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Wearable devices enable RR interval (RRi) measurements during various conditions. We aimed to assess the validity of the Polar H10 for RRi acquisition during pre-rest stabilization, rest, sympathetic nervous system activity stimulation and recovery conditions for heart rate variability (HRV) analysis in ski mountaineers. RRi were simultaneously obtained via electrocardiogram and the Polar H10 with V800 wrist-watch among eleven elite athletes in the supine position. Short-term (5-min) and ultra-short-term (1-min) heart rate (HR) and HRV parameters were analyzed. Mean absolute percentage difference between parameters from different devices ranged from 0% to 5.4%. Intraclass correlation and concordance correlations ranged between 0.76 and 1.00. Limits of agreement (LoA) for short-term measures did not exceed the defined maximum acceptable difference (SWC) through all conditions for mean RRi, HR, time-domain and nonlinear indices, and for frequency-domain (fast-Fourier-related) during the rest condition. LoA exceeded the SWC for mean, minimal and maximal HR, time-domain and nonlinear parameters from select 1-minute samples in all conditions. The Polar H10 provides RRi that could be used for short-and ultra-short-term HRV analysis from stable resting conditions in elite ski mountaineers. Ultra-short-term parameters from exercise should be analyzed with caution especially from later minutes of activity.

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.

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 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? - The presence of positional sleep disordered breathing in pts. with arrhythmias is reported. - Positional dependence of the disordered breathing is presented even in pts. with almost normal AHI results.

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 symptom‑limited ETs. RESULTS All ETs were clinically negative. During the median (interquartile range) follow‑up of 22 (12) months, 39 patients (22 men) developed symptoms (the AVR group). This group was compared with 50 asymptomatic non‑AVR 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 β‑blockers, this was not significant (P = 0.08). In the β‑blocker 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 β‑blockers. 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 β‑blockers who did not achieve 85% of predicted maximal heart rate had a higher probability of AVR. The influence of the use of β‑blockers on the decision to perform AVR in this patient population warrants further revision.

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.

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 parameter q > 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.

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.

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.

Using information theoretic measures, interaction between heart rhythm, time series of diastolic intervals and repolarization in the ventricles is analyzed. Transfer entropy and joint transfer entropy are calculated. Results for a group of healthy individuals and LQTS1 patients are compared. An asymmetry in the direction of information flow between the variables analyzed is found. Information flows for the LQTS1 patients are smaller than for the healthy.

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.

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.

BACKGROUND: Atrial fibrillation (AF) is a common complication in patients with hypertrophic cardiomyopathy (HCM) and may contribute to high cardiovascular morbidity and mortality. Therefore, it is important to assess parameters associated with AF in HCM patients. HYPOTHESIS: The aim of the study was to evaluate AF prevalence in patients with HCM and to investigate risk factors for AF. METHODS: Five hundred and forty‐six HCM patients aged below 65 were included into analysis. Clinical and echocardiographic parameters were analyzed. RESULTS: In 141 patients (25.8%) AF episodes were recorded. The following factors were identified as risk factors for AF in patients with HCM: age ≥ 45 years (OR 2.38, CI 1.40‐4.05, P = 0.001), past history of presyncope or syncope (OR 2.25, CI 1.35‐3.74, P = 0.002), non‐sustained ventricular tachycardia (nsVT) (OR 2.70, CI 1.60‐4.57, P

Background Congenitally corrected transposition of the great arteries (ccTGA) is a rare clinical condition in which the morphologically right ventricle sustains systemic circulation. This congenital heart anomaly exposes patients with ccTGA to adverse events over time. Strategies to identify persons who are at high risk of clinical events will be crucial for improving patient outcomes. Thus the aim of this study was to identify screening tools that enable morbidity and mortality risk stratification in adults with ccTGA. Methods This was a prospective observational study. Electrocardiography, laboratory testing, echocardiography, and cardiopulmonary exercise testing were performed at baseline. A Cox proportional hazards regression analysis was conducted to establish determinants of composite clinical endpoints, including death, heart transplantation, systemic ventricular device assist implantation, worsening of heart failure, vascular events, tricuspid valve regurgitation requiring intervention, and clinically relevant arrhythmias. Results Fifty-one patients—30 male and 21 female—with a mean age of 36 years were studied. During a median follow-up period of 3.15 years, 19 patients experienced 39 clinical events. Detectable high-sensitivity troponin T (hsTnT) combined with echocardiography-derived systemic right ventricular end-diastolic (sRVED) area were the best predictors of adverse outcomes (hazard ratio [HR] = 6.25, P = 0.02 and HR = 1.05, P = 0.02, respectively). Conclusions A combination of detectable hsTnT and an increased sRVED area are the best predictors of adverse clinical events in adults with ccTGA. This observation may be useful to guide follow-up, as both risk determinants are widely available and simple to obtain in everyday practice.

