Diurnal QT analysis in patients with sotalol after cardioversion of atrial fibrillation.

BACKGROUND: The risk of ventricular arrhythmias in patients on QT prolonging drugs is indicated to be increased early after cardioversion (CV) of atrial fibrillation (AF) to sinus rhythm (SR). Sotalol, used to prevent AF relapse, prolongs cardiac repolarization and corrected QT interval (QTc). A pronounced QTc prolongation is an established marker of pro-arrhythmias. Our objective was to use novel technique to quantify and evaluate the diurnal variation of the QTc interval after elective CV to SR in patients on sotalol or metoprolol. METHODS: Fifty patients underwent twelve-lead Holter recording for 24 hr after elective CV for persistent AF. All patients had the highest tolerable stable dose of sotalol (n = 27) or metoprolol (n = 23). Measurements of QT and RR intervals were performed on all valid beats. RESULTS: A clear diurnal variation of both HR and QTc was seen in both groups, more pronounced in patients on sotalol, where a high percentage of heartbeats with QTc >500 ms was observed, especially at night. Six patients (22%) on sotalol but none on metoprolol had >20% of all heart beats within the 24-hour recording with QTc >500 ms. CONCLUSION: Twenty-four-hour Holter recordings with QT-measurement immediately after CV demonstrated that one in five patients on sotalol had >20% of all heart beats with prolonged QTc >500 ms, especially during night-time. The QTc diurnal variation was retained in patients on ß-blockade or a potent class III anti-arrhythmic drug with ß-blocking properties.

T-wave and its association with myocardial fibrosis on cardiovascular magnetic resonance examination.

BACKGROUND: Risk stratification in non-ischemic myocardial disease poses a challenge. While cardiovascular magnetic resonance (CMR) is a comprehensive tool, the electrocardiogram (ECG) provides quick impactful clinical information. Studying the relationships between CMR and ECG can provide much-needed risk stratification. We evaluated the electrocardiographic signature of myocardial fibrosis defined as presence of late gadolinium enhancement (LGE) or extracellular volume fraction (ECV) ≥29%. METHODS: We evaluated 240 consecutive patients (51% female, 47.1 ± 16.6 years) referred for a clinical CMR who underwent 12-lead ECGs within 90 days. ECG parameters studied to determine association with myocardial fibrosis included heart rate, QRS amplitude/duration, T-wave amplitude, corrected QT and QT peak, and Tpeak-Tend. Abnormal T-wave was defined as low T-wave amplitude ≤200 µV or a negative T wave, both in leads II and V5. RESULTS: Of the 147 (61.3%) patients with myocardial fibrosis, 67 (28.2%) had ECV ≥ 29%, and 132 (54.6%) had non-ischemic LGE. An abnormal T-wave was more prevalent in patients with versus without myocardial fibrosis (66% versus 42%, p < .001). Multivariable analysis demonstrated that abnormal T-wave (OR 1.95, 95% CI 1.09-3.49, p = .03) was associated with myocardial fibrosis (ECV ≥ 29% or LGE) after adjustment for clinical covariates (age, gender, history of hypertension, and heart failure). Dynamic nomogram for predicting myocardial fibrosis using clinical parameters and the T-wave was developed: https://normogram.shinyapps.io/CMR_Fibrosis/. CONCLUSION: Low T-wave amplitude ≤ 200 µV or negative T-waves are independently associated with myocardial fibrosis. Prospective evaluation of T-wave amplitude may identify patients with a high probability of myocardial fibrosis and guide further indication for CMR.

2021 ISHNE/ HRS/ EHRA/ APHRS collaborative statement on mHealth in Arrhythmia Management: Digital Medical Tools for Heart Rhythm Professionals: From the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society.

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/ Heart Rhythm Society/ European Heart Rhythm Association/ Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self-management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored.

Low lead one ratio predicts clinical outcomes in left bundle branch block.

