Technical mistakes during the acquisition of the electrocardiogram

Advancing Fairness in Cardiac Care: Strategies for Mitigating Bias in Artificial Intelligence Models Within Cardiology

In the dynamic field of medical artificial intelligence (AI), cardiology stands out as a key area for its technological advancements and clinical application. In this review we explore the complex issue of data bias, specifically addressing those encountered during the development and implementation of AI tools in cardiology. We dissect the origins and effects of these biases, which challenge their reliability and widespread applicability in health care. Using a case study, we highlight the complexities involved in addressing these biases from a clinical viewpoint. The goal of this review is to equip researchers and clinicians with the practical knowledge needed to identify, understand, and mitigate these biases, advocating for the creation of AI solutions that are not just technologically sound, but also fair and effective for all patients.

Meta-Analysis of the Performance of AI-Driven ECG Interpretation in the Diagnosis of Valvular Heart Diseases

Valvular heart diseases (VHDs) significantly impact morbidity and mortality rates worldwide. Early diagnosis improves patient outcomes. Artificial intelligence (AI) applied to electrocardiogram (ECG) interpretation presents a promising approach for early VHD detection. We conducted a meta-analysis on the efficacy of AI models in this context. We reviewed databases including PubMed, MEDLINE, Embase, Scopus, and Cochrane until August 20, 2023, focusing on AI for ECG-based VHD detection. The outcomes included pooled accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value. The pooled proportions were derived using a random-effects model with 95% confidence intervals (CIs). Study heterogeneity was evaluated with the I-squared statistic. Our analysis included 10 studies, involving ECG data from 713,537 patients. The AI algorithms mainly screened for aortic stenosis (n = 6), mitral regurgitation (n = 4), aortic regurgitation (n = 3), mitral stenosis (n = 1), mitral valve prolapse (n = 2), and tricuspid regurgitation (n = 1). A total of 9 studies used convolution neural network models, whereas 1 study combined the strengths of support vector machine logistic regression and multilayer perceptron for ECG interpretation. The collective AI models demonstrated a pooled accuracy of 81% (95% CI 73 to 89, I² = 92%), sensitivity was 83% (95% CI 77 to 88, I² = 86%), specificity was 72% (95% CI 68 to 75, I² = 52%), PPV was 13% (95% CI 7 to 19, I² = 90%), and negative predictive value was 99% (95% CI 97 to 99, I² = 50%). The subgroup analyses for aortic stenosis and mitral regurgitation detection yielded analogous outcomes. In conclusion, AI-driven ECG offers high accuracy in VHD screening. However, its low PPV indicates the need for a combined approach with clinical judgment, especially in primary care settings.

The electrocardiographic manifestations of pectus excavatum before and after surgical correction

BACKGROUND

Pectus excavatum (PEx) can cause cardiopulmonary limitations due to cardiac compression and displacement. There is limited data on electrocardiogram (ECG) alterations before and after PEx surgical repair, and ECG findings suggesting cardiopulmonary limitations have not been reported. The aim of this study is to explore ECG manifestations of PEx before and after surgery including associations with exercise capacity.

METHODS

A retrospective review of PEx patients who underwent primary repair was performed. ECGs before and after surgical correction were evaluated and the associations between preoperative ECG abnormalities and cardiopulmonary function were investigated.

RESULTS

In total, 310 patients were included (mean age 35.1 ± 11.6 years). Preoperative ECG findings included a predominant negative P wave morphology in V1, and this abnormal pattern significantly decreased from 86.9% to 57.4% (p < 0.001) postoperatively. The presence of abnormal P wave amplitude in lead II (>2.5 mm) significantly decreased from 7.1% to 1.6% postoperatively (p < 0.001). Right bundle branch block (RBBB) (9.4% versus 3.9%, p < 0.001), rsr' patterns (40.6% versus 12.9%, p < 0.001), and T wave inversion in leads V1-V3 (62.3% vs 37.7%, p < 0.001) were observed less frequently after surgery. Preoperative presence of RBBB (OR = 4.8; 95%CI 1.1-21.6) and T wave inversion in leads V1-3 (OR = 2.3; 95%CI 1.3-4.2) were associated with abnormal results in cardiopulmonary exercise testings.