Background: Previous reports on patients with radiofrequency catheter ablation (RFCA) of accessory pathway (AP) and atrial fibrillation (AF) include only short follow-up periods. The aim of this study was to analyze predictors of recurrence of AF in patients after successful RFCA of APs over long term follow-up periods. Methods: Of the 1,007 patients who underwent non-pharmacological treatment of APs (between the years 1993–2008), data of 100 consecutive patients were retrospectively analyzed (75 men, mean age 43.6 ± 14.7), with the longest period of follow-up (mean 11.3 ± 3.5 years) after successful RFCA of AP. In Group 1, there were 72 patients (54 men, mean age 40.66 ± 13.85 years) without documented episodes of AF after RFCA of AP. Group 2 consisted of 28 patients (21 men, mean age 50.79 ± 14.49 years) with AF episodes despite successful elimination of AP. Results: In univariate analysis, patients from Group 1 were significantly younger at the time of ablation than patients from Group 2 (40.66 ± 13.85 vs. 50.79 ± 14.49 years; p = 0.002), had shorter history of AF episodes (4.11 ± 4.07 vs. 8.25 ± 7.50 years; p = 0.024) and had less frequently documented atrial tachycardia (AT) prior to ablation (3.39 vs. 20.00%; p = 0.022). In multivariate analysis, the history of AF in years (p = 0.043), was an independent risk factor for AF recurrences. Conclusions: Older patient age, longer history of AF and AT prior to RFCA of APs identified a subgroup of patients who required additional treatment. In the multivariate analysis, the history of AF in years (p = 0.043) was a risk factor for AF recurrence.

Background: Data regarding long-term follow-up of radiofrequency catheter ablation (RFCA) of accessory pathways (APs) in patients with Ebstein’s anomaly (EA) are limited. The procedures are challenging due to multiple or wide APs. Methods: Analysis was performed on clinical and periprocedural data of patients with EA referred to the centre in order to perform catheter ablation of AP. The group consisted of 22 patients (female 40.9%, mean age 33.6 ± 19.1 years). The follow-up utilized electrocardiogram and Holter monitoring. Results: Twenty-two patients had 33 accessory pathways (8 patients had multiple APs, 11 patients broad AP). Twenty-nine different arrhythmias were ablated: 20 orthodromic atrioventricular reciprocating tachycardia (O-AVRT), 5 antidromic atrioventricular reciprocating tachycardia (A-AVRT), 3 slow/ fast atrioventricular nodal reentry tachycardia (s/f AVNRT) and 1 cavotricuspid-isthmus-dependent atrial flutter (CTI-AFL). In 3 (13.6%) patients multiple ablation targets for RFCA ablation were observed. The acute procedural success rate after the first RFCA performed was: 100% for AVNRT, 77.3% for APs and 50.0% for CTI-AFL ablation. Follow-up (mean 95.7 ± 49.8 months) was completed in 86.4% of patients. One patient had paroxysmal atrial fibrillation not targeted during ablation. One patient died due to heart failure 12 years after RFCA. Three patients who underwent RFCA of accessory pathways in the mid-1990s were lost in follow-up. Conclusions: Radiofrequency ablation in patients with EA is challenging but safe and have a high short-term as well as long-term success rate.

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.

Background: Water immersion may cause adverse cardiovascular events, including arrhythmias in patients with damaged cardiac muscle, e.g. with cardiac failure. So far, there have been rather few reports on arrhythmia induced by water training in patients with coronary artery disease (CAD). The aim of the study was to assess the influence of exercise training in moderately cold water (28–30°C) on arrhythmia and physical capacity in stable CAD patients with preserved left ventricular (LV) function. Methods: Sixty-two post-myocardial infarction male patients, mean age 50.9 ± 7.9 years, participated in 16 water-based trainings (WBT), which lasted 55-min, twice a week in water at 28–30°C. Each subject underwent 24 h Holter on-land monitoring (Holter-24) once during the study and twice in-water Holter monitoring (Holter-W) during WBT. Before and after WBT cardiopulmonary exercise test (CPET) was performed. The following parameters were analyzed: peak oxygen consumption (peak VO2), mean number of ventricular ectopic beats ( VEBs) and supraventricular ectopic beats (SVEBs) during Holter-24 and Holter-W, the percentage of men who developed arrhythmia during CPET vs. Holter-24 and vs. Holter-W. Results: WBT significantly improved patients’ physical capacity, and more often provoked arrhythmia, mainly SVEBs, than CPET or daily activity assessed during Holter-24. During WBT 58% men developed VEBs and 62% SVEBs. Conclusions: 1. WBT provoked arrhythmias significantly more often than did CPET and normal daily activity. 2. Owing to WBT patients improved their physical capacity which was still maintained at 1-year follow-up.

