Telemedicine in arrhythmology.

Telemedicine can be defined as a health care service that, specifically in the field of diagnostics, employs remote transfer of a large volume of data from a large number of subjects at the same time. This data is subsequently processed on a central basis and returned to a large number of health care providers by whom the service was ordered on national or international level. In arrhythmology, telemedicine is used particularly in long-term ECG monitoring to diagnose arrhythmias and check out treatment outcome via external recorders, smart watch, and implantable devices. To facilitate analysis of large telemedicine data volume, artificial intelligence is being increasingly exploited.

QRS detection and classification in Holter ECG data in one inference step.

While various QRS detection and classification methods were developed in the past, the Holter ECG data acquired during daily activities by wearable devices represent new challenges such as increased noise and artefacts due to patient movements. Here, we present a deep-learning model to detect and classify QRS complexes in single-lead Holter ECG. We introduce a novel approach, delivering QRS detection and classification in one inference step. We used a private dataset (12,111 Holter ECG recordings, length of 30 s) for training, validation, and testing the method. Twelve public databases were used to further test method performance. We built a software tool to rapidly annotate QRS complexes in a private dataset, and we annotated 619,681 QRS complexes. The standardised and down-sampled ECG signal forms a 30-s long input for the deep-learning model. The model consists of five ResNet blocks and a gated recurrent unit layer. The model's output is a 30-s long 4-channel probability vector (no-QRS, normal QRS, premature ventricular contraction, premature atrial contraction). Output probabilities are post-processed to receive predicted QRS annotation marks. For the QRS detection task, the proposed method achieved the F1 score of 0.99 on the private test set. An overall mean F1 cross-database score through twelve external public databases was 0.96 ± 0.06. In terms of QRS classification, the presented method showed micro and macro F1 scores of 0.96 and 0.74 on the private test set, respectively. Cross-database results using four external public datasets showed micro and macro F1 scores of 0.95 ± 0.03 and 0.73 ± 0.06, respectively. Presented results showed that QRS detection and classification could be reliably computed in one inference step. The cross-database tests showed higher overall QRS detection performance than any of compared methods.

Catheter ablation versus antiarrhythmic drugs with risk factor modification for treatment of atrial fibrillation: a protocol of a randomised controlled trial (PRAGUE-25 trial).

INTRODUCTION: Atrial fibrillation (AF), with a prevalence of 2%, is the most common cardiac arrhythmia. Catheter ablation (CA) has been documented to be superior to treatment by antiarrhythmic drugs (AADs) in terms of sinus rhythm maintenance. However, in obese patients, substantial weight loss was also associated with AF reduction. So far, no study has compared the modern non-invasive (AADs combined with risk factor modification (RFM)) approach with modern invasive (CA) treatment. The aim of the trial is to compare the efficacy of modern invasive (CA) and non-invasive (AADs with risk factor management) treatment of AF. METHODS AND ANALYSIS: The trial will be a prospective, multicentre, randomised non-inferiority trial. Patients with symptomatic AF and a body mass index >30 will be enrolled and randomised to the CA or RFM arm (RFM+AAD) in a 1:1 ratio. In the CA arm, pulmonary vein isolation (in combination with additional lesion sets in non-paroxysmal patients) will be performed. For patients in the RFM+AAD arm, the aim will be a 10% weight loss over 6-12 months, increased physical fitness and a reduction in alcohol consumption. The primary endpoint will be an episode of AF or regular atrial tachycardia lasting >30 s. The secondary endpoints include AF burden, clinical endpoints associated with AF reoccurrence, changes in the quality of life assessed using dedicated questionnaires, changes in cardiorespiratory fitness and metabolic endpoints. An AF freedom of 65% in the RFM+AAD and of 60% in the CA is expected; therefore, 202 patients will be enrolled to achieve the non-inferiority with 80% power, 5% one-sided alpha and a non-inferiority margin of 12%. ETHICS AND DISSEMINATION: The PRAGUE-25 trial will determine if modern non-invasive AF treatment strategies are non-inferior to CA. The study was approved by the Ethics Committee of the University Hospital Kralovske Vinohrady. Results of the study will be disseminated on scientific conferences and in peer-reviewed scientific journals. After the end of follow-up, data will be available upon request to principal investigator. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT04011800).