CONCLUSION

Electrocardiographic abnormalities in PEx are frequent and can revert to normal following surgery. Preoperative RBBB and T wave inversion in leads V1-3 suggested a reduction in exercise capacity, serving as a marker for the need for further cardiovascular evaluation of these patients.

Evaluating a Novel Infant Heart Rate Detector for Neonatal Resuscitation Efforts: Protocol for a Proof-of-Concept Study

BACKGROUND

Over 10 million newborns worldwide undergo resuscitation at birth each year. Pediatricians may use electrocardiogram (ECG), pulse oximetry (PO), and stethoscope in determining heart rate (HR), as HR guides the need for and steps of resuscitation. HR must be obtained quickly and accurately. Unfortunately, the current diagnostic modalities are either too slow, obtaining HR in more than a minute, or inaccurate. With time constraints, a reliable robust heart rate detector (HRD) modality is required. This paper discusses a protocol for conducting a methods-based comparison study to determine the HR accuracy of a novel real-time HRD based on 3D-printed dry-electrode single-lead ECG signals for cost-effective and quick HR determination. The HRD's HR results are compared to either clinical-grade ECG or PO monitors to ensure robustness and accuracy.

OBJECTIVE

The purpose of this study is to design and examine the feasibility of a proof-of-concept HRD that quickly obtains HR using biocompatible 3D-printed dry electrodes for single-lead neonatal ECG acquisition. This study uses a novel HRD and compares it to the gold-standard 3-lead clinical ECG or PO in a hospital setting.

METHODS

A cross-sectional study is planned to be conducted in the neonatal intensive care unit or postpartum unit of a large community teaching hospital in Toronto, Canada, from June 2023 to June 2024. In total, 50 newborns will be recruited for this study. The HRD and an ECG or PO monitor will be video recorded using a digital camera concurrently for 3 minutes for each newborn. Hardware-based signal processing and patent-pending embedded algorithm-based HR estimation techniques are applied directly to the raw collected single-lead ECG and displayed on the HRD in real time during video recordings. These data will be annotated and compared to the ECG or PO readings at the same points in time. Accuracy, F1-score, and other statistical metrics will be produced to determine the HRD's feasibility in providing reliable HR.

RESULTS

The study is ongoing. The projected end date for data collection is around July 2024.

CONCLUSIONS

The study will compare the novel patent-pending 3D-printed dry electrode-based HRD's real-time HR estimation techniques with the state-of-the-art clinical-grade ECG or PO monitors for HR accuracy and examines how fast the HRD provides reliable HR. The study will further provide recommendations and important improvements that can be made to implement the HRD for clinical applications, especially in neonatal resuscitation efforts. This work can be seen as a stepping stone in the development of robust dry-electrode single-lead ECG devices for HR estimations in the pediatric population.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/45512.

Telemedicine in the Era of a Pandemic: Usefulness of a Novel Three-Lead ECG

The 12-lead electrocardiogram (ECG) is a first-line diagnostic tool for patients with cardiac symptoms. As observed during the COVID-19 pandemic, the ECG is essential to the initial patient evaluation. The novel KardioPal three-lead-based ECG reconstructive technology provides a potential alternative to a standard ECG, reducing the response time and cost of treatment and improving patient comfort. Our study aimed to evaluate the diagnostic accuracy of a reconstructed 12-lead ECG obtained by the KardioPal technology, comparing it with the standard 12-lead ECG, and to assess the feasibility and time required to obtain a reconstructed ECG in a real-life scenario. A prospective, nonrandomized, single-center, adjudicator-blinded trial was conducted on 102 patients during the COVID-19 pandemic at the Dedinje Cardiovascular Institute in Belgrade. The KardioPal system demonstrated a high feasibility rate (99%), with high specificity (96.3%), sensitivity (95.8%), and diagnostic accuracy (96.1%) for obtaining clinically relevant matching of reconstructed 12-lead compared to the standard 12-lead ECG recording. This novel technology provided a significant reduction in ECG acquisition time and the need for personnel and space for obtaining ECG recordings, thereby reducing the risk of viral transmission and the burden on an already overwhelmed healthcare system such as the one experienced during the COVID-19 pandemic.

