Association of the Heart Rate Variability Response to Active Standing with the Severity of Calcific Aortic Valve Disease: Novel Insights of a Neurocardiovascular Pathology.

The aim of this work was to obtain insights of the participation of the autonomic nervous system in different stages of calcific aortic valve disease (CAVD) by heart rate variability (HRV) analysis. Studying subjects with no valve impairments and CAVD patients, we also sought to quantify the independent contribution or explanatory capacity of the aortic valve echocardiographic parameters involved in the HRV changes caused by active standing using hierarchical partitioning models to consider other variables or potential confounders. We detected smaller adjustments of the cardiac autonomic response at active standing caused specifically by the aortic valve deterioration. The highest association (i.e., the highest percentage of independent exploratory capacity) was found between the aortic valve area and the active standing changes in the short-term HRV scaling exponent α1 (4.591%). The valve's maximum pressure gradient echocardiographic parameter was present in most models assessed (in six out of eight models of HRV indices that included a valve parameter as an independent variable). Overall, our study provides insights with a wider perspective to explore and consider CAVD as a neurocardiovascular pathology. This pathology involves autonomic-driven compensatory mechanisms that seem generated by the aortic valve deterioration.

Correlation between Angiotensin Serum Levels and Very-Low-Frequency Spectral Power of Heart Rate Variability during Hemodialysis.

Cardiovascular regulatory mechanisms that fail to compensate for ultrafiltration and cause hypovolemia during hemodialysis (HD) are not completely understood. This includes the interaction between the autonomic nervous system and the biochemistry that regulates blood pressure and modulates cardiac activity and vascular tone in response to hypovolemia in patients treated with HD. The objective was to evaluate the association of spectral indices of heart rate variability (HRV) with serum levels of angiotensin II, angiotensin 1-7, nitric oxide and total antioxidant capacity during HD. Electrocardiographic records were obtained from 20 patients during HD (3 h), from which HRV data and spectral power data in the very-low-frequency (VLF), low-frequency (LF) and high-frequency (HF) bands were generated. Three blood samples per patient were collected during HD (0.0, 1.5, 3.0 h) to determine the levels of biomarkers involved in the pressor response during HD. Angiotensin II had a positive correlation with VLF (r = 0.390) and with LF/HF (r = 0.359) and a negative correlation with LF (r = -0.262) and HF (r = -0.383). There were no significant correlations between HRV and the other biomarkers. These results suggest that during HD, VLF could reflect the serum levels of angiotensin II, which may be associated with the autonomic response to HD.

Baroreflex Sensitivity Assessment Using the Sequence Method with Delayed Signals in End-Stage Renal Disease Patients.

Impaired baroreflex sensitivity (BRS) is partially responsible for erratic blood pressure fluctuations in End-Stage Renal Disease (ESRD) patients on chronic hemodialysis (HD), which is related to autonomic nervous dysfunction. The sequence method with delayed signals allows for the measurement of BRS in a non-invasive fashion and the investigation of alterations in this physiological feedback system that maintains BP within healthy limits. Our objective was to evaluate the modified delayed signals in the sequence method for BRS assessment in ESRD patients without pharmacological antihypertensive treatment and compare them with those of healthy subjects. We recruited 22 healthy volunteers and 18 patients with ESRD. We recorded continuous BP to obtain a 15-min time series of systolic blood pressure and interbeat intervals during the supine position (SP) and active standing (AS) position. The time series with delays from 0 to 5 heartbeats were used to calculate the BRS, number of data points, number of sequences, and estimation error. The BRS from the ESRD patients was smaller than in healthy subjects (p < 0.05). The BRS estimation with the delayed sequences also increased the number of data points and sequences and decreased the estimation error compared to the original time series. The modified sequence method with delayed signals may be useful for the measurement of baroreflex sensitivity in ESRD patients with a shorter recording time and maintaining an estimation error below 0.01 in both the supine and active standing positions. With this framework, it was corroborated that baroreflex sensitivity in ESRD is decreased when compared with healthy subjects.

