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Reduced respiratory sinus arrhythmia, quantified as expiration-triggered sinus arrhythmia (ETA) from simultaneous electrocardiogram and respiration recordings, is a strong long-term mortality predictor in myocardial infarction survivors. Here, we investigated whether ETA also predicts mortality risk in the general elderly population. ETA was quantified from 30-min electrocardiogram and respiration recordings in 1788 general population subjects aged ≥60 years, who were then followed for a median of 4.0 years (median age 72 years, 58% female). Four-year all-cause mortality was 4.6%. Abnormal ETA using a predefined cutoff (≤0.19 ms) was associated with a 4-year mortality of 6.9%, compared to 3.7% in the remaining participants (p = 0.0022). ETA remained a significant mortality predictor in multivariable Cox analysis, also considering a modified Framingham score incorporating sex, age, smoking, cholesterol, blood pressure, antihypertensive medication, family history, diabetes and clinical atherosclerosis (multivariable hazard ratio 1.81; 95% confidence interval 1.17–2.81; p = 0.008). Combined risk prediction by ETA (using an optimized cutoff of ≤0.86 ms) and the Framingham score stratified patients into a low-risk (both parameters normal), an intermediate-risk (one parameter abnormal) and a high-risk group (both parameters abnormal), with 4-year mortality rates of 1.9%, 4.4% and 10.1%, respectively. We conclude that in elderly general population subjects, ETA is a mortality risk predictor that complements classical clinical risk stratification.

Cardiotocography (CTG) is the most common technique for electronic fetal monitoring and consists of the simultaneous recording of fetal heart rate (FHR) and uterine contractions. In analogy with the adult case, spectral analysis of the FHR signal can be used to assess the functionality of the autonomic nervous system. To do so, several methods can be employed, each of which has its strengths and limitations. This paper aims at performing a methodological investigation on FHR spectral analysis adopting 4 different spectrum estimators and a novel PRSA-based spectral method. The performances have been evaluated in terms of the ability of the various methods to detect changes in the FHR in two common pregnancy complications: intrauterine growth restriction (IUGR) and gestational diabetes. A balanced dataset containing 2178 recordings distributed between the 32nd and 38th week of gestation was used. The results show that the spectral method derived from the PRSA better differentiates high-risk pregnancies vs. controls compared to the others. Specifically, it more robustly detects an increase in power percentage within the movement frequency band and a decrease in high frequency between pregnancies at high risk in comparison to those at low risk. [ABSTRACT FROM AUTHOR]

