (Area_6–20) showed the strongest predictive power between survival (n = 34) and mortality (n = 6) groups among all the parameters. The value of Area_6–20 21.2 served as a significant predictor of mortality or heart transplant (p = 0.0014).

Conclusion

The area under the MSE curve for scale 6 to 20 is not relevant to β-blockers and could further warrant independent risk stratification for the prognosis of CHF patients.     

Blood pressure and heart rate variability are linked with hyperphosphatemia in chronic kidney disease patients

ABSTRACT

Hyperphosphatemia is a common complication of chronic kidney disease (CKD) and is associated with cardiovascular disease (CVD), which has contributed to an increase in mortality of CKD patients. The onset of CVD often varies by time-of-day. Acute myocardial infarction or ventricular arrhythmia occurs most frequently during early morning. Blood pressure (BP) and heart rate circadian rhythms account for the diurnal variations in CVD. Preservation of normal circadian time structure from the cardiomyocyte level to the whole organ system is essential for cardiovascular health and CVD prevention. Independent risk factors, such as reduced heart rate variability (HRV) and increased BP variability (BPV), are particularly prevalent in patients with CKD. Analysis of HRV is an important clinical tool for characterizing cardiac autonomic status, and reduced HRV has prognostic significance for various types of CVD. Circadian BP rhythms are classified as extreme dipper, dipper, non-dipper or riser. It has been reported that nocturnal riser BP pattern contributes to cardiovascular threats. Previous studies have indicated that the circadian rhythm of serum phosphate in CKD patients is consistent with the general population, with the highest diurnal value observed in the early morning hours, followed by a progressive decrease to the lowest value of the day, which occurs around 11:00 am. Rhythm abnormalities have become the main therapeutic target for treating CVD in CKD patients. It has been reported that high levels of serum phosphate are associated with reduced HRV and increased BPV in CKD patients. However, the mechanisms related to interactions between hyperphosphatemia, HRV and BPV have not been fully elucidated. This review focuses on the evidence and discusses the potential mechanisms related to the effects of hyperphosphatemia on HRV and BPV.