Phase-rectified Signal Averaging Research Articles

Phase-rectified signal averaging method to predict intermediate perinatal outcomes in infants with very preterm fetal growth restriction – a secondary analysis of TRUFFLE-trial

Background: Phase-rectified signal averaging (PRSA) – an innovative signal processing technique- is currently the best method in adult cardiology to predict survival after myocardial infarction. Our own research group firstly applied this method in fetal medicine. The new parameter “average acceleration capacity” (AAC) for surveillance of the fetal autonomic nervous system was derived and validated in prospective studies at hospital “Klinikum rechts der Isar”. AAC differentiated significantly better between growth restricted (FGR) fetuses and controls than the currently used computerized CTG parameter “short term variation” (STV). These results could be confirmed meanwhile by several other centres. The aim of this study was to investigate the longitudinal course of PRSA related patterns in severely growth restricted fetuses and their prognostic accuracy regarding perinatal and neurological outcome.

Brain sparing effect in growth-restricted fetuses is associated with decreased cardiac acceleration and deceleration capacities: a case-control study.

Phase rectified signal averaging (PRSA) is a new method of fetal heart rate variability (fHRV) analysis that quantifies the average acceleration (AC) and deceleration capacity (DC) of the heart. The aim of this study was to evaluate AC and DC of fHR [recorded by trans-abdominal fetal electrocardiogram (ta-fECG)] in relation to Doppler velocimetry characteristics of intrauterine growth restriction (IUGR). Prospective case-control study. Single third referral centre. IUGR (n=66) between 25 and 40 gestational weeks and uncomplicated pregnancies (n=79). In IUGR the nearest ta-fECG monitoring to delivery was used for PRSA analysis and Doppler velocimetry parameters obtained within 48hours. AC and DC were computed at s=T=9. The relation was evaluated between either AC or DC and Doppler velocimetry parameters adjusting for gestational age at monitoring, as well as the association between either AC or DC and IUGR with or without brain sparing. In IUGRs there was a significant association between either AC and DC and middle cerebral artery pulsatility index (PI; P=0.01; P=0.005), but the same was not true for uterine or umbilical artery PI (P>0.05). Both IUGR fetuses with and without brain sparing had lower AC and DC than controls, but this association was stronger for IUGRs with brain sparing. Our study observed for the first time that AC and DC at PRSA analysis are associated with middle cerebral artery PI, but not with uterine or umbilical artery PI, and that there is a significant decrease of AC and DC in association with brain sparing in IUGR fetuses from 25weeks of gestation to term. Brain sparing in IUGR fetuses is associated with decreased acceleration and deceleration capacities of the heart.

Can ECG monitoring identify seizures?

BackgroundSeizures affect the autonomic control of the heart rate and respiration, and changes in these two variables are known to occur during, and even before the EEG onset of the seizure. GoalThis work aims to quantify these changes and use them to identify the ECG onset. MethodsSingle-lead ECG signals were recorded from patients suffering from focal and generalized seizures. Two algorithms are proposed: one quantifies changes in the QRS morphology using principal component analysis, and one assesses cardiorespiratory interactions using phase rectified signal averaging. ResultsPositive predictive values of 86.6% and 77.5% and sensitivities of 100% and 90% were achieved for focal and generalized seizures respectively. ConclusionResults for focal seizures are in accordance with the literature, and detection of generalized seizures is improved after including respiratory information. SignificanceThese findings could improve monitoring systems in epilepsy, and closed-loop techniques that aim to stop seizures.

Study of atrial activities for abnormality detection by phase rectified signal averaging technique

Non-invasive detection of Atrial Fibrillation (AF) and Atrial Flutter (AFL) from ECG at the time of their onset can prevent forthcoming dangers for patients. In most of the previous detection algorithms, one of the steps includes filtering of the signal to remove noise and artefacts present in the signal. In this paper, a method of AF and AFL detection is proposed from ECG without the conventional filtering stage. Here Phase Rectified Signal Average (PRSA) technique is used with a novel optimized windowing method to achieve an averaged signal without quasi-periodicities. Both time domain and statistical features are extracted from a novel SQ concatenated section of the signal for non-linear Support Vector Machine (SVM) based classification. The performance of the proposed algorithm is tested with the MIT-BIH Arrhythmia database and good performance parameters are obtained, as indicated in the result section.

