Clinical and genetic yield of familial screening after a sudden unexplained death at a young age.

BACKGROUND: In a population under 45 years of age, the predominant causes of sudden cardiac death (SCD) are inherited cardiac diseases. Determining the underlying cause may help identify relatives at risk and prevent further events but is more difficult if an autopsy has not been performed. AIMS: We aimed to assess the diagnostic value of clinical and genetic screening in relatives of young non-autopsied sudden unexplained death (SUD) victims. MATERIAL AND METHODS: Eighty-seven relatives of 65 young non-autopsied SUD victims from 39 families were evaluated from 2016 to 2019. The relatives underwent extensive noninvasive cardiac workup. Genetic examinations were performed in 39 families. RESULTS: The definite diagnoses were made in 17 of 39 (44%) families. Cardiomyopathies were identified in 10 families (5 hypertrophic, 4 dilated, and 1 arrhythmogenic), followed by long QT syndrome (5 families). In 3 families, probable diagnoses were made, whereas in 20 families no diagnosis was achieved. In total, definite and probable diagnoses were made in 18 and 5 patients, respectively. All affected relatives were offered medical management, one of them died of heart failure and one underwent transplantation during the median follow-up of 3 years. Disease-causing variants were found in 7 of 39 (18%) probands; all in families with a definite diagnosis. Variants of unknown significance were found in 2 probands. CONCLUSION: Screening of relatives of SUD victims is warranted and may save lives, even if it is not guided by autopsy results. Genetic testing in families without the disease phenotype has little effectiveness.

Heart rate dynamics and asymmetry during sympathetic activity stimulation and post-stimulation recovery in ski mountaineers-a pilot exploratory study.

There is a lack of studies on non-linear heart rate (HR) variability in athletes. We aimed to assess the usefulness of short-term HR dynamics and asymmetry parameters to evaluate the neural modulation of cardiac activity based on non-stationary RR interval series by studying their changes during sympathetic nervous system activity stimulation (isometric handgrip test) and post-stimulation recovery in professional ski mountaineers. The correlation between the changes in the parameters and the respiratory rate (RespRate) and also the duration of the career was analyzed. Short-term (5 min) and ultra-short-term (1 min) rates of patterns with no variations (0V), number of acceleration runs of length 1 (AR1), and short-term Porta's Index were greater, whereas Guzik's Index (GI) was smaller during sympathetic stimulation compared to rest. GI increased and the number of AR1 decreased during recovery. Greater increases in GI and RMSSD were associated with greater decreases in RespRate during recovery. Greater increases in RespRate from rest to short-term sympathetic stimulation were associated with greater increases in 0V (Max-min method) and AR1 but also with greater decreases in decelerations of short-term variance and accelerations and decelerations of long-term variance. Greater increases in 0V (Max-min method) and number of AR1 during sympathetic stimulation were associated with a shorter career duration. Greater decreases in these parameters during recovery were associated with a longer career duration. Changes in measures of HR dynamics and asymmetry, calculated based on short-term non-stationary RRi time series induced by sympathetic stimulation and post-stimulation recovery, reflected sympathovagal shift and were associated with condition-related alterations in RespRate and career duration in athletes who practice ski mountaineering.

Reliability of Symbolic Analysis of Heart Rate Variability and Its Changes During Sympathetic Stimulation in Elite Modern Pentathlon Athletes: A Pilot Study.