Cardiac Autonomic Response to Active Standing in Calcific Aortic Valve Stenosis.

Aortic stenosis is a progressive heart valve disorder characterized by calcification of the leaflets. Heart rate variability (HRV) analysis has been proposed for assessing the heart response to autonomic activity, which is documented to be altered in different cardiac diseases. The objective of the study was to evaluate changes of HRV in patients with aortic stenosis by an active standing challenge. Twenty-two volunteers without alterations in the aortic valve (NAV) and twenty-five patients diagnosed with moderate and severe calcific aortic valve stenosis (AVS) participated in this cross-sectional study. Ten minute electrocardiograms were performed in a supine position and in active standing positions afterwards, to obtain temporal, spectral, and scaling HRV indices: mean value of all NN intervals (meanNN), low-frequency (LF) and high-frequency (HF) bands spectral power, and the short-term scaling indices (α1 and αsign1). The AVS group showed higher values of LF, LF/HF and αsign1 compared with the NAV group at supine position. These patients also expressed smaller changes in meanNN, LF, HF, LF/HF, α1, and αsign1 between positions. In conclusion, we confirmed from short-term recordings that patients with moderate and severe calcific AVS have a decreased cardiac parasympathetic supine response and that the dynamic of heart rate fluctuations is modified compared to NAV subjects, but we also evidenced that they manifest reduced autonomic adjustments caused by the active standing challenge.

Dynamical interaction between heart rate and blood pressure of end-stage renal disease patients evaluated by cross recurrence plot diagonal analysis.

The assessment of spontaneous variability of blood pressure and heart rate is based on specific physiological hypotheses about dynamic features, for example, the baroreflex modulation of heart rate over time in daily life. Usually, arterial baroreflex control of heart rate is explored without delays between blood pressure and heart rate data points, within a narrow range of values, excluding the analysis of saturation regions or low-threshold changes. In this work, we examine the dynamic interactions between systolic blood pressure (SBP) and interbeat interval (IBI), in 15-min length time series and for the first time using the analysis of diagonals derived from a cross-recurrence plots in healthy persons and end-stage renal disease (ESRD) patients. We found that ESRD patients have stronger intermittent dynamical interactions between IBI and SBP, but they lose most of the dynamical interactions. Although healthy subjects exhibit a continuously changing order of precedence between IBI and SBP at different lags, ESRD patients preserve this changing order of precedence only for lags >0 beats.NEW & NOTEWORTHY This study is the first to compare the time-variant pattern of systolic blood pressure (SBP) and interbeat interval (IBI) coupling between ESRD patients and healthy volunteers through the analysis of diagonal in cross-recurrence plots, and in the face of an orthostatic challenge. Our results demonstrated alternant interactions on the order of precedence (IBI → SBP or SBP→ IBI) at different time delays. This pattern is different in resting position and during active standing for the two groups studied, and interestingly, some association patterns are lost in ESRD patients. These patterns of alternant interactions on the order of precedence could be related to autonomic neural activities and cardiovascular synchronization at different scales both in time and space. This could reflect physiological adaptive flexibility of cardiovascular regulation. Losing some association patterns in ESRD may be the result of chronic adjustments of many physiological mechanisms (including chronic sympathetic hyperactivity), which could increase cardiovascular vulnerability to hemodynamic challenges.

Development and multi-cohort validation of a clinical score for predicting type 2 diabetes mellitus.

