Background Clinical, electrocardiographic, and genomic factors have been associated with the drug-induced type 1 Brugada pattern (DI-T1BP), in response to sodium channel blocker provocation (SCBP). However, prior analyses have been concerned with prediction of the DI-T1BP rather than the validity of the diagnosis of concealed Brugada syndrome (BrS). We sought to analyse and compare the ECG response to SCBP with ajmaline in a cohort of healthy controls (HC) and a definite BrS group (Def-BrS) to develop a diagnostic score. Methods Healthy controls (HC) were systematically recruited as part of a clinical trial. Following comprehensive cardiovascular screening, eligible subjects underwent SCBP with ajmaline. We identified a Def-BrS cohort, defined as a DI-T1BP and a Shanghai Score (SS) > 3.5, from consecutive patients with suspected BrS undergoing SCBP with ajmaline using the identical protocol. Def-BrS and HC were divided equally into discovery and validation cohorts. Digital ECG acquisition facilitated automated measurement of ECG parameters. A multivariable analysis compared ECG parameters between the HC and Def-BrS cohorts. A logistic regression analysis identified ECG characteristics that accurately predicted the diagnosis of Def-BrS. This model was then assessed in the validation cohort. Results Two-hundred-and-forty-eight volunteers completed an online questionnaire, 103 accepted an invitation to undergo further screening and 100 were recruited into the HC group. Three HCs developed a DI-T1BP. From 1241 patients undergoing SCBP, 166 were Def-BrS. There were no demographic differences between the HC discovery and validation groups or between the Def-BrS discovery and validation groups. Following multivariable logistic regression analysis, QRS duration, mean anterior lead ST segment amplitude at baseline, maximum change in QRS duration, anterior ST segment amplitude and QRS area after SCBP, were independently associated with Def-BrS. The combined model was an excellent discriminator for Def-BrS, with an area under the curve of 0.95 [95% confidence interval (CI) = 0.912 – 0.989], P<0.001 in the discovery groups and 0.97 [95% CI = 0.948 – 0.998], P<0.001 in the validation groups. Conclusion The yield of the DI-T1BP in HCs is 3%. However, there are distinct ECG parameters at baseline and in response to SCBP that favour a definite diagnosis of BrS. These observations permit the quantifiable refinement of the ECG diagnosis of concealed BrS, avoiding the pitfalls of relying upon the DI-T1BP alone.

There has been interest relating to automated analysis of a lead I ECG to detect cardiac arrhythmias.Little interest has been shown in the accuracy of using lead I as opposed to 6 limb leads or the full 12 lead ECG.The aim of this small study was to assess the efficacy of using only lead I but also to look at the effect of analysing a single 30s recording as a continuous recording versus five 10s overlapping recordings constituting a 30s record.One hundred 10s digital 12 lead ECGs with atrial fibrillation (AF) were used.Chest leads were removed and the 6 limb leads then used for analysis of rhythm.Similarly, lead I alone was used.Separately 100 single lead I ECGs classified as AF in the PhysioNet 2017 database were analysed, both as single 30s recordings and as five 10s ECGs commencing at 0, 5, 10, 15 and 20s from the start of the recording.An algorithm made the diagnosis from 5 reports.All analyses were made with the Glasgow Program.For the 10s 12 lead ECGs, 96% were reported as AF using 6 limb leads and 93% using lead I.For the 30s recordings, 92% were reported as AF using a single 30s analysis and 91% as AF using the five ECGs.In conclusion, one lead and 6 leads are not as sensitive as 12 leads in detecting AF, while five 10s reports combined are no more sensitive than a single 30s report though more specific.