Exploring novel algorithms for atrial fibrillation detection by driving graduate level education in medical machine learning.

During the lockdown of universities and the COVID-Pandemic most students were restricted to their homes. Novel and instigating teaching methods were required to improve the learning experience and so recent implementations of the annual PhysioNet/Computing in Cardiology (CinC) Challenges posed as a reference. For over 20 years, the challenges have proven repeatedly to be of immense educational value, besides leading to technological advances for specific problems. In this paper, we report results from the class 'Artificial Intelligence in Medicine Challenge', which was implemented as an online project seminar at Technical University Darmstadt, Germany, and which was heavily inspired by the PhysioNet/CinC Challenge 2017 'AF Classification from a Short Single Lead ECG Recording'. Atrial fibrillation is a common cardiac disease and often remains undetected. Therefore, we selected the two most promising models of the course and give an insight into the Transformer-based DualNet architecture as well as into the CNN-LSTM-based model and finally a detailed analysis for both. In particular, we show the model performance results of our internal scoring process for all submitted models and the near state-of-the-art model performance for the two named models on the official 2017 challenge test set. Several teams were able to achieve F1scores above/close to 90% on a hidden test-set of Holter recordings. We highlight themes commonly observed among participants, and report the results from the self-assessed student evaluation. Finally, the self-assessment of the students reported a notable increase in machine learning knowledge.

Long-term ECG monitoring.

ECG recording represents an essential method for the diagnosis of heart rhythm disturbances. Long-term monitoring helps to identify arrhythmias that have not been detected by means of standard 12-lead ECG or 24-48 hour ECG Holter. With time, ECG monitoring facilities improve, the ECG recorders are becoming smaller, and the recording time is prolonging. At present, continuous ECG recording is generally available. Smart watches and fitness bracelets further expand monitoring options in patients with known or suspected arrhythmia. Individual type and frequency of symptoms remain the most significant criterion for the selection of suitable ECG recorder and recording time.

Comparison of two modes of long-term ECG monitoring to assess the efficacy of catheter ablation for paroxysmal atrial fibrillation.

AIMS: Optimal ECG monitoring in detecting recurrences of atrial fibrillation (AF) or atrial tachycardia (AT) after catheter ablation has not been well established. The purpose of this prospective study was to compare the utility of daily ECG monitoring with episodic card recorder (ECR) vs. periodic monitoring with episodic loop recorder (ELR) for the detection of post-blanking AF/AT recurrences during early (Months 4-6) and late (Months 7-12) periods after catheter ablation for paroxysmal AF. METHODS: The study included 105 consecutive patients, who received ECR for 12 months and were instructed to send at least 2 random ECG recordings daily with extra-recordings during symptoms. The patients were simultaneously monitored for one week with ELR at the end of each period (Months 6 and 12). RESULTS: Thirty-one and 12 patients with AF/AT recurrence were identified by means of ECR and ELR, respectively. In patients with complete and valid data, ELR technology was inferior to ECR by detecting AF/AT in 5 (31%) of 16 and 5 (26%) of 19 patients with arrhythmia identified by ECR in the early and late period, respectively. Overall, ELR had a sensitivity of 8/23 (35%) for detecting AF/AT recurrence. There was no single patient with AF/AT recurrence on ELR that would not be known from ECR monitoring. Only 2 patients with arrhythmia recurrence were completely asymptomatic throughout the study period. CONCLUSION: Daily ECG monitoring with ECR was better than periodic monitoring with ELR in detecting AF/AT recurrences during the follow-up periods. Entirely asymptomatic patients with AF/AT recurrences were rare.

Functional improvement after successful catheter ablation for long-standing persistent atrial fibrillation.