BACKGROUND AND AIMS: Many countries lack resources to identify patients at risk of developing Type 2 diabetes mellitus (diabetes). We aimed to develop and validate a diabetes risk score based on easily accessible clinical data. METHODS: Prospective study including 5277 participants (55.0% women, 51.8±10.5 years) free of diabetes at baseline. Comparison with two other published diabetes risk scores (Balkau and Kahn clinical, respectively 5 and 8 variables) and validation on three cohorts (Europe, Iran and Mexico) was performed. RESULTS: After a mean follow-up of 10.9 years, 405 participants (7.7%) developed diabetes. Our score was based on age, gender, waist circumference, diabetes family history, hypertension and physical activity. The area under the curve (AUC) was 0.772 for our score, vs. 0.748 (p<0.001) and 0.774 (p = 0.668) for the other two. Using a 13-point threshold, sensitivity, specificity, positive and negative predictive values (95% CI) of our score were 60.5 (55.5-65.3), 77.1 (75.8-78.2), 18.0 (16.0-20.1) and 95.9 (95.2-96.5) percent, respectively. Our score performed equally well or better than the other two in the Iranian [AUC 0.542 vs. 0.564 (p = 0.476) and 0.513 (p = 0.300)] and Mexican [AUC 0.791 vs. 0.672 (p<0.001) and 0.778 (p = 0.575)] cohorts. In the European cohort, it performed similarly to the Balkau score but worse than the Kahn clinical [AUC 0.788 vs. 0.793 (p = 0.091) and 0.816 (p<0.001)]. Diagnostic capacity of our score was better than the Balkau score and comparable to the Kahn clinical one. CONCLUSION: Our clinically-based score shows encouraging results compared to other scores and can be used in populations with differing diabetes prevalence.

Analysis of diagonals in cross recurrence plots between heart rate and systolic blood pressure during supine position and active standing in healthy adults.

The inter beat interval (IBI) duration and systolic blood pressure (SBP) are cardiovascular variables related through several feedback mechanisms. We propose the analysis of diagonal lines in cross recurrence plots (CRPs) from IBI and SBP embedded within the same phase space to identify events where trajectories of both variables concur. The aim of the study was to describe the relationship between IBI and SBP of healthy subjects using CRP and diagonal analysis during baseline condition-supine position (SP)-and how the relationship changes during the physiological stress of active standing (AS). IBI and SBP time series were obtained from continuous blood pressure recordings during SP and AS (15 min each) in 19 young healthy subjects. IBI and SBP time series were embedded within a five-dimensional phase space using an embedding delay estimated from cross correlation between IBI and SBP. During SP, mean CRP showed high determinism (≥85%) and also brief but repeated events where both variables stay within a reduced space. Most quantitative recurrences analysis indexes of CRP increased significantly (p < 0.05) during AS. CRP analysis showed short diagonals indicating a very strong deterministic relationship between IBI and SBP with intermittent unlocking periods. The strength of IBI and SBP relationship increased during the physiological stress of AS. The CRP method allowed a rigorous quantitative description of the deterministic association between these two variables. Diagonal lines were intermittent and not always parallel, showing that there is not a defined and unique rhythm. This suggests the activation of different influences at different times and with different precedence between the heart rate and blood pressure in response to AS.

Multifractal Analysis Reveals Decreased Non-linearity and Stronger Anticorrelations in Heart Period Fluctuations of Fibromyalgia Patients.

Objective: To characterize the multifractal behavior of the beat to beat heart-period or RR fluctuations in fibromyalgia patients (FM) in comparison with healthy-matched subjects. Methods: Multifractral detrended fluctuation analysis (MDFA) was used to study multifractality in heartbeat times-series from 30 female healthy subjects and 30 female patients with fibromyalgia during day and night periods.The multifractal changes as derived from the magnitude and sign analysis of these RR fluctuations were also assessed. Results: The RR fluctuations dynamics of healthy subjects showed a broad multifractal spectrum. By contrast, a noticeable decrease in multifractality and non-linearity was observed for patients with fibromyalgia. In addition, the spectra corresponding to FM subjects were located on the average to the right of the spectra of healthy individuals, indicating that the local scaling exponents reflect a smoother behavior compared to healthy dynamics. Moreover, the multifractal analysis as applied to the magnitude and sign heartbeat series confirmed that, in addition to a decreased nonlinearity, fibromyalgia patients presented stronger anticorrelation in directionality, which did not remain invariant for small or rather larger fluctuations as it occurred in healthy subjects. Conclusion: When compared to healthy controls, fibromyalgia patients display decreased nonlinearity and stronger anticorrelations in heart period fluctuations. These findings reinforce the hypothesis of the potential role of the dysfunctional autonomic nervous system in the pathogenesis of fibromyalgia.