The influence of electrocardiogram (ECG) filters on the heights of R and T waves in children

Anesthesiologists often compare intraoperative and preoperative electrocardiogram (ECG) waveforms in patients undergoing general anesthesia. In addition, many intraoperative ECG monitors have filters for removing electrocautery noise. In pediatric anesthesiology practice, we often note the appearance of elevated T waves-specifically, an increase in their height-with the use of such filters, even though no actual clinical change has occurred, which possibly leads to misdiagnosis. We investigated changes in R and T wave heights and in the T/R ratio according to the use of the strong (S) versus the diagnostic (D) filtering mode during pediatric anesthesiology. Primary outcomes were the dependence of the heights of the R and T waves on the filter mode and the correlation between rates of change in the R- and T-wave heights and heart rate (HR). In the S mode, the height of the R wave was lower (p = 0.013, η² = 0.28) and the T/R ratio was higher than the corresponding values in the D mode (χ² = 20.46, p < 0.001). The T/R ratios were also higher in the S mode than in the D mode, and when the D mode was changed to the S mode during tachycardia, there was a strong correlation between the rate of reduction in the R wave and HR (r = 0. 573, p = 0.041). Significant differences in the heights of the R wave and in the T/R ratio occur when using different intraoperative ECG filtering modes. Specifically, in S mode, a greater relative increase in T wave height may occur due to a significant decrease in R wave height. To avoid spurious diagnoses, anesthesiologists should be familiar with these potentially purely filter-driven changes whenever ECG is intraoperatively monitored.

Standardization in Performing and Interpreting Electrocardiograms

Excellence in recording and interpretation of electrocardiogram (ECG) is a necessity for optimal electrocardiography. This includes data to properly interpret the ECG, including data on age, gender, cardiovascular diagnosis, medications, abnormal laboratory findings (eg, data on electrolytes), and the indications for the electrocardiogram. The ECG needs to be performed by a qualified technician and interpreted by an experienced physician.

Feasibility study of a 3D camera to reduce electrode repositioning errors during longitudinal ECG acquisition

INTRODUCTION

Longitudinal monitoring of sometimes subtle waveform changes of the 12‑lead electrocardiogram (ECG) is complicated by patient-specific and technical factors, such as the inaccuracy of electrode repositioning. This feasibility study uses a 3D camera to reduce electrode repositioning errors, reduce ECG waveform variability and enable detailed longitudinal ECG monitoring.

METHODS

Per subject, three clinical ECGs were obtained during routine clinical follow-up. Additionally, two ECGs were recorded guided by two 3D cameras, which were used to capture the precordial electrode locations and direct electrode repositioning. ECG waveforms and parameters were quantitatively compared between 3D camera guided ECGs and clinical ECGs. Euclidian distances between original and repositioned precordial electrodes from 3D guided ECGs were measured.

RESULTS

Twenty subjects (mean age 65.1 ± 8.2 years, 35% females) were included. The ECG waveform variation between routine ECGs was significantly higher compared to 3D guided ECGs, for both the QRS complex (correlation coefficient = 0.90 vs 0.98, p < 0.001) and the STT segment (correlation coefficient = 0.88 vs. 0.96, p < 0.001). QTc interval variation was reduced for 3D camera guided ECGs compared to routine clinical ECGs (5.6 ms vs. 9.6 ms, p = 0.030). The median distance between 3D guided repositioned electrodes was 10.0 [6.4-15.2] mm, and did differ between males and females (p = 0.076).

CONCLUSIONS

3D guided repositioning of precordial electrodes resulted in, a low repositioning error, higher agreement between waveforms of consecutive ECGs and a reduction of QTc variation. These findings suggest that longitudinal monitoring of disease progression using 12‑lead ECG waveforms is feasible in clinical practice.