INTRODUCTION: We evaluated the association between a novel electrocardiographic (ECG) marker of late, rightward electrocardiographic forces (termed the lead one ratio [LOR]), and left ventricular ejection fraction (LVEF), myocardial scar, and clinical outcomes in patients with left bundle branch block (LBBB). METHODS AND RESULTS: LOR was calculated in patients with LBBB from a derivation cohort (n = 240) and receiver operator characteristic curves identified optimal threshold values for predicting myocardial scar and LVEF less than 35%. An independent validation cohort of patients with LBBB (n = 196) was used to test the association of LOR with the myocardial scar, LVEF, and the likelihood of death, heart transplant or left ventricular assist device (LVAD) implantation. The optimal thresholds in the derivation cohort were LOR less than 13.7 for identification of scar (sensitivity 55%, specificity 80%), and LOR less than 12.1 for LVEF less than 35% (sensitivity 49%, specificity 80%). In the validation cohort, LOR less than 13.7 was not associated with scar size or presence (P > 0.05 for both). LOR less than 12.1 was associated with lower LVEF (30 [20-40] versus 40 [25-55]%; P = 0.002) and predicted LVEF less than 35% in univariable (odds ratio [OR], 2.2 [1.2-4.1]; P = 0.01) and multivariable analysis (OR, 2.2 [1.2-4.3]; P = 0.02). LOR less than 12.1 was associated with scar presence when patients with nonischemic cardiomyopathy were excluded (OR = 7.2 [1.5-33.2]; P = 0.002). LOR less than 12.1 had an adjusted hazard ratio of 1.53 ([1.05-2.21]; P = 0.03) for death, transplant or LVAD implantation. CONCLUSIONS: In conclusion, ECG LOR less than 12.1 predicts reduced-LV systolic function and poorer prognosis in patients with LBBB.

Surgical ablation of atrial fibrillation during mitral-valve surgery.

BACKGROUND: Among patients undergoing mitral-valve surgery, 30 to 50% present with atrial fibrillation, which is associated with reduced survival and increased risk of stroke. Surgical ablation of atrial fibrillation has been widely adopted, but evidence regarding its safety and effectiveness is limited. METHODS: We randomly assigned 260 patients with persistent or long-standing persistent atrial fibrillation who required mitral-valve surgery to undergo either surgical ablation (ablation group) or no ablation (control group) during the mitral-valve operation. Patients in the ablation group underwent further randomization to pulmonary-vein isolation or a biatrial maze procedure. All patients underwent closure of the left atrial appendage. The primary end point was freedom from atrial fibrillation at both 6 months and 12 months (as assessed by means of 3-day Holter monitoring). RESULTS: More patients in the ablation group than in the control group were free from atrial fibrillation at both 6 and 12 months (63.2% vs. 29.4%, P<0.001). There was no significant difference in the rate of freedom from atrial fibrillation between patients who underwent pulmonary-vein isolation and those who underwent the biatrial maze procedure (61.0% and 66.0%, respectively; P=0.60). One-year mortality was 6.8% in the ablation group and 8.7% in the control group (hazard ratio with ablation, 0.76; 95% confidence interval, 0.32 to 1.84; P=0.55). Ablation was associated with more implantations of a permanent pacemaker than was no ablation (21.5 vs. 8.1 per 100 patient-years, P=0.01). There were no significant between-group differences in major cardiac or cerebrovascular adverse events, overall serious adverse events, or hospital readmissions. CONCLUSIONS: The addition of atrial fibrillation ablation to mitral-valve surgery significantly increased the rate of freedom from atrial fibrillation at 1 year among patients with persistent or long-standing persistent atrial fibrillation, but the risk of implantation of a permanent pacemaker was also increased. (Funded by the National Institutes of Health and the Canadian Institutes of Health Research; ClinicalTrials.gov number, NCT00903370.).

Baseline adverse electrical remodeling and the risk for ventricular arrhythmia in Cardiac Resynchronization Therapy Recipients (MADIT CRT).

