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Background: Undetected atrial fibrillation (AF) poses a significant risk of stroke and cardiovascular mortality. However, diagnosing AF in real-time can be challenging as the arrhythmia is often not captured instantly. To address this issue, a deep-learning model was developed to diagnose AF even during periods of arrhythmia-free windows., Methods: The proposed method introduces a novel approach that integrates clinical data and electrocardiograms (ECGs) using a colorization technique. This technique recolors ECG images based on patients' demographic information while preserving their original characteristics and incorporating color correlations from statistical data features. Our primary objective is to enhance atrial fibrillation (AF) detection by fusing ECG images with demographic data for colorization. To ensure the reliability of our dataset for training, validation, and testing, we rigorously maintained separation to prevent cross-contamination among these sets. We designed a Dual-input Mixed Neural Network (DMNN) that effectively handles different types of inputs, including demographic and image data, leveraging their mixed characteristics to optimize prediction performance. Unlike previous approaches, this method introduces demographic data through color transformation within ECG images, enriching the diversity of features for improved learning outcomes., Results: The proposed approach yielded promising results on the independent test set, achieving an impressive AUC of 83.4%. This outperformed the AUC of 75.8% obtained when using only the original signal values as input for the CNN. The evaluation of performance improvement revealed significant enhancements, including a 7.6% increase in AUC, an 11.3% boost in accuracy, a 9.4% improvement in sensitivity, an 11.6% enhancement in specificity, and a substantial 25.1% increase in the F1 score. Notably, AI diagnosis of AF was associated with future cardiovascular mortality. For clinical application, over a median follow-up of 71.6 ± 29.1 months, high-risk AI-predicted AF patients exhibited significantly higher cardiovascular mortality (AF vs. non-AF; 47 [18.7%] vs. 34 [4.8%]) and all-cause mortality (176 [52.9%] vs. 216 [26.3%]) compared to non-AF patients. In the low-risk group, AI-predicted AF patients showed slightly elevated cardiovascular (7 [0.7%] vs. 1 [0.3%]) and all-cause mortality (103 [9.0%] vs. 26 [6.4%]) than AI-predicted non-AF patients during six-year follow-up. These findings underscore the potential clinical utility of the AI model in predicting AF-related outcomes., Conclusions: This study introduces an ECG colorization approach to enhance atrial fibrillation (AF) detection using deep learning and demographic data, improving performance compared to ECG-only methods. This method is effective in identifying high-risk and low-risk populations, providing valuable features for future AF research and clinical applications, as well as benefiting ECG-based classification studies., Competing Interests: Declarations. Ethics approval and consent to participate: This study was approved by the Institutional Review Board (2017–10-009BC) at Taipei Veterans General Hospital, Taipei, Taiwan. All methods were carried out following the regulations of the Institutional Review Board. The Internal Review Board of Taipei Veterans General Hospital granted an exemption from the need to secure informed consent due to the thorough de-identification of patient data. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

The predictive value of non-invasive electrocardiographic examination findings for the risk of sudden cardiac death (SCD) in populations with structurally normal hearts remains unclear. This study aimed to investigate the characteristics of the QRS vectorcardiography of surface electrocardiography in patients with structurally normal hearts who experienced SCD. We consecutively enrolled patients who underwent vectorcardiography between March 2017 and December 2018 in a tertiary referral medical center. These patients didn't have structural heart diseases, histories of congestive heart failure, or reduced ejection fraction, and they were classified into SCD (with aborted SCD history and cerebral performance category score of 1) and control groups (with an intervention for atrioventricular node reentrant tachycardia and without SCD history). A total of 162 patients (mean age, 54.3±18.1 years; men, 75.9%), including 59 in the SCD group and 103 in the control group, underwent propensity analysis. The baseline demographic variables, underlying diseases, QRS loop descriptors (the percentage of the loop area, loop dispersion, and inter-lead QRS dispersion), and other electrocardiographic parameters were compared between the two groups. In the univariate and multivariate analyses, a smaller percentage of the loop area (odds ratio, 0.0003; 95% confidence interval, 0.00-0.02; p<0.001), more significant V4-5 dispersion (odds ratio, 1.04; 95% confidence interval, 1.02-1.07; p = 0.002), and longer QRS duration (odds ratio, 1.05; 95% confidence interval, 1.00-1.10; p = 0.04) were associated with SCD. In conclusion, the QRS loop descriptors of surface electrocardiography could be used as non-invasive markers to identify patients experiencing aborted SCD from a healthy population. A decreased percentage of loop area and elevated V4-5 QRS dispersion values assessed using vectorcardiography were associated with an increased risk of SCD in patients with structurally normal hearts., Competing Interests: The authors have declared that no competing interests exist.