Parameters influence on acceleration and deceleration capacity based on trans-abdominal ECG in early fetal growth restriction at different gestational age epochs

ObjectiveIntrauterine growth restriction (IUGR) is characterized by chronic nutrient deprivation and hypoxemia that alters the autonomous nervous system regulation of fetal heart rate variability (fHRV). Phase-rectified signal averaging (PRSA) is a new algorithm capable to identify periodic and quasi-periodic patterns of HR, and which is used to quantify the average acceleration and deceleration capacity (AC/DC) of the heart. The computation of AC/DC depends on the parameters T and s, which we set so that s=T. T and s determine the periodicities that can be detected (the larger T the smaller the frequency of oscillations for which the method is most sensitive). The aim of the study was to evaluate the influence of the parameter T on PRSA computation, based on trans-abdominally acquired fetal ECG (ta-fECG), in early IUGR (<34 weeks of gestation) at two different gestational age epochs. Study designAC/DC were calculated for different T values (1÷45) on fetal RR intervals derived from ta-fECG in 22 IUGR and in 37 appropriate for gestational age (AGA) fetuses matched for gestational age, in two gestational age epochs: very preterm group (≥26÷<30 weeks), and preterm group (≥30÷<34 weeks), respectively. ResultsAC/DC were significantly lower in IUGR than in AGA fetuses for all T≥5 values (p<0.05). The best area under the receiver operating characteristic curve (AUC) in identifying IUGR at time of recording was observed for T9 [AUC AC-T9 0.87, 95% confidence interval (CI) 0.77–0.96; and AUC DC-T9 0.89, 95% CI 0.81–0.98), and in range of T 7÷15. In the same T interval, AC/DC were significantly lower in very preterm than in preterm IUGR group (p<0.05), while there were no differences in AGA fetuses at two gestational age epochs (p>0.05), respectively. The AUCs of AC-T9 and DC-T9 significantly outperformed that obtained by short-term variation (AUC 0.77, 95% CI 0.65–0.90; p=0.009 and p=0.003, respectively). ConclusionsOur study shows that within the range of T parameter 1÷45, T=9 proved to be the best value to discriminate the AC and DC of the fetal heart rate of IUGR from AGA fetuses prior to 34 weeks of gestation. These significant differences are emphasized in very preterm gestational age epochs.

Evaluation of acceleration and deceleration cardiac processes using phase-rectified signal averaging in healthy and idiopathic dilated cardiomyopathy subjects

The aim of the present study was to investigate the suitability of the Phase-Rectified Signal Averaging (PRSA) method for improved risk prediction in cardiac patients. Moreover, this technique, which separately evaluates acceleration and deceleration processes of cardiac rhythm, allows the effect of sympathetic and vagal modulations of beat-to-beat intervals to be characterized. Holter recordings of idiopathic dilated cardiomyopathy (IDC) patients were analyzed: high-risk (HR), who suffered sudden cardiac death (SCD) during the follow-up; and low-risk (LR), without any kind of cardiac-related death. Moreover, a control group of healthy subjects was analyzed. PRSA indexes were analyzed, for different time scales T and wavelet scales s, from RR series of 24 h-ECG recordings, awake periods and sleep periods. Also, the behavior of these indexes from simulated data was analyzed and compared with real data results. Outcomes demonstrated the PRSA capacity to significantly discriminate healthy subjects from IDC patients and HR from LR patients on a higher level than traditional temporal and spectral measures. The behavior of PRSA indexes agrees with experimental evidences related to cardiac autonomic modulations. Also, these parameters reflect more regularity of the autonomic nervous system (ANS) in HR patients.