Objectives: To establish the correlation between phase‐rectified signal averaging (PRSA) outputs obtained from a novel self‐applicable non‐invasive fetal electrocardiography (NIFECG) monitor with those from computerized cardiotocography (cCTG). A secondary objective was to evaluate the potential for remote assessment of fetal wellbeing by determining the relationship between PRSA and short‐term variation (STV). Methods: This was a prospective observational study of women with a singleton pregnancy over 28 + 0 weeks' gestation attending a London teaching hospital for cCTG assessment. Participants underwent concurrent cCTG and NIFECG monitoring for up to 60 min. Averaged accelerative (AAC) and decelerative (ADC) capacities and STV were derived by postprocessing and filtration of signals, generating fully (F) and partially (P) filtered results. Linear correlation and accuracy and precision analysis were performed to assess the relationship between PRSA outputs from cCTG and NIFECG, using varying anchor thresholds, and their association with STV. Results: A total of 306 concurrent cCTG and NIFECG traces were collected from 285 women. F‐filtered NIFECG PRSA (eAAC/eADC) results were generated from 65% of traces, whereas cCTG PRSA (cAAC/cADC) outputs were generated from all. Strong correlations were observed between cAAC and F‐filtered eAAC (r = 0.879, P < 0.001) and between cADC and F‐filtered eADC (r = 0.895, P < 0.001). NIFECG anchor detection decreased significantly with increasing signal loss, and NIFECG PRSA indices showed considerable deviation from those of cCTG when derived from traces in which fewer than 100 anchors were detected. Removing anchor filters from NIFECG traces to generate P‐filtered PRSA outputs weakened the correlation (AAC: r = 0.505, P < 0.001; ADC: r = 0.560, P < 0.001). Lowering the anchor threshold to 100 increased the yield of eAAC and eADC outputs to approximately 74%, whilst maintaining strong correlation with cAAC (r = 0.839, P < 0.001) and cADC (r = 0.815, P < 0.001), respectively. Both cAAC and cADC showed a very strong linear relationship with cCTG STV (r = 0.928, P < 0.001 and r = 0.911, P < 0.001, respectively). Similar findings were observed with eAAC (r = 0.825, P < 0.001) and eADC (r = 0.827, P < 0.001). Conclusions: PRSA appears to be a method of fetal assessment equivalent to STV, but, due to its innate ability to eliminate artifacts, it generates interpretable NIFECG traces with high accuracy at a higher rate. These findings raise the possibility of self‐applied at‐home or remote fetal heart‐rate monitoring with automated reporting, thus enabling increased surveillance in high‐risk women without impacting on service demand. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Objective: Cardiotocography is widely used to assess fetal well‐being during labour. The positive predictive value of current clinical algorithms to identify hypoxia‐ischaemia is poor. In experimental studies, fetal hypotension is the strongest predictor of hypoxic‐ischaemic injury. Cohort studies suggest that deceleration area and deceleration capacity of the fetal heart rate trace correlate with fetal acidaemia, but it is not known whether they are indices of fetal arterial hypotension. Design: Prospective, controlled study. Setting: Laboratory. Sample: Near‐term fetal sheep. Methods: One minute of complete umbilical cord occlusions (UCOs) every 5 minutes (1:5 min, n = 6) or every 2.5 minutes (1:2.5 min, n = 12) for 4 hours or until fetal mean arterial blood pressure fell <20 mmHg. Main outcome measures: Deceleration area and capacity during the UCO series were related to evolving hypotension. Results: The 1:5 min group developed only mild metabolic acidaemia, without hypotension. By contrast, 10/12 fetuses in the 1:2.5‐min group progressively developed severe metabolic acidaemia and hypotension, reaching 16.8 ± 0.9 mmHg after 71.2 ± 6.7 UCOs. Deceleration area and capacity remained unchanged throughout the UCO series in the 1:5‐min group, but progressively increased in the 1:2.5‐min group. The severity of hypotension was closely correlated with both deceleration area (P < 0.001, R2 = 0.66, n = 18) and capacity (P < 0.001, R2 = 0.67, n = 18). Deceleration area and capacity predicted development of hypotension at a median of 103 and 123 minutes before the final occlusion, respectively. Conclusions: Both deceleration area and capacity were strongly associated with developing fetal hypotension, supporting their potential to improve identification of fetuses at risk of hypotension leading to hypoxic‐ischaemic injury during labour. Deceleration area and capacity of fetal heart rate identify developing hypotension during labour‐like hypoxia. Deceleration area and capacity of fetal heart rate identify developing hypotension during labour‐like hypoxia. [ABSTRACT FROM AUTHOR]

Abstract Background Phase-rectified signal averaging (PRSA) was often applied to assess the cardiac vagal modulation. Despite its broad use, this method suffers from the confounding effects of anomalous variants of sinus rhythm. This study aimed to improve the original PRSA method in deceleration capacity (DC) quantification. Methods The refined deceleration capacity (DC ref ) was calculated by excluding from non-vagally mediated abnormal variants of sinus rhythms. Holter recordings from 202 healthy subjects and 51 patients with end-stage renal disease (ESRD) have been used for validity. The DC ref was compared to original DC (DC org ) by the area under receiver operating characteristic curve. Results Experimental results demonstrate that the original and refined DCs calculated from 24-h, 2-h, and 30-min Holter recordings are significantly lower in patients with ESRD than those in the healthy group. In receiver operating characteristic curve analysis, the DC ref provides better performance than the DC org in distinguishing between the patients with ESRD and healthy control subjects. Furthermore, the refined PRSA technique enhances the low frequency and attenuates high frequency components for spectral analysis in ESRD patients. Conclusions The DC ref appears to reduce the influence of non-vagally mediated abnormal variants of sinus rhythm and highlighting the pathological influence. DC ref , especially assessed from short-term electrocardiography recordings, may be complementary to existing autonomic function assessment, risk stratification, and efficacy prediction strategies.