Background: Brugada syndrome is a major cause of sudden cardiac death in young people and has distinctive electrocardiographic (ECG) features. We aimed to develop a deep learning-enabled ECG model for automatic screening for Brugada syndrome to identify these patients at an early point in time, thus allowing for life-saving therapy., Methods: A total of 276 ECGs with a type 1 Brugada ECG pattern (276 type 1 Brugada ECGs and another randomly retrieved 276 non-Brugada type ECGs for 1:1 allocation) were extracted from the hospital-based ECG database for a 2-stage analysis with a deep learning model. After trained network for identifying right bundle branch block pattern, we transferred the first-stage learning to the second task to diagnose the type 1 Brugada ECG pattern. The diagnostic performance of the deep learning model was compared with that of board-certified practicing cardiologists. The model was further validated in an independent ECG data set collected from hospitals in Taiwan and Japan., Results: The diagnoses by the deep learning model (area under the receiver operating characteristic curve [AUC] 0.96, sensitivity 88.4%, specificity 89.1%) were highly consistent with the standard diagnoses (kappa coefficient 0.78). However, the diagnoses by the cardiologists were significantly different from the standard diagnoses, with only moderate consistency (kappa coefficient 0.63). In the independent ECG cohort, the deep learning model still reached a satisfactory diagnostic performance (AUC 0.89, sensitivity 86.0%, specificity 90.0%)., Conclusions: We present the first deep learning-enabled ECG model for diagnosing Brugada syndrome, which appears to be a robust screening tool with a diagnostic potential rivalling trained physicians., (Copyright © 2021 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Background: Whether ectopic atrial rhythm (EAR) is a high-risk cardiovascular phenotype (eg, the manifestation of a diseased sinoatrial node) or just a benign accelerated ectopic pacemaker remains unclear., Objective: We aimed to analyze the cardiovascular outcomes and underlying mechanisms in patients with EAR., Methods: From a 12-lead electrocardiogram hospital-based electrocardiogram database, a total of 2896 adults with EAR were propensity score matched at 1:5 with 14,480 patients with sinus rhythm (SR). Patients were retrospectively followed up for cardiovascular mortality (the primary outcome) and permanent pacemaker implantation (the secondary outcome). Heart rate variability was analyzed to compare autonomic function between patients with EAR and those with SR., Results: The prevalence of EAR was 1.13%, which increased with age. Compared with the matched patients, those with EAR had a higher risk of cardiovascular mortality (adjusted hazard ratio 1.93; 95% confidence interval 1.52-2.44; P < .0001) and permanent pacemaker implantation (adjusted hazard ratio 5.94; 95% confidence interval 3.89-9.09; P < .0001) according to the Cox proportional hazards regression model. The risk of cardiovascular mortality was similar across the subgroups on the basis of age, sex, hypertension, type 2 diabetes mellitus, congestive heart failure, myocardial infarction, stroke, and chronic kidney diseases. In patients with EAR, the low frequency/high frequency and standard deviation of the mean normal-to-normal intervals/root mean square of successive RR interval differences ratios for heart rate variability were both lower than those in patients with SR. This implied autonomic imbalance in patients with EAR., Conclusion: Patients with EAR have a higher risk of cardiovascular mortality and permanent pacemaker implantation, which was associated with autonomic imbalance., (Copyright © 2020. Published by Elsevier Inc.)

Background: Signal-averaged electrocardiogram (SAECG) provides not only diagnostic information but also the prognostic implication of ablation in arrhythmogenic right ventricular cardiomyopathy (ARVC)., Objective: This study aimed to validate the role of SAECG in identifying arrhythmogenic substrates requiring an epicardial approach in ARVC., Methods: Ninety-one patients with a definite diagnosis of ARVC who underwent successful ablation for drug-refractory ventricular arrhythmia were enrolled and classified into 2 groups: group 1 who underwent successful ablation at the endocardium only and group 2 who underwent successful ablation requiring an additional epicardial approach. The baseline characteristics of patients and SAECG parameters were obtained for analysis., Results: Male predominance, worse right ventricular (RV) function, higher incidence of syncope, and depolarization abnormality were observed in group 2. Moreover, the number of abnormal SAECG criteria was higher in group 2 than in group 1. After a multivariate analysis, the independent predictors of the requirement of epicardial ablation included the number of abnormal SAECG criteria (odds ratio 2.8, 95% confidence interval 1.4-5.4; P = .003) and presence of syncope (odds ratio 11.7; 95% confidence interval 2.7-50.4; P = .001). In addition, ≥2 abnormal SAECG criteria were associated with larger RV endocardial unipolar low-voltage zone (P < .001), larger RV endocardial/epicardial bipolar low-voltage zone/scar (P < .05), and longer RV endocardial/epicardial total activation time (P < .001 and P = .004, respectively)., Conclusion: The number of abnormal SAECG criteria was correlated with the extent of diseased epicardial substrates and could be a potential surrogate marker for predicting the requirement of epicardial ablation in patients with ARVC., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Intracardiac electrogram recording is influenced by the electrode size and inter-electrode spacing. Smaller electrodes with a closer inter-electrode spacing may improve the mapping resolution and outcome., Methods: Substrate mapping of the left atrium and residual pulmonary vein (PV) potentials during sinus rhythm was sequentially performed using a 3.5-mm electrode tip catheter and a 1-mm electrode multielectrode catheter in 33 patients (Group 1) that underwent repeat atrial fibrillation (AF) procedures. PV gap identification and electrophysiological characteristics were compared. Arrhythmia freedom was compared with a propensity matched (1:2) control group (66 patients, Group 2) undergoing repeat AF procedures guided by wide inter-electrode spacing catheter., Results: In the Group 1 patients, the total area of residual PV potentials measured using the 1-mm catheter was larger than that measured by the 3.5-mm catheter. Overall 1.97 ± 0.59 (1-3) and 1.49 ± 0.62 (1-3) PVs were identified by the 1-mm electrode and 3.5 mm catheters, respectively (P = 0.02). The gaps not identified by the 3.5 mm catheter had a smaller width and lower voltage. Radiofrequency catheter ablation in the areas with residual PV potentials identified by the 1-mm catheter resulted in complete electrical isolation of the PVs. Arrhythmia freedom at one year of follow-up was achieved in 26 of 33 (78.8%) patients in Group 1, which was significantly higher than the matched control group (33/66 [50%], P < 0.05)., Conclusion: In the patients with a previous PV isolation, mapping with small, closely spaced electrodes can increase the detection rate of residual PV potentials and improve the outcome., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Introduction: Various ECG algorithms have been proposed to identify the origin of idiopathic outflow tract (OT)-ventricular arrhythmia (VA). However, electrocardiographic features of failed and recurrent right ventricular outflow tract (RVOT) ablation of idiopathic OT-VAs have not been clearly elucidated., Methods and Results: A total of 264 consecutive patients (mean age: 44.0 ± 13.0 years, 96 male) undergoing RVOT ablation for OT-VAs with a transition ≥V 3 , including 241 patients (91.6%) with initially successful procedures and 23 patients (8.4%) with failed ablation. Detailed clinical characteristics and ECG features were analyzed and compared between the two groups. VAs with failed RVOT ablation had larger peak deflection index (PDI), longer V 2 R wave duration (V 2 Rd), smaller V 2 S wave amplitude, higher R/S ratio in V 2 , higher V 3 R wave amplitude, and larger V 2 transition ratio than those with successful ablation. Multivariate analysis demonstrated that PDI, V 2 Rd, V 2 transition ratio, and pacemapping score acquired during mapping independently predicted failed ablation (P  =  0.01, P  =  0.01, P  =  0.01, and P < 0.001, respectively). In 31 recurrent cases (12.8%) after initially successful ablation, multivariate Cox regression analysis showed that only the earliest activation time acquired during mapping predicted the recurrences after successful ablation (P  =  0.001). The recurrent cases displayed different ECG features comparing with those with failed ablation., Conclusion: The electrocardiographic features of failed RVOT ablation of idiopathic OT-VAs with a transition ≥V 3 were characterized by PDI, V 2 Rd, V 2 transition ratio, and pacemapping score acquired during mapping, unlike the recurrent RVOT ablation., (© 2017 Wiley Periodicals, Inc.)