Indicators of accumulated fat are stronger associated with prehypertension compared with indicators of circulating fat: A cross-sectional study.

Recently, prehypertension has been considered as a risk factor for cardiovascular disease because it can progress to hypertension. The association between obesity and dyslipidemia with raised blood pressure has been reported in some studies; however, the ability of indicators of such conditions to predict prehypertension has been scarcely explored. In this cross-sectional study, we compared the ability of indicators of accumulated and circulating fat to discriminate between prehypertensive and normotensive Mexico City residents (n = 1377). The indicators were classified based on the parameters needed for their calculation: including only circulating fat (IOCFi) (e.g., Castelli risk indexes), including only accumulated fat (IOAFi) (e.g., waist circumference [WC]), and mixed (e.g., lipid accumulation product [LAP]). We compared the areas under the receiving operating characteristic curves (AURCs) and estimated the cutoff points for each indicator and their associated risk of prehypertension. The IOAFi had the greatest AURCs, followed by mixed and IOCFi; the AURCs for WC were the highest (AURC = 0.688 and 0.666 for women and men, respectively). The highest odds ratios for prehypertension were those associated with the cutoff points for IOAFi and LAP (e.g., OR = 2.8 for women with WC > 83.5 cm and OR = 2.6 for men with WC > 87.5 cm). Early detecting people at risk of cardiovascular disease is a necessity and given that WC had a better performance than the other indexes and it is relatively easy to measure, it has the potential of being used as a complementary measure in routine clinical examinations and by the general population as an auto-screening measurement to detect prehypertension.

Sign and magnitude scaling properties of heart rate variability in patients with end-stage renal failure: Are these properties useful to identify pathophysiological adaptations?

The scaling properties of heart rate variability data are reliable dynamical features to predict mortality and for the assessment of cardiovascular risk. The aim of this manuscript was to determine if the scaling properties, as provided by the sign and magnitude analysis, can be used to differentiate between pathological changes and those adaptations basically introduced by modifications of the mean heart rate in distinct manoeuvres (active standing or hemodialysis treatment, HD), as well as clinical conditions (end stage renal disease, ESRD). We found that in response to active standing, the short-term scaling index (α1) increased in healthy subjects and in ESRD patients only after HD. The sign short-term scaling exponent (α1sign) increased in healthy subjects and ESRD patients, showing a less anticorrelated behavior in active standing. Both α1 and α1sign did show covariance with the mean heart rate in healthy subjects, while in ESRD patients, this covariance was observed only after HD. A reliable estimation of the magnitude short-term scaling exponent (α1magn) required the analysis of time series with a large number of samples (>3000 data points). This exponent was similar for both groups and conditions and did not show covariance with the mean heart rate. A surrogate analysis confirmed the presence of multifractal properties (α1magn > 0.5) in the time series of healthy subjects and ESDR patients. In conclusion, α1 and α1sign provided insights into the physiological adaptations during active standing, which revealed a transitory impairment before HD in ESRD patients. The presence of multifractal properties indicated that a reduced short-term variability does not necessarily imply a declined regulatory complexity in these patients.

Effects of Orthostatism and Hemodialysis on Mean Heart Period and Fractal Heart Rate Properties of Chronic Renal Failure Patients.