AIMS: Identifying patients who benefit from restored sinus rhythm (SR) would optimize the selection of candidates for ablation of long-standing persistent atrial fibrillation (LSPAF). This prospective study sought to identify the hitherto unknown factors associated with global functional improvement after successful radiofrequency catheter ablation of LSPAF. METHODS AND RESULTS: In 171 LSPAF patients (84% of the total consecutive 203 patients) who were examined in SR 12 months after ablation, the individual per cent change from baseline value in maximum oxygen consumption at exercise test (VO2 max), left ventricular ejection fraction (LVEF), N-terminal prohormone of brain natriuretic peptide (NT-proBNP), and five-dimensional descriptive system (EQ-5D) of quality-of-life questionnaire were classified in quartiles by 0 (worse) to 3 (best) grades. The individual grades were summed into a composite score (SCORE, 0 … 12) reflecting global functional improvement. Significant improvement in VO2 max (3.4 ± 4.7 mL/kg/min), LVEF (7.5 ± 9.1%), NT-proBNP (-861 ± 809 pg/mL), and EQ-5D (0.7 ± 0.12) was observed (all P < 0.0001). On multivariable analysis, younger age (P = 0.001), male gender (P = 0.02), timely post-ablation left atrial appendage (LAA) outflow (P = 0.005) with improvement in outflow velocity (P = 0.0002), and withdrawal of Class I/III antiarrhythmic drugs (P < 0.05) were positively and independently correlated with the SCORE. CONCLUSIONS: Younger male patients benefited most from catheter ablation of LSPAF. Delayed or non-improved LAA outflow and inability to discontinue Class I/III antiarrhythmic medication reduced the post-ablation functional improvement.

Multivariate Analysis of Correspondence between Left Atrial Volumes Assessed by Echocardiography and 3-Dimensional Electroanatomic Mapping in Patients with Atrial Fibrillation.

BACKGROUND: Left atrial (LA) enlargement is a predictor of worse outcome after catheter ablation for atrial fibrillation (AF). Widely used two-dimensional (2D)-echocardiography is inaccurate and underestimates real LA volume (LAV). We hypothesized that baseline clinical characteristics of patients can be used to adjust 2D-ECHO indices of LAV in order to minimize this disagreement. METHODS: The study enrolled 535 patients (59 ± 9 years; 67% males; 43% paroxysmal AF) who underwent catheter ablation for AF in three specialized centers. We investigated multivariately the relationship between 2D-echocardiographic indices of LA size, specifically LA diameter in M-mode in the parasternal long-axis view (LAD), LAV assessed by the prolate-ellipsoid method (LAVEllipsoid), LAV by the planimetric method (LAVPlanimetry), and LAV derived from 3D-electroanatomic mapping (LAVCARTO). RESULTS: Cubed LAD of 106 ± 45 ml, LAVEllipsoid of 72 ± 24 ml and LAVPlanimetry of 88 ± 30 ml correlated only modestly (r = 0.60, 0.69, and 0.53, respectively) with LAVCARTO of 137 ± 46 ml, which was significantly underestimated with a bias (±1.96 standard deviation) of -31 (-111; +49) ml, -64 (-132; +2) ml, and -49 (-125; +27) ml, respectively; p < 0.0001 for their mutual difference. LA enlargement itself, age, gender, type of AF, and the presence of structural heart disease were independent confounders of measurement error of 2D-echocardiographic LAV. CONCLUSION: Accuracy and precision of all 2D-echocardiographic LAV indices are poor. Their agreement with true LAV can be significantly improved by multivariate adjustment to clinical characteristics of patients.

Sinus rhythm restoration and arrhythmia noninducibility are major predictors of arrhythmia-free outcome after ablation for long-standing persistent atrial fibrillation: a prospective study.