Objective Both the central nervous system and the autonomic nervous system are complex physiological networks which modulate the heart rate. They are spatially extended, have built-in delays and work on many time scales simultaneously-nonhomogeneous networks with multifractal dynamics. The object of our research was the analysis of human heart rate variability (HRV) using the nonlinear multiscale multifractal analysis (MMA) method for several cardiovascular diseases. The analysis of HRV (night-time recordings) involved six groups of patients: 61 healthy persons, 104 cases with aortic valve stenosis, 42 with hypertrophic cardiomyopathy, 36 with atrial fibrillation, 70 patients with coronary artery disease and 19 with congestive heart failure. 85% of patients formed a training data set (282 subjects) and 15% formed a test data set (50 subjects). Approach Multiscale multifractal analysis allows one to analyze the complexity of HRV and find the scaling properties of its fluctuations. The main result of MMA is the Hurst surface, the shape of which changes depending on the medical case analyzed. We prepared six criteria to distinguish a multifractal pattern for healthy subjects. We also prepared additional criteria, enabling one to recognize atrial fibrillation. Main results For the training data set, we obtained the following accuracy statistics in distinguishing the patients from the healthy: 68% for coronary artery disease, 67% for hypertrophic cardiomyopathy, 88% for atrial fibrillation, 74% for aortic valve stenosis and 83% for congestive heart failure. For the complete training data set we obtained an accuracy of 73%, and 80% for the test data set (mean for ten random selections of the test data set). Significance The results of MMA presented here provide an additional input into the diagnostic process and may help to create a paradigm for future studies on medical screening methods, especially in that MMA focuses on very low frequencies of HRV not easily accessible by standard medical techniques. Satisfactory statistics for screening using both MMA and the unfiltered version of LF/HF indicate that the nature of the complete network moderating heart rhythm needs to be studied and that sinus rhythm in clinical patients may not always be separated from arrhythmia when its incidence is large.

INTRODUCTION Unexplained sudden cardiac arrest (SCA), occurs in up to 10% of patients and is often attributed to an inherited arrhythmia syndrome. Family screening and genetic testing may help clarify the cause of unexplained SCA. OBJECTIVES We aimed to assess the usefulness of clinical evaluation and genetic testing in patients after unexplained SCA and in their families. PATIENTS AND METHODS In the years 2014-2017, we studied 44 unrelated patients after unexplained SCA and 96 of their relatives. All patients and relatives underwent comprehensive cardiac evaluation. In 31 patients with SCA, next generation sequencing (NGS) was performed. The Kaplan-Meier survival curve was constructed to compare the event-free survival depending on clinical diagnosis or genotype. An adverse event was defined as an adequate implantable cardioverter-defibrillator discharge. RESULTS Based on the clinical evaluation, diagnosis was established in 39% of probands (long QT syndrome 21%; short QT syndrome 7%; Brugada syndrome 7%; catecholaminergic polymorphic ventricular tachycardia, 2%; and early repolarization syndrome, 2%). Ventricular arrhythmia was identified in the relatives of 19% of probands. In 18 of the 31 probands (54.8%), 23 rare gene variants were identified, of which only 2 were classified as pathogenic. The event-free survival over a median of 4.5 years was similar in patients with or without clinical diagnosis and in carriers and noncarriers of a rare genetic variant. CONCLUSIONS This study shows the significance of an extensive clinical assessment in unexplained SCA victims and their relatives. Routine genetic testing by NGS has low diagnostic and prognostic value.