Abstract 17230: Respiratory Sinus Arrhythmia Quantified from Standard ECG for Risk Stratification of Post-Infarction Patients

Objectives: Respiratory sinus arrhythmia (RSA) reflects modulation of the sinoatrial node discharge frequency by the autonomic nervous system. Impaired autonomic function is associated with adverse outcome in cardiac patients. We developed a method for calculating RSA from standard ECG recordings and investigated its association with mortality in survivors of acute myocardial infarction. Methods: Consecutive patients (n=941, mean age 61 years, 19% female) presenting with acute myocardial infarction and sinus rhythm were enrolled between May 2000 and March 2005 and followed up until August 2010. The main study outcome was 5-year all-cause mortality. Patients underwent 30-minute ECG recordings. Auxiliary respiratory muscle activity derived from high pass-filtered ECG signal was used to define respiratory phase. The influence of expiration on RR intervals (RRI) was assessed by bivariate phase-rectified signal averaging (PRSA), and RSA PRSA was quantified by Haar wavelet analysis. RSA PRSA ≤0 was defined as abnormal. Results: During the follow-up, 72 patients died. Five-year mortality rates in patients with normal and abnormal RSA PRSA were 4% and 14%, respectively. Under univariable analysis, RSA PRSA was a significant predictor of death (p&lt;0.001), as were GRACE score (p&lt;0.001), LVEF (p&lt;0.001), and the presence of diabetes mellitus (p&lt;0.001). Under multivariable analysis, RSA PRSA , GRACE score, LVEF, and diabetes mellitus were independently and significantly associated with outcome. Conclusions: Respiratory sinus arrhythmia, quantified by bivariate PRSA from standard ECG recordings, is an independent predictor of mortality risk in post-infarction patients.

Acceleration and deceleration capacity of fetal heart rate in an in-vivo sheep model.

BackgroundFetal heart rate (FHR) variability is an indirect index of fetal autonomic nervous system (ANS) integrity. FHR variability analysis in labor fails to detect early hypoxia and acidemia. Phase-rectified signal averaging (PRSA) is a new method of complex biological signals analysis that is more resistant to non-stationarities, signal loss and artifacts. It quantifies the average cardiac acceleration and deceleration (AC/DC) capacity.ObjectiveThe aims of the study were: (1) to investigate AC/DC in ovine fetuses exposed to acute hypoxic-acidemic insult; (2) to explore the relation between AC/DC and acid-base balance; and (3) to evaluate the influence of FHR decelerations and specific PRSA parameters on AC/DC computation.MethodsRepetitive umbilical cord occlusions (UCOs) were applied in 9 pregnant near-term sheep to obtain three phases of MILD, MODERATE, and SEVERE hypoxic-acidemic insult. Acid-base balance was sampled and fetal ECGs continuously recorded. AC/DC were calculated: (1) for a spectrum of T values (T = 1÷50 beats; the parameter limits the range of oscillations detected by PRSA); (2) on entire series of fetal RR intervals or on “stable” series that excluded FHR decelerations caused by UCOs.ResultsAC and DC progressively increased with UCOs phases (MILD vs. MODERATE and MODERATE vs. SEVERE, p<0.05 for DC = 2–5, and AC = 1–3). The time evolution of AC/DC correlated to acid-base balance (0.4<<0.9, p<0.05) with the highest for . PRSA was not independent from FHR decelerations caused by UCOs.ConclusionsThis is the first in-vivo evaluation of PRSA on FHR analysis. In the presence of acute hypoxic-acidemia we found increasing values of AC/DC suggesting an activation of ANS. This correlation was strongest on time scale dominated by parasympathetic modulations. We identified the best performing parameters (), and found that AC/DC computation is not independent from FHR decelerations. These findings establish the basis for future clinical studies.

Assessment of coupling between trans-abdominally acquired fetal ECG and uterine activity by bivariate phase-rectified signal averaging analysis.