The aim of this work was to evaluate the short-term fractal index (α1 ) of heart rate variability (HRV) in chronic renal failure (CRF) patients by identifying the effects of orthostatism and hemodialysis (HD), and by evaluating the correlation between α1 and the mean RR interval from sinus beats (meanNN). HRV time series were derived from ECG data of 19 CRF patients and 20 age-matched healthy subjects obtained at supine and orthostatic positions (lasting 5 min each). Data from CRF patients were collected before and after HD. α1 was calculated from each time series and compared by analysis of variance. Pearson's correlations between meanNN and α1 were calculated using the data from both positions by considering three groups: healthy subjects, CRF before HD and CRF after HD. At supine position, α1 of CRF patients after HD (1.17 ± 0.30) was larger (P < 0.05) than in healthy subjects (0.89 ± 0.28) but not before HD (1.10 ± 0.34). α1 increased (P < 0.05) in response to orthostatism in healthy subjects (1.29 ± 0.26) and CRF patients after HD (1.34 ± 0.31), but not before HD (1.25 ± 0.37). Whereas α1 was correlated (P < 0.05) with the meanNN of healthy subjects (r = -0.562) and CRF patients after HD (r = -0.388), no significance in CRF patients before HD was identified (r = 0.003). Multiple regression analysis confirmed that α1 was mainly predicted by the orthostatic position (in all groups) and meanNN (healthy subjects and patients after HD), showing no association with the renal disease condition in itself. In conclusion, as in healthy subjects, α1 of CRF patients correlates with meanNN after HD (indicating a more irregular-like HRV behavior at slower heart rates). This suggests that CRF patients with stable blood pressure preserve a regulatory adaptability despite a shifted setting point of the heart period (i.e., higher heart rate) in comparison with healthy subjects.

Hemodynamic Response to Hemodialysis With Ultrafiltration Rate Profiles Either Gradually Decreasing or Gradually Increasing.

Hemodialysis (HD) is usually performed with the gradually decreasing ultrafiltration rate (UFR) profile (dUFR). The aim of the present study was to compare the hemodynamic response to HD with the dUFR to that of HD with the gradually increasing UFR profile (iUFR). The study population included 10 patients (three women, mean age: 28 ± 8 years) undergoing maintenance HD who had reached dry weight without taking antihypertensive medications. Each patient received (in random order) one HD session with the dUFR and another with the iUFR (both with 3 h total UFR = 2200 mL). Hemodynamic response was evaluated with a brachial blood pressure (BP) monitor, echocardiogram and Portapres to measure digital BP, heart rate, cardiac output, stroke volume, and peripheral resistance. Mean values were compared at each HD hour during the first 3 h of a 4-h HD session. The HD characteristics, including Kt/V, were similar for both UFR profiles. Relative blood volume decreased more gradually and linearly with the iUFR. Hemodynamic variables were not significantly different between the two profiles, but brachial BP was more stable with the iUFR. Digital diastolic BP increased with both profiles. Peripheral resistance increased with both profiles, and tended to increase more with the iUFR. Echocardiographic variables changed similarly during the HD session with both profiles. In conclusion, these two UFR profiles are similar in most hemodynamic variables. The statistical equivalence of both profiles suggests that either could be prescribed based on the clinical characteristics of the patient.

Cardiac Autonomic Response to Active Standing in Adults With Vasovagal Syncope.