INTRODUCTION: Adverse electrical remodeling (AER), represented here as the sum absolute QRST integral (SAI QRST), has previously been shown to be directly associated with the risk for ventricular arrhythmia (VA). Cardiac resynchronization therapy (CRT) is known to reduce the risk for VA through various mechanisms, including reverse remodeling, and we aimed to evaluate the association between baseline AER and the risk for VA in CRT recipients. METHODS AND RESULTS: The study population comprised 961 CRT-D implanted patients from the MADIT CRT study. The relationship between SAI QRST, VA risk, and VA risk/death was evaluated as a continuous and as a categorical variable-tertiles (T1 ≤ 0.527, T2 0.528-0.766, T3 > 0.766). In a multivariable model, AER was inversely associated with the risk of VA. Each unit increase in SAI QRST was associated with 64% (P  =  0.007) and 54% (P  =  0.003) decrease in the risk of VA and VA/death, respectively. Patients with high SAI QRST (T3) and medium SAI QRST (T2) had 52% (P < 0.001) and 32% (P  =  0.027) reduced risk for VA and 44% (P  =  0.002) and 26% (P  =  0.055) reduced risk for VA/death as compared with patients with low SAI QRST (T1), respectively. CONCLUSION: In CRT implanted patients with mild heart failure, baseline AER was inversely associated with the risk for VA and VA/death; this is a finding that contradicts the relationship previously reported in non-CRT implanted patients. We theorize that CRT may abate the process of AER; however, characterization of this mechanism requires further study.

The 43rd International Society for Computerized Electrocardiology ECG initiative for the automated detection of strict left bundle branch block.

The presence of left bundle branch block (LBBB) is an important predictor of benefit from cardiac resynchronization therapy (CRT). New "strict" electrocardiographic (ECG) criteria for LBBB have been shown to better predict benefit from CRT. The "strict" LBBB criteria include: QRS duration ≥140 ms (men) or ≥130 ms (women), QS- or rS-configurations of the QRS complex in leads V1 and V2, and mid-QRS notching or slurring in ≥2 of leads V1, V2, V5, V6, I and aVL. The "strict" LBBB criteria are not regularly used and most hospital automated ECG systems and physicians still use more conventional LBBB criteria. As part of the 43rd International Society for Computerized Electrocardiology (ISCE) meeting, we conducted an initiative on the automated detection of "strict" LBBB where industry and academic investigators could present their algorithm results on digital 12-lead ECGs with varying QRS morphologies from the MADIT-CRT trial (300 training and 302 test set ECGs that were manually adjudicated for "strict" LBBB presence). The results revealed a 64-82% accuracy, 48-76% sensitivity and 46-87% specificity for automated "strict" LBBB detection from 7 participants. Most mismatches were likely attributed to differences in detection and absence of specific definitions for notches and slurs while differences in QRS duration and S-waves in leads V1 and V2 were less problematic. The full unblinded training and test datasets including all ECG signals are being made available through the Telemetric and Holter ECG Warehouse (THEW) for further exploration.

The ability of the electrocardiogram in left bundle branch block to detect myocardial scar determined by cardiovascular magnetic resonance.

AIMS: We aimed to improve the electrocardiographic 2009 left bundle branch block (LBBB) Selvester QRS score (2009 LBSS) for scar assessment. METHODS: We retrospectively identified 325 LBBB patients with available ECG and cardiovascular magnetic resonance imaging (CMR) with late gadolinium enhancement from four centers (142 [44%] with CMR scar). Forty-four semi-automatically measured ECG variables pre-selected based on the 2009 LBSS yielded one multivariable model for scar detection and another for scar quantification. RESULTS: The 2009 LBSS achieved an area under the curve (AUC) of 0.60 (95% confidence interval 0.54-0.66) for scar detection, and R2 = 0.04, p < 0.001, for scar quantification. Multivariable modeling improved scar detection to AUC 0.72 (0.66-0.77) and scar quantification to R2 = 0.21, p < 0.001. CONCLUSIONS: The 2009 LBSS detects and quantifies myocardial scar with poor accuracy. Improved models with extensive comparison of ECG and CMR had modest performance, indicating limited room for improvement of the 2009 LBSS.

Prediction of sudden and non-sudden cardiac death in post-infarction patients with reduced left ventricular ejection fraction by periodic repolarization dynamics: MADIT-II substudy.

