An improved method to detect arrhythmia using ensemble learning-based model in multi lead electrocardiogram (ECG)

Arrhythmia is a life-threatening cardiac condition characterized by irregular heart rhythm. Early and accurate detection is crucial for effective treatment. However, single-lead electrocardiogram (ECG) methods have limited sensitivity and specificity. This study propose an improved ensemble learning approach for arrhythmia detection using multi-lead ECG data. Proposed method, based on a boosting algorithm, namely Fine Tuned Boosting (FTBO) model detects multiple arrhythmia classes. For the feature extraction, introduce a new technique that utilizes a sliding window with a window size of 5 R-peaks. This study compared it with other models, including bagging and stacking, and assessed the impact of parameter tuning. Rigorous experiments on the MIT-BIH arrhythmia database focused on Premature Ventricular Contraction (PVC), Atrial Premature Contraction (PAC), and Atrial Fibrillation (AF) have been performed. The results showed that the proposed method achieved high sensitivity, specificity, and accuracy for all three classes of arrhythmia. It accurately detected Atrial Fibrillation (AF) with 100% sensitivity and specificity. For Premature Ventricular Contraction (PVC) detection, it achieved 99% sensitivity and specificity in both leads. Similarly, for Atrial Premature Contraction (PAC) detection, proposed method achieved almost 96% sensitivity and specificity in both leads. The proposed method shows great potential for early arrhythmia detection using multi-lead ECG data.

Pause-Dependent Paroxysmal Episode of Third-Degree Atrioventricular Block Triggered by Premature Atrial Contraction

BACKGROUND Paroxysmal third-degree atrioventricular block (AVB) can exhibit a vast array of symptoms, but commonly, paroxysmal AVB leads to presyncope, syncope, or possibly sudden cardiac death. We present a rare case of pause-dependent paroxysmal AVB that was triggered by a premature atrial contraction. CASE REPORT A 65-year-old man with frequent episodes of presyncope and syncope for 3 weeks was admitted to our hospital for further diagnosis. A resting 12-lead electrocardiogram showed an incomplete right bundle branch block, and a 24-h Holter recording showed multiple episodes of third-degree AVB. Intracardiac tracing revealed that the block site was distal, at the infra-His-Purkinje system. CONCLUSIONS This case highlights a rare case of pause-dependent paroxysmal AVB that was triggered by a premature atrial contraction. This type of AVB is an abrupt, unexpected, repetitive block of atrial impulses as they propagate to the ventricles. It is relatively rare, and due to its transient nature, it is often under recognized and can lead to sudden cardiac death.

Higher Frequency of Premature Atrial Contractions Correlates With Atrial Fibrillation Detection after Cryptogenic Stroke

BACKGROUND

Covert atrial fibrillation (AF) is a major cause of cryptogenic stroke. This study investigated whether a dose-dependent relationship exists between the frequency of premature atrial contractions (PACs) and AF detection in patients with cryptogenic stroke using an insertable cardiac monitor (ICM).

METHODS

We enrolled consecutive patients with cryptogenic stroke who underwent ICM implantation between October 2016 and September 2020 at 8 stroke centers in Japan. Patients were divided into 3 groups according to the PAC count on 24-hour Holter ECG: ≤200 (group L), >200 to ≤500 (group M), and >500 (group H). We defined a high AF burden as above the median of the cumulative duration of AF episodes during the entire monitoring period. We evaluated the association of the frequency of PACs with AF detection using log-rank trend test and Cox proportional hazard model and with high AF burden using logistic regression model, adjusting for age, sex, CHADS2 score.

RESULTS

Of 417 patients, we analyzed 381 patients with Holter ECG and ICM data. The median age was 70 (interquartile range, 59.5-76.5), 246 patients (65%) were males, and the median duration of ICM recording was 605 days (interquartile range, 397-827 days). The rate of new AF detected by ICM was higher in groups with more frequent PAC (15.5%/y in group L [n=277] versus 44.0%/y in group M [n=42] versus 71.4%/y in group H [n=62]; log-rank trend P<0.01). Compared with group L, the adjusted hazard ratios for AF detection in groups M and H were 2.11 (95% CI, 1.24-3.58) and 3.23 (95% CI, 2.07-5.04), respectively, and the adjusted odds ratio for high AF burden in groups M and H were 2.57 (95% CI, 1.14-5.74) and 4.25 (2.14-8.47), respectively.

CONCLUSIONS

The frequency of PACs was dose-dependently associated with AF detection in patients with cryptogenic stroke.

Predicting risk of AF in ischaemic stroke using sinus rhythm ECG abnormalities: A meta-analysis

OBJECTIVE

To identify ECG changes in sinus rhythm that may be used to predict subsequent development of new AF.

METHOD

We identified prospective and retrospective cohort or case control studies evaluating ECG patterns from a 12-lead ECG in sinus rhythm taken in hospital or community predicting subsequent development of new AF. For each identified ECG predictor, we then identify absolute event rates and pooled risk ratios (RR) using an aggregate level random effects meta-analysis.

RESULTS

We identified 609,496 patients from 22 studies. ECG patterns included P wave terminal force V1 (PTFV1), interatrial block (IAB) and advanced interatrial block (aIAB), abnormal P wave axis (aPWA), PR prolongation and atrial premature complexes (APCs). Pooled risk ratios reached significance for each of these; PTFV1 RR 1.48 (95% CI 1.04-2.10), IAB 2.54 (95% CI 1.64-3.93), aIAB 4.05 (95% CI 2.64-6.22), aPWA 1.89 (95% CI 1.25-2.85), PR prolongation 2.22 (95% CI 1.27-3.87) and APCs 3.71 (95% CI 2.23-6.16). Diabetes reduced the predictive value of PR prolongation.