The role of the electrocardiogram in identifying the risk of sudden cardiac death

Introduction: Sudden cardiac death (SCD) represents the unexpected and sudden death of young apparently healthy people. Alarge number of examined cases referred to professional athletes. There is not enough data in the literature related to those who performed sports in a sporadic and recreational manner. In order to prevent SCD, a screening protocol was determined, in which, an ECG performed at rest plays a important role. Based on the established criteria, changes on the ECG can be treated as normal, borderline and abnormal. An abnormal result indicates a risk of SCD. Objective: The aim of this study was to determine the risk of SCD in students who practice physical activity recreationally. Methods: The research involved 500 students (both sexes) of the 1st and 3rd year of study on the University of Pristina situated in Kosovska Mitrovica. As part of the regular systematic examination, an ECG was performed at rest. The risk of SCD was determined by analyzing the changes on the ECG and grouping them based on screening recommendations. Results: The obtained results show that 44% of students had changes on the ECG and that 8% of students had an abnormal result indicated a possible risk of sudden cardiac death. Conclusion: Therefore, timely recognizing and interpreting ECG changes in accordance with screening recommendations is an imperative for identification and possible prevention of SCD.

The Human Organism as an Integrated Interaction Network: Recent Conceptual and Methodological Challenges

The field of Network Physiology aims to advance our understanding of how physiological systems and sub-systems interact to generate a variety of behaviors and distinct physiological states, to optimize the organism's functioning, and to maintain health. Within this framework, which considers the human organism as an integrated network, vertices are associated with organs while edges represent time-varying interactions between vertices. Likewise, vertices may represent networks on smaller spatial scales leading to a complex mixture of interacting homogeneous and inhomogeneous networks of networks. Lacking adequate analytic tools and a theoretical framework to probe interactions within and among diverse physiological systems, current approaches focus on inferring properties of time-varying interactions-namely strength, direction, and functional form-from time-locked recordings of physiological observables. To this end, a variety of bivariate or, in general, multivariate time-series-analysis techniques, which are derived from diverse mathematical and physical concepts, are employed and the resulting time-dependent networks can then be further characterized with methods from network theory. Despite the many promising new developments, there are still problems that evade from a satisfactory solution. Here we address several important challenges that could aid in finding new perspectives and inspire the development of theoretic and analytical concepts to deal with these challenges and in studying the complex interactions between physiological systems.

Accuracy and knowledge in 12-lead ECG placement among nursing students and nurses: a web-based Italian study

BACKGROUND AND AIM

Electrocardiogram (ECG) is considered the most used diagnostic tool to identify many cardiological disease and conditions that require the monitoring and recording of heart's electric activity. The aim of this study is the validation and application of a web-survey, addressed to nursing students and nurses, in order to evaluate the degree of accuracy and the knowledge on the correct positioning of the 12-leads ECG.

METHODS

The study was a cross-sectional questionnaire-based study. The survey comprised 30 items, mainly multiple-choice questions.  The participants were 484 nurses and nursing students. In the study, no exclusion criteria were adopted, but fill in the questionnaire any nurse on duty during the data collection period and/or any nursing student during the data collection period. Statistical analyses were performed using the SAS v. 9.4. In the study, no exclusion criteria were adopted.

RESULTS

A total of 484 nursing students and nurses comprising of 149 males (30.79%) and 335 females (69.21%) responded. In full findings showed good psychometric properties and good reliability. The Cronbach's alpha coefficient for the study is 0.76 (number of items = 17, number of obs= 484). The mean age of responders was 32.01 (Standard deviation (SD) 9.63). A logistic multivariate regression demonstrated significant differences.

CONCLUSIONS

It is evident from our findings and those from other countries, that more education is required to ensure that mistaken interpretation, misdiagnosis, patient mismanagement and/or inappropriate procedures due to 12 leads ECG misplacement does not occur.

Suspected Brugada Phenocopy Secondary to Coronary Slow Flow

Brugada syndrome (BrS) is a genetic condition that accentuates the risk of potentially lethal ventricular arrhythmias and sudden cardiac death (SCD) in a structurally normal heart. The Brugada electrocardiographic pattern may manifest separately from the syndrome—this clinical scenario has been described as Brugada phenocopy (BrP). Many etiologies of BrP have been reported, but it has not yet been reported as a result of coronary slow flow (CSF) phenomenon. This case report highlights a suspected coronary slow flow-associated Brugada type 1 electrocardiographic pattern, which subsequently normalized following the institution of guideline-directed medical therapy for acute coronary syndrome.