Purpose: Differentiation between idiopathic left posterior fascicular ventricular arrhythmias (LPF-VAs) and posterior papillary muscle (PPM) VAs is of clinical value. This study aimed to develop an algorithm to distinguish PPM-VAs from LPF-VAs., Methods: This study enrolled 73 consecutive cases, including 31 with PPM-VAs and 42 with LPF-VAs, undergoing successful ablation by using 3D mapping and intracardiac echography to confirm the origin of the VAs. Electrocardiographic and electrophysiological parameters were compared between two groups., Results: The 12-lead electrocardiography of the PPM-VAs was characterized by a longer QRS duration than that in LPF-VAs (154.4 ± 14.5 vs. 132.3 ± 13.1 ms, P < 0.001). A QRS duration ≥133 ms was observed in all patients (100%) with PPM-VAs and 13/42 (31.0%) patients with LPF-VAs. The conduction duration from the earliest left ventricular activation site of the VA to the proximal right bundle branch (VA-RBB) was longer in patients with PPM-VAs than LPF-VAs (51.3 ± 12.2 vs. 23.6 ± 7.7 ms, P < 0.001). Based on the ROC analysis, a VA-RBB >36 ms was recognized in 28/31 patients with PPM-VAs (90.3%) and 2/42 with LPF-VAs (4.8%). An algorithm incorporating a QRS duration of ≥133 ms with a conduction duration of a VA-RBB of >36 ms could yield a sensitivity of 90.3% and specificity of 100% for discriminating PPM-VAs from LPF-VAs., Conclusions: The novel algorithm incorporating a QRS duration of ≥133 ms with a conduction duration of the VA-RBB of >36 ms could be useful in differentiating PPM-VAs from LPF-VAs.