CONCLUSION

APC and aIAB were most predictive of AF, while IAB, PR prolongation, PTFV1 and aPWA were also significantly associated with development of AF. These support their use in a screening tool to identify at risk cohorts who may benefit from further investigation, or following stroke, with empirical anticoagulation.

Utility of short-time electrocardiogram to assess risk for atrial arrhythmia recurrence: Impact of atrial premature beat occurrence 1 day after pulmonary vein isolation for atrial fibrillation

INTRODUCTION

Atrial premature beats (APBs) are the trigger for atrial fibrillation (AF). We sought to investigate the clinical significance of APB occurrence 1 day after pulmonary vein isolation (PVI) for AF using a short-time electrocardiogram.

METHODS

A total of 206 patients undergoing PVI for paroxysmal AF were included. Electrocardiogram recording for 100 consecutive beats was performed 1 day after PVI. The patients were divided into two groups: those with reproducible APBs (≥1 beat) during reassessment (APB group, n = 49) or those without (non-APB group, n = 157). Late recurrence was defined as atrial tachyarrhythmia recurrence 3-12 months after PVI. The impact of APB occurrence on outcomes was investigated.

RESULTS

Late recurrence occurred in 19 patients (9.2%). The presence of low-voltage areas, left atrial volume, and recurrence rate were higher in the APB group than in the non-APB group. In the APB group, the patients with recurrence had lower prematurity index (PI, coupling interval of APB/previous cycle length) compared to those without. Receiver-operating characteristic analysis revealed PI (<59.3) to be a predictive factor of recurrence (area under the curve: 0.733). The study subjects were then reclassified into three groups according to the absence of APB occurrence (n = 157), presence thereof with PI ≥ 59.3 (n = 33), and presence with PI < 59.3 (n = 16). The multivariate Cox models revealed that APB with PI < 59.3 was an independent predictor for recurrence (hazard ratio, 8.735; p < 0.001).

CONCLUSION

A short-time electrocardiogram enables risk assessment for arrhythmia recurrence, and APB with low PI 1 day after PVI is a powerful predictor.

Premature atrial contractions promote local directional heterogeneities in conduction velocity vectors

AIMS

Loss of cell-to-cell communication results in local conduction disorders and directional heterogeneity (LDH) in conduction velocity (CV) vectors, which may be unmasked by premature atrial contractions (PACs). We quantified LDH and examined differences between sinus rhythm (SR) and spontaneous PACs in patients with and without atrial fibrillation (AF).

METHODS AND RESULTS

Intra-operative epicardial mapping of the right and left atrium (RA, LA), Bachmann's bundle (BB) and pulmonary vein area (PVA) was performed in 228 patients (54 with AF). Conduction velocity vectors were computed at each electrode using discrete velocity vectors. Directions and magnitudes of individual vectors were compared with surrounding vectors to identify LDH. Five hundred and three PACs [2 (1-3) per patient; prematurity index of 45 ± 12%] were included. During SR, most LDH were found at BB and LA [11.9 (8.3-14.9) % and 11.3 (8.0-15.2) %] and CV was lowest at BB [83.5 (72.4-94.3) cm/s, all P < 0.05]. Compared with SR, the largest increase in LDH during PAC was found at BB and PVA [+13.0 (7.7, 18.3) % and +12.5 (10.8, 14.2) %, P < 0.001]; CV decreased particularly at BB, PVA and LA [-10.0 (-13.2, -6.9) cm/s, -9.3 (-12.5, -6.2) cm/s and -9.1 (-11.7, -6.6) cm/s, P < 0.001]. Comparing patients with and without AF, more LDH were found during SR in AF patients at PVA and BB, although the increase in LDH during PACs was similar for all sites.

CONCLUSION

Local directional heterogeneity is a novel methodology to quantify local heterogeneity in CV as a possible indicator of electropathology. Intra-operative high-resolution mapping indeed revealed that LDH increased during PACs particularly at BB and PVA. Also, patients with AF already have more LDH during SR, which becomes more pronounced during PACs.

Differences in Left Atrial Size and Function and Supraventricular Ectopy Between Black and White Participants in the ARIC Study

Background Black Americans have more atrial fibrillation risk factors but lower atrial fibrillation risk than White Americans. Left atrial (LA) enlargement and/or dysfunction, frequent atrial tachycardia (AT), and premature atrial contractions (PAC) are associated with increased atrial fibrillation risk. Racial differences in these factors may exist that could explain the difference in atrial fibrillation risk. Methods and Results We included 2133 ARIC (Atherosclerosis Risk in Communities) study participants (aged 74±4.5 years[mean±SD], 59% women, 27% Black participants) who had echocardiograms in 2011 to 2013 and wore the Zio XT Patch (a 2-week continuous heart monitor) in 2016 to 2017. Linear regression was used to analyze (1) differences in AT/day or PAC/hour between Black and White participants, (2) differences in LA measures between Black and White participants, and (3) racial differences in the association of LA measures with AT or PAC frequency. Compared with White participants, Black participants had a higher prevalence of cardiovascular risk factors and disease, lower AT frequency, greater LA size, and lower LA function. After multivariable adjustments, Black participants had 37% (95% CI, 24%-47%) fewer AT runs/day than White participants. No difference in PAC between races was noted. Greater LA size and reduced LA function are associated with more AT and PAC runs; however, no race interaction was present. Conclusions Differences in LA measures are unlikely to explain the difference in atrial fibrillation risk between Black and White individuals. Despite more cardiovascular risk factors and greater atrial remodeling, Black participants have lower AT frequency than White participants. Future research is needed to elucidate the protective mechanisms that confer resilience to atrial arrhythmias in Black individuals.