A review of automated sleep stage scoring based on physiological signals for the new millennia

BACKGROUND AND OBJECTIVE

Sleep is an important part of our life. That importance is highlighted by the multitude of health problems which result from sleep disorders. Detecting these sleep disorders requires an accurate interpretation of physiological signals. Prerequisite for this interpretation is an understanding of the way in which sleep stage changes manifest themselves in the signal waveform. With that understanding it is possible to build automated sleep stage scoring systems. Apart from their practical relevance for automating sleep disorder diagnosis, these systems provide a good indication of the amount of sleep stage related information communicated by a specific physiological signal.

METHODS

This article provides a comprehensive review of automated sleep stage scoring systems, which were created since the year 2000. The systems were developed for Electrocardiogram (ECG), Electroencephalogram (EEG), Electrooculogram (EOG), and a combination of signals.

RESULTS

Our review shows that all of these signals contain information for sleep stage scoring.

CONCLUSIONS

The result is important, because it allows us to shift our research focus away from information extraction methods to systemic improvements, such as patient comfort, redundancy, safety and cost.

Suspected hyponatremia-induced Brugada phenocopy

Brugada syndrome is a genetic condition that predisposes to an increased risk of ventricular fibrillation and sudden cardiac death in a structurally normal heart. The Brugada type 1 electrocardiogram (ECG) pattern may occur independently of the actual syndrome, and this clinical phenomenon is often referred to as Brugada phenocopy. There are several other factors which have been known to induce this electrocardiographic pattern, and currently, there is a paucity of literature with respect to the pattern that is observed in patients with electrolyte disturbances, specifically hyponatremia. This case report highlights a suspected hyponatremia-induced Brugada type 1 ECG pattern, which subsequently normalized following resolution of the electrolyte derangement.

Premature ventricular contractions of the right ventricular outflow tract: Upward displacement of the ECG unmasks ST elevation in V1 associated with the presence of low voltage areas

INTRODUCTION AND AIMS

Frequent premature ventricular contractions (PVCs) originating from the right ventricular outflow tract (RVOT) are usually considered a benign entity and the ECG is typically normal. The aim of this study was to assess whether upward displacement of the ECG to the second intercostal space (ICS) would reveal any abnormal pattern.

METHODS

A total of 18 consecutive patients with apparently normal hearts were studied, mean age 44±16 years, 12 women, who underwent catheter ablation of the RVOT due to frequent PVCs. A 12-lead ECG was performed in the standard position and repeated in a higher position, at the level of the second ICS. Three-dimensional bipolar electroanatomical voltage mapping (EVM) was performed in all patients and low voltage areas (LVAs) were defined as areas with amplitude <1.5 mV.

RESULTS

The ECG in the second ICS was normal in eleven patients but in seven (39%) it revealed a pattern of ST-segment elevation in V1. EVM revealed the presence of LVAs in six patients (33%) which included the earliest activation site (EAS) in five. The ST elevation was associated with the presence of LVAs (p<0.0001) and with the LVAs at the EAS (p=0.002).

CONCLUSION

In this group of patients with apparently normal hearts and with frequent PVCs of the RVOT, upward displacement of the ECG revealed the presence of ST elevation in more than one third of patients, and the ST elevation was associated with the presence of LVAs in the RVOT.

Recent advances in the treatment of Brugada syndrome

INTRODUCTION

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome characterized by ST-segment elevation in right precordial ECG leads and associated with sudden cardiac death in young adults. The ECG manifestations of BrS are often concealed but can be unmasked by sodium channel blockers and fever. Areas covered: Implantation of a cardioverter defibrillator (ICD) is first-line therapy for BrS patients presenting with prior cardiac arrest or documented VT. A pharmacological approach to therapy is recommended in cases of electrical storm, as an adjunct to ICD and as preventative therapy. The goal of pharmacological therapy is to produce an inward shift to counter the genetically-induced outward shift of ion channel current flowing during the early phases of the ventricular epicardial action potential. This is accomplished by augmentation of I_Ca using □□adrenergic agents or phosphodiesterase III inhibitors or via inhibition of I_to. Radiofrequency ablation of the right ventricular outward flow tract epicardium is effective in suppressing arrhythmogenesis in BrS patients experiencing frequent appropriate ICD-shocks. Expert commentary: Understanding of the pathophysiology and approach to therapy of BrS has advanced considerably in recent years, but there remains an urgent need for development of cardio-selective and ion-channel-specific I_to blockers for treatment of BrS.