BACKGROUND:Automated measurements of electrocardiographic (ECG) intervals by current-generation digital electrocardiographs are critical to computer-based ECG diagnostic statements, to serial comparison of ECGs, and to epidemiological studies of ECG findings in populations. A previous study demonstrated generally small but often significant systematic differences among 4 algorithms widely used for automated ECG in the United States and that measurement differences could be related to the degree of abnormality of the underlying tracing. Since that publication, some algorithms have been adjusted, whereas other large manufacturers of automated ECGs have asked to participate in an extension of this comparison. METHODS:Seven widely used automated algorithms for computer-based interpretation participated in this blinded study of 800 digitized ECGs provided by the Cardiac Safety Research Consortium. All tracings were different from the study of 4 algorithms reported in 2014, and the selected population was heavily weighted toward groups with known effects on the QT interval: included were 200 normal subjects, 200 normal subjects receiving moxifloxacin as part of an active control arm of thorough QT studies, 200 subjects with genetically proved long QT syndrome type 1 (LQT1), and 200 subjects with genetically proved long QT syndrome Type 2 (LQT2). RESULTS:For the entire population of 800 subjects, pairwise differences between algorithms for each mean interval value were clinically small, even where statistically significant, ranging from 0.2 to 3.6milliseconds for the PR interval, 0.1 to 8.1milliseconds for QRS duration, and 0.1 to 9.3milliseconds for QT interval. The mean value of all paired differences among algorithms was higher in the long QT groups than in normals for both QRS duration and QT intervals. Differences in mean QRS duration ranged from 0.2 to 13.3milliseconds in the LQT1 subjects and from 0.2 to 11.0milliseconds in the LQT2 subjects. Differences in measured QT duration (not corrected for heart rate) ranged from 0.2 to 10.5milliseconds in the LQT1 subjects and from 0.9 to 12.8milliseconds in the LQT2 subjects. CONCLUSIONS:Among current-generation computer-based electrocardiographs, clinically small but statistically significant differences exist between ECG interval measurements by individual algorithms. Measurement differences between algorithms for QRS duration and for QT interval are larger in long QT interval subjects than in normal subjects. Comparisons of population study norms should be aware of small systematic differences in interval measurements due to different algorithm methodologies, within-individual interval measurement comparisons should use comparable methods, and further attempts to harmonize interval measurement methodologies are warranted.

AIMS:The objective of the study was to develop normal limits of the ECG in an apparently healthy population of South Asians living in India. METHODS:Three centres contributed to recording 12 lead ECGs on identical digital electrocardiographs. Apparently healthy volunteers were recruited and ECGs were first transferred to a local database and then to Glasgow where all ECGs were analysed by the same University of Glasgow ECG Interpretation Program. RESULTS:A total of 963 individuals were recruited into the study (30.4% female) with an age range of 18-83 years. QRS duration was longer in males than females, QT interval was longer in females than males, and QRS voltages in general were higher in males than females and in younger compared to older individuals. CONCLUSION:Findings in general paralleled those in other populations and suggested that criteria for a white Caucasian population could be applied to a South Asian Indian population.

Atrial Fibrillation (AF) is a common cardiac arrhythmia which, if left untreated, can lead to ischaemic stroke. A number of low cost hand held devices which use a single lead I ECG to facilitate detection of a cardiac arrhythmia have recently appeared on the market. This study aimed to assess the accuracy of using limited lead ECG recordings for the detection of AF using the University of Glasgow (Uni-G) ECG analysis program. A 12-lead ECG dataset consisting of 98 confirmed cases of AF and 98 confirmed cases of Sinus rhythm, 49 with PVCs and 49 with PACs, all of which were correctly reported by the Uni-G program and a further 9 cases of confirmed AF which had not been correctly reported by the Uni-G program was used. Each 12-lead ECG was processed to generate two separate ECGs, one with only lead I available and another with only leads I and II available. The sensitivity of reporting AF using a single lead ECG and a 2-lead ECG was identical at 93.8%. However, specificity was greater in the 2-lead ECG at 94.8% compared to 83.6% in the single lead ECG. The results show that a single lead ECG or a 2-lead ECG recording could be effective in screening populations for cardiac arrhythmias.