Background: The changes of signal averaged ECG (SAECG) in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) undergoing radiofrequency catheter ablation (RFCA) of ventricular arrhythmias (VAs) remains unknown., Methods: Between 2010 and 2014, a total of 81 ARVD/C patients underwent endocardial and/or epicardial RFCA for drug-refractory VAs. Seventy patients (mean age 46.2±14.1years, 37 males) achieving acute procedure success (negative inducibility) were enrolled. Baseline characteristics, non-invasive examinations and SAECG (before and 3months after RFCA) were collected retrospectively., Results: After successful RFCA, the electrical parameters of SAECG changed in 39 patients (55.7%), including 28 patients (40%) with electrical regression (group 1), and 11 patients (15.7%) with electrical progression (group 3). Thirty-one patients (44.3%) showed no significant SAECG change (group 2). During a mean follow-up of 17.8±10.7months, 23 patients (32.9%) had VA recurrences, including 4 in group 1, 12 in group 2, and 7 in group 3. In comparisons with groups 2 and 3, group 1 patients had a significantly better VA recurrence-free survival (P=0.02). In multivariable Cox regression analysis, electrical regression was found to be associated with fewer VA recurrences (P=0.02, OR: 0.28, 95% CI: 0.10-0.83)., Conclusions: Electrical regression of SAECG after RFCA in ARVD/C was found to be associated with fewer VA recurrences., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Radiofrequency ablation of ventricular arrhythmias (VAs) originating from the continuum between the aortic sinus of Valsalva (ASV) and the left ventricular (LV) summit is a challenge., Objectives: The objectives of this study were to investigate the electrocardiographic, electrophysiological, and anatomical characteristics of VAs and to develop an algorithm for predicting the successful ablation site., Methods: We recruited 66 patients (mean age, 47 ± 15 years; 42 male patients) with symptomatic VAs originating from the continuum between the ASV and the LV summit who underwent radiofrequency ablation. Patients were classified into 4 groups (group 1: ASV, n = 20; group 2: subvalvular region, n = 15; group 3: great cardiac vein/anterior interventricular vein [GCV/AIV], n = 16; group 4: epicardium requiring pericardial access, n = 15). The QRS morphological characteristics of VAs were compared between the 4 groups., Results: Electrocardiographic analysis revealed that the aVL/aVR Q-wave ratio is useful in the prediction of successful ablation sites in the ASV, subvalvular area, GCV/AIV, and epicardium requiring pericardial access at cutoff values of ≤1.415, 1.416-1.535, 1.536-1.740, and >1.740, respectively. The aVL/aVR Q-wave ratio was well correlated with the distance between the successful ablation site and the tip of the LV summit. A distance of >18.9 mm and an LV myocardial thickness of >9.1 mm predicted the need for the epicardial or GCV/AIV approaches. There were no major procedural complications. Eight patients (12.1%) developed VA recurrence during a mean follow-up of 15.9 months (interquartile range 9.2-24.2 months)., Conclusion: The aVL/aVR Q-wave ratio is a useful parameter for predicting the successful ablation sites of VAs originating from the continuum between the ASV and the LV summit., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Radiofrequency catheter ablation (RFCA) is an effective therapeutic strategy in eliminating drug-refractory idiopathic right ventricular outflow tract ventricular arrhythmias (RVOT VAs). It remains unclear what factors affect early and late VA recurrences after ablation., Objective: The aim of our study was to elucidate the differences between early and late recurrences after acute successful RFCA of RVOT VAs in a long-term follow-up., Methods: A total of 220 patients with acute successful RFCA of RVOT VAs were enrolled. Detailed clinical characteristics and assessments by noninvasive and invasive electrophysiology study were explored to predict the overall, early (≤1 year), and late VA (>1 year) recurrences., Results: During a mean follow-up of 34.15 ± 33.74 months, 45 of 220 patients (20.5%) documented recurrence of RVOT VAs after the initial RFCA. Of these patients, 26 patients (57.8%) with recurrent VAs showed similar morphology, and 19 (42.2%) were different. Patients with recurrent VAs were associated with a higher incidence of hypertension, higher systolic blood pressure, identification of foci by pace mapping alone, shorter earliest activation time, more radiofrequency pulses required, and VA originating from the anterior free wall. Multivariate analysis demonstrated that mapping strategy and shorter earliest activation time preceding VA were associated with early recurrences (hazard ratio [HR] 2.26; 95% confidence interval [CI] 1.49-3.42; P < .001; and HR 0.91; 95% CI 0.85-0.98; P = .008, respectively), whereas hypertension was associated with late recurrence (HR 3.48; 95% CI 1.34-9.07; P = .001)., Conclusion: RFCA is an effective strategy in the elimination of RVOT VAs. However, early and late recurrences occur commonly. Patients with early and late VA recurrences demonstrated nonuniform patterns of clinical characteristics and electrophysiological properties., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Signal averaged electrocardiogram (SAECG) is a specific and non-invasive tool useful for arrhythmogenic right ventricular cardiomyopathy (ARVC) diagnosis. However, its role in risk stratification of patients with ARVC remains largely undefined., Methods: Sixty-four patients fulfilling Task Force ARVC criteria (mean age: 47 ± 14 years-old, 56% male, 50% definite ARVC) were enrolled. The baseline demographic, electrocardiographic, structural, and electrophysiological characteristics were collected. Patients with SAECG fulfilling all 3 Task Force criteria (3+ SAECG) were categorized into group 1, and those fulfilled 2 or less criterion were categorized into group 2. The study endpoints were unstable ventricular arrhythmia (VA), device detectable sustained fast VA (cycle lengths < 240 ms) and cardiovascular death., Results: During a mean follow-up of 21 ± 20 months, 15 primary endpoints including 12 unstable VAs and 3 device-detected fast VAs were met. One patient died of electrical storm, and one patient underwent heart transplantation. The presence of 3+ SAECG predicted malignant events in all patients with definite and non-definite ARVC (p < 0.01, OR = 30.5, 95% CI = 2.5-373.7) and in patients with definite ARVC alone (p = 0.03, OR = 11.1, 95% CI = 1.3-93.9). Patients diagnosed with non-definite ARVC without 3+ SAECG were free from malignant events., Conclusions: SAECG fulfilling all 3 Task Force criteria was an independent risk predictor of malignant events in ARVC patients. SAECG may play a valuable role in ARVC risk stratification., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Introduction: Antitachycardia pacing (ATP), a quick, painless, and effective therapy available in implantable cardioverter-defibrillators (ICDs), can terminate most, but not all, sustained ventricular tachycardias (VTs). This study investigated the possible ventricular electrogram (EGM) factors for predicting the effectiveness of ATP therapy from ICD recordings., Methods and Results: In this study, we analyzed 113 EGMs of VT episodes acquired from 20 patients who received ATP or shock to terminate tachyarrhythmias during follow-up after ICD implantations. The relationship between the outcome of ATP and VT EGM features (such as voltage, width, cycle length, and beat-to-beat morphologic variation) was investigated. The divergence (beat-to-beat morphologic variation) of the VT EGMs was determined by calculating the total deviation of all EGMs away from the average template after all VT EMGs were aligned. In total, 72 (63.7%) successful (Group I) and 41 (36.3%) unsuccessful (Group II) ATP therapy episodes were analyzed. The mean amplitude, cycle length, and EGM width were similar between these 2 groups (P > 0.05). A multivariate analysis demonstrated that the only predictor of successful ATP was the divergence among the VT EGMs (0.56 ± 0.32 vs 1.07 ± 0.64, P < 0.001, for Groups 1 and 2, respectively). The optimal cutoff value for determining a successful ATP therapy was 0.73 (with an area under the curve of 0.769, sensitivity of 81.9% [95% CI = 71.1-90.0], and specificity of 65.9% [95% CI = 49.4-79.9], P < 0.0001)., Conclusion: Signal analyses from stored EGMs of VT can predict the response of ATP therapy in patients with ICD implantations. A lesser ventricular beat-to-beat morphologic variation in the intracardiac recordings from ICDs correlated with a higher probability of a successful ATP., (© 2013 Wiley Periodicals, Inc.)

Background: Alteration in ventricular repolarization has been reported in patients with spinal cord injuries (SCIs). However, its clinical impact remains unclear., Objective: The purpose of this study was to investigate the correlation between SCIs and ventricular repolarization and the associated clinical impact., Methods: One hundred forty-four patients with an SCI were retrospectively reviewed and were divided into two groups (SCI level ≤ T6, n = 110; SCI level >T6, n = 34). The electrocardiograms were reviewed during acute phase (at emergency room) and chronic phase (>1 year)., Results: There were no differences in the underlying diseases or in ASIA score between the two groups, except there were more patients with tetraplegia among those with an SCI level ≤ T6. For the electrophysiological parameters from the electrocardiograms, the patients with an SCI level ≤ T6 had longer QTc and PR interval than those with an SCI level >T6 during acute phase. In the chronic phase, there were no differences in the electrophysiological parameters between the two groups. Only in patients with an SCI level ≤ T6 did a Kaplan-Meier analysis show that QTc prolongation could predict 30-day mortality after the acute injury. After multivariate Cox regression analysis, only tetraplegia and QTc prolongation were independent predictors of 30-day mortality (odds ratios 7.85 and 34.62, respectively). In patients with an SCI level ≤ T6, the QTc intervals were shorter in the chronic phase than those during the acute phase., Conclusion: QTc interval was associated with the level of acute SCI and predicted the 30-day mortality., (Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The noncontact mapping (NCM) system possesses the merit of global endocardial recording for unipolar and activation mapping., Objective: We aimed to evaluate the unipolar electrogram characteristics and activation pattern over the bipolar complex fractionated atrial electrogram (CFAE) sites during atrial fibrillation (AF)., Methods: Twenty patients (age 55 +/- 11 years old, 15 males) who underwent NCM and ablation of AF (paroxysmal/persistent = 13/7) were included. Both contact bipolar (32-300 Hz) and NCM virtual unipolar electrograms (0.5-300 Hz) were simultaneously recorded along with the activation pattern (total 223 sites, 11 +/- 4 sites/patient). A CFAE was defined as a mean bipolar cycle length of