PURPOSE: Little is known about the autonomic response to active standing in vasovagal syncope, and most works have focused on children or adolescents. The aim of this work was to study the changes in cardiac autonomic modulation in adult patients with vasovagal syncope through heart rate variability analysis with linear and short-term complexity (alpha-1) indexes during supine position and active standing, in patients with positive or negative head-up tilt test (HUTT). METHODS: Twenty-five patients with vasovagal syncope were included. Heart rate variability linear and short-term complexity (alpha-1) indexes were recorded during an active standing test (15 minutes in each position) and compared among patients grouped by HUTT outcome and between positions. RESULTS: During supine position, positive HUTT (+HUTT) patients had longer mean RR (1016 [850-1051] milliseconds), higher pNN50 (17.7 [9.2-26.2]), lower sympathovagal balance (1.3 [0.5-1.7]), and alpha-1 (0.9 [0.8-1.0]) than negative HUTT (-HUTT) patients (871 [776-969] milliseconds, 8.8 [2.1-14.5], 2.9 [1.3-3.9], and 1.2 [1.0-1.1], respectively). During active standing, heart rate and alpha-1 increased in both groups; in +HUTT patients, pNN50 decreased, whereas sympathovagal balance increased. The magnitude of change between positions of sympathovagal balance and alpha-1 was 6.1 and 4.8 times larger in +HUTT than -HUTT patients, respectively. CONCLUSIONS: The underlying cardiac autonomic mechanism in vasovagal syncope may involve different autonomic patterns in subjects with a history of recurrent syncope and +HUTT or -HUTT.

Preserved autonomic heart rate modulation in chronic renal failure patients in response to hemodialysis and orthostatism.

BACKGROUND: The aim of this work was to measure the impact of active orthostatism and hemodialysis (HD) upon heart rate variability (HRV) in chronic renal failure (CRF) patients before and after HD. METHODS: Nineteen healthy subjects (age 27 ± 8 years old, 13 were female) and 19 unmedicated CRF patients with HD thrice per week (average HD vintage = 12 months, age 32 ± 9 years old, 11 were female) were included. Five-minute length HRV time series were obtained during supine position and orthostatism. Recordings from CRF patients were obtained before and after HD. Time domain and frequency domain HRV indexes were compared by analysis of variance. The correlation between each HRV index and change in sympathetic weighting induced by different maneuvers was tested by Kendall's Tau correlation. A p value <0.05 was considered statistically significant. RESULTS: HRV indexes which are associated with sympathetic activity increased in response to orthostatism in the healthy group, e.g., low-frequency to high-frequency (LF/HF) ratio, Ln (LF/HF) = -0.3 ± 0.9 versus 0.9 ± 0.9. CRF patients before HD had higher sympathetic weighting than healthy participants, even in supine position, Ln (LF/HF) = 0.6 ± 1.0, but such a difference was accentuated during orthostatism, Ln (LF/HF) = 1.5 ± 1.0, and after HD: Ln (LF/HF) = 0.8 ± 1.3 (supine position) and 2.5 ± 2.1 (orthostatism). All HRV indexes were associated with increments in sympathetic weighting between maneuvers (Kendall's correlations absolute values ≥ 0.24). CONCLUSION: Unmedicated young CRF patients treated with hemodynamically stable maintenance HD showed preserved capacity of autonomic response (with gradual sympathetic increases) induced by cardiovascular challenges such as orthostatism and HD.

Nonlinear dynamics of heart rate variability in response to orthostatism and hemodialysis in chronic renal failure patients: recurrence analysis approach.

We studied the response of heart rate variability to hemodialysis and orthostatism using traditional linear indexes and 9 recurrence quantification analysis indexes to reveal changes in the heart rate dynamics. Twenty healthy subjects and 19 chronic renal failure patients treated with hemodialysis thrice a week were included. Five-minute heart rate variability time series were obtained during supine position (clinostatism) and orthostatism from each participant; recordings in renal patients were repeated after hemodialysis. Linear indexes were consistent with sympathetic predominance in response to orthostatism in the control group. Renal patients before hemodialysis showed increased sympathetic predominance in clinostatism, with further increase in orthostatism and hemodialysis. In response to orthostatism, 4 recurrence indexes changed in the control group, while in renal patients any of them changed before hemodialysis and 1 changed after hemodialysis. In clinostatism, renal patients (both before and after hemodialysis) had higher laminarity, trapping time, and recurrence time than the control group. Recurrence indexes showed that the heart rate dynamics in renal patients are different from healthy subjects, suggesting loss of access to some regulatory conditions. These findings are consistent with reports of sympathetic stimulation induced by hemodialysis and active standing.