The fetal autonomic nervous system responds to uterine contractions during active labor as identified by changes in the accelerations and decelerations of fetal heart rate (FHR). Thus, this exploratory study aimed to characterize the asymmetry differences of beat-to-beat FHR accelerations and decelerations in preterm and term fetuses during active labor. In an observational study, we analyzed 10 min of fetal R-R series collected from women during active preterm labor (32–36 weeks of pregnancy, n = 17) and active term labor (38–40 weeks of pregnancy, n = 27). These data were used to calculate the Deceleration Reserve (DR), which is a novel parameter that quantifies the asymmetry of the average acceleration and deceleration capacity of the heart. In addition, relevant multiscale asymmetric indices of FHR were also computed. Lower values of DR, calculated with the input parameters of T = 50 and s = 10, were associated with labor occurring at the preterm condition (p = 0.0131). Multiscale asymmetry indices also confirmed significant (p < 0.05) differences in the asymmetry of FHR. Fetuses during moderate premature labor may experience more decaying R-R trends and a lower magnitude of decelerations compared to term fetuses. These differences of FHR dynamics might be related to the immaturity of the fetal cardiac autonomic nervous system as identified by this system response to the intense uterine activity at active labor.

Hysteresis of the baroreflex (BR) is the result of the different BR sensitivity (BRS) when arterial pressure (AP) rises or falls. This phenomenon has been poorly studied and almost exclusively examined by applying pharmacological challenges and static approaches disregarding causal relations. This study inspects the asymmetry of the cardiac BR (cBR) and vascular sympathetic BR (sBR) in physiological closed loop conditions from spontaneous fluctuations of physiological variables, namely heart period (HP) and systolic AP (SAP) leading to the estimation of cardiac BRS (cBRS) and muscle sympathetic nerve activity (MSNA) and diastolic AP (DAP) leading to the estimation of vascular sympathetic BRS (sBRS). The assessment was carried out in 12 young healthy subjects undergoing incremental head-up tilt with table inclination gradually increased from 0 to 60°. Two analytical methods were exploited and compared, namely the sequence (SEQ) and phase-rectified signal averaging (PRSA) methods. SEQ analysis is based on the detection of joint causal schemes representing the HP and MSNA burst rate delayed responses to spontaneous SAP and DAP modifications, respectively. PRSA analysis averages HP and MSNA burst rate patterns after aligning them according to the direction of SAP and DAP changes, respectively. Since cBRSs were similar when SAP went up or down, hysteresis of cBR was not detected. Conversely, hysteresis of sBR was evident with sBRS more negative when DAP was falling than rising. sBR hysteresis was no longer visible during sympathetic activation induced by the orthostatic challenge. These results were obtained via the SEQ method, while the PRSA technique appeared to be less powerful in describing the BR asymmetry due to the strong association between BRS estimates computed over positive and negative AP variations. This study suggests that cBR and sBR provide different information about the BR control, sBR exhibits more relevant non-linear features that are evident even during physiological changes of AP, and the SEQ method can be fruitfully exploited to characterize the BR hysteresis with promising applications to BR branches different from cBR and sBR.

Hysteresis of the baroreflex (BR) is the result of the different BR sensitivity (BRS) when arterial pressure (AP) rises or falls. This phenomenon has been poorly studied and almost exclusively examined by applying pharmacological challenges and static approaches disregarding causal relations. This study inspects the asymmetry of the cardiac BR (cBR) and vascular sympathetic BR (sBR) in physiological closed loop conditions from spontaneous fluctuations of physiological variables, namely heart period (HP) and systolic AP (SAP) leading to the estimation of cardiac BRS (cBRS) and muscle sympathetic nerve activity (MSNA) and diastolic AP (DAP) leading to the estimation of vascular sympathetic BRS (sBRS). The assessment was carried out in 12 young healthy subjects undergoing incremental head-up tilt with table inclination gradually increased from 0 to 60°. Two analytical methods were exploited and compared, namely the sequence (SEQ) and phase-rectified signal averaging (PRSA) methods. SEQ analysis is based on the detection of joint causal schemes representing the HP and MSNA burst rate delayed responses to spontaneous SAP and DAP modifications, respectively. PRSA analysis averages HP and MSNA burst rate patterns after aligning them according to the direction of SAP and DAP changes, respectively. Since cBRSs were similar when SAP went up or down, hysteresis of cBR was not detected. Conversely, hysteresis of sBR was evident with sBRS more negative when DAP was falling than rising. sBR hysteresis was no longer visible during sympathetic activation induced by the orthostatic challenge. These results were obtained via the SEQ method, while the PRSA technique appeared to be less powerful in describing the BR asymmetry due to the strong association between BRS estimates computed over positive and negative AP variations. This study suggests that cBR and sBR provide different information about the BR control, sBR exhibits more relevant non-linear features that are evident even during physiological changes of AP, and the SEQ method can be fruitfully exploited to characterize the BR hysteresis with promising applications to BR branches different from cBR and sBR. [ABSTRACT FROM AUTHOR]