Transition of the heart rate and atrial premature complex after cryoballoon vs. radiofrequency ablation for paroxysmal atrial fibrillation

The temporal changes in ambulatory monitoring findings after cryoballoon (CB) ablation of atrial fibrillation (AF) have not been well elucidated. This study aims to compare the details of ambulatory monitoring after CB and radiofrequency catheter (RFC) ablation for AF. Of 724 consecutive AF patients who underwent initial ablation using a CB or RFC, 508 (254 pairs) were selected using propensity score matching. Ambulatory monitoring was performed at 1, 3, 6, 12, 24 and 36 months after the procedure. After 1, 3 and 6 months, the number of total heart beats (THBs) was larger in the CB group than in the RFC group. It gradually decreased and became significantly similar by 12 months after ablation. THBs significantly increased 1, 3, 6 and 12 months after ablation in both the RFC and CB groups and became statistically similar by 24 months after ablation. The atrial premature contraction burden was higher in the RFC group than in the CB group at 3 months after ablation. THB and APC burden after AF ablation were significantly different between the RF and CB groups. THBs returned to statistically similarity by 2 years after ablation in both groups.

Life's Simple 7 cardiovascular health score and premature atrial contractions: The atherosclerosis risk in communities (ARIC) study

BACKGROUND

Premature atrial contractions (PACs) are associated with increased risk of atrial fibrillation (AF) and ischemic stroke. Although lifestyle and risk factor modification reduces AF incidence, their relationship to PACs frequency is unclear. We assessed the association of Life's Simple 7 (LS7) and individual LS7 factors in midlife with PACs frequency in late life in the Atherosclerosis Risk in Communities (ARIC) Study.

METHODS

We followed 1924 participants from ARIC clinic Visit 3 (1993--95) to Visit 6 (2016-17) when a 2-week continuous heart rhythm monitor (Zio®XT Patch) was applied. LS7 factors were assessed at Visit 3 and a composite score was calculated. PACs frequency was categorized as minimal (<0.1%), occasional (≥0.1%-5%) and frequent (>5%). Logistic regression was used to evaluate the association of LS7 score and individual factors with PACs frequency.

RESULTS

Each 1-point LS7 score increase was associated with lower odds of frequent PACs vs. no PACs (OR [95% CI]: 0.87 [0.78, 0.98]) and frequent PACs vs. occasional PACs (OR [95% CI]: 0.88 [0.79, 0.98]). Of the individual LS7 factors, compared with ideal physical activity, poor physical activity was associated with 81% higher odds of frequent PACs vs. no PACs. Compared with ideal BMI, poor BMI was associated with 41% higher odds of occasional PACs vs. no PACs.

CONCLUSION

Lifestyle risk factors, particularly physical activity and BMI, are associated with higher odds of PACs frequency. More research is needed to determine whether modifying these risk factors in midlife would prevent frequent PACs, and thereby prevent AF and stroke in older age.

Frequent Premature Atrial Contractions Are Associated With Poorer Cognitive Function in the Atherosclerosis Risk in Communities (ARIC) Study

OBJECTIVE

To evaluate the association of premature atrial contraction (PAC) frequency with cognitive test scores and prevalence of dementia or mild cognitive impairment (MCI).

MATERIALS AND METHODS

We conducted a cross-sectional analysis using Atherosclerosis Risk in Communities study visit 6 (January 1, 2016, through December 31, 2017) data. We included 2163 participants without atrial fibrillation (AF) (age mean ± SD, 79±4 years; 1273 (58.9%) female; and 604 (27.97.0% Black) who underwent cognitive testing and wore a leadless, ambulatory electrocardiogram monitor for 14 days. We categorized PAC frequency based on the percent of beats: less than 1%, minimal; 1% to <5%, occasional; greater than or equal to 5%, frequent. We derived cognitive domain-specific factor scores (memory, executive function, language, and global z-score). Dementia and MCI were adjudicated.

RESULTS

During a mean analyzable time of 12.6±2.6 days, 339 (15.7%) had occasional PACs and 107 (4.9%) had frequent PACs. Individuals with frequent PACs (vs minimal) had lower executive function factor scores by 0.30 (95% CI, -0.46 to -0.14) and lower global factor scores by 0.20 (95% CI, -0.33 to -0.07) after multivariable adjustment. Individuals with frequent PACs (vs minimal) had higher odds of prevalent dementia or MCI after multivariable adjustment (odds ratio, 1.74; 95% CI, 1.09 to 2.79). These associations were unchanged with additional adjustment for stroke.

CONCLUSION

In community-dwelling older adults without AF, frequent PACs were cross-sectionally associated with lower executive and global cognitive function and greater prevalence of dementia or MCI, independently of stroke. Our findings lend support to the notion that atrial cardiomyopathy may be a driver of AF-related outcomes. Further research to confirm these associations prospectively and to elucidate underlying mechanisms is warranted.

Novel Density Poincaré Plot Based Machine Learning Method to Detect Atrial Fibrillation From Premature Atrial/Ventricular Contractions

OBJECTIVE

Detection of Atrial fibrillation (AF) from premature atrial contraction (PAC) and premature ventricular contraction (PVC) is difficult as frequent occurrences of these ectopic beats can mimic the typical irregular patterns of AF. In this paper, we present a novel density Poincaré plot-based machine learning method to detect AF from PAC/PVCs using electrocardiogram (ECG) recordings.

METHODS

First, we propose the generation of this new density Poincaré plot which is derived from the difference of the heart rate (DHR) and provides the overlapping phase-space trajectory information of the DHR. Next, from this density Poincaré plot, several image processing domain-based approaches including statistical central moments, template correlation, Zernike moment, discrete wavelet transform and Hough transform features are used to extract suitable features. Subsequently, the infinite latent feature selection algorithm is implemented to rank the features. Finally, classification of AF vs. PAC/PVC is performed using K-Nearest Neighbor, Support vector machine (SVM) and Random Forest (RF) classifiers. Our method is developed and validated using a subset of Medical Information Mart for Intensive Care (MIMIC) III database containing 10 AF and 10 PAC/PVC subjects. Results- During the segment-wise 10-fold cross-validation, SVM achieved the best performance with 98.99% sensitivity, 95.18% specificity and 97.45% accuracy with the extracted features. In subject-wise scenario, RF achieved the highest accuracy of 91.93%. Moreover, we further validated the proposed method using two other databases: wearable armband ECG data and the Physionet AFPDB. 100% PAC detection accuracy was obtained for both databases without any further training.