Baroreflex sensitivity estimation by the sequence method with delayed signals.

OBJECTIVE: To evaluate a modified sequence method with delayed time series for baroreflex sensitivity (BRS) estimation during supine position and orthostatism in healthy human beings. METHODS: Nineteen clinically healthy volunteers (12 men, age 28.4 ± 6.2 years old) were included. Blood pressure recordings were obtained during supine position and orthostatism (15 min each) with a Finometer. Systolic blood pressure (SBP) and inter beat intervals (IBI) measured from all heartbeats were used to estimate BRS in both positive and negative sequences, with SBP delayed between 0 and 5 heartbeats. BRS estimations were compared by ANOVA, p < 0.05 was considered significant. Optimal recording time based on fixed BRS error estimation was calculated for each time series. RESULTS: BRS estimation was similar between positive and negative sequences in all conditions (BRS = 12.0 ± 2.0 ms/mmHg in supine position, delay 0). BRS with no delay was similar to BRS with delays between 1 and 5 heartbeats. Compared to supine position, BRS was smaller in orthostatism in all delays (BRS = 8.0 ± 2.0 ms/mmHg with delay 0). The shortest optimal recording time with delayed time series was similar in supine position and orthostatism (4.3 ± 1.7 vs. 3.74 ± 0.07 min, respectively). Estimation error was linearly correlated to IBI, regardless of the delay. CONCLUSION: BRS estimation with sequence method improves with delayed time series, during supine position and orthostatism. Reduced BRS estimation error and recording time from this method could benefit studies with large populations or patients with low tolerance to orthostatism.

Relation of the baroreflex mechanism with the photoplethysmographic volume in healthy humans during orthostatism.

OBJECTIVE: Our aim was to evaluate the effect of the baroreflex mechanism upon peripheral blood volume during sympathetic stimulation by orthostatism. METHODS: Nineteen clinically healthy volunteers were included (12 men), 28.4 ± 6.2 years old. Blood pressure was monitored with a Finometer and blood volume with a photoplethysmograph during supine position and orthostatism (15 minutes each), in order to obtain systolic blood pressure (SBP), diastolic blood pressure (DBP), systolic volume (SysV), diastolic volume (DiaV), and inter beat intervals (IBI) measurements. Baroreflex sensitivity index (IBI/SBP) and baroreflex effect on blood volume (IBI/SysV) were estimated by the sequence method. The pertinence of using only systolic values was tested by linear regression analysis of systolic versus diastolic measurements. RESULTS: More than 70% of DBP and DiaV variations can be explained by SBP and SysV, respectively (p<0.001), with coherence >0.5 in frequencies between 0.04 and 0.15 Hz. IBI/SBP and IBI/SysV were linearly correlated (R>0.4) and both decreased during orthostatism (p<0.05). CONCLUSION: The sequence method showed a strong baroreflex effect upon peripheral blood volume that became more apparent during sympathetic stimulation with orthostatism. This approach could be clinically useful for the evaluation of blood volume regulation for many diseases such as diabetes mellitus and heart failure, and during therapeutic interventions such as hemodialysis.

Relation of the baroreflex mechanism with the photoplethysmographic volume in healthy humans during orthostatism / Relación del mecanismo barorreflejo con el volumen fotopletismográfico en humanos sanos durante ortostatismo