AIMS: To test the value of Periodic Repolarization Dynamics (PRD), a recently validated electrocardiographic marker of sympathetic activity, as a novel approach to predict sudden cardiac death (SCD) and non-sudden cardiac death (N-SCD) and to improve identification of patients that profit from ICD-implantation. METHODS AND RESULTS: We included 856 post-infarction patients with left-ventricular ejection fraction (LVEF) ≤30% of the MADIT-II trial in sinus rhythm. Of these, 507 and 348 patients were randomized to ICD or conventional treatment. PRD was assessed from multipolar 10-min baseline ECGs. Primary and secondary endpoints were total mortality, SCD and N-SCD. Multivariable analyses included treatment group, QRS-duration, New York Heart Association classification, blood-urea nitrogen, diabetes mellitus, beta-blocker therapy and LVEF. During follow-up of 20.4 months, 119 patients died (53 SCD and 36 N-SCD). On multivariable analyses, increased PRD was a significant predictor of mortality (standardized coefficient 1.37[1.19-1.59]; P < 0.001) and SCD (1.40 [1.13-1.75]; P = 0.003) but also predicted N-SCD (1.41[1.10-1.81]; P = 0.006). While increased PRD predicted SCD in conventionally treated patients (1.61[1.23-2.11]; P < 0.001), it was predictive of N-SCD (1.63[1.28-2.09]; P < 0.001) and adequate ICD-therapies (1.20[1.03-1.39]; P = 0.017) in ICD-treated patients. ICD-treatment substantially reduced mortality in the lowest three PRD-quartiles by 53% (P = 0.001). However, there was no effect in the highest PRD-quartile (mortality increase by 29%; P = 0.412; P < 0.001 for difference) as the reduction of SCD was compensated by an increase of N-SCD. CONCLUSION: In post-infarction patients with impaired LVEF, PRD is a significant predictor of SCD and N-SCD. Assessment of PRD is a promising tool to identify post-MI patients with reduced LVEF who might benefit from intensified treatment.

The QT Scale: A Weight Scale Measuring the QTc Interval.

INTRODUCTION: Despite the strong evidence of the clinical utility of QTc prolongation as a surrogate marker of cardiac risk, QTc measurement is not part of clinical routine either in hospital or in physician offices. We evaluated a novel device ("the QT scale") to measure heart rate (HR) and QTc interval. METHOD: The QT scale is a weight scale embedding an ECG acquisition system with four limb sensors (feet and hands: lead I, II, and III). We evaluated the reliability of QT scale in healthy subjects (cohort 1) and cardiac patients (cohorts 2 and 3) considering a learning (cohort 2) and two validation cohorts. The QT scale and the standard 12-lead recorder were compared using intraclass correlation coefficient (ICC) in cohorts 2 and 3. Absolute value of heart rate and QTc intervals between manual and automatic measurements using ECGs from the QT scale and a clinical device were compared in cohort 1. RESULTS: We enrolled 16 subjects in cohort 1 (8 w, 8 m; 32 ± 8 vs 34 ± 10 years, P = 0.7), 51 patients in cohort 2 (13 w, 38 m; 61 ± 16 vs 58 ± 18 years, P = 0.6), and 13 AF patients in cohort 3 (4 w, 9 m; 63 ± 10 vs 64 ± 10 years, P = 0.9). Similar automatic heart rate and QTc were delivered by the scale and the clinical device in cohort 1: paired difference in RR and QTc were -7 ± 34 milliseconds (P = 0.37) and 3.4 ± 28.6 milliseconds (P = 0.64), respectively. The measurement of stability was slightly lower in ECG from the QT scale than from the clinical device (ICC: 91% vs 80%) in cohort 3. CONCLUSION: The "QT scale device" delivers valid heart rate and QTc interval measurements.

Evaluation of the ECG based Selvester scoring method to estimate myocardial scar burden and predict clinical outcome in patients with left bundle branch block, with comparison to late gadolinium enhancement CMR imaging.