BACKGROUND: The impact of restoring sinus rhythm (SR) by initial ablation in patients with long-standing persistent atrial fibrillation (LSPAF) is not fully established. OBJECTIVE: The purpose of this study was to investigate the prognostic value of SR restoration at the initial procedure and arrhythmia noninducibility at the final repeat procedure for long-term outcome. METHODS: A total of 203 patients (22% female; age 59 ± 9 years) underwent stepwise catheter ablation for LSPAF. RESULTS: The procedural end-point of SR restoration was achieved in 50% of patients. During follow-up (median 48 months) and after 1.7 procedures per patient, 72% of patients were free from arrhythmia off antiarrhythmic drugs. Failure to restore SR was independently predicted by left atrial (LA) long-axis diameter ≥68 mm (relative risk [RR] 1.55, P = .03], proportion of high-voltage LA sites <20% (RR 1.62, P = .02), and left atrial appendage (LAA) atrial fibrillation cycle length (AFCL) <155 ms (RR 1.5, P = .05). Arrhythmia recurrence after the initial procedure was predicted by SR nonrestoration (RR 2.99, P <.000001) and LAA AFCL ≥155 ms (RR 1.90, P = .0002). Arrhythmia recurrence after the final procedure was predicted by SR nonrestoration at the initial procedure (RR 2.83, P = .0007), persistent AF duration ≥24 months (RR 2.74, P = .002), LAA outflow velocity <40 cm/s (RR 2.21, P = .006), and LAA AFCL ≥155 ms (RR 1.92, P = .02). In 115 patients with repeat procedure(s), failure to achieve arrhythmia noninducibility at the final procedure (19% of patients) was associated with arrhythmia recurrence (RR 8.9, P < .000001). CONCLUSION: SR restoration at the initial procedure and arrhythmia noninducibility at the last repeat procedure were major predictors of arrhythmia-free outcome after ablation for LSPAF.

Improvement in quality of life after catheter ablation for paroxysmal versus long-standing persistent atrial fibrillation: a prospective study with 3-year follow-up.

BACKGROUND: Changes in quality of life (QoL) after catheter ablation for long-standing persistent atrial fibrillation (LSPAF) are not well described. We sought to compare QoL improvement after catheter ablation of paroxysmal atrial fibrillation (PAF) versus that after LSPAF. METHODS AND RESULTS: A total of 261 PAF and 126 LSPAF ablation recipients were prospectively followed for arrhythmia recurrence, QoL, hospital stay, and sick leave. In PAF versus LSPAF groups, 1.3±0.6 versus 1.6±0.7 procedures were performed per patient (P<0.00001) during a 3-year follow-up. Good arrhythmia control was achieved in 86% versus 87% of patients (P=0.69) and in 69% versus 69% of patients not receiving antiarrhythmic drugs (P=0.99). The baseline QoL was better in the PAF than in the LSPAF group (European Quality of Life Group instrument self-report questionnaire visual analog scale: 66.4±14.2 versus 61.0±14.2, P=0.0005; European Quality of Life Group 3-level, 5-dimensional descriptive system: 71.4±9.2 versus 67.7±13.8, P=0.002). Postablation 3-year increase in QoL was significant in both groups (all P<0.00001) and significantly lower in PAF versus LSPAF patients (visual analog scale: +5.0±14.5 versus +10.2±12.8, P=0.001; descriptive system: +5.9±14.3 versus +9.3±13.9, P=0.03). In multivariate analysis, LSPAF, less advanced age, shorter history of AF and good arrhythmia control were consistently associated with postablation 3-year improvement in QoL. Days of hospital stay for cardiovascular reasons and days on sick leave per patient/year were significantly reduced in both groups. CONCLUSIONS: Patients with LSPAF had worse baseline QoL. The magnitude of QoL improvement after ablation of LSPAF was significantly greater compared with after ablation of PAF, particularly when good arrhythmia control was achieved without the use of antiarrhythmic drugs.

A prospective evaluation of haemodynamics, functional status, and quality of life after radiofrequency catheter ablation of long-standing persistent atrial fibrillation.