Background and Purpose: Most studies on heart rate variability (HRV) in professional athletes concerned linear, time-, and frequency-domain indices, and there is lack of studies on non-linear parameters in this group. The study aimed to determine the inter-day reliability, and group-related and individual changes of short-term symbolic dynamics (SymDyn) measures during sympathetic nervous system activity (SNSa) stimulation among elite modern pentathletes. Methods: Short-term electrocardiographic recordings were performed in stable measurement conditions with a 7-day interval between tests. SNSa stimulation via isometric handgrip strength test was conducted on the second day of study. The occurrence rate of patterns without variations (0V), with one variation (1V), two like (2LV), and two unlike variations (2UV) obtained using three approaches (the Max-min, the σ, and the Equal-probability methods) were analyzed. Relative and absolute reliability were evaluated. Results: All SymDyn indices obtained using the Max-min method, 0V, and 2UV obtained using the σ method, 2UV obtained using the Equal-probability method presented acceptable inter-day reliability (the intraclass correlation coefficient between .91 and .99, Cohen's d between -.08 and .10, the within-subject coefficient of variation between 4% and 22%). 2LV, 2UV, and 0V obtained using the Max-min and σ methods significantly decreased and increased, respectively, during SNSa stimulation-such changes were noted for all athletes. There was no significant association between differences in SymDyn parameters and respiratory rate in stable conditions and while comparing stable conditions and SNSa stimulation. Conclusion: SymDyn indices may be used as reliable non-respiratory-associated parameters in laboratory settings to detect autonomic nervous system (ANS) activity modulations in elite endurance athletes. These findings provide a potential solution for addressing the confounding influence of respiration frequency on HRV-derived inferences of cardiac autonomic function. For this reason, SymDyn may prove to be preferable for field-based monitoring where measurements are unsupervised.

Assessment of time irreversibility in a time series using visibility graphs.

In this paper, we studied the time-domain irreversibility of time series, which is a fundamental property of systems in a nonequilibrium state. We analyzed a subgroup of the databases provided by University of Rochester, namely from the THEW Project. Our data consists of LQTS (Long QT Syndrome) patients and healthy persons. LQTS may be associated with an increased risk of sudden cardiac death (SCD), which is still a big clinical problem. ECG-based artificial intelligence methods can identify sudden cardiac death with a high accuracy. It follows that heart rate variability contains information about the possibility of SCD, which may be extracted, provided that appropriate methods are developed for this purpose. Our aim was to assess the complexity of both groups using visibility graph (VG) methods. Multivariate analysis of connection patterns of graphs built from time series was performed using multiplex visibility graph methods. For univariate time series, time irreversibility of the ECG interval QT of patients with LQTS was lower than for the healthy. However, we did not observe statistically significant difference in the comparison of RR intervals time series of the two groups studied. The connection patterns retrieved from multiplex VGs have more similarity with each other in the case of LQTS patients. This observation may be used to develop better methods for SCD risk stratification.

Asymmetric multiscale multifractal analysis (AMMA) of heart rate variability.

Objective.The physiological activity of the heart is controlled and modulated mostly by the parasympathetic and sympathetic nervous systems. Heart rate variability (HRV) analysis is therefore used to observe fluctuations that reflect changes in the activity in these two branches. Knowing that acceleration and deceleration patterns in heart rate fluctuations are asymmetrically distributed, the ability to analyze HRV asymmetry was introduced into MMA.Approach. The new method is called asymmetric multiscale multifractal analysis (AMMA) and the analysis involved six groups: 36 healthy persons, 103 cases with aortic valve stenosis, 36 with hypertrophic cardiomyopathy, 32 with atrial fibrillation, 59 patients with coronary artery disease (CAD) and 13 with congestive heart failure.Main results. Analyzing the results obtained for the 6 groups of patients based on the AMMA method, i.e. comparing the Hurst surfaces for heart rate decelerations and accelerations, it was noticed that these surfaces differ significantly. And the differences occur in most groups for large fluctuations (multifractal parameterq > 0). In addition, a similarity was found for all groups for the AMMA Hurst surface for decelerations to the MMA Hurst surface-heart rate decelerations (lengthening of the RR intervals) appears to be the main factor determining the shape of the complete Hurst surface and so the multifractal properties of HRV. The differences between the groups, especially for CAD, hypertrophic cardiomyopathy and aortic valve stenosis, are more visible if the Hurst surfaces are analyzed separately for accelerations and decelerations.Significance. The AMMA results presented here may provide additional input for HRV analysis and create a new paradigm for future medical screening. Note that the HRV analysis using MMA (without distinguishing accelerations from decelerations) gave satisfactory screening statistics in our previous studies.