CONCLUSION

Our proposed density Poincaré plot-based method showed superior performance when compared with four existing algorithms; thus showing the efficacy of the extracted image domain-based features.

SIGNIFICANCE

From intensive care unit's ECG to wearable armband ECGs, the proposed method is shown to discriminate PAC/PVCs from AF with high accuracy.

Frequent Premature Atrial Contractions as a Poor Prognostic Factor in Cryptogenic Stroke Patients with Concomitant Non-Sustained Atrial Tachycardia

In cryptogenic stroke patients, early detection of new-onset atrial fibrillation (AF) and recurrent stroke is required to prevent poor clinical outcomes. Therefore, we investigated the predictors of new-onset AF and recurrent stroke in cryptogenic stroke patients without previously diagnosed AF. In total, 390 patients who were diagnosed with stroke and non-sustained atrial tachycardia (NSAT) on 24-hour Holter monitoring were followed up to assess new-onset AF and recurrent stroke. The 5-year event-free survival as well as the predictors of recurrent stroke or new-onset AF were investigated. Based on receiver operating characteristic analysis, frequent premature atrial contractions (PACs) were defined as PACs >44 beats/day. The median follow-up period was 35 months. The composite event rate was 11.5%. In Kaplan-Meier analysis, the 5-year cumulative incidence of composite events was higher in cryptogenic stroke patients with frequent PACs than in those without frequent PACs. Multivariate analysis revealed that current smoking, increased left atrial volume index, and frequent PACs were poor prognostic predictors of composite event, and frequent PACs were an independent poor prognostic factor of new-onset AF in cryptogenic stroke patients. Therefore, frequent PACs might be associated with poor clinical outcomes (new-onset AF and recurrent stroke) in cryptogenic stroke patients with concomitant NSAT.

Association between excessive premature atrial complexes and cryptogenic stroke: results of a case-control study

OBJECTIVE

Recent anticoagulation trials in all-comer cryptogenic stroke patients have yielded equivocal results, reinvigorating the focus on identifying reproducible markers of an atrial myopathy. We investigated the role of excessive premature atrial complexes (PACs) in ischaemic stroke, including cryptogenic stroke and its association with vascular risk factors.

METHODS AND RESULTS

A case-control study was conducted utilising a multicentre institutional stroke database to compare 461 patients with an ischaemic stroke or transient ischaemic attack (TIA) with a control group consisting of age matched patients without prior history of ischaemic stroke/TIA. All patients underwent 24-hour Holter monitoring during the study period and atrial fibrillation was excluded. An excessive PAC burden, defined as ≥200 PACs/24 hours, was present in 25.6% and 14.7% (p<0.01), of stroke/TIA and control patients, respectively. On multivariate regression, excessive PACs (OR 1.97; 95% CI 1.29 to 3.02; p<0.01), smoking (OR 1.58; 95% CI 1.06 to 2.36; p<0.05) and hypertension (OR 1.53; 95% CI 1.07 to 2.17; p<0.05) were independently associated with ischaemic stroke/TIA. Excessive PACs remained the strongest independent risk factor for the cryptogenic stroke subtype (OR 1.95; 95% CI 1.16 to 3.28; p<0.05). Vascular risk factors that promote atrial remodelling, increasing age (≥75 years, OR 3.64; 95% CI 2.08 to 6.36; p<0.01) and hypertension (OR 1.54; 95% CI 1.01 to 2.34; p<0.05) were independently associated with excessive PACs.

CONCLUSIONS

Excessive PACs are independently associated with cryptogenic stroke and may be a reproducible marker of atrial myopathy. Prospective studies assessing their utility in guiding stroke prevention strategies may be warranted.

A Pilot Randomized Trial of Oral Magnesium Supplementation on Supraventricular Arrhythmias

Low magnesium may increase the risk of atrial fibrillation. We conducted a double-blind pilot randomized trial to assess adherence to oral magnesium supplementation (400 mg of magnesium oxide daily) and a matching placebo, estimate the effect on circulating magnesium concentrations, and evaluate the feasibility of using an ambulatory heart rhythm monitoring device (ZioPatch) for assessing premature atrial contractions. A total of 59 participants were randomized; 73% were women, and the mean age was 62 years. A total of 98% of the participants completed the follow-up. In the magnesium supplement group, 75% of pills were taken, and in the placebo group, 83% were taken. The change in magnesium concentrations was significantly greater for those given the magnesium supplements than for those given the placebo (0.07; 95% confidence interval: 0.03, 0.12 mEq/L; p = 0.002). The ZioPatch wear time was approximately 13 of the requested 14 days at baseline and follow-up. There was no difference by intervention assignment in the change in log premature atrial contractions burden, glucose, or blood pressure. Gastrointestinal changes were more common among the participants assigned magnesium (50%) than among those assigned the placebo (7%), but only one person discontinued participation. In sum, compliance with the oral magnesium supplementation was very good, and acceptance of the ZioPatch monitoring was excellent. These findings support the feasibility of a larger trial for atrial fibrillation (AF) prevention with oral magnesium supplementation.

A confused ECG with multiple rhythms caused by atrial premature contractions: A case report

INTRODUCTION

Atrial premature contractions (APCs) are commonly encountered in clinical practice. The APCs may influence heart conduction system and induce other arrhythmia. The disorder of atrioventricular conduction is related to electrophysiological phenomena, difficult to understand and diagnose.