Introduction: Cardiovascular autonomic nervous system (CV-ANS) function is negatively impacted after concussion. The arterial baroreflex buffers pressor and depressor challenges through efferent modulation of cardiac chronotropism and inotropism, and peripheral vascular tone. Baroreceptor sensitivity (BRS) reflects the capacity of the CV-ANS to accommodate dynamic metabolic demands in the periphery. The impact of concussion on BRS has yet to be defined. Methods: Cardiovascular autonomic nervous system assessment (e.g., electrocardiogram and beat-to-beat systolic blood pressure [SBP]) was performed the seated upright position at rest within 48 h (V1) of concussion and 1 wk later (V2) in 10 intercollegiate male athletes with concussion and 10 noninjured male athletes. Changes in HR, SBP, high- and low-frequency HR variabilities (HF-HRV and LF-HRV, respectively), LF-SBP variability and BRS for increasing (BRSn-Up) and decreasing (BRSn-Dn) SBP excursions, and overall BRS (BRSn-Avg) were assessed for differences at V1 and V2. Results: The concussion (age, 20 ± 1 yr; height, 1.79 ± 0.14 m; weight, 83 ± 10 kg) and control (age, 20 ± 1 yr; height, 1.78 ± 0.10 m; weight, 79 ± 13 kg) groups were matched for demographics. Concussed athletes had a significantly reduced BRSn-Up, BRSn-Dn, and BRSn-Avg compared with controls at V1 or V2; these changes occurred without differences in conventional markers of CV-ANS function (e.g., HF-HRV, LF-HRV, LF-SBP), HR, or SBP at either visit. Conclusions: Reduced BRS is a postconcussive consequence of CV-ANS dysfunction during the first postinjury week. Because SBP was similar between groups, it may be speculated that reduced BRS was not afferent in origin, but represents a postinjury consequence of the central nervous system after injury. [ABSTRACT FROM AUTHOR]

Objectives: Maternal gestational diabetes mellitus (GDM) is known to influence fetal physiology. Phase-rectified signal averaging (PRSA) is an innovative signal-processing technique that can be used to investigate fetal heart signals. The PRSA-calculated variables average acceleration capacity (AAC) and average deceleration capacity (ADC) are established indices of autonomic nervous system (ANS) function. The aim of this study was to evaluate the influence of GDM on the fetal cardiovascular and ANS function in human pregnancy using PRSA.Methods: This was a prospective clinical case-control study of 58 mothers with diagnosed GDM and 58 gestational-age matched healthy controls in the third trimester of pregnancy. Fetal cardiotocography (CTG) recordings were performed in all cases at entry to the study, and a follow-up recording was performed in 19 GDM cases close to delivery. The AAC and ADC indices were calculated by the PRSA method and fetal heart rate short-term variation (STV) by CTG software according to Dawes-Redman criteria.Results: Mean gestational age of both groups at study entry was 35.7 weeks. There was a significant difference in mean AAC (1.97 ± 0.33 bpm vs 2.42 ± 0.57 bpm; P < 0.001) and ADC (1.94 ± 0.32 bpm vs 2.28 ± 0.46 bpm; P < 0.001) between controls and fetuses of diabetic mothers. This difference could not be demonstrated using standard computerized fetal CTG analysis of STV (controls, 10.8 ± 3.0 ms vs GDM group, 11.3 ± 2.5 ms; P = 0.32). Longitudinal fetal heart rate measurements in a subgroup of women with diabetes were not significantly different from those at study entry.Conclusions: Our findings show increased ANS activity in fetuses of diabetic mothers in late gestation. Analysis of human fetal cardiovascular and ANS function by PRSA may offer improved surveillance over conventional techniques linking GDM pregnancy to future cardiovascular dysfunction in the offspring. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Phase-rectified signal averaging (PRSA) has been known to be a useful method to detect periodicities in non-stationary biological signals. Determination of quasi-periodicities in electroencephalogram (EEG) is a candidate for quantifying the changes in the depth of anesthesia (DOA). In this paper, DOA monitoring capacity of periodicities detected using PRSA was quantified by assessing EEG signals collected from 56 patients during surgery. The method is compared with sample entropy (SampEn), detrended fluctuation analysis (DFA), and permutation entropy (PE). The performance of quasi-periodicities defined by deceleration capacity and acceleration capacity was tested using the area under the receiver operating characteristic curve (AUC) and Pearson correlation coefficient. During the surgery, a significant difference ( $p <0.05$ ) in the quasi-periodicities was observed among three different stages under general anesthesia. There is a larger mean AUC and correlation coefficient of quasi-periodicities compared with SampEn, DFA, and PE using expert assessment of conscious level and bispectral index as the gold standard, respectively. Quasi-periodicities detected using PRSA in EEG signals are a powerful monitor of DOA and perform more accurate and robust results compared with SampEn, DFA, and PE. The results do provide a valuable reference to researchers in the field of clinical applications. [ABSTRACT FROM AUTHOR]