Information Flow Between Heart Rhythm, Repolarization, and the Diastolic Interval Series for Healthy Individuals and LQTS1 Patients.

Using information theoretic measures, relations between heart rhythm, repolarization in the tissue of the heart, and the diastolic interval time series are analyzed. These processes are a fragment of the cardiovascular physiological network. A comparison is made between the results for 84 (42 women) healthy individuals and 65 (45 women) long QT syndrome type 1 (LQTS1) patients. Self-entropy, transfer entropy, and joint transfer entropy are calculated for the three time series and their combinations. The results for self-entropy indicate the well-known result that regularity of heart rhythm for healthy individuals is larger than that of QT interval series. The flow of information depends on the direction with the flow from the heart rhythm to QT dominating. In LQTS1 patients, however, our results indicate that information flow in the opposite direction may occur-a new result. The information flow from the heart rhythm to QT dominates, which verifies the asymmetry seen by Porta et al. in the variable tilt angle experiment. The amount of new information and self-entropy for LQTS1 patients is smaller than that for healthy individuals. However, information transfers from RR to QT and from DI to QT are larger in the case of LQTS1 patients.

Exercise test in patients with asymptomatic aortic stenosis: clinically useful or not?

INTRODUCTION: Aortic valve replacement (AVR) is recommended for symptomatic patients with severe aortic stenosis (AS). In asymptomatic AS (AAS), exercise testing (ET) is recommended; however, it remains controversial. OBJECTIVES: The aim of our study was to assess the importance of ET in patients with AAS. PATIENTS AND METHODS: A total of 89 patients with AAS (53 men; mean [SD] age, 59.5 [11.7] years) underwent 244 symptom­limited ETs. RESULTS: All ETs were clinically negative. During the median (interquartile range) follow­up of 22 (12) months, 39 patients (22 men) developed symptoms (the AVR group). This group was compared with 50 asymptomatic non­AVR patients. In the multivariable Cox analysis, the maximal heart rate during ET less than 85% of age- and sex-adjusted maximal predicted heart rate (THR less than 85%) was related to AVR (P = 0.01). After adjusting for the use of ß­blockers, this was not significant (P = 0.08). In the ß­blocker subgroup, the THR less than 85% was significantly related to AVR in the univariable Cox analysis (hazard ratio, 2.2; 95% CI, 1.07-4.9; P = 0.03) and after adjusting for age (P = 0.047). This relationship was not observed in patients who did not receive ß­blockers. CONCLUSION: In patients with AAS, ET is safe; however, in our study group, the results were not cru­ cial in making a decision to perform AVR. Patients treated with ß­blockers who did not achieve 85% of predicted maximal heart rate had a higher probability of AVR. The influence of the use of ß­blockers on the decision to perform AVR in this patient population warrants further revision.

Changes in Short-Term and Ultra-Short Term Heart Rate, Respiratory Rate, and Time-Domain Heart Rate Variability Parameters during Sympathetic Nervous System Activity Stimulation in Elite Modern Pentathlonists-A Pilot Study.

Monitoring of markers reflecting cardiac autonomic activity before and during stressful situations may be useful for identifying the physiological state of an athlete and may have medical or performance implications. The study aimed to determine group and individual changes in short-term (5 min) and ultra-short-term (1 min) heart rate (HR), respiratory rate (RespRate), and time-domain heart rate variability (HRV) parameters during sympathetic nervous system activity (SNSa) stimulation among professional endurance athletes. Electrocardiographic recordings were performed in stable measurement conditions (Baseline) and during SNSa stimulation via isometric handgrip in 12 elite modern pentathlonists. Significant increases in short-term HR and decreases in time-domain HRV parameters with no changes in RespRate were observed during SNSa stimulation. Significant differences were observed between Baseline (all minutes) and the last (i.e., 5th) minute of SNSa stimulation for ultra-short-term parameters. Analysis of intra-individual changes revealed some heterogeneity in responses. The study provides baseline responses of HR, RespRate, and time-domain HRV parameters to SNSa stimulation among elite pentathlonists, which may be useful for identifying abnormal responses among fatigued or injured (e.g., concussed) athletes. More attention to individual analysis seems to be necessary when assessing physiological responses to sympathetic stimuli in professional endurance athletes.