CASE REPORT

We presented a 15-year-old male patient whose baseline electrocardiogram (ECG) was confused with multiple rhythms. Electrophysiological study results showed sinus rhythm with nonconducted APCs in bigeminal rhythm. Nonconducted APCs were blocked without H wave. Some APCs conducted to ventricle with longer AH interval and HV interval. When APCs were abolished by radiofrequency ablation, this patient was free from any arrhythmia during follow-up.

CONCLUSION

We considered that the basic rhythm of the baseline ECG was sinus rhythm with atrial bigeminy rhythm and narrow QRS extrasystoles (junctional); some APCs were blocked and some APCs conducted to ventricle with aberrant QRS complexes. The phenomenon of baseline ECG was caused by the APCs.

Non-invasive localization of atrial ectopic beats by using simulated body surface P-wave integral maps

Non-invasive localization of continuous atrial ectopic beats remains a cornerstone for the treatment of atrial arrhythmias. The lack of accurate tools to guide electrophysiologists leads to an increase in the recurrence rate of ablation procedures. Existing approaches are based on the analysis of the P-waves main characteristics and the forward body surface potential maps (BSPMs) or on the inverse estimation of the electric activity of the heart from those BSPMs. These methods have not provided an efficient and systematic tool to localize ectopic triggers. In this work, we propose the use of machine learning techniques to spatially cluster and classify ectopic atrial foci into clearly differentiated atrial regions by using the body surface P-wave integral map (BSPiM) as a biomarker. Our simulated results show that ectopic foci with similar BSPiM naturally cluster into differentiated non-intersected atrial regions and that new patterns could be correctly classified with an accuracy of 97% when considering 2 clusters and 96% for 4 clusters. Our results also suggest that an increase in the number of clusters is feasible at the cost of decreasing accuracy.

Yield of 48-hour Holter monitoring in children with unexplained palpitations and significance of associated symptoms

OBJECTIVE

To determine the yield of 48-hour Holter monitoring in children with unexplained palpitations and the significance of associated symptoms.

METHODS

This descriptive study was conducted at the Children's Hospital and Institute of Child Health, Lahore, Pakistan, from January 1 to December 31, 2015. All children above 5 years of age with history of intermittent palpitations and normal basic cardiovascular workup were enrolled. A 48-hour Holter study was performed using Motara Holter Monitoring System. Frequency of various symptoms and abnormal Holter findings were analysed. SPSS 21 was used for data analysis.

RESULTS

Of the 107 patients, 69(64.5%) were males and 38(34.5%) females. The median age was 10 years (interquartile range: 5-18 years). Most common concomitant symptoms with palpitation included syncope/pre-syncope in 35(32.7%) patients, chest pain 22(20.5%), shortness of breath 21(19.6%) and colour change/pallor 11(10.3%). Holter recording was positive in 40(37%) patients. Frequent premature ventricular contractions 12(11.2%) and atrial ectopic beats 9(8.4%) were the most common findings. Holter findings were significantly more common in patients with history of shortness of breath and colour change/pallor during palpitations (p=0.002).

CONCLUSIONS

Extended 24-hour Holter monitoring in children with palpitations was an inexpensive, non-invasive investigation with a reasonably high diagnostic yield in detecting arrhythmias.

ECG Case of the Month: Wide-QRS Rhythm in a Man with a Clotted Dialysis Fistula

A 57-year-old man with diabetes mellitus, systemic arterial hypertension, and end-stage kidney disease came to the hospital because his arteriovenous fistula used for hemodialysis had clotted. His blood hemoglobin level was 12.8 g/dL (reference, 13.5-17.5); and serum chemistry levels were creatinine 6.7 mg/dL (0.7-1.3), sodium 132 mEq/L (136-146), potassium 4.0 mEq/L (3.5-5.1), chloride 94 mEq/L (98-106), carbon dioxide 24 mEQ/L (23-29), calcium 9.1 mg/dL (8.4-10.2), and phosphorus 9.1 mg/dL (2.7-4.5). An electrocardiogram was recorded (Figure 1).

Novel non-invasive algorithm to identify the origins of re-entry and ectopic foci in the atria from 64-lead ECGs: A computational study

Atrial tachy-arrhytmias, such as atrial fibrillation (AF), are characterised by irregular electrical activity in the atria, generally associated with erratic excitation underlain by re-entrant scroll waves, fibrillatory conduction of multiple wavelets or rapid focal activity. Epidemiological studies have shown an increase in AF prevalence in the developed world associated with an ageing society, highlighting the need for effective treatment options. Catheter ablation therapy, commonly used in the treatment of AF, requires spatial information on atrial electrical excitation. The standard 12-lead electrocardiogram (ECG) provides a method for non-invasive identification of the presence of arrhythmia, due to irregularity in the ECG signal associated with atrial activation compared to sinus rhythm, but has limitations in providing specific spatial information. There is therefore a pressing need to develop novel methods to identify and locate the origin of arrhythmic excitation. Invasive methods provide direct information on atrial activity, but may induce clinical complications. Non-invasive methods avoid such complications, but their development presents a greater challenge due to the non-direct nature of monitoring. Algorithms based on the ECG signals in multiple leads (e.g. a 64-lead vest) may provide a viable approach. In this study, we used a biophysically detailed model of the human atria and torso to investigate the correlation between the morphology of the ECG signals from a 64-lead vest and the location of the origin of rapid atrial excitation arising from rapid focal activity and/or re-entrant scroll waves. A focus-location algorithm was then constructed from this correlation. The algorithm had success rates of 93% and 76% for correctly identifying the origin of focal and re-entrant excitation with a spatial resolution of 40 mm, respectively. The general approach allows its application to any multi-lead ECG system. This represents a significant extension to our previously developed algorithms to predict the AF origins in association with focal activities.