Perspectives of human verification via binary QRS template matching of single-lead and 12-lead electrocardiogram

Objective

This study aims to validate the 12-lead electrocardiogram (ECG) as a biometric modality based on two straightforward binary QRS template matching characteristics. Different perspectives of the human verification problem are considered, regarding the optimal lead selection and stability over sample size, gender, age, heart rate (HR).

Methods

A clinical 12-lead resting ECG database, including a population of 460 subjects with two-session recordings (>1 year apart) is used. Cost-effective strategies for extraction of personalized QRS patterns (100ms) and binary template matching estimate similarity in the time scale (matching time) and dissimilarity in the amplitude scale (mismatch area). The two-class person verification task, taking the decision to validate or to reject the subject identity is managed by linear discriminant analysis (LDA). Non-redundant LDA models for different lead configurations (I,II,III,aVF,aVL,aVF,V1-V6) are trained on the first half of 230 subjects by stepwise feature selection until maximization of the area under the receiver operating characteristic curve (ROC AUC). The operating point on the training ROC at equal error rate (EER) is tested on the independent dataset (second half of 230 subjects) to report unbiased validation of test-ROC AUC and true verification rate (TVR = 100-EER). The test results are further evaluated in groups by sample size, gender, age, HR.

Results and discussion

The optimal QRS pattern projection for single-lead ECG biometric modality is found in the frontal plane sector (60°-0°) with best (Test-AUC/TVR) for lead II (0.941/86.8%) and slight accuracy drop for -aVR (-0.017/-1.4%), I (-0.01/-1.5%). Chest ECG leads have degrading accuracy from V1 (0.885/80.6%) to V6 (0.799/71.8%). The multi-lead ECG improves verification: 6-chest (0.97/90.9%), 6-limb (0.986/94.3%), 12-leads (0.995/97.5%). The QRS pattern matching model shows stable performance for verification of 10 to 230 individuals; insignificant degradation of TVR in women by (1.2–3.6%), adults ≥70 years (3.7%), younger <40 years (1.9%), HR<60bpm (1.2%), HR>90bpm (3.9%), no degradation for HR change (0 to >20bpm).

Experiences in digitizing and digitally measuring a paper-based ECG archive

BACKGROUND

No established method for digitizing and digital measuring of paper electrocardiograms (ECG) exists. We describe a paper ECG digitizing and digital measuring process, and report comparability to manual measurements.

METHODS

A paper ECG was recorded from 7203 health survey participants in 1978-1980. With specific software, the ECGs were digitized (ECG Trace Tool), and measured digitally (EASE). A sub-sample of 100 ECGs was selected for manual measurements.

RESULTS

The measurement methods showed good agreement. The mean global (EASE)-(manual) differences were 1.4ms (95% CI 0.5-2.2) for PR interval, -1.0ms (95% CI -1.5-[-0.5]) for QRS duration, and 11.6ms (95% CI 10.5-12.7) for QT interval. The mean inter-method amplitude differences of RampV5, RampV6, SampV1, TampII and TampV5 ranged from -0.03mV to 0.01mV.

CONCLUSIONS

The presented paper-to-digital conversion and digital measurement process is an accurate and reliable method, enabling efficient storing and analysis of paper ECGs.