A Pilot Study of the Reliability and Agreement of Heart Rate, Respiratory Rate and Short-Term Heart Rate Variability in Elite Modern Pentathlon Athletes.

Research on reliability of heart rate variability (HRV) parameters in athletes has received increasing attention. The aims of this study were to examine the inter-day reliability of short-term (5 min) and ultra-short-term (1 min) heart rate (HR), respiratory rate (RespRate) and HRV parameters, agreement between short-term and ultra-short-term parameters, and association between differences in HR, RespRate and HRV parameters in elite modern pentathletes. Electrocardiographic recordings were performed in stable measurement conditions with a week interval between tests. Relative reliability was evaluated by intra-class correlation coefficients, absolute reliability was evaluated by within-subject coefficient of variation, and agreement was evaluated using Bland-Altman (BA) plot with limits of agreement and defined a priori maximum acceptable difference. Short-term HR, RespRate, log transformed (ln) root mean square of successive normal-to-normal interval differences (lnRMSSD), ln high frequency (lnHF) and SD2/SD1 HRV indices and ultra-short-term HR, RespRate and lnRMSSD presented acceptable, satisfactory inter-day reliability. Although there were no significant differences between short-term and ultra-short-term HR, RespRate and lnRMSSD, no parameter showed acceptable differences with BA plots. Differences in time-domain and non-linear HRV parameters were more correlated with differences in HR than with differences in RespRate. Inverse results were observed for frequency-domain parameters. Short-term HR, RespRate, lnRMSSD, lnHF, and SD2/SD1 and ultra-short-term HR, RespRate and lnRMSSD could be used as reliable parameters in endurance athletes. However, practitioners should interpret changes in HRV parameters with regard to concomitant differences in HR and RespRate and caution should be taken before considering 5 min and 1 min parameters as interchangeable.

The effect of persistent U-shaped patterns in RR night-time series on the heart rate variability complexity in healthy humans.

OBJECTIVE: U-shaped patterns, characteristic periods of time observed in tachograms, are a specific subgroup among very low frequency components characterized by relatively short periods of smooth accelerations followed by decelerations of heart rhythm. In this study, we characterize this phenomenon and its effect on heart rate variability (HRV) parameters. APPROACH: We calculated linear (the mean and standard deviation of RR intervals, RMSSD, pNN50 and the power of the frequency components) and nonlinear (V0, V1 and V2 Porta's symbolic analysis, Shannon and Sample entropy, Guzik's and Porta's asymmetry indexes, the exponents α1 and α2 of detrended fluctuation analysis and the Hurst surface h(q,s) of multiscale multifractal analysis (MMA)) HRV parameters for 65 RR interval night-time series (39 females, 37.5(11.3) years old and 26 males, 41.7(16.5) years old; all without organic heart diseases). All parameters were calculated for original data and for the three kinds of test data in which the following parts of the time series were replaced by 1/f noise: (A) the U-shape patterns annotated in a given data set, (B) randomly chosen windows of similar size as the U-shaped patterns, (C) acceleration-deceleration events shorter than U-shaped patterns. MAIN RESULTS: We found that the U-shaped patterns, as the most persistent structures in RR night-time intervals series, affect the long-range correlation properties (measured by α2). We also found that the U-shaped patterns importantly strictly affect the shape of h(q,s) surface at different scales s. Removing the U-shaped patterns results in the shape of the h(q,s) surface losing the properties characteristic for healthy heart rhythm. The largest quantitative effect of U-shaped patterns was obtained for the power of the VLF component. The mean percentage difference of the VLF component between the original data and the A to C type test data were 19.4%, -4.3% and 5.3%, respectively. SIGNIFICANCE: Although percentage contribution of U-shaped patterns is small compared to the whole night-time series (on the average 3.1%(1.7%) with a standard deviation of 1.7%), these patterns have a considerable impact on the HRV parameters describing the VLF, persistency, nonlinear correlations and multifractal properties.