Objective: Our aim was to evaluate the effect of the baroreflex mechanism upon peripheral blood volume during sympathetic stimulation by orthostatism. Methods: Nineteen clinically healthy volunteers were included (12 men), 28.4 ± 6.2 years old. Blood pressure was monitored with a Finometer and blood volume with a photoplethysmo-graph during supine position and orthostatism (15 minutes each), in order to obtain systolic blood pressure (SBP), diastolic blood pressure (DBP), systolic volume (SysV), diastolic volume (DiaV), and inter beat intervals (IBI) measurements. Baroreflex sensitivity index (IBI/SBP) and baroreflex effect on blood volume (IBI/SysV) were estimated by the sequence method. The pertinence of using only systolic values was tested by linear regression analysis of systolic versus diastolic measurements. Results: More than 70% of DBP and DiaV variations can be explained by SBP and SysV, respectively (p<0.001), with coherence >0.5 in frequencies between 0.04 and 0.15 Hz. IBI/SBP and IBI/SysV were linearly correlated (R>0.4) and both decreased during orthostatism (p<0.05). Conclusion: The sequence method showed a strong baroreflex effect upon peripheral blood volume that became more apparent during sympathetic stimulation with orthostatism. This approach could be clinically useful for the evaluation of blood volume regulation for many diseases such as diabetes mellitus and heart failure, and during therapeutic interventions such as hemodialysis.

Objetivo: Evaluar el efecto del mecanismo barorreflejo sobre el volumen sanguíneo periférico durante estimulación inducida por ortostatismo. Métodos: Se incluyeron 19 voluntarios sanos (12 hombres), con edad de 28.4 ± 6.2 años. La presión arterial se midió con un Finometer y el volumen sanguíneo con un fotopletismógrafo, ambos durante posiciones supina y ortostatismo activo (15 minutos cada una), para obtener los valores de presión arterial sistólica (PAS), presión arterial diastólica (PAD), volumen sistólico (VS), volumen diastólico (VD) e intervalo inter pulso (IIP). Se estimó la sensibilidad barorrefleja (IIP/PAS) y el efecto barorreflejo sobre el volumen sanguíneo (IIP/VS) mediante el método de secuencias. La pertinencia de usar sólo variables sistólicas, se evaluó mediante análisis de regresión lineal de las mediciones sistólicas versus las diastólicas. Resultados: Más de 70% de las variaciones de presión arterial diastólica y volumen diastólico pueden ser explicadas mediante presión arterial sistólica y volumen sistólico, respectivamente (p<0.001), con coherencia >0.5 en frecuencias entre 0.04 y 0.15 Hz. IIP/PAS y IIP/VS tuvieron correlación positiva (R>0.4) y ambos disminuyeron durante ortostatismo (p<0.05). Conclusiones: El método de secuencias demostró un importante efecto barorreflejo sobre el volumen sanguíneo periférico que se hizo más notable durante estimulación simpática con ortostatismo. Este enfoque podría ser clínicamente útil en la evaluación de la regulación del volumen sanguíneo en distintas enfermedades como diabetes mellitus o falla cardiaca, y durante intervenciones terapéuticas como la hemodiálisis.

Visual three-dimensional representation of beat-to-beat electrocardiogram traces during hemodiafiltration.

This study evaluated the usefulness of the three-dimensional representation of electrocardiogram traces (3DECG) to reveal acute and gradual changes during a full session of hemodiafiltration (HDF) in end-stage renal disease (ESRD) patients. Fifteen ESRD patients were included (six men, nine women, age 46 ± 19 years old). Serum electrolytes, blood pressure, heart rate, and blood urea nitrogen (BUN) were measured before and after HDF. Continuous electrocardiograms (ECGs) obtained by Holter monitoring during HDF were used to produce the 3DECG. Several major disturbances were identified by 3DECG images: increase in QRS amplitude (47%), decrease in T-wave amplitude (33%), increase in heart rate (33%), and occurrence of arrhythmia (53%). Different arrhythmia types were often concurrent and included isolated supraventricular premature beats (N = 5), atrial fibrillation or atrial bigeminy (N = 2), and isolated premature ventricular beats (N = 6). Patients with decrease in T-wave amplitude had higher potassium and BUN (both before HDF and total removal) than those without decrease in T-wave amplitude (P < 0.05). Concurrent acute and gradual ECG changes during HDF are identified by the 3DECG, which could be useful as a preventive and prognostic method.