AIMS: Clinical benefit from ablation for long-standing persistent atrial fibrillation has remained unknown. We hypothesized that successful ablation of long-standing persistent atrial fibrillation would improve haemodynamics, functional status, and quality of life. METHODS AND RESULTS: A total of 160 patients (aged 59 ± 9 years, 23% females) undergoing ablation of long-standing (median of 28 months) persistent atrial were enrolled in this prospective study. Morphological and functional echocardiographic parameters, N-terminal prohormone of brain natriuretic peptide (NT-proBNP), maximum oxygen consumption during exercise test (VO2 max), and quality of life were assessed at baseline and 1 year after the ablation.  At the 1-year follow-up visit, 81% patients were examined in sinus rhythm (after repeat ablation in 38% patients). Left atrial appendage outflow velocity increased from 44 ± 20 to 58 ± 23 cm/s, left ventricular ejection fraction from 54 ± 9 to 59 ± 5%, and VO2 max from 20.4 ± 6.4 to 23.7 ± 8.1 mL/kg/min; NT-proBNP decreased from median 897 (interquartile range 603-1424) to 230 (interquartile range 120-420) pg/mL (all P < 0.0001). These beneficial effects of ablation were predominantly associated with the presence of sinus rhythm. Quality of life (range 0-100) increased significantly (EQ-5D index: from 68.8 ± 12.5 to 75.4 ± 14.4; EQ-VAS score: from 62.8 ± 13.2 to 70.6 ± 13.8; both P < 0.0001). CONCLUSION: Ablation of long-standing persistent atrial fibrillation was associated with significant recovery of haemodynamics and exercise capacity that projected onto the long-term improvement in quality of life.

Atrial fibrillation ablation: a cost or an investment?

In the last decade, catheter ablation (CA) became a viable therapeutic approach for symptomatic patients with atrial fibrillation (AF) non-responsive to antiarrhythmic drugs (AAD). The economic analysis of CA is complex due to the presence of several confounding factors, such as the pattern of AF (paroxysmal AF, persistent or long-term persistent AF), the patient population (age, presence/absence of underlying structural heart disease, comorbidities, etc.), the different techniques for ablation (with impact on complexity and cost of the procedure, as well as on efficacy and safety), and the learning curve and experience of an individual centre (with impact on efficacy and cost effectiveness). At present, CA appears to be cost effective mainly in patients with paroxysmal AF who are refractory to AADs, especially if the success of the procedure and, thus, the benefit in quality of life remains >5 years, with a low complication rate. More data are needed on cost effectiveness of CA of persistent and long-term persistent AF or of AF associated with heart failure. Atrial fibrillation ablation is unlikely to be cost effective for patients who have preserved quality of life despite their AF or for patients whose quality of life is not expected to improve substantially despite elimination of AF (e.g. patients with poor quality of life mainly due to other health problems). These observations may help in the selection of candidates for AF ablation.

Septal ventricular tachycardia with alternating LBBB-RBBB morphology in isolated ventricular noncompaction.

Knowledge on ventricular tachycardia (VT) in isolated ventricular noncompaction (IVNC) is limited. We report on a patient with IVNC who presented with cardiogenic shock due to an incessant drug-resistant VT that was cured by radiofrequency ablation. The VT had characteristics of a deep septal focal arrhythmia, which was distinctive by ablation-induced alternation of the rightward and leftward exits, and was difficult to ablate from either side of the ventricular septum.

Left atrial voltage during atrial fibrillation in paroxysmal and persistent atrial fibrillation patients.

BACKGROUND: Left atrial (LA) endocardial voltage characteristics assessed during atrial fibrillation (AF) have not been previously compared in different AF types. This study was aimed at investigating the LA voltages and volumes in patients with paroxysmal and persistent AF. METHODS: LA electroanatomic voltage maps acquired during AF were compared between consecutive patients without major structural heart disease undergoing first catheter ablation for paroxysmal AF (n = 100) or persistent AF (n = 100). The groups were comparable in baseline clinical characteristics. RESULTS: Patients with persistent AF presented with lower median LA voltage (median 0.41, interquartile range [IQR] 0.31-0.51 mV versus median 0.99, IQR 0.47-1.56 mV; P < 0.001), and maximum LA voltage (4.07 +/- 1.76 vs 6.42 +/- 2.16 mV; P < 0.001). They also had a higher proportion of the LA points exhibiting voltage <0.2 mV (30 +/- 20 vs 12 +/- 11%; P < 0.001) and voltage 0.2-1.0 mV (55 +/- 15 vs 42 +/- 19%; P < 0.001). They further displayed higher LA volume/body surface area (75 +/- 16 vs 58 +/- 13 mL/m(2); P < 0.001). In the multivariate regression model, both LA voltage (P < 10(-9)) and LA volume (P < 10(-5)) were significant determinants of AF type. CONCLUSION: Patients with persistent AF had significantly lower LA voltage compared with patients with paroxysmal AF even after adjustment for differences in indexed LA volume. LA voltage represents an independent covariate of clinical manifestation of AF.