Introduction: Paroxysmal supraventricular tachycardia (PSVT) is often associated with paroxysmal atrial fibrillation (AF). However, the relationship between PSVT and AF is still unclear. The aim of this study was to investigate the clinical and electrophysiological characteristics in patients with PSVT and AF, and to demonstrate the origin of the AF before the radiofrequency (RF) ablation of AF., Methods and Results: Four hundred and two consecutive patients with paroxysmal AF (338 had a pure PV foci and 64 had a non-PV foci) that underwent RF ablation were included. Twenty-one patients (10 females; mean age 47 +/- 18 years) with both PSVT and AF were divided into two groups. Group 1 consisted of 14 patients with inducible atrioventricular nodal reentrant tachycardia (AVNRT) and AF. Group 2 consisted of seven patients with Wolff-Parkinson-White (WPW) syndrome and AF. Patients with non-PV foci of AF had a higher incidence of AVNRT than those with PV foci (11% vs. 2%, P = 0.003). Patients with AF and atypical AVNRT had a higher incidence of AF ectopy from the superior vena cava (SVC) than those with AF and typical AVNRT (86% vs. 14%, P = 0.03). Group 1 patients had smaller left atrial (LA) diameter (36 +/- 3 vs. 41 +/- 3 mm, P = 0.004) and higher incidence of an SVC origin of AF (50% vs. 0%, P = 0.047) than did those in Group 2., Conclusion: The SVC AF has a close relationship with AVNRT. The effect of atrial vulnerability and remodeling may differ between AVNRT and WPW syndrome.

Background: Temporal variation in complex fractionated atrial electrograms (CFAEs) exists during atrial fibrillation (AF)., Objective: This study sought to quantify the variation in CFAEs using a fractionation interval (FI) algorithm and to define the shortest optimal recording duration required to consistently characterize the magnitude of the fractionation., Methods: Twenty-seven patients undergoing AF mapping in the left atrium were studied. The FI and frequency analysis were performed at each mapped site for recording durations of 1 to 8 seconds. The magnitude of the fractionation was quantified by the FI algorithm, which calculated the mean interval between multiple, discrete deflections during AF. The results from each duration were statistically compared with the maximal-duration recording, as a standard. The FI values were compared with the dominant frequency values obtained from the associated frequency spectra., Results: The FIs obtained from recording durations between 5 and 8 seconds had a smaller variation in the FI (P < .05) and, for those sites with a FI < 50 ms, the fractionation was typically continuous. The fast-Fourier Transform spectra obtained from the CFAE sites with recording durations of >5 seconds harbored higher dominant frequency values than those with shorter recording durations (8.1 +/- 2.5 Hz vs. 6.8 +/- 0.98 Hz, P < .05). The CFAE sites with continuous fractionation were located within the pulmonary veins and their ostia in 77% of patients with paroxysmal AF, and in only 29% of patients with nonparoxysmal AF (P < .05)., Conclusion: The assessment of fractionated electrograms requires a recording duration of > or =5 seconds at each site to obtain a consistent fractionation. Sites with the shortest FIs consistently identified sites with the fastest electrogram activity throughout the entire left atrium and pulmonary veins.

Background: The optimal recording technique of the electrogram voltage for detecting abnormal atrial tissue remains unclear. The aim of this study was to compare the impact of various recording techniques on the electrogram voltage after the delivery of ablation therapy in the human right atrium (RA)., Material and Methods: Noncontact mapping was performed in 27 patients with typical atrial flutter (mean age = 63 +/- 16, males = 20). Noncontact unipolar and bipolar electrograms were obtained before and after cavotricuspid isthmus (CTI) linear ablation. All unipolar electrograms were acquired with both wide-band filtering (0.5-300 Hz) and narrow-band filtering (32-300 Hz). The unipolar voltage measurements included both the peak-to-peak voltage and peak-negative voltage (PNV) for both filter settings., Results: A comparison of the electrogram voltage along the ablation line before and after the ablation demonstrated a greater reduction in the unipolar PNV with wide-band filtering (70 +/- 24%) than in any of the other recording modalities (P = 0.03). It was the most sensitive and specific recording technique to predict conduction block (cut-off Value 0.35 mV; sensitivity = 94.4% and specificity = 80%). A comparison of the electrogram voltage between the ablated atrial myocardium and nearby nonablated myocardium showed that the unipolar PNV with the wide-band filtering remained the most sensitive method to detect the acute ablative tissue injury, whereas the peak-to-peak bipolar voltage was the most specific method., Conclusion: The noncontact unipolar electrogram using the PNV with wide-band filter settings (0.5-300 Hz) provided the most sensitive recording technique for detecting acute ablative tissue injury.