Background About 30% of patients do not have an effective cardiac resynchronization therapy (CRT). Routine assessment of CRT by devices interrogation (DI) is not entirely reliable. Additional information provide detailed QRS analysis in 24-hour ECG, however it is time-consuming. The aim of the study was the assessment of R/S ratio variability in lead V1 between selected fragments of 24-hour ECG as a predictor of incomplete biventricular pacing (BIVP) during full 24-hour ECG. Methods The 12-lead 24-hour ECGs of 43 patients with sinus rhythm were studied. During 24-hour ECG the 6-minute walk test (6MWT) was performed. The CRT was assessed by analyzing DI and full 24-hour ECG and four 1-minute fragments of these ECG recordings: during the minimum and the maximum heart rate and at the 1st and last minute of 6MWT. Results During DI the effective (>95%) BIVP was present in 36 patients (83.7%). Analysis of full 24-hour ECG confirmed appropriate BIVP in 31 patients (72%) and suspected incomplete BIVP (≤95%) in 12 patients (28%). In 9/12 patients the R/S ratio variability in lead V1 was visible between selected ECG fragments of 24-hour ECG. These results were not associated with the results of DI but were significantly associated with full 24-hour analysis of QRS. Conclusions R/S variability in lead V1 between selected fragments of 24-hour ECG can be considered a predictor of potentially incomplete BIVP confirmed by further complete 24-hour ECG analysis in patients with appropriate pacing reported during DI.

Background: Estimation of sudden cardiac death (SCD) risk is an integral part of clinical management of patients with hypertrophic cardiomyopathy (HCM). Identification of novel biomarkers of this disease can provide additional criteria for SCD risk stratification. Soluble suppression of tumourigenicity (sST2) and galectin-3 (Gal-3) are useful biomarkers for prognosis of heart failure (HF). Both of them appear to mediate cardiac fibrosis — an important pathogenetic process in HCM. Data about sST2 and Gal-3 usefulness in patients with HCM are limited. Aim: The aim of this study was to evaluate sST2 and Gal-3 as potential novel biomarkers for better risk stratification in hypertrophic cardiomyopathy. Methods: Serum sST2 and serum Gal-3 levels were measured in 57 patients with HCM and in 18 healthy controls. The patients with HCM underwent routine evaluation including medical history, physical examination, blood tests (including N-terminal pro-B-type natriuretic peptide [NT-proBNP] and high-sensitivity cardiac troponin T [hs-cTnT] measurements), 12-lead electrocardiography (ECG), 48-h Holter monitoring and two-dimensional (2D) echocardiography with the assessment of the maximal left ventricular wall thickness, left atrial diameter, maximal left ventricular outflow tract gradient, and left ventricular ejection fraction. Risk of SCD at five years according to HCM SCD-risk calculator was evaluated. The control group underwent ECG, 2D echocardiography, and NT-proBNP measurements to exclude asymptomatic heart disease. Results: Concentrations of sST2 and Gal-3 were significantly higher in patients with HCM than in controls (14.9 ± 5.8 ng/mL vs. 11.7 ± 3.3 ng/mL, p = 0.03 and 8.4 ng/mL [6.8–10.0] vs. 6.2 ng/mL [5.8–7.7], p = 0.005, respectively). Levels of sST2 and Gal-3 were considerably different in the New York Heart Association (NYHA) groups (p = 0.008, p = 0.009, respectively). Patients who presented non-sustained ventricular tachycardia (nsVT) on 48-h Holter monitoring had higher levels of sST2 (19.1 ng/mL [12.2–24.2] vs. 13.2 ng/mL [10.0–17.1], p = 0.02). There were no significant relationships between sST2 and Gal-3 levels and HCM SCD-risk, history of syncope presence, family history of SCD, and echocardio­graphic parameters. Conclusions: Gal-3 levels and sST2 levels were higher in patients with HCM than in the control group. There were significant differences in Gal-3 levels between NYHA classes, but no correlations between Gal-3 levels and other parameters were found. Apart from differences in sST2 levels between NYHA classes, we demonstrated higher levels of sST2 in patients with nsVT. These findings suggest that sST2 may be useful as an additional biomarker for better risk stratification in hypertrophic cardiomyopathy.