Objective: To analyze the effect of maternal betamethasone given for fetal lung maturation on fetal short-term variation (STV) and average acceleration and deceleration capacity (AAC/ADC). Both of these factors are calculated by phase-rectified signal averaging (PRSA) and represent new parameters to assess the fetal autonomic nervous system.Study Design: A longitudinal prospective study including 26 pregnant women at risk for preterm delivery was performed. Two injections of 12mg betamethasone were administered intramuscularly at a 24h interval for lung maturation. Cardiotocography recordings were performed at defined time intervals: day 0 (before the first injection) and days 1, 2, 4 after the first corticosteroid administration. AAC/ADC and STV were calculated.Results: An increase of all parameters (STV, AAC and ADC) was documented between day 0 and day 1. Between day 1 and day 2, all three indices were significantly reduced (p<0.05). STV declined by 19.8%, AAC by 10.1% and ADC by 14.8%. A normalization of these values was seen after 96h.Conclusion: Similar to STV, AAC/ADC shows significant changes after maternal betamethasone administration. The corticosteroid-induced transient decrease of the levels needs to be taken into account in the assessment of the fetal status to avoid misinterpretation of these parameters. [ABSTRACT FROM AUTHOR]

Background: Respiratory sinus arrhythmia (RSA), a measure of cardiac vagal modulation, provides cardiac risk stratification information. RSA can be quantified from Holter recordings as the high-frequency component of heart rate variability or as the variability of RR intervals in individual respiratory cycles. However, as a risk predictor, RSA is neither exceptionally sensitive nor specific.Objectives: This study aimed to improve RSA determination by quantifying the amount of sinus arrhythmia related to expiration (expiration-triggered sinus arrhythmia [ETA]) from short-term recordings of electrocardiogram and respiratory chest excursions, and investigated the predictive power of ETA in survivors of acute myocardial infarction.Methods: Survivors of acute myocardial infarction (N = 941) underwent 30-min recordings of electrocardiogram and respiratory chest excursions. ETA was quantified as the RR interval change associated with expiration by phase-rectified signal averaging. Primary outcome was 5-year all-cause mortality. Univariable and multivariable Cox regression was used to investigate the association of ETA with mortality.Results: ETA was a strong predictor of mortality, both in univariable and multivariable analysis. In a multivariable model including respiratory rate, left ventricular ejection fraction, diabetes mellitus, and GRACE score, ETA ≤0.19 ms was associated with a hazard ratio of 3.41 (95% confidence interval: 1.10 to 5.89, p < 0.0001). In patient subgroups defined by abnormal left ventricular ejection fraction, increased respiratory rate, high GRACE score, or presence of diabetes mellitus, patients were classified as high or low risk on the basis of ETA.Conclusions: Expiration-triggered sinus arrhythmia (ETA) is a potent and independent post-infarction risk marker. [ABSTRACT FROM AUTHOR]

Objective Recent studies suggest that phase-rectified signal averaging ( PRSA), measured in antepartum fetal heart rate ( FHR) traces, may sensitively indicate fetal status; however, its value has not been assessed during labour. We determined whether PRSA relates to acidaemia in labour, and compare its performance to short-term variation ( STV), a related computerised FHR feature. Design Historical cohort. Setting Large UK teaching hospital. Population All 7568 Oxford deliveries that met the study criteria from April 1993 to February 2008. Methods We analysed the last 30 minutes of the FHR and associated outcomes of infants. We used computerised analysis to calculate PRSA decelerative capacity (DCPRSA), and its ability to predict umbilical arterial blood pH ≤ 7.05 using receiver operator characteristic (ROC) curves and event rate estimates (EveREst). We compared DCPRSA with STV calculated on the same traces. Main outcome measure Umbilical arterial blood pH ≤ 7.05. Results We found that PRSA could be measured in all cases. DCPRSA predicted acidaemia significantly better than STV: the area under the ROC curve was 0.665 (95% CI 0.632-0.699) for DCPRSA, and 0.606 (0.573-0.639) for STV ( P = 0.007). EveREst plots showed that in the worst fifth centile of cases, the incidence of low pH was 17.75% for DCPRSA but 11.00% for STV ( P < 0.001). DCPRSA was not highly correlated with STV. Conclusions DCPRSA of the FHR can be measured in labour, and appears to predict acidaemia more accurately than STV. Further prospective evaluation is warranted to assess whether this could be clinically useful. The weak correlation between DCPRSA and STV suggests that they could be combined in multivariate FHR analyses. [ABSTRACT FROM AUTHOR]