Heart Rate Variability in Children and Adolescents with Cerebral Palsy-A Systematic Literature Review.

Cardiac autonomic dysfunction has been reported in patients with cerebral palsy (CP). The aim of this study was to assess the existing literature on heart rate variability (HRV) in pediatric patients with CP and a special attention was paid to the compliance of the studies with the current HRV assessment and interpretation guidelines. A systematic review was performed in PubMed, Web of Science, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases searched for English language publications from 1996 to 2019 using Medical Subject Headings (MeSH) terms "heart rate variability" and "cerebral palsy" in conjunction with additional inclusion criteria: studies limited to humans in the age range of 0-18 years and empirical investigations. Out of 47 studies, 12 were included in the review. Pediatric patients with CP presented a significantly higher resting heart rate and reduced HRV, different autonomic responses to movement stimuli compared to children with normal development, but also reduced HRV parameters in the children dependent on adult assistance for mobility compared to those generally independent. None of the included studies contained the necessary details concerning RR intervals acquisition and HRV measurements as recommended by the guidelines. Authors of HRV studies should follow the methodological guidelines and recommendations on HRV measurement, because such an approach may allow a direct comparison of their results.

A different background of arrhythmia in siblings with a positive family history of sudden death at young age.

We present two symptomatic sisters who had a positive family history of sudden death. None of them had structural heart disease. In the 25-year-old proband, complex ventricular arrhythmia, cardiac conduction system disease, and skeletal muscle weakness were found. Genetic examination showed a pathogenic intronic variant in the desmin gene in the proband only. In the elder sister with palpitations, complex ventricular arrhythmia (>46 000 ectopic beats) was removed by radiofrequency ablation. This family case shows that complex ventricular arrhythmia may have different background within one family, genetic examinations should be performed in a person with broadest spectrum of symptoms.

Positional sleep disordered breathing in patients with arrhythmia. Should we advise our patients to avoid supine position during sleep?

BACKGROUND: Sleep disordered breathing [SDB] is a well-known problem in patients with cardiovascular diseases. Around 50% of pts. with SDB present positional sleep disordered breathing [PSDB]. AIMS: The aim of this study was the investigation of the frequency of PSDB in patients with different forms of arrhythmias. METHODS: We analyzed the presence of SDB in 53 pts. with diagnosed atrial fibrillation (paroxysmal or persistent), 88 pts. before ablation of ventricular ectopy and 110 pts. that had Holter monitoring due to the symptoms suggesting arrhythmia. RESULTS: Finally, we could collect all the data in 243 pts. - 150 men 93 women. AHI < 15 was recorded in 136 (56%) pts., AHI > 15 in 107 (44%) pts. Moderate sleep disordered breathing was diagnosed in 59 (24%) pts. (AHI 15-30), severe sleep disordered breathing (AHI > 30) was recognized in 48 (20%) pts. In all of the analyzed groups, AHI in supine position was significantly higher than in nonsupine position. PSDB was recorded in 55% of pts. with AHI > 15 and in 29% of pts. (n = 14) with AHI > 30. Percentage of time in supine position was an independent factor related with the presence of at least moderate or severe sleep disordered breathing. CONCLUSION: 1. Moderate or severe SDB is recorded in 44% of pts. with arrhythmias, almost 50% of them have positional SDB. 2. Percent of time of sleeping in supine position has an important independent impact on the presence of SDB. 3. Big studies should be conducted to verify if avoidance of sleeping in supine position may improve clinical outcome. CONDENSED ABSTRACT: Sleep disordered breathing SDB is a frequent problem of pts. with cardiovascular diseases. It may influence the prognosis. Moderate or severe SDB is recorded in 44% of pts. with arrhythmias, almost 50% of them have positional SDB. Percent of time of sleeping in supine position has an important independent impact on the presence of SDB. 3. Big studies should be conducted to verify if avoidance of sleeping in supine position may improve clinical outcome. What is new?