Results of complex left atrial ablation of long-lasting persistent atrial fibrillation.

PURPOSE: The aim of the study was to identify variables associated with successful long-term maintenance of sinus rhythm (SR) after a single ablation of long-lasting persistent atrial fibrillation (AF). METHODS: Complex left atrial (LA) ablation was performed in 100 patients. Restoration of SR by ablation was the desired procedure endpoint. RESULTS: SR was restored by ablation in 38 patients during the first procedure. Following one ablation, 50 patients remained in SR for 31 +/- 14 months. SR maintenance was associated with shorter duration of the persistent AF (median 14 vs. 22 months; P = 0.05), lower proportion of the LA points exhibiting voltage <0.2 mV (median 20% vs. 33%; P = 0.006), and higher proportion of LA points showing voltage >1 mV (median 15% vs. 11%; P = 0.02). CONCLUSION: Among clinical variables, shorter duration of persistent AF and higher voltage recorded around the LA predicted long-term maintenance of SR after single ablation.

Heart rate turbulence after atrial premature complexes depends on coupling interval and atrioventricular nodal conduction.

BACKGROUND: Positive Turbulence onset (TO) after atrial premature complexes (APCs) was found temporally related to spontaneous episodes of atrial fibrillation. This study tested the hypothesis that heart rate turbulence (HRT) after APCs is influenced by APC prematurity independently of the prematurity of conducted ventricular complexes. METHODS: We studied 33 patients (mean age = 58 +/- 16 years, 19 men), 11 of whom had structural heart disease, who were referred for electrophysiological studies of supraventricular or ventricular arrhythmias. Sequences of single right atrial extrastimuli were delivered with coupling intervals adjusted to reach 60% prematurity of conducted ventricular complexes. Descriptors of HRT were compared between patients with slow versus fast atrioventricular (AV) conduction of APCs. RESULTS: The early RR interval dynamics after APCs was prominently modulated by the suppression of sinus node automaticity by the direct effect of APCs. This effect was significantly greater after earlier APCs with longer AV conduction times than after later coupled APCs with shorter AV conduction times. CONCLUSIONS: The early phase of HRT is strongly influenced by the coupling interval of APCs, independently of the prematurity of conducted ventricular complexes. Consequently, the more positive TO preceding spontaneous atrial fibrillation episodes might be an epiphenomenon of incidental short-coupled APCs with delayed AV conduction, likely to trigger atrial fibrillation.

Heart rate dependence of the QT interval duration: differences among congenital long QT syndrome subtypes.

INTRODUCTION: The heart rate dependence of QT interval duration is abnormal in patients with congenital long QT syndrome. Patients with LQT1 have a defective I(Ks) current, a major determinant of QT response to heart rate. METHODS AND RESULTS: We studied the heart rate dependence of QT interval duration in different long QT syndrome genotypes and control subjects using computerized QT measurements obtained from Holter recordings. The dependence of QT duration on heart rate is steeper in long QT syndrome than in control subjects (0.347 +/- 0.263 vs 0.162 +/- 0.083 at heart rate 100 beats/min; P < 0.05). In addition, QT interval is significantly longer in LQT2 and LQT3 than in LQT1 patients at slow (533 +/- 23 ms vs 468 +/- 30 ms at heart rate 60 beats/min; P < 0.0001) but not at rapid heart rate. The heart rate dependence of QT interval is steeper in LQT2 and LQT3 than in LQT1 (0.623 +/- 0.245 vs 0.19 +/- 0.079 at heart rate 100 beats/min; P < 0.05). For a given heart rate, the QT intervals vary more in LQT2 and LQT3 than in LQT1 patients (25.98 +/- 11.18 ms vs 14.39 +/- 1.55 ms; P < 0.01). CONCLUSION: Individual long QT syndrome genotypes differ with respect to QT interval dependence on heart rate. These differences may relate to the propensity of LQT2 and LQT3 patients to develop arrhythmias during bradycardia.