BACKGROUND: Myocardial scar burden quantification is an emerging clinical parameter for risk stratification of sudden cardiac death and prediction of ventricular arrhythmias in patients with left ventricular dysfunction. We investigated the relationships among semiautomated Selvester score burden and late gadolinium enhancement-cardiovascular magnetic resonance (LGE-CMR) assessed scar burden and clinical outcome in patients with underlying heart failure, left bundle branch block (LBBB) and implantable cardioverter-defibrillator (ICD) treatment. METHODS: Selvester QRS scoring was performed on all subjects with ischemic and nonischemic dilated cardiomyopathy at Skåne University Hospital Lund (2002-2013) who had undergone LGE-CMR and 12-lead ECG with strict LBBB pre-ICD implantation. RESULTS: Sixty patients were included; 57% nonischemic dilated cardiomyopathy and 43% ischemic cardiomyopathy with mean left ventricular ejection fraction of 27.6% ± 11.7. All patients had scar by Selvester scoring. Sixty-two percent had scar by LGE-CMR (n = 37). The Spearman correlation coefficient for LGE-CMR and Selvester score derived scar was r = .35 (p = .007). In scar negative LGE-CMR, there was evidence of scar by Selvester scoring in all patients (range 3%-33%, median 15%). Fourteen patients (23%) had an event during the follow-up period; 11 (18%) deaths and six adequate therapies (10%). There was a moderate trend indicating that presence of scar increased the risk of clinical endpoints in the LGE-CMR analysis (p = .045). CONCLUSION: There is a modest correlation between LGE-CMR and Selvester scoring verified myocardial scar. CMR based scar burden is correlated to clinical outcome, but Selvester scoring is not. The Selvester scoring algorithm needs to be further refined in order to be clinically relevant and reliable for detailed scar evaluation in patients with LBBB.

Validation of an automatic diagnosis of strict left bundle branch block criteria using 12-lead electrocardiograms.

AIMS: Strict left bundle branch block (LBBB) criteria were recently proposed to identify LBBB patients to benefit most from cardiac resynchronization therapy (CRT). The aim of our study was to automate identification of strict LBBB in order to facilitate its broader application. METHODS: We developed a series of algorithms to automatically detect and measure parameters required for strict LBBB criteria and proposed a definition of QRS notch detection. The algorithms were developed using training (n = 20) and validation (n = 592) sets consisting of signal-averaged 12-lead ECGs (1,000 Hz sampling) recorded from 612 LBBB patients from Multicenter Automatic Defibrillator Implantation Trial-CRT. Four trained clinicians independently performed adjudication on 148 different ECGs for comparing automatic and manually adjudicated results, in addition to 13 ECGs for evaluation of intraobserver variability and 32 ECGs for interobserver variability. We assessed the performance of the automated algorithms using manually adjudicated ECGs as references. RESULTS: Overall sensitivity and specificity for detecting strict LBBB were 95% and 86%, respectively. The mean absolute deviation (MAD) of QRS duration and notch/slur locations for the automated method versus the manual method was below 1 ms, and MAD values were lower than 2 ms for interobserver and intraobserver variability. Sensitivity and specificity for detecting notch and slur locations were 87% and 96% for notches and 78% and 90% for slurs using the automatic method. In addition 95% and 93% agreements for notches and 90% and 88% agreements for slurs were reached for intra- and interobserver. CONCLUSION: The proposed algorithms automatically measure QRS features for the diagnosis of strict LBBB. Our study shows good performance in reference to manual results.

Population-based beat-to-beat QT analysis from Holter recordings in the long QT syndrome.

The increasing dissemination of wearable ECG recorders (e.g. Holter, patches, and strap sensors) enables the acquisition of large amounts of data during long periods of time. However, the clinical value of these long-term continuous recordings is hindered by the lack of automatic tools to extract clinically relevant information (other than non-sinus and life-threatening rhythms) from such long-term data, particularly when targeting population-based research. In this work, we propose and test a new tool for analyzing beat-to-beat interval measurements and extracting features from Holter ECGs. Specifically, we assess the adaptation of the QT interval following sudden changes in heart rate in the primary long QT types (1 & 2). We find that in long QT syndrome type 2, certain QT adaptation patterns can indicate a higher risk for cardiac events.