BACKGROUND AND PURPOSE:Automated measurements of electrocardiographic (ECG) intervals are widely used by clinicians for individual patient diagnosis and by investigators in population studies. We examined whether clinically significant systematic differences exist in ECG intervals measured by current generation digital electrocardiographs from different manufacturers and whether differences, if present, are dependent on the degree of abnormality of the selected ECGs. METHODS:Measurements of RR interval, PR interval, QRS duration, and QT interval were made blindly by 4 major manufacturers of digital electrocardiographs used in the United States from 600 XML files of ECG tracings stored in the US FDA ECG warehouse and released for the purpose of this study by the Cardiac Safety Research Consortium. Included were 3 groups based on expected QT interval and degree of repolarization abnormality, comprising 200 ECGs each from (1) placebo or baseline study period in normal subjects during thorough QT studies, (2) peak moxifloxacin effect in otherwise normal subjects during thorough QT studies, and (3) patients with genotyped variants of congenital long QT syndrome (LQTS). RESULTS:Differences of means between manufacturers were generally small in the normal and moxifloxacin subjects, but in the LQTS patients, differences of means ranged from 2.0 to 14.0 ms for QRS duration and from 0.8 to 18.1 ms for the QT interval. Mean absolute differences between algorithms were similar for QRS duration and QT intervals in the normal and in the moxifloxacin subjects (mean ≤6 ms) but were significantly larger in patients with LQTS. CONCLUSIONS:Small but statistically significant group differences in mean interval and duration measurements and means of individual absolute differences exist among automated algorithms of widely used, current generation digital electrocardiographs. Measurement differences, including QRS duration and the QT interval, are greatest for the most abnormal ECGs.

Electrocardiograms may not be reviewed by a specialist for several hours after recording. This may lead to delayed clinical action in certain cases. To circumvent the problem, significantly abnormal ECGs are flagged through the provision of headline statements, sometimes known as critical values. The University of Glasgow ECG analysis program has been augmented to include 6 such headline statements. This significantly enhances the clinical utility of the software.

This study aimed to compare the QRS duration in a large population of healthy individuals living in Nigeria with a Caucasian population living in Scotland. The Nigerian population consisted of 782 males and 479 females with an age range of 20–87 years. The Caucasian population consisted of 859 males and 637 females with an age range from 18–82 years. For the Nigerian population, the overall QRS duration for males was 87.9 ± 9.4ms and for females, it was 83.4 ± 7.6ms. For the Caucasian population, the overall QRS duration in males was 93.7 ± 9.8ms and in females was 86.1 ± 7.7ms. In both populations, the mean QRS duration was higher in males than in females. There was a significantly longer QRS duration in Caucasian males and females compared to their Nigerian counterparts. However, the upper limits of normal QRS duration differed little between the two races.

Continuing uncertainty exists about standardized procedures for the placement of electrocardiographic (ECG) chest electrodes, technical variability being the largest error source for short-term variations in amplitudes and waveforms of the chest lead ECGs. To avoid presumed attenuation of ECG amplitudes by abundant breast tissue, anterolateral chest electrodes in women are often placed under the breasts and too low. There is also considerable uncertainty about locating the midclavicular line and the V4 electrode, particularly in obese persons and in women. We examined the effect of breast tissue protuberance on ECG amplitudes using ECG and anthropometric data on 6,814 women included in the Atherosclerosis Research in Communities Study (ARIC). The R wave amplitudes in anterolateral chest leads and the SokolowLyon voltage decreased (P < .001 for all), and RaVL and the Cornell voltage increased significantly with increasing breast protuberance (P < .001 for all). However, these effects were small (15 μV or less for each 1-cm increment in breast protuberance), and R2 values were less than .01, indicating that breast protuberance alone explained less than 1 % of ECG amplitude variations. When chest size and breast protuberance estimates were entered simultaneously into a multivariate regression model, chest size appeared to dominate, and model R2 values increased for positive associations with RaVL (R2 = .12) and the Cornell voltage (R2 = .04). Combined model R2 values remained ⩽.01 for all other ECG amplitudes. A detailed step-by-step standardized electrode placement procedure was formulated. Because of the difficulties encountered in locating the left midclavicular line by visual inspection, we introduced well-defined procedures for identification and documentation of lateral chest electrode placement locations as a quality control method for clinical trials. Population data from the Third National Health and Nutrition Survey on the distributions by sex and race of chest electrode V4 and V6 locations and anthropometric data on chest size and shape are presented in order to facilitate evaluation of the comparability of electrode placement procedures in various studies and for quality control in clinical trials. It is concluded that standardized procedures to document chest electrode placement locations are feasible. Breast tissue appears to have a practically negligible effect on ECG amplitudes, and in women, the placement of chest electrodes on the breast rather than under the breast is recommended in order to facilitate the precision of electrode placement at the correct horizontal level and at the correct lateral positions.