Atrial tachy-arrhythmias are associated with irregular excitation waves arising from re-entrant excitation, multiple wavelets or rapid focal activity. Identifying the origin of the irregular activity may be vital for diagnosis and treatment of the disorder. Where invasive and non-invasive methods provide approaches for such identification, both have associated disadvantages. In this study, we used a biophysically detailed model of the human atria and torso to develop an algorithm based on the correlation between the electrocardiogram (ECG) signal from a 64-lead vest and the location of rapid focal and re-entrant excitation. Using the properties of the atrial activation and the ECG signals, we developed a focus-location algorithm which is able to distinguish rapid focal activity from re-entrant scroll waves centred in the same location. Based on simulated data, the algorithm had success rates of 93% and 76% for correctly identifying the origin of focal and re-entrant excitation, respectively, and 88% for distinguish focal and re-entrant excitation, with no false positives. Inherited from our previous algorithm, it is also easily generalizable to any multi-lead ECG system.

Electrocardiographic Predictors of Incident Atrial Fibrillation

Atrial fibrillation (AF) is likely secondary to multiple different pathophysiological mechanisms that are increasingly but incompletely understood. Motivated by the hypothesis that 3 previously described electrocardiographic predictors of AF identify distinct AF mechanisms, we sought to determine if these electrocardiographic findings independently predict incident disease. Among Cardiovascular Health Study participants without prevalent AF, we determined whether left anterior fascicular block (LAFB), a prolonged QTC, and atrial premature complexes (APCs) each predicted AF after adjusting for each other. We then calculated the attributable risk in the exposed for each electrocardiographic marker. LAFB and QTC intervals were assessed on baseline 12-lead electrocardiogram (n = 4,696). APC count was determined using 24-hour Holter recordings obtained in a random subsample (n = 1,234). After adjusting for potential confounders and each electrocardiographic marker, LAFB (hazard ratio [HR] 2.1, 95% confidence interval [CI] 1.1 to 3.9, p = 0.023), a prolonged QTC (HR 2.5, 95% CI 1.4 to 4.3, p = 0.002), and every doubling of APC count (HR 1.2, 95% CI 1.1 to 1.3, p <0.001) each remained independently predictive of incident AF. The attributable risk of AF in the exposed was 35% (95% CI 13% to 52%) for LAFB, 25% (95% CI 0.6% to 44%) for a prolonged QTC, and 34% (95% CI 26% to 42%) for APCs. In conclusion, in a community-based cohort, 3 previously established electrocardiogram-derived AF predictors were each independently associated with incident AF, suggesting that they may represent distinct mechanisms underlying the disease.

Electrocardiogram PR Interval Is a Surrogate Marker to Predict New Occurrence of Atrial Fibrillation in Patients with Frequent Premature Atrial Contractions

The clinical significance of prolonged PR interval has not been evaluated in patients with frequent premature atrial contractions (PACs). We investigated whether prolonged PR interval could predict new occurrence of atrial fibrillation (AF) in patients with frequent PACs. We retrospectively analyzed 684 patients with frequent PACs (> 100 PACs/day) who performed repeated 24-hour Holter monitoring. Prolonged PR interval was defined as longer than 200 msec. Among 684 patients, 626 patients had normal PR intervals (group A) and 58 patients had prolonged PR intervals (group B). After a mean follow-up of 59.3 months, 14 patients (24.1%) in group B developed AF compared to 50 patients (8.0%) in group A (P < 0.001). Cox regression analysis showed that prolonged PR interval (hazard ratio [HR], 1.950; 95% CI, 1.029-3.698; P = 0.041), age (HR, 1.033; 95% CI, 1.006-1.060; P = 0.015), and left atrial (LA) dimension (HR, 1.061; 95% CI, 1.012-1.112; P = 0.015) were associated with AF occurrence. Prolonged PR interval, advanced age, and enlarged LA dimension are independent risk factors of AF occurrence in patients with frequent PACs.

Fetal and Neonatal Arrhythmias

Cardiac arrhythmias are an important aspect of fetal and neonatal medicine. Premature complexes of atrial or ventricular origin are the main cause of an irregular heart rhythm. The finding is typically unrelated to an identifiable cause and no treatment is required. Tachyarrhythmia most commonly relates to supraventricular reentrant tachycardia, atrial flutter, and sinus tachycardia. Several antiarrhythmic agents are available for the perinatal treatment of tachyarrhythmias. Enduring bradycardia may result from sinus node dysfunction, complete heart block and nonconducted atrial bigeminy as the main arrhythmia mechanisms. The management and outcome of bradycardia depend on the underlying mechanism.

Ectopies from the superior vena cava after pulmonary vein isolation in patients with atrial fibrillation

Episodes of atrial fibrillation (AF) are mainly initiated by triggers from pulmonary veins (PVs). The superior vena cava (SVC) has been identified as a second major substrate of non-PV foci, but the electrophysiologic features of the SVC have not been fully investigated. We hypothesized that SVC ectopies are suppressed by predominant features of PV ectopies and tend to appear after PV isolation (PVI). We evaluated the electrophysiological characteristics and clinical implications of SVC ectopies in patients with AF during catheter ablation using high-dose isoproterenol and the atrial overdrive pacing maneuver. The manifestation patterns and modes of onset (coupling interval and appearance interval) of ectopies from both the PVs and SVC were investigated. 205 patients were enrolled [153 males and 52 females; mean age 64 ± 10 years; paroxysmal in 143 patients (69.8 %), persistent in 40 (19.5 %), and long-standing persistent in 22 patients (10.7 %)]. Before PVI, PV ectopies were detected in 182/205 patients (89 %). SVC ectopies were rarely observed before PVI but were significantly more frequent after the completion of PVI (3/205 vs. 14/205 patients, p = 0.011). The coupling interval (CI) and % CI (CI/preceding the A-A interval × 100) of PV ectopies were significantly shorter than those of SVC ectopies (211 ± 78 vs. 282 ± 106 ms, p = 0.021, and 34 ± 9 vs. 51 ± 17 %, p < 0.001, respectively). The appearance intervals of the PV ectopies were shorter than those of the SVC ectopies (6.3 ± 4.0 vs. 10.7 ± 6.7 s, p = 0.030). During repeat procedures, PVs with reconnection to the left atrium were less frequently observed in patients with SVC firing than in patients without SVC firing (1.7 ± 1.5 vs. 2.9 ± 1.1 PVs, p = 0.029). We demonstrated that PVI tends to manifest SVC ectopies with less spontaneous activity and that an elimination of predominant ectopies from the PVs may affect appearance of SVC ectopy.