Couplings between uterine contractions (UC) and fetal heart rate (fHR) provide important information on fetal condition during labor. At present, couplings between UC and fHR are assessed by visual analysis and interpretation of cardiotocography. The application of computerized approaches is restricted due to the non-stationarity of the signal, missing data and noise, typical for fHR. Herein, we propose a novel approach to assess couplings between UC and fHR, based on a signal-processing algorithm termed bivariate phase-rectified signal averaging (BPRSA).MethodsElectrohysterogram (EHG) and fetal electrocardiogram (fECG) were recorded non-invasively by a trans-abdominal device in 73 women at term with uneventful singleton pregnancy during the first stage of labor. Coupling between UC and fHR was analyzed by BPRSA and by conventional cross power spectral density analysis (CPSD). For both methods, degree of coupling was assessed by the maximum coefficient of coherence (CPRSA and CRAW, respectively) in the UC frequency domain. Coherence values greater than 0.50 were consider significant. CPRSA and CRAW were compared by Wilcoxon test.ResultsAt visual inspection BPRSA analysis identified coupled periodicities in 86.3% (63/73) of the cases. 11/73 (15%) cases were excluded from further analysis because no 30 minutes of fECG recording without signal loss was available for spectral analysis. Significant coupling was found in 90.3% (56/62) of the cases analyzed by BPRSA, and in 24.2% (15/62) of the cases analyzed by CPSD, respectively. The difference between median value of CPRSA and CRAW was highly significant (0.79 [IQR 0.69–0.90] and 0.29 [IQR 0.17–0.47], respectively; p<0.0001).ConclusionBPRSA is a novel computer-based approach that can be reliably applied to trans-abdominally acquired EHG-fECG. It allows the assessment of correlations between UC and fHR patterns in the majority of labors, overcoming the limitations of non-stationarity and artifacts. Compared to standard techniques of cross-correlations, such as CPSD, BPRSA is significantly superior.

The effect of augmentation of labour with syntocinon on the fetal CTG using objective computerised analysis: a nested case–control study

ObjectiveTo investigate the effect of syntocinon augmentation on the fetal cardiotocogram (CTG) using computerised analysis. We hypothesised that syntocinon will have no direct effects on the fetal heart rate if used correctly. Study designA retrospective, nested case–control study. SettingIntrapartum CTG records from the digital archive at the John Radcliffe Hospital, Oxford, UK. Subjects110 women with singleton pregnancies of >36 weeks gestation, no known congenital abnormality, spontaneous onset of labour and syntocinon augmentation for failure to progress, with start time of syntocinon recorded, from between August 1998 and December 1999, extensively matched to 110 controls who had normally progressing labours. MethodsEight different CTG features were measured during four time points with OxSys, a computerised numerical analysis system. Statistical analysisDifferences in the CTG features over time in cases and controls using ANOVA and Friedman's ANOVA and at each time point between case–control pairs using Student's t-test and the Wilcoxon signed rank test. ResultsAfter administration, syntocinon increased the frequency, decreased the duration and decreased the resting time between contractions (p<0.001), resulting in no significant difference between normally progressing labours and those requiring augmentation. The case group had a significantly higher signal stability index (SSI) and fewer decelerations compared to the control group – differences which disappeared after augmentation was commenced (p=0.025 and 0.033 respectively). Syntocinon did not affect the baseline heart rate, short term variability (STV) or phase rectified signal averaging (PRSA) (p=0.518, 0.215 and 0.138) in comparison with controls. There was a significant increase in the PRSA in babies born with acidaemia (arterial pH≤7.05) 60–120min after syntocinon was commenced that was not seen with in babies with a normal pH (p=0.002). ConclusionSyntocinon “normalises” ineffective uterine activity without any direct effect on the fetal heart rate. Therefore its administration does not confound objective computerised analysis. There may be a specific response in PRSA shortly after commencing syntocinon augmentation in the fetus which is subsequently born acidaemic which requires further investigation.