Aims Acceleration and deceleration capacity (AC and DC) for beat-to-beat short-term heart rate dynamics are powerful predictors of mortality after acute myocardial infarction (AMI). We examined if AC and DC for minute-order long-term heart rate dynamics also have independent predictive value. Methods and results We studied 24-hr Holter electrcardiograms in 708 post-AMI patients who were followed up for up to 30 months thereafter. Acceleration capacity and DC was calculated with the time scales of T (window size defining heart rate) and s (wavelet scale) from 1 to 500 s and compared their prognostic values with conventional measures (ACconv and DCconv) that were calculated with (T,s) = [1,2 (beat)]. During the follow-up, 47 patients died. Both increased ACconv and decreased DCconv predicted mortality (C statistic, 0.792 and 0.797). Concordantly, sharp peaks of C statistics were observed at (T,s) = [2,7 (sec)] for both increased AC and decreased DC (0.762 and 0.768), but there were larger peaks of C statistics at around [30,60 (sec)] for both (0.783 and 0.796). The C statistic was greater for DC than AC at (30,60) (P = 0.0012). Deceleration capacity at (30,60) was a significant predictor even after adjusted for ACconv (P = 0.020) and DCconv (P = 0.028), but the predictive power of AC at (30,60) was no longer significant. Conclusion A decrease in DC for minute-order long-term heart rate dynamics is a strong predictor for post-AMI mortality and the predictive power is independent of ACconv and DCconv for beat-to-beat short-term heart rate dynamics. [ABSTRACT FROM PUBLISHER]

Objective: This study aims to compare average acceleration capacity (AAC), a new parameter to assess the dynamic capacity of the fetal autonomous nervous system, and short term variation (STV) in fetuses affected by intrauterine growth restriction (IUGR) and healthy fetuses. Methods: A prospective observational study was performed, including 39 women with IUGR singleton pregnancies (estimated fetal weight <10th percentile and umbilical artery resistance index >95th percentile) and 43 healthy control pregnancies matched according to gestational age at recording. Ultrasound biometries and Doppler examination were performed for identification of IUGR and control fetuses, with subsequent analysis of fetal heart rate, resulting in STV and AAC. Follow-up for IUGR and control pregnancies was done, with perinatal outcome variables recorded. Results: AAC [IUGR mean value 2.0 bpm (interquartile range = 1.6-2.1), control 2.7 bpm (2.6-3.0)] differentiates better than STV [IUGR 7.4 ms (5.3-8.9), control 10.9 ms (9.2-12.7)] between IUGR and control. The area under the curve for AAC is 97 % [95% CI = (0.95-1.0)], for STV 85 % (CI = 0.76-0.93; p < 0.01). Positive predictive value for STV is 77% and negative predictive value is 81%. For AAC both positive and negative predictive values are 90%. Conclusions: AAC shows an improvement to discriminate between normal and compromised fetuses at a single moment in time, in comparison with STV. [ABSTRACT FROM AUTHOR]

Deceleration capacity (DC) of heart rate is a novel indicator of autonomic nervous system (ANS) activity. In this paper, we proposed a modified DC index based on improved phase-rectified signal averaging (PRSA) algorithm. Sinusoidal analysis is applied to elucidate the rationality of the improved PRSA. Then the validity of the modified DC is verified by the databases of chronic heart failure (CHF) patients and control group. Both the conventional and modified DCs are significantly lower in CHF patients than that in the control group (2.12 ± 2.98 vs. 6.34 ± 1.92 ms, P < 0.0001 and 5.45 ± 2.48 vs. 10.64 ± 1.76 ms, P < 0.0001, respectively). And the modified DC provides higher accuracy in distinguishing CHF than the conventional one (87.4 vs. 82.1%). The results indicate that the suggested technique enhances the performance of PRSA and improves the efficiency of DC in assessing ANS activity in CHF patients. [ABSTRACT FROM AUTHOR]