[Disturbances of heart rhythm in patients after myocardial infarction with obstructive sleep apnea during outpatient rehabilitation]

We studied specific features of heart rhythm disturbances observed during outpatient rehabilitation of 432 patients after first myocardial infarction. In 94 of these patients (21.8%) we diagnosed obstructive sleep apnea syndrome (OSAS). We noted substantial preponderance of pathologic ectopy related to OSAS with most significant detection of frequent ventricular extrasystoles. Their paired variant and polymorphic forms in patients with OSAS were 3.4 and 7.4 times, respectively, more frequent than in patients without OSAS. Frequency of ventricular ectopy rose with increase of severity of OSAS and was maximal during nocturnal hours. Analysis of correlations revealed association between OSAS and frequencies of ventricular and supraventricular extrasystoles.

CONCLUSION

After myocardial infarction patients should be thoroughly examined for timely detection of OSAS and corresponding correction of their rehabilitation program.

Unstable QT interval dynamics precedes ventricular tachycardia onset in patients with acute myocardial infarction: a novel approach to detect instability in QT interval dynamics from clinical ECG

BACKGROUND

Instability in ventricular repolarization in the presence of premature activations (PA) plays an important role in arrhythmogenesis. However, such instability cannot be detected clinically. This study developed a methodology for detecting QT interval (QTI) dynamics instability from the ECG and explored the contribution of PA and QTI instability to ventricular tachycardia (VT) onset.

METHODS AND RESULTS

To examine the contribution of PAs and QTI instability to VT onset, ECGs of 24 patients with acute myocardial infarction, 12 of whom had sustained VT (VT) and 12 nonsustained VT (NSVT), were used. From each patient ECG, 2 10-minute-long ECG recordings were extracted, 1 right before VT onset (onset epoch) and 1 at least 1 hour before it (control epoch). To ascertain how PA affects QTI dynamics stability, pseudo-ECGs were calculated from an MRI-based human ventricular model. Clinical and pseudo-ECGs were subdivided into 1-minute recordings (minECGs). QTI dynamics stability of each minECG was assessed with a novel approach. Frequency of PAs (f(PA)) and the number of minECGs with unstable QTI dynamics (N(us)) were determined for each patient. In the VT group, f(PA) and N(us) of the onset epoch were larger than in control. Positive regression relationships between f(PA) and N(us) were identified in both groups. The simulations showed that both f(PA) and the PA degree of prematurity contribute to QTI dynamics instability.

CONCLUSIONS

Increased PA frequency and QTI dynamics instability precede VT onset in patients with acute myocardial infarction, as determined by novel methodology for detecting instability in QTI dynamics from clinical ECGs.

[Wavelet modulus maxima of multifractality based analysis of the pathological ECG signals]

In this paper, wavelet moudulus maxima based multifractal analysis was used to study the multifractal characteristics of the atrial premature beat (APB) signal, the premature ventricular contraction (PVC) signal and normal ECG signal. By analyzing the multifractal spectrum, it was obtained that three kinds of signals had different multifractal strengths. Normal ECG signals had the strongest singularity strength. The PVC beats had the second stronger singularity strength. And the APB beats had the weakest singularity strength. The T test indicated that above-mentioned analysis could disclose significant differences among these three signals. It has meaningful reference for clinical diagnosing and distinguishing with PVC and APB signals.

[Hurst index based analysis of sinus arrhythmia and atrial arrhythmia]

This study sought to disclose whether Hurst index can be used as a criterion for distinguishing sinus and atrial arrhythmia signals. Normal sinus rhythm beats, atrial premature contraction (APC) beats, and sinus bradycardia (SBR) signals, were taken from the MIT-BIH standard database. Hurst index method was used to distinguish the two kinds of arrhythmia. The results showed that the Hurst exponents of three kinds of signals were larger than 0.5, but they were in different value region. The data indicated that the long-term relevant character was the best for normal signal, better for sinus bradycardia, and the worst for atrial premature beats. So Hurst index is a useful identification criterion for distinguishing sinus and atrial arrhythmia signals.

[Scale invariance based analysis of pathological ECG signals]

In this paper, the multifractal detrended fluctuation analysis method was used to study the multifractal characteristics of atrial premature beat (APB) signals, of premature ventricular contraction (PVC) signals and of normal ECG signals. By analyses of Hurst index, Renyi index and multifractal spectrum, three kinds of signals were noted to have different degrees of long-range correlation and multifractal characteristics. Normal ECG signals had the strongest fractality, the PVC beats had stronger fractality and the APB beats had the weakest fractality. When the fluctuations function order was positive, the three kinds of signals showed distinct long-range correlation properties. These findings are of good reference to diagnosing and distinguishing between PVC and APB signals in clinical medicine.

[Detection of premature ventricular contraction and atrial premature contraction based on mode entropy]

Electrocardiogram (ECG) beat classification is essential for timely diagnosis of serious heart disorders. Premature ventricular contraction (PVC) and atrial premature contraction (APC) are serious threats against human lives. In order to cope with difficulties in diagnosis, a mode entropy based technique is herein proposed to classify normal sinus rhythm (NSR), APC and PVC, As is well known that the accuracy of most methods for detecting NSR, APC, PVC, etc is now between 90% to 98%, but most of them need large data sets. After calculation of the mode entropy value of NSR, PVC and APC, the results were analyzed and compared. The detection method based on the mode entropy technique is proven to be rational and accurate, and it does not need large data sets.