Introduction: Ventricular arrhythmia (VA) commonly originate from the left ventricular summit (LVS) and results in left ventricular (LV) dysfunction in some patients; however, factors related to LV cardiomyopathy have not been well elucidated. Therefore, this study aimed to investigate the risk factors for LV cardiomyopathy and the outcomes of patients with LVS VA. Methods: Between 2013 and 2018, a total of 139 patients (60.7% men; mean age 53.2 ± 13.9 years old) underwent catheter ablation for LVS VA in two centers. Detailed patient demographics, electrocardiograms, electrophysiological characteristics, and clinical outcomes were analyzed. LV cardiomyopathy was defined as left ventricular ejection fraction (LVEF) <50%. Results: Acute procedural success was achieved in 92.8% of patients. There were 40 patients (28.8%) with LV cardiomyopathy, and the mean LVEF improved from 37.5 ± 9.3% to 48.5 ± 10.2% after ablation (p <.001). After multivariate analysis, the independent factors of LV dysfunction were wider QRS duration (QRSd) of the VA (odds ratio [OR] 1.02; 95% confidence interval [CI]: 1.00–1.04; p =.046) and the absolute earliest activation time discrepancy (AEAD) between epicardium and endocardium (OR 1.05; 95% CI: 1.00–1.09; p =.048). After ablation, the LV function was completely recovered in 20 patients (50%). The factors for LV dysfunction without recovery included wider premature ventricular complex (PVC) QRSd (OR 1.09; 95% CI: 1.02–1.17; p =.012) and poorer LVEF (OR 0.85; 95% CI: 0.74–0.97; p =.020). Conclusion: In patients with VA from the LVS, PVC QRSd and AEAD are factors associated with deteriorating LV systolic function. Catheter ablation can reverse LV remodeling. Narrower QRSd and better LVEF are associated with better recovery of LV function after ablation. [ABSTRACT FROM AUTHOR]

Instruction: We hypothesized that real‐time simultaneous amplitude frequency electrogram transform (SAFE‐T) during sinus rhythm (SR) is able to identify and characterize the drivers of atrial fibrillation (AF) in nonparoxysmal (NP) AF. Methods: Twenty‐one NPAF patients (85.71% males, mean age 52 years old) underwent substrate mapping during SR (SAFE‐T and voltage) and during AF (complex fractionated atrial electrograms [CFAE] and similarity index [SI]). After pulmonary veins isolation, extensive substrate ablation was performed with the endpoint of procedural termination or elimination of all SI sites (>63% similarities). Sites with procedural termination and non‐termination sites were tagged for postablation SR analysis using SAFE‐T. Results: In 74 CFAE sites identified (average of 3 ± 2 sites per person), 28 (37.84%) were identified as termination sites demonstrating a high SI compared with the non‐termination sites (80.11 ± 9.57% vs. 45.96 ± 13.38%, p <.001) during AF. During SR, these termination sites have high SAFE‐T values and harbor a highly resonant, localized, repetitive high frequency components superimposed in the low frequency components compared with non‐termination sites (5.70 ± 3.04 vs. 1.49 ± 1.66 Hz·mV, p <.001). In the multivariate analysis, the termination sites have higher SAFE‐T and SI value (p <.001). Conclusion: AF procedural termination sites harbored signal characteristics of repetitive, high frequency component of individualized electrogram during SR, which can be masked by the low frequency fractionated electrogram and are difficult to see from the bipolar electrogram. Thus, SAFE‐T mapping is feasible in identifying and characterizing sites of AF drivers. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to assess the comparative efficacy of four ablation strategies on the incidence rates of freedom from atrial fibrillation (AF) or atrial tachycardia (AT) through a 3‐year follow‐up in patients with persistent AF. Background: The optimal substrate modification strategies using catheter ablation for patients with persistent AF remain unclear. Methods: Patients with persistent AF were enrolled consecutively to undergo each of four ablation strategies: (a) Group 1 (Gp 1, n = 69), pulmonary vein isolation (PVI) plus rotor ablation assisted by similarity index and phase mapping; (b) Gp 2 (n = 75), PVI plus linear ablations at the left atrium; (c) Gp 3 (n = 42), PVI plus the elimination of complex fractionated atrial electrograms; (d) Gp 4 (n = 67), PVI only. Potential confounders were adjusted via a multivariate survival parametric model. Results: Baseline characteristics were similar across the four groups. At a follow‐up period of 34.9 ± 38.6 months, patients in Gp 1 showed the highest rate of freedom from AF compared with the other three groups (p =.002), while patients in Gp 3 and 4 showed lower rates of freedom from AT than those of the other two groups (p =.006). Independent predictors of recurrence of AF were the ablation strategy (p =.002) and left atrial diameter (LAD) (p =.01). Conclusion: In patients with persistent AF, a substrate modification strategy using rotor ablation assisted by similarity index and phase mapping provided a benefit for maintaining sinus rhythm compared with the other strategies. Both ablation strategy and baseline LAD predicted the 3‐year outcomes of freedom from AT/AF [ABSTRACT FROM AUTHOR]

Introduction: A drug provocation test (DPT) is important for the diagnosis of Brugada syndrome (BrS). The link, however, between dynamic changes of electrocardiography (ECG) features after DPT and unstable ventricular arrhythmia (VA) in BrS remains unknown. Methods: Between 2014 and 2019, we assessed 27 patients with BrS (median age: 37.0 [interquartile range, IQR: 22.0–51.0] years; 25 men), including 9 (33.3%) with a history of unstable VA and 18 (66.7%) without. All patients in the study presented with Brugada‐like ECG features before DPT. The ECG parameters and dynamic changes (∆) in 12‐lead ECGs recorded from the second, third, and fourth intercostal spaces (ICS) before and at 1, 6, 12, 18, and 24 h after DPT (oral flecainide 400 mg) were analyzed. Results: The total amplitude of V1 at the third ICS 18 and 24 h after DPT was significantly lower in patients with a history of unstable VA than in those without. Patients with BrS and unstable VAs had a significantly larger ∆ amplitude of V1 at the second ICS 12 h after DPT than in those without unstable VAs (0.28 [0.18–0.41] mV vs. 0.08 [0.01–0.15] mV, p =.01). A multivariate analysis revealed that the amplitude of V1 at the third ICS 18 and 24 h after DPT and the ∆ amplitude of V1 at the second ICS 12 h after DPT were associated with a history of unstable VA. Conclusion: Nonuniform changes and spatiotemporal differences in precordial ECG features after DPT were observed in patients with BrS and these may be surrogate markers for risk stratification. [ABSTRACT FROM AUTHOR]