JT interval: What does this interval mean?

The JTp interval gained interest as a marker differentiating effects of drugs on cardiac ion channels. For JTp interval, both the beginning - identification of J point and identification of T wave end remains the subject of substantial variability. We aimed to analyze diagnostic and prognostic performance of JTp interval in the International LQTS Registry data. ECGs from 804 gene carriers and 1139 non-carriers from LQT1 families, 735 carriers and 1145 non-carriers from LQT2 families, and 238 carriers and 554 non-carriers from LQT3 families were evaluated. The diagnostic performance of JTpc was similar to QTc in LQT1 and LQT3 patients but inferior in LQT2 patients, whereas repolarization duration in general had limited diagnostic performance in LQT3 patients. The prognostic significance for predicting cardiac events in LQT1 and LQT2 patients was similar for JTpc and QTc. In LQT3 patients, JTpc fails to be associated with arrhythmic events.

An evaluation of multiple algorithms for the measurement of the heart rate corrected JTpeak interval.

Interest in the effects of drugs on the heart rate-corrected JTpeak (JTpc) interval from the body-surface ECG has spawned an increasing number of scientific investigations in the field of regulatory sciences, and more specifically in the context of the Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative. We conducted a novel initiative to evaluate the role of automatic JTpc measurement technologies by comparing their ability to distinguish multi- from single-channel blocking drugs. A set of 5232 ECGs was shared by the FDA (through the Telemetric and Holter ECG Warehouse) with 3 ECG device companies (AMPS, Mortara, and Philips). We evaluated the differences in drug-concentration effects on these measurements between the commercial and the FDA technologies. We provide a description of the drug-induced placebo-corrected changes from baseline for dofetilide, quinidine, ranolazine, and verapamil, and discuss the various differences across all technologies. The results revealed only small differences between measurement technologies evaluated in this study. It also confirms that, in this dataset, the JTpc interval distinguishes between multi- and single-channel (hERG) blocking drugs when evaluating the effects of dofetilide, quinidine, ranolazine, and verapamil. However, in the case of quinidine and dofetilide, we noticed a poor consistency across technologies because of the lack of standard definitions for the location of the peak of the T-wave (T-apex) when the T-wave morphology is abnormal.

Convergence of models of human ventricular myocyte electrophysiology after global optimization to recapitulate clinical long QT phenotypes.

In-silico models of human cardiac electrophysiology are now being considered for prediction of cardiotoxicity as part of the preclinical assessment phase of all new drugs. We ask the question whether any of the available models are actually fit for this purpose. We tested three models of the human ventricular action potential, the O'hara-Rudy (ORD11), the Grandi-Bers (GB10) and the Ten Tusscher (TT06) models. We extracted clinical QT data for LQTS1 and LQTS2 patients with nonsense mutations that would be predicted to cause 50% loss of function in IKs and IKr respectively. We also obtained clinical QT data for LQTS3 patients. We then used a global optimization approach to improve the existing in silico models so that they reproduced all three clinical data sets more closely. We also examined the effects of adrenergic stimulation in the different LQTS subsets. All models, in their original form, produce markedly different and unrealistic predictions of QT prolongation for LQTS1, 2 and 3. After global optimization of the maximum conductances for membrane channels, all models have similar current densities during the action potential, despite differences in kinetic properties of the channels in the different models, and more closely reproduce the prolongation of repolarization seen in all LQTS subtypes. In-silico models of cardiac electrophysiology have the potential to be tremendously useful in complementing traditional preclinical drug testing studies. However, our results demonstrate they should be carefully validated and optimized to clinical data before they can be used for this purpose.

Computational cardiology and risk stratification for sudden cardiac death: one of the grand challenges for cardiology in the 21st century.

Risk stratification in the context of sudden cardiac death has been acknowledged as one of the major challenges facing cardiology for the past four decades. In recent years, the advent of high performance computing has facilitated organ-level simulation of the heart, meaning we can now examine the causes, mechanisms and impact of cardiac dysfunction in silico. As a result, computational cardiology, largely driven by the Physiome project, now stands at the threshold of clinical utility in regards to risk stratification and treatment of patients at risk of sudden cardiac death. In this white paper, we outline a roadmap of what needs to be done to make this translational step, using the relatively well-developed case of acquired or drug-induced long QT syndrome as an exemplar case.