Re-entrant atrial arrhythmias are common in patients after cardiac surgery. To date, however, no studies have reported the safety and efficacy of radiofrequency (RF) ablation of macro-re-entrant atrial arrhythmias in a unique, homogeneous group of patients after surgical replacement of the aortic valve and single right atriotomy.Among over 4,000 RF catheter ablations performed at the authors' center between 2008 and 2014, eight patients (seven males, one female; mean age 55.1 ± 19.9 years) after aortic valve replacement (AVR) and without history of any other cardiosurgical procedures were identified with documented macro-re-entrant atrial arrhythmia. The mechanism of macro-re-entrant arrhythmia was analyzed, as well as the safety and efficacy of RF ablation in a group of patients after AVR and single right atrial free wall atriotomy.The average time from surgery to RF catheter ablation was 11.3 ± 11.3 years (range: 4-35 years). In five patients with permanent arrhythmia, entrainment mapping proved these arrhythmias to be cavotricuspid isthmus- dependent, in three patients with paroxysmal atrial arrhythmia cavotricuspid isthmus-dependent atrial flutter was induced during the electrophysiological study. Intra-atrial re-entrant tachycardia was neither recorded nor induced in any patient. Successful ablation of cavotricuspid isthmus is defined as the termination of arrhythmia, and bidirectional block in cavotricuspid isthmus was achieved in all patients. A long-term follow up, based on a seven-day Holter monitoring, was conducted in all patients, with a mean observation time of 40.1 ± 28.6 months after the procedure. Among the patients, ablated arrhythmia (cavotricuspid isthmusdependent atrial flutter) recurred in one patient, atrial fibrillation occurred in three patients, and an atrial tachycardia in one patient.In the presented series of patients, cavotricuspid isthmus-dependent atrial flutter was shown to be the mechanism of post-cardiosurgical macro-re-entrant clinical arrhythmia in all subjects. Atrial fibrillation was frequently observed among those patients during follow up.

INTRODUCTION Syncope and sudden cardiac arrest are known complications of aortic stenosis (AS). OBJECTIVES The aim of the study was to investigate the incidence of these complications in patients with severe symptomatic AS and to analyze whether basic clinical data and electrocardiographic (ECG) and echocardiographic parameters can be the markers of these complications. PATIENTS AND METHODS The incidence of syncope and sudden cardiac arrest and its correlations with clinical and diagnostic data (ECG, echocardiography, Holter monitoring) were analyzed in 514 patients (mean age, 60 ±11 y) with severe symptomatic AS before valve replacement. RESULTS Syncope was reported in 167 patients (32%), and aborted cardiac arrest in 14 (2.7%; ventricular fibrillation, 13 patients; third-degree atrioventricular block, 1 patient). None of the analyzed parameters was related to syncope. Patients with a history of sudden cardiac arrest had higher New York Heart Association class (P = 0.01), more frequent history of syncope (P = 0.017), higher left ventricular mass index (P = 0.02), lower ejection fraction (P = 0.004), longer QRS duration (P = 0.048), corrected QT (P = 0.002), QT dispersion (P = 0.007), and a higher number of ventricular arrhythmias in 24-hour Holter monitoring (P = 0.002). A multivariate analysis showed correlations between syncope, ejection fraction of less than 45%, and QTd exceeding 60 ms and aborted cardiac arrest. At least 2 of these parameters were observed in 8 of 14 patients (P

The heart rate variability of 10 healthy males (age 26 - 4/+ 3 y) and 49 patients with hypertrophic cardiomyopathy (HCM) (25 males, 24 females, age 29.5 - 11.5/+ 10.5 y) was studied. We applied Kramers-Moyal expansion to extract the drift and diffusion terms of the Langevin equation for the RR interval time series. These terms may be used for a stochastic reconstruction of the time series and for description of the properties of heart rate variability. New parameters characterizing the diffusion term are proposed: the coefficients of the linear fit to the left (LCF) and right (RCF) branch of the dependence of the diffusion term on the rescaled heart rate. Relations of the new parameters to classical echocardiography parameters were studied. Using the relation between the difference LCF-RCF and the left ventricular systolic diameter, the HCM patients studied were divided into three groups. In addition, comparison of the properties of the heart rate variability in the HCM group with that obtained for the healthy young men showed that the parameter LCF-RCF may be treated as a measure of the effect of HCM on heart rate variability and may have diagnostic value.

Percutaneous alcohol septal ablation (ASA) becomes an alternative option of treatment for symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). The procedure relieves left ventricular outflow tract obstruction, but produces a myocardial scar in patients who already have a substrate for life-threatening ventricular arrhythmia. To examine the effect of ASA on the occurrence of non-sustained ventricular tachycardia (nsVT) on 24 h ambulatory Holter monitoring in HOCM patients. Sixty-one consecutive patients (34 males, mean age 48 years), who underwent ASA between 1997 and 2003 were analyzed. Holter recordings were performed in each patient before and after ablation. Follow-up ranged from 60 to 125 months (median 116 months). The mean number of Holter recordings per patient was 2.7 (range 1–11) before and 8.3 (range 2–23) after ASA (p