Phase-rectified signal averaging for intrapartum electronic fetal heart rate monitoring is related to acidaemia at birth.

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. Historical cohort. Large UK teaching hospital. All 7568 Oxford deliveries that met the study criteria from April 1993 to February 2008. We analysed the last 30 minutes of the FHR and associated outcomes of infants. We used computerised analysis to calculate PRSA decelerative capacity (DC(PRSA)), and its ability to predict umbilical arterial blood pH ≤ 7.05 using receiver operator characteristic (ROC) curves and event rate estimates (EveREst). We compared DC(PRSA) with STV calculated on the same traces. Umbilical arterial blood pH ≤ 7.05. We found that PRSA could be measured in all cases. DC(PRSA) predicted acidaemia significantly better than STV: the area under the ROC curve was 0.665 (95% CI 0.632-0.699) for DC(PRSA), 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 DC(PRSA) but 11.00% for STV (P < 0.001). DC(PRSA) was not highly correlated with STV. DC(PRSA) 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 DC(PRSA) and STV suggests that they could be combined in multivariate FHR analyses.

Automated Assessment of Cardiac Autonomic Function by Means of Deceleration Capacity from Noisy, Nonstationary ECG Signals: Validation Study

Assessment of heart rate variability by means of deceleration capacity (DC) provides a noninvasive probe of cardiac autonomic activity. However, clinical use of DC is limited by the need of manual review of the ECG signals to eliminate artifacts, noise, and nonstationarities. To validate a novel approach to fully automatically assess DC from noisy, nonstationary signals We analyzed 100 randomly selected ECG tracings recorded for 10 minutes by routine monitor devices (GE DASH 4000, sample size 100 Hz) in a medical emergency department. We used a novel automated R-peak detection algorithm, which is mainly based on a Shannon energy envelope estimator and a Hilbert transformation. We transformed the automatically generated RR interval time series by phase-rectified signal averaging (PRSA) to assess DC of heart rate (DCauto ). DCauto was compared to DCmanual , which was obtained from the same manually preprocessed ECG signals. DCauto and DCmanual showed good correlation and agreement, particularly if a low-pass filter was implemented into the PRSA algorithm. Correlation coefficient between DCauto and DCmanual was 0.983 (P < 0.0001). Average difference between DCauto and DCmanual was -0.23±0.49 ms with limits of agreement ranging from -1.19 to 0.73 ms. Significantly lower correlations were observed when a different R-peak detection algorithm or conventional heart rate variability (HRV) measures were tested. DC can be fully automatically assessed from noisy, nonstationary ECG signals.

Impaired Cardiac Baroreflex Sensitivity Predicts Response to Renal Sympathetic Denervation in Patients With Resistant Hypertension

This study sought to evaluate cardiac baroreflex sensitivity (BRS) as a predictor of response to renal sympathetic denervation (RDN). 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. 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. 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. Impaired cardiac BRS identifies patients with resistant hypertension who respond to RDN.

Average acceleration and deceleration capacity of fetal heart rate in normal pregnancy and in pregnancies complicated by fetal growth restriction

Objective: To study fetal heart rate (FHR), its short term variability (STV), average acceleration capacity (AAC), and average deceleration capacity (ADC) throughout uncomplicated gestation, and to perform a preliminary comparison of these FHR parameters between small-for dates (SFD) and control fetuses. Methods: Prospective observational study of 7 h FHR-recordings obtained with a fetal-ECG monitor in the second half of uncomplicated pregnancies (n = 90) and pregnancies complicated by fetal SFD (n = 30). FHR and STV were calculated according to established analysis. True beat-to-beat FHR, recorded at 1 ms accuracy, was used to calculate AAC and ADC using Phase Rectified Signal Averaging (PRSA). Mean values of FHR, STV, AAC, and ADC derived from recordings in SFD fetuses were compared with the reference curves. Results: Compared with the control group the mean z-scores for STV, AAC, and ADC in SFD fetuses were lower by 1.0 SD, 1.5 SD, and 1.7 SD, respectively (p < 0.0001 for all comparisons). In SFD fetuses, both the AAC and ADC z-scores were lower than the STV z-scores (p < 0.02 and p < 0.002, respectively). Conclusions: Analysis of the AAC and ADC as recorded with a high resolution fECG recorder may differentiate better between normal and SFD fetuses than STV.