Usefulness of routine electrocardiography for heart disease screening in patients with spondyloarthropathy or rheumatoid arthritis

OBJECTIVE

To assess the usefulness of routine electrocardiography for heart disease screening in patients with spondyloarthropathy (SpA) or rheumatoid arthritis (RA).

METHODS

We included consecutive patients with SpA or RA or with degenerative joint disease (control group) admitted over a 6-month period and free of cardiovascular events. A 12-lead electrocardiogram (ECG) was obtained and was interpreted by a cardiologist who was unaware of the diagnosis.

RESULTS

We included 108 patients with SpA (mean duration, 11+/-10 years), 106 with RA (mean duration, 12+/-9 years), and 74 with degenerative joint disease (controls). No patient had cardiovascular symptoms or a prior history of cardiovascular disease. The only difference in cardiovascular risk factors across the three populations was a higher prevalence of diabetes in the RA and control groups. We found no differences between the SpA or RA groups and the control group regarding the rates of the following ECG findings: premature beats, atrioventricular block (2.8% in the SpA group, 1.9% in the RA group, and 2.7% in the control group), complete or incomplete left bundle branch block (0.9%, 0.9%, and 2.7%, respectively), complete right bundle branch bloc or left bundle branch block (0.9%, 4.7%, and 4.1%, respectively); and abnormalities suggesting myocardial ischemia (10.2%, 19.8%, and 17.6%, respectively).

CONCLUSION

In patients with SpA or RA who have no cardiovascular symptoms or history of cardiovascular disease, a routine ECG shows no increase in the cardiac abnormalities specifically associated with these joint diseases, compared to controls with degenerative joint disease.

Premature atrial contraction induces torsades de pointes in a patient of Takotsubo cardiomyopathy with QT prolongation

Although the prognosis for patients with stress-induced cardiomyopathy (Takotsubo cardiomyopathy) is relatively good, some patients with this syndrome develop torsades de pointes, which can be fatal. The present report describes a patient with Takotsubo cardiomyopathy and torsades de pointes induced by premature atrial contraction associated with QT interval prolongation, hypokalemia and hypomagnesemia.

[Detection of sinus arrhythmia and atrial arrhythmia based on base-scale entropy]

As is known in literature, the Base-scale Entropy Measure is useful for analyzing short-term heart rate variability signals. In this study, the method is applied to detect cardiac arrhythmias, including sinus and atrial arrhythmia. We detect and analyze normal sinus rhythm (NSR), atrial premature contraction (APC) and sinus bradycardia (SBR) signals. The selected data of NSR are obtained from the MIT-BIH normal sinus database, while others are from the MIT-BIH arrhythmia database. The results show the Base-scale Entropy can also detect sinus and atrial arrhythmia.

Pattern and possible contributing factors to dialysis-associated arrhythmia in young patients

We studied dialysis-associated arrhythmia in 48 uraemic patients < 35 years on chronic haemodialysis (HD) (> 3 months). Holter findings showed only minor arrhythmia; atrial in 42% of patients and ventricular in 38%. ST-segment depression > 1 mm was observed in 58% of patients; 80% had arrhythmia, and 36% experienced anginal pain. HD caused a significant increase in QTc, QTdc and Ca2+ level, while K+ level was significantly decreased. Patients who experienced arrhythmia during HD had higher left ventricular mass and left ventricular mass index, lower post-dialysis K+ level, higher QTc and QTdc both before and after HD. They were more frequently hypertensive. ST-segment depression was significantly related to ventricular arrhythmia.

Alternate patterns of ventricular activation during supraventricular bigeminy

Several investigators have previously noted that in the presence of bigeminal atrial extrasystoles, the premature beats may exhibit an alternate pattern of ventricular excitation either in the form of alternating left and right bundle-branch block, or alternating right bundle-branch block and normal intraventricular conduction. However, the association of alternating intraventricular conduction with other types of supraventricular bigeminy has rarely been documented. In this report we present five diverse forms of supraventricular bigeminy exhibiting the phenomenon of alternating ventricular excitation on the early beats. Our findings suggest that the exact mechanism of supraventricular bigeminy is irrelevant in terms of subsequent ventricular events. Practically any type of supraventricular bigeminy may result in an alternate pattern of ventricular activation.

Negative sequence voltages in spontaneous atrial fibrillation or flutter

BACKGROUND

The patho-physiology of initiation of atrial fibrillation (af) or flutter (AF) is not known. Would it be possible that the real explanation is hidden in physics territory but not in medicine? Could it be possible that the heart behaves like a biological generator in physics? Can an abnormal inscription direction (AID) or an abnormal slow conduction (ASC) of the P loop explain the genesis of af or AF?

METHODS

A total of 160 emergency Frank vectorcardiographic tracings was recorded by one physician from 55 patients with acute myocardial infarction.

RESULTS

Thirty (54%) patients had abnormal inscription direction of the P loop. Seven (13%) among 55 patients developed af or AF. Six of the seven had AID of the P loop. All seven had right or left atrial enlargement. They were among 50 patients (91%) with abnormal atrium enlargement. Four among the seven had ASC of the P loop. There were 27 patients (49%) among the total 55 with ASC of the P loop.

CONCLUSIONS

The heart is a biological generator, which has also inherited the same problems as generators. The types of figure-of-eight or clockwise rotation of the P loop, which are linked with the partial or complete negative sequence in physics have been documented. Based on negative sequence voltages in physics, a new theory of af, AF, or atrial premature contraction has been proposed.