The Need to Apply Medical Device Informatics in Developing Standards for Safe Interoperable Medical Systems

Medical device and health information technology systems are increasingly interdependent with users demanding increased interoperability. Related safety standards must be developed taking into account these systems' perspective. In this article, we describe the current development of medical device standards and the need for these standards to address medical device informatics. Medical device information should be gathered from a broad range of clinical scenarios to lay the foundation for safe medical device interoperability. Five clinical examples show how medical device informatics principles, if applied in the development of medical device standards, could help facilitate the development of safe interoperable medical device systems. These examples illustrate the clinical implications of the failure to capture important signals and device attributes. We provide recommendations relating to the coordination between historically separate standards development groups, some of which focus on safety and effectiveness and others focus on health informatics. We identify the need for a shared understanding among stakeholders and describe organizational structures to promote cooperation such that device-to-device interactions and related safety information are considered during standards development.

Clinical location of the fourth and fifth intercostal spaces as a percent of the length of the sternum

OBJECTIVES

To verify accurate placement of the precordial ECG leads by identifying the 4th and 5th intercostal spaces as a function of the length of the sternum. This should decrease the percentage of lead misplacement leading to misdiagnoses.

METHODS

The population consisted of patients and healthy volunteers. The proposed method compared palpation of the 4th and 5th intercostal spaces to a percentile of the sternal length. Location of the 4th and 5th intercostal space using a simple device was evaluated to assist in proper placement of the precordial leads to obtain accurate diagnosis.

RESULTS

The location of the 4th and 5th intercostal space is related to the length of the sternum. It is 77% of the sternal length that measures 15cm for the 4th intercostal space. The position of the V1 and V2 electrodes decreases to 57% when the sternal length is 26cm. Similar data was obtained to locate the 5th intercostal space with proper position of V4-V6 electrodes. Tables are provided to facilitate this process. An instrument was designed to measure the 4th and 5th intercostal space as a function of the sternal length.

CONCLUSIONS

The location of the 4th and 5th intercostal space is identified based on the length of the sternum.

Prevalence and incidence of Q-wave unrecognized myocardial infarction in general population: Diagnostic value of the electrocardiogram. The REGICOR study

BACKGROUND

Diagnosis of unrecognized myocardial infarction (UMI) remains an open question in epidemiological and clinical studies, inhibiting effective secondary prevention of myocardial infarction. We aimed to determine the prevalence and incidence of Q-wave UMI in asymptomatic individuals aged 35 to 74years, and to ascertain the positive predictive value (PPV) of asymptomatic Q-wave to diagnose UMI.

METHODS

Two population-based cross-sectional studies were conducted, in 2000 (with 10-year follow-up) and in 2005. A baseline electrocardiogram was obtained for each participant. Imaging techniques (echocardiography, cardiac magnetic resonance imaging, and myocardial perfusion single-photon emission computerized tomography) were used to confirm UMI in patients with asymptomatic Q-wave.

RESULTS

The prevalence of confirmed Q-wave UMI in the 5580 participants was 0.18% (95% confidence interval [CI]: 0.10-0.33) and the incidence rate was 27.1 Q-wave UMI per 100,000person-years. The proportion of confirmed Q-wave UMI with respect to all prevalent MI was 8.1% (95% CI: 4.4-14.2). The PPV of asymptomatic Q-wave to diagnose Q-wave UMI was 29.2% (95% CI: 18.2-43.2%) overall, but much higher (75%, 95% CI: 40.9-92.9%) in participants with 10-year CHD risk ≥10%, compared to lower-risk participants.

CONCLUSION

Opportunistic identification of asymptomatic Q-waves by routine electrocardiogram overestimates actual Q-wave UMI, which represents 8% to 13% of all myocardial infarction in the population aged 35 to 74years. This overestimation is particularly high in the population at low cardiovascular risk. In epidemiological studies and in clinical practice, diagnosis of a pathologic Q-wave in asymptomatic patients requires detailed analysis of imaging tests to confirm or rule out myocardial necrosis.

Inter-lead correlation analysis for automated detection of cable reversals in 12/16-lead ECG

BACKGROUND AND OBJECTIVE

A crucial factor for proper electrocardiogram (ECG) interpretation is the correct electrode placement in standard 12-lead ECG and extended 16-lead ECG for accurate diagnosis of acute myocardial infarctions. In the context of optimal patient care, we present and evaluate a new method for automated detection of reversals in peripheral and precordial (standard, right and posterior) leads, based on simple rules with inter-lead correlation dependencies.

METHODS