Abstract: Phase-Rectified Signal Averaging (PRSA) was shown to be a powerful tool for the study of quasi-periodic oscillations and nonlinear effects in non-stationary signals. Here we present a bivariate PRSA technique for the study of the inter-relationship between two simultaneous data recordings. Its performance is compared with traditional cross-correlation analysis, which, however, does not work well for non-stationary data and cannot distinguish the coupling directions in complex nonlinear situations. We show that bivariate PRSA allows the analysis of events in one signal when the other signal is in a certain phase or state; it is stable in the presence of noise and impassible to non-stationarities. [Copyright &y& Elsevier]

Low umbilical artery pH is a marker for neonatal acidosis and is associated with an increased risk for neonatal complications. The phase-rectified signal averaging (PRSA) features have demonstrated superior discriminatory or diagnostic ability and good interpretability in many biomedical applications including fetal heart rate analysis. However, the performance of PRSA method is sensitive to values of the selected parameters which are usually either chosen based on a grid search or empirically in the literature. In this paper, we examine PRSA method through the lens of dynamical systems theory and reveal the intrinsic connection between state space reconstruction and PRSA. From this perspective, we then introduce a new feature that can better characterize dynamical systems comparing with PRSA. Our experimental results on an open-access intrapartum Cardiotocography database demonstrate that the proposed feature outperforms state-of-the-art PRSA features in pH-based fetal heart rate analysis.

The fetal autonomic nervous system responds to uterine contractions during active labor as identified by changes in the accelerations and decelerations of fetal heart rate (FHR). Thus, this exploratory study aimed to characterize the asymmetry differences of beat-to-beat FHR accelerations and decelerations in preterm and term fetuses during active labor. In an observational study, we analyzed 10 min of fetal R-R series collected from women during active preterm labor (32–36 weeks of pregnancy, n = 17) and active term labor (38–40 weeks of pregnancy, n = 27). These data were used to calculate the Deceleration Reserve (DR), which is a novel parameter that quantifies the asymmetry of the average acceleration and deceleration capacity of the heart. In addition, relevant multiscale asymmetric indices of FHR were also computed. Lower values of DR, calculated with the input parameters of T = 50 and s = 10, were associated with labor occurring at the preterm condition (p = 0.0131). Multiscale asymmetry indices also confirmed significant (p < 0.05) differences in the asymmetry of FHR. Fetuses during moderate premature labor may experience more decaying R-R trends and a lower magnitude of decelerations compared to term fetuses. These differences of FHR dynamics might be related to the immaturity of the fetal cardiac autonomic nervous system as identified by this system response to the intense uterine activity at active labor. [ABSTRACT FROM AUTHOR]

Heart rate variability related to heart rate decelerations and accelerations is reduced in patients with type 1 diabetes compared to healthy individuals both in resting 10-min and ambulatory 24-h ECGs. [ABSTRACT FROM AUTHOR]

Background: Phase-rectified signal averaging (PRSA) was often applied to assess the cardiac vagal modulation. Despite its broad use, this method suffers from the confounding effects of anomalous variants of sinus rhythm. This study aimed to improve the original PRSA method in deceleration capacity (DC) quantification.Methods: The refined deceleration capacity (DCref) was calculated by excluding from non-vagally mediated abnormal variants of sinus rhythms. Holter recordings from 202 healthy subjects and 51 patients with end-stage renal disease (ESRD) have been used for validity. The DCref was compared to original DC (DCorg) by the area under receiver operating characteristic curve.Results: Experimental results demonstrate that the original and refined DCs calculated from 24-h, 2-h, and 30-min Holter recordings are significantly lower in patients with ESRD than those in the healthy group. In receiver operating characteristic curve analysis, the DCref provides better performance than the DCorg in distinguishing between the patients with ESRD and healthy control subjects. Furthermore, the refined PRSA technique enhances the low frequency and attenuates high frequency components for spectral analysis in ESRD patients.Conclusions: The DCref appears to reduce the influence of non-vagally mediated abnormal variants of sinus rhythm and highlighting the pathological influence. DCref, especially assessed from short-term electrocardiography recordings, may be complementary to existing autonomic function assessment, risk stratification, and efficacy prediction strategies. [ABSTRACT FROM AUTHOR]