Interaction between age and aerobic fitness in determining heart rate dynamics

Heart rate variability (HRV) and phase-rectified signal averaging (PRSA) estimates of heart rate dynamics are diminished in older people compared with younger people. However, it is not fully elucidated whether these differences are related to age per se or to the concomitant influence of aerobic fitness. Aerobic fitness (peak oxygen uptake, gas exchange threshold, oxygen uptake kinetics, exercise economy) was assessed in 70 healthy adults (41 male) aged 18–57 years. Participants also underwent a 24 h, ambulatory ECG for the derivation of HRV and PRSA variables. HRV was most sensitive to age and aerobic fitness when measured during the morning period (6 am–12 pm). HRV and PRSA were both diminished with age and were higher in aerobically superior participants. The decline in HRV with age was predominantly attributable to age itself (33%), with aerobic fitness representing an additional modulating factor. The present study also provides tentative evidence that assessment of the influence of aerobic fitness should not rely on O2peak alone. These findings demonstrate that age per se is an important factor in determining HRV. However, given the clinical importance of diminished HRV and the immutable nature of aging, the potential significance of physical activity/training to enhance cardiac regulatory function should not be underestimated.

Spontaneous baroreflex sensitivity: Prospective validation trial of a novel technique in survivors of acute myocardial infarction

Low baroreflex sensitivity (BRS) indicates poor prognosis after acute myocardial infarction. Noninvasive BRS assessment is complicated by nonstationarities and noise in electrocardiogram and pressure signals. Phase-rectified signal averaging is a novel signal processing technology overcoming these problems. To prospectively validate a BRS measure (baroreflex sensitivity assessed by means of phase-rectified signal averaging [BRS(PRSA)]) based on this technology. Nine hundred forty-one consecutive acute myocardial infarction survivors aged 80 years or younger in sinus rhythm were prospectively enrolled at 2 German university hospitals. All patients underwent 30-minute recordings of electrocardiogram and arterial blood pressures (Portapres; TNO-TPD Biomedical Instrumentation, Amsterdam, Netherlands) within the first 2 weeks after myocardial infarction. BRS(PRSA) was prospectively dichotomized at 1.58 ms/mm Hg. Primary end point was all-cause mortality at 5 years. Multivariable analyses included Global Registry of Acute Coronary Events score (dichotomized at ≥120), sex, BRS(PRSA), left ventricular ejection fraction (dichotomized at ≤35%), and diabetes mellitus. BRS(PRSA) was compared with 3 standard noninvasive BRS measures, that is, the sequence method, the transfer function method, and the correlation method. During follow-up, 72 patients (7.7%) died. BRS(PRSA) stratified the study population into a high-risk group of 405 patients (≤1.58 ms/mm Hg) with an estimated 5-year mortality of 14.2% and a low-risk group of 536 patients (>1.58 ms/mm Hg) with a 5-year mortality of 2.8% (P <.0001). On multivariable analysis, BRS(PRSA) ≤ 1.58 ms/mm Hg was associated with a hazard ratio of 3.1 (confidence interval 1.7-5.6; P = .001). Predictive power of BRS(PRSA) ≤ 1.58 ms/mm Hg was particularly strong in patients with a Global Registry of Acute Coronary Events score of ≥120 or with a left ventricular ejection fraction of ≤35%. BRS(PRSA) is a powerful and independent predictor of mortality in postinfarction patients especially when assessed in patients with a Global Registry of Acute Coronary Events score of ≥120 or a left ventricular ejection fraction of ≤35%.