Introduction: Adjunctive driver‐guided ablation in addition to pulmonary vein isolation has been proposed as a strategy to improve procedural success and outcomes for various populations with atrial fibrillation (AF). First, this study aimed to evaluate the different mapping techniques for driver/rotor identification and second to evaluate the benefits of driver/rotor‐guided ablation in patients with paroxysmal and persistent AF (PerAF). Methods: We searched the electronic database in PubMed using the keywords "atrial fibrillation," "rotor," "rotational driver," "atrial fibrillation source," and "drivers" for both randomized controlled trials and observational controlled trials. Clinical studies reporting efficacy or safety outcomes of driver‐guided ablation for paroxysmal AF or (PerAF) were identified. We performed subgroup analyses comparing different driver mapping methods in patients with PerAF. The odds ratios (ORs) with random effects were analyzed. Results: Out of 175 published articles, seven met the inclusion criteria, of which two were randomized controlled trials, one was quasiexperimental study, and four observational studies (three case‐controlled studies and one cross‐sectional study). Overall, adjunctive driver‐guided ablation was associated with higher rates of acute AF termination (OR: 4.62, 95% confidence interval [CI]: 2.12‐10.08; P < 0.001), lower recurrence of any atrial arrhythmia (OR: 0.44, 95% CI: 0.30‐0.065; P < 0.001), and comparable complication incidence. Conclusions: Adjunctive driver‐guided catheter ablation suggested an increased freedom from AF/AT relative to conventional strategies, irrespective of the mapping techniques. Furthermore, phase mapping appears to be superior to electrogram‐based driver mapping in PerAF ablation. [ABSTRACT FROM AUTHOR]

Introduction: The signal characteristics of intracardiac bipolar electrograms at the origin of idiopathic RVOT-VT during sinus rhythm remain unclear. Objective: The study sought to develop a novel real-time/online technique, simultaneous amplitude frequency electrogram transformation (SAFE-T), to quantify and localize the diseased ventricular substrate in idiopathic RVOT-VT. Methods: We retrospectively investigated the intracardiac bipolar recordings in 70 consecutive patients (26% male, mean age 42±12 years) who underwent successful radiofrequency catheter ablation of idiopathic RVOT-VT. We quantified the extent of the frequency fraction of ventricular potentials during sinus rhythm or ventricular pacing using a novel formula, the product of instantaneous amplitude and frequency, and showed that in a 3D geometry as an online SAFE-T map. Results: The characteristics of the HHT spectra of electrograms derived from VT origins demonstrated high frequency components (>70 Hz), which were independent of the rhythm. The density of the abnormal potentials at the VT origins were higher (VT origins, 7.5±2.3 sites/cm2 vs. surrounding myocardium, 1.5±1.3 sites/cm2, p<0.001), and were significantly decreased after ablation (0.7±0.6 sites/cm2, p<0.001). A small region of abnormal potentials were observed in the VT origins (mean area of 1.5±0.8 cm2). The SAFE-T maps predicted the VT origins with 92% sensitivity, 78% specificity with optimal cut-off value of >3.0 Hz·mV. Conclusion: The online SAFE-T map was feasible for quantifying the diseased ventricular substrate, irrespective of the rhythm of activation, and can be used to identify the optimal ablation targets for idiopathic RVOT-VT. We found a limited region of abnormal potentials where the RVOT-VT origins were successfully ablated. [ABSTRACT FROM AUTHOR]

Background: The impact of non-sustained ventricular tachycardia (NSVT) on the risk of thromboembolic event and clinical outcomes in patients without structural heart disease remains undetermined. This study aimed to evaluate the association between NSVT and clinical outcomes. Methods: The study population of 5903 patients was culled from the “Registry of 24-hour ECG monitoring at Taipei Veterans General Hospital” (REMOTE database) between January 1, 2002 and December 31, 2004. Of that total, we enrolled 3767 patients without sustained ventricular tachycardia, structural heart disease, and permanent pacemaker. For purposes of this study, NSVT was defined as 3 or more consecutive beats arising below the atrioventricular node with an RR interval of <600 ms (>100 beats/min) and lasting < 30 seconds. Result: There were 776 deaths, 2042 hospitalizations for any reason, 638 cardiovascular (CV)-related hospitalizations, 350 ischemic strokes, 409 transient ischemic accident (TIA), 368 new-onset heart failure (HF), and 260 new-onset atrial fibrillation (AF) with a mean follow-up duration of 10 ± 1 years. In multivariate analysis, the presence of NSVT was independently associated with death (hazard ratio [HR]: 1.362, 95% confidence interval [CI]: 1.071–1.731), CV hospitalization (HR: 1.527, 95% CI: 1.171–1.992), ischemic stroke (HR: 1.436, 95% CI: 1.014–2.032), TIA (HR 1.483, 95% CI: 1.069–2.057), and new-onset HF (HR: 1.716, 95% CI: 1.243–2.368). There was no significant association between the presence of NSVT and all-cause hospitalization or new-onset AF. Conclusion: In patients without structural heart disease, presence of NSVT on 24-hour monitoring was independently associated with death, CV hospitalization, ischemic stroke, TIA, and new onset heart failure. [ABSTRACT FROM AUTHOR]

Introduction: The characteristics of endocardial electrograms needed to detect the overlying abnormal epicardial substrates in arrhythmogenic right ventricular cardiomyopathy with epicardial ventricular tachycardia (VT) remain unclear. This study investigated which of the endocardial electrogram characteristics could predict the overlying abnormal epicardial substrates. Methods and Results: In 20 consecutive patients (median age: 46 years, 11men) undergoing epicardial VT ablation, detailed endocardial and epicardial mappings were obtained by using the CARTO 3 system. The endocardial electrographic characteristics (unipolar peak-to-peak voltage, unipolar peak-negative-voltage, bipolar voltage, and bipolar electrogram duration) of the opposite endocardium and epicardium in RV were retrospectively investigated (N = 1,697 paired points, 84 ± 60 pairs/patient). Endocardial predictors of the presence of epicardial dense scar (<0.5 mV), low voltage zones (LVZ; ⩽1.5 mV), and ablation targets (by using activation mapping, entrainment mapping, and pace mapping) were analyzed. Results: In the multivariable analysis, (1) unipolar peak-negative voltage independently predicted the presence of epicardial LVZ, epicardial dense scar, and ablation targets; (2) bipolar voltage could not predict epicardial lesions; and (3) bipolar electrogram duration predicted epicardial LVZ, but not dense scar or ablation targets. The endocardial unipolar peak-negative voltage of <1.66 mV (89% sensitivity and 53% specificity) was the optimal cutoff point for predicting epicardial dense scar. Conclusions: In patients with RV epicardial VT, the presence of unipolar peak-negative voltage of <1.66 mV in the endocardium predicted the presence of epicardial dense scar (<0.5 mV) and potential ablation targets in the overlying epicardium. [ABSTRACT FROM AUTHOR]