Background: Phase-rectified signal averaging, an innovative signal processing technique, can be used to investigate quasi-periodic oscillations in noisy, nonstationary signals that are obtained from fetal heart rate. Phase-rectified signal averaging is currently the best method to predict survival after myocardial infarction in adult cardiology. Application of this method to fetal medicine has established significantly better identification than with short-term variation by computerized cardiotocography of growth-restricted fetuses.Objective: The aim of this study was to determine the longitudinal progression of phase-rectified signal averaging indices in severely growth-restricted human fetuses and the prognostic accuracy of the technique in relation to perinatal and neurologic outcome.Study Design: Raw data from cardiotocography monitoring of 279 human fetuses were obtained from 8 centers that took part in the multicenter European "TRUFFLE" trial on optimal timing of delivery in fetal growth restriction. Average acceleration and deceleration capacities were calculated by phase-rectified signal averaging to establish progression from 5 days to 1 day before delivery and were compared with short-term variation progression. The receiver operating characteristic curves of average acceleration and deceleration capacities and short-term variation were calculated and compared between techniques for short- and intermediate-term outcome.Results: Average acceleration and deceleration capacities and short-term variation showed a progressive decrease in their diagnostic indices of fetal health from the first examination 5 days before delivery to 1 day before delivery. However, this decrease was significant 3 days before delivery for average acceleration and deceleration capacities, but 2 days before delivery for short-term variation. Compared with analysis of changes in short-term variation, analysis of (delta) average acceleration and deceleration capacities better predicted values of Apgar scores <7 and antenatal death (area under the curve for prediction of antenatal death: delta average acceleration capacity, 0.62 [confidence interval, 0.19-1.0]; delta short-term variation, 0.54 [confidence interval, 0.13-0.97]; P=.006; area under the curve for prediction Apgar <7: average deceleration capacity <24 hours before delivery, 0.64 [confidence interval, 0.52-0.76]; short-term variation <24 hours before delivery, 0.53 [confidence interval, 0.40-0.65]; P=.015). Neither phase-rectified signal averaging indices nor short-term variation showed predictive power for developmental disability at 2 years of age (Bayley developmental quotient, <95 or <85).Conclusion: The phase-rectified signal averaging method seems to be at least as good as short-term variation to monitor progressive deterioration of severely growth-restricted fetuses. Our findings suggest that for short-term outcomes such as Apgar score, phase-rectified signal averaging indices could be an even better test than short-term variation. Overall, our findings confirm the possible value of prospective trials based on phase-rectified signal averaging indices of autonomic nervous system of severely growth-restricted fetuses. [ABSTRACT FROM AUTHOR]

Objectives: This study sought to evaluate cardiac baroreflex sensitivity (BRS) as a predictor of response to renal sympathetic denervation (RDN)., Background: Catheter-based RDN is a novel treatment option for patients with resistant arterial hypertension. It is assumed that RDN reduces efferent renal and central sympathetic activity., Methods: Fifty patients (age 60.3 ± 13.8 years [mean ± SD mean systolic blood pressure (BP) on ambulatory blood pressure monitoring (ABPM) 157 ± 22 mm Hg, despite medication with 5.4 ± 1.4 antihypertensive drugs) underwent RDN. Prior to RDN, a 30-min recording of continuous arterial BP (Finapres; TNO-TPD Biomedical Instrumentation, Amsterdam, the Netherlands) and high-resolution electrocardiography (1.6 kHz in orthogonal XYZ leads) was performed in all patients under standardized conditions. Cardiac BRS was assessed by phase-rectified signal averaging (BRSPRSA) according to previously published technologies. Response to RDN was defined as a reduction of mean systolic BP on ABPM by 10 mm Hg or more at 6 months after RDN., Results: Six months after RDN, mean systolic BP on ABPM was significantly reduced from 157 ± 22 mm Hg to 149 ± 20 mm Hg (p = 0.003). Twenty-six of the 50 patients (52%) were classified as responders. BRSPRSA was significantly lower in responders than nonresponders (0.16 ± 0.75 ms/mm Hg vs. 1.54 ± 1.73 ms/mm Hg; p < 0.001). Receiver-operator characteristics analysis revealed an area under the curve for prediction of response to RDN by BRSPRSA of 81.2% (95% confidence interval: 70.0% to 90.1%; p < 0.001). On multivariable logistic regression analysis, reduced BRSPRSA was the strongest predictor of response to RDN, which was independent of all other variables tested., Conclusions: Impaired cardiac BRS identifies patients with resistant hypertension who respond to RDN., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)