Exercise training slows down heart rate and improves deceleration and acceleration capacity in patients with heart failure

Controlled physical training has been shown to be a valuable therapeutic addition to a pharmacological treatment in patients with chronic heart failure (CHF). It is speculated that repeated physical training can improve the autonomic modulation of the cardiovascular system in patients with CHF. The present study evaluates autonomic function in patients with CHF by means of heart rate variability and the phase-rectified signal averaging of heart rate that allows the quantification of the acceleration capacity and deceleration capacity. Two groups of patients with CHF treated with comparable pharmacological medications were enrolled into this study. One group entered a 24-week training program, whereas another group remained without it. After the completion of the study, there was a significant increase of mean RR interval, high- and low-frequency power of heart rate variability, and the magnitudes of deceleration capacity and acceleration capacity only in patients who underwent the cardiac rehabilitation program with controlled physical training.

Bivariate phase-rectified signal averaging for assessment of spontaneous baroreflex sensitivity: normalization of the results

Background Previously proposed technique for assessment of spontaneous baroreflex sensitivity (BRS) based on bivariate phase-rectified signal averaging measures averaged R-R interval (RRI) changes triggered by beat-to-beat increases in systolic blood pressure (SBP). In this study, we investigate a normalized version of the method that relates the averaged RRI changes to the triggering blood pressure changes, thus providing the results in measurement units comparable with existing literature. Methods Data of previously reported prospective observational study were used. In each of 146 heart failure patients presenting with sinus rhythm, 10-minute recordings of electrocardiogram and arterial and blood pressures were obtained in the supine resting position. The averaged RRI increases initiated by beat-to-beat SBP increases were measured (original BRS result in milliseconds) and normalized for the averaged beat-to-beat SBP increases (normalized BRS result in milliseconds per millimeters of mercury). Both results were compared in terms of predicting all-cause mortality during a mean follow-up of 2.7 ± 1.1 years when 42 patients (28.8%) died. Results Both types of results were highly correlated ( r = 0.938, P < .001) and led to similarly strong separation of high- and low-risk groups. The receiver operator characteristics of both indices were well within the 95% confidence intervals of each other, and the areas under the characteristics were practically identical: 71.1% (95% confidence interval, 60.7%-80.9%) for original BRS and 69.7% (58.9%-79.2%) for normalized BRS. Conclusion The results might question the concept of a linear relationship between the SBP changes and RRI changes. The phase-rectified signal averaging–based assessment of BRS may be used with equal legitimacy in the nonnormalized and normalized forms; the normalized form provides results in conventional measurement units.

Heart rate turbulence and phase-rectified signal averaging: methods and clinical application

Heart rate turbulence and phase-rectified signal averaging: methods and clinical application

New computerized fetal heart rate analysis for surveillance of intrauterine growth restriction

Decreased fetal heart rate variability is associated with higher perinatal morbidity and mortality in intrauterine growth restriction (IUGR). This study used a new method [phase-rectified signal averaging (PRSA)] to calculate acceleration- and deceleration-related fluctuations of the fetal heart rate. Cardiotocograms from 74 growth-restricted and 161 normal fetuses were included. Both groups were matched for gestational age. The transformed PRSA signal was quantified by the acceleration-related parameter-averaged acceleration capacity (AAC) and compared to the standard short-term variation (STV). Mann-Whitney test and receiver operator characteristic (ROC) curves were used for statistical analysis. For AAC, the median values of the IUGR group and control group were 1.97 bpm [interquartile range (IQR): 1.66-2.23] and 2.49 bpm (IQR: 2.24-2.72), respectively. For STV, these values were 5.44 ms (IQR: 4.49-7.38) and 7.79 ms (IQR: 6.35-9.66), respectively. The area under the ROC curve was 81.4% for AAC and 70.5% for STV. The results of AAC are in both groups comparable to STV. Longitudinal studies are needed to investigate the association of AAC with the clinical outcome of the newborn.