Macroreentrant and Focal Atrial Tachycardias. Background: Atrial tachycardias (ATs) are commonly observed following catheter ablation of atrial fibrillation (AF). The aim of this study was to identify ECG characteristics that differentiate focal from macroreentrant ATs after circumferential pulmonary vein isolation (CPVI). Methods and Results: One hundred and twenty ATs that occurred after CPVI were mapped using a 3-dimensional mapping system in 87 patients with AF. Further ablation was performed to eliminate the ATs. The surface ECGs of 68 ATs in 41 consecutive patients (Group 1) were analyzed retrospectively to create diagnostic algorithms. The algorithms were tested in the second 46 consecutive patients (Group 2). Patients with macroreentrant AT had lower left atrial (LA) voltage than those with focal AT (1.3 ± 0.3 vs 1.5 ± 0.2 mV, P = 0.01). Focal AT had a higher incidence of a positive polarity in V6 compared with macroreentrant AT (88% vs 55%, P = 0.03). The positive amplitude of the flutter/P waves in V6 was higher for focal AT than macroreentrant AT. The cycle lengths of the focal ATs were longer than those for macroreentrant AT (296 ± 107 vs 244 ± 25 ms, P < 0.001). Right atrial macroreentrant AT had a higher incidence of a negative polarity in at least 1 precordial lead compared with LA macroreentry. The positive flutter waves in V1 could differentiate roof/mitral isthmus dependent from non-roof/mitral isthmus dependent macroreentry. This algorithm correctly differentiated the focal from macroreentrant ATs with a sensitivity of 94%, specificity of 91%, and predictive accuracy of 92% in Group 2. Conclusion: Different electrophysiological properties may facilitate the differentiation between macroreentrant and focal ATs after CPVI. (J Cardiovasc Electrophysiol, Vol. 22, pp. 748-755, July 2011) [ABSTRACT FROM AUTHOR]

To evaluate contemporary trends of clinical characteristics, etiologies, and underlying diseases, and their relationship between different bradyarrhythmias in patients undergoing temporary pacemakers (TPMs). This study included 509 patients (77 ± 11 year, 74% males) with symptomatic bradyarrhythmias requiring TPMs between 2002 and 2008. Demographics, electrocardiographic indications, etiologies, underlying diseases, and the outcome of permanent pacemaker (PPM) implants within 30 days were analyzed. Atrioventricular conduction dysfunction (AVCD) (64.0%) dominated in all bradyarrhythmias, with idiopathic degeneration (61%) as its major etiology. Antiarrhythmic drug (38%) was the leading cause in sinoatrial node dysfunction (SAND). There was an increasing trend in AVCD, while a decreasing trend in SAND. Regarding etiologies for TPM, an increasing trend was found in idiopathic degeneration, whereas a decreasing trend in acute coronary syndrome (ACS). Idiopathic degeneration had an odds ratio (OR) of 1.9 for AVCD (P = 0.001), whereas electrolyte/acid-base disturbances (OR = 3.7, P = 0.001), β-blockers (OR = 2.4, P = 0.002), and chronic renal disease (OR = 1.9, P = 0.01) were associated with SAND. Patients with intrinsic etiologies for TPM had a high incidence of PPM implantation within 30 days than those with extrinsic causes (67.5% vs 3.8%, P < 0.0001) Increasing trends in patients requiring TPMs were observed in the elderly patients and those with AVCD and idiopathic degeneration, while decreasing trends were observed in those with SAND and ACS. Idiopathic degeneration was associated with AVCD, whereas extrinsic etiologies were related to SAND. Patients with intrinsic etiologies had a higher incidence of PPM implantation than those with extrinsic factors for TPM. (PACE 2010; 33:1475-1484) [ABSTRACT FROM AUTHOR]

Introduction: The left atrial (LA) substrate plays an important role in the maintenance of atrial fibrillation (AF). However, little is known about the acute effect of circumferential pulmonary vein isolation (CPVI). This study was to investigate the acute change of LA activation, voltage and P wave in surface electrocardiogram (ECG) after CPVI. Methods and Results: Electroanatomic mapping (NavX) was performed in 50 patients with AF (mean age = 54 ± 10 years, 36 males) who underwent only CPVI. The mean peak-to-peak bipolar voltage and total activation time of LA were obtained during sinus rhythm before and immediately after CPVI. The average duration and amplitude of P waves in 12-lead ECG were also analyzed before and after CPVI. Change in the earliest LA breakthrough sites could cause decreased LA total activation time. Downward shift in the breakthrough site was inversely proportional to the proximity of the breakthrough site to the radiofrequency lesions. A shortening of P-wave duration and decrease in voltage after CPVI were observed after CPVI. Patients with recurrent AF had less voltage reduction in the atrial wall 1 cm from the circumferential PV lesions compared with those without recurrent AF (60.1 ± 11.7% vs 74.1 ± 6.6%, P = 0.002). Reduction of voltage ≤64.4% in this area after CPVI is related with recurrent AF. Conclusion: CPVI could result in acute change of LA substrate, involving LA activation and voltage. Less reduction of voltage in the atrial wall adjacent to the circumferential PV lesions after CPVI may be associated to the recurrence of AF. [ABSTRACT FROM AUTHOR]

The article presents a medical case of a 51-year-old patient who developed incessant wide QRS tachycardia after pulmonary vein isolation and pacemaker implantation for the treatment of tachycardia-bradycardia syndrome. Five months after the surgery, he presented with palpitations and exertional dyspnea. A 12-lead electrocardiography revealed a wide QRS tachycardia, with a rapid regular ventricular paced rhythm and irregular P waves.