Automatic QRS Selvester scoring system in patients with left bundle branch block.

AIMS: The Selvester QRS scoring system uses quantitative criteria from the standard 12-lead electrocardiogram (ECG) to estimate the myocardial scar size of patients, including those with left bundle branch block (LBBB). Automation of the scoring system could facilitate the clinical use of this technique which requires a set of multiple QRS patterns to be identified and measured. METHODS AND RESULTS: We developed a series of algorithms to automatically detect and measure the QRS parameters required for Selvester scoring. The 'QUantitative and Automatic REport of Selvester Score' was designed specifically for the analysis of ECGs from patients meeting new strict criteria for complete LBBB. The algorithms were designed using a training (n = 36) and a validation (n = 180) set of ECGs, consisting of signal-averaged 12-lead ECGs (1000 Hz sampling) recorded from 216 LBBB patients from the MADIT-CRT. We assessed the performance of the methods using expert manually adjudicated ECGs. The average of absolute differences between automatic and adjudicated Selvester scoring was 1.2 ± 1.5 points. The range of average differences for continuous measurements of wave locations and interval durations varied between 0 and 6 ms. Erroneous detection of Q, R, S, R', and S' waves (oversensed or missed) were 3, 1, 1, 16, and 6%, respectively. Seven percent of notches detected in the first 40 ms were misdetected. CONCLUSION: We propose an efficient computerized method for the automatic measurement of the Selvester score in patients with the strict LBBB.

QT interval variability in body surface ECG: measurement, physiological basis, and clinical value: position statement and consensus guidance endorsed by the European Heart Rhythm Association jointly with the ESC Working Group on Cardiac Cellular Electrophysiology.

This consensus guideline discusses the electrocardiographic phenomenon of beat-to-beat QT interval variability (QTV) on surface electrocardiograms. The text covers measurement principles, physiological basis, and clinical value of QTV. Technical considerations include QT interval measurement and the relation between QTV and heart rate variability. Research frontiers of QTV include understanding of QTV physiology, systematic evaluation of the link between QTV and direct measures of neural activity, modelling of the QTV dependence on the variability of other physiological variables, distinction between QTV and general T wave shape variability, and assessing of the QTV utility for guiding therapy. Increased QTV appears to be a risk marker of arrhythmic and cardiovascular death. It remains to be established whether it can guide therapy alone or in combination with other risk factors. QT interval variability has a possible role in non-invasive assessment of tonic sympathetic activity.

Cloud-based privacy-preserving remote ECG monitoring and surveillance.

BACKGROUND: The number of technical solutions for monitoring patients in their daily activities is expected to increase significantly in the near future. Blood pressure, heart rate, temperature, BMI, oxygen saturation, and electrolytes are few of the physiologic factors that will soon be available to patients and their physicians almost continuously. The availability and transfer of this information from the patient to the health provider raises privacy concerns. Moreover, current data encryption approaches expose patient data during processing, therefore restricting their utility in applications requiring data analysis. METHODS: We propose a system that couples health monitoring techniques with analytic methods to permit the extraction of relevant information from patient data without compromising privacy. This proposal is based on the concept of fully homomorphic encryption (FHE). Since this technique is known to be resource-heavy, we develop a proof-of-concept to assess its practicality. Results are presented from our prototype system, which mimics live QT monitoring and detection of drug-induced QT prolongation. RESULTS: Transferring FHE-encrypted QT and RR samples requires about 2 Mbps of network bandwidth per patient. Comparing FHE-encrypted values--for example, comparing QTc to a given threshold-runs quickly enough on modest hardware to alert the doctor of important results in real-time. CONCLUSIONS: We demonstrate that FHE could be used to securely transfer and analyze ambulatory health monitoring data. We present a unique concept that could represent a disruptive type of technology with broad applications to multiple monitoring devices. Future work will focus on performance optimizations to accelerate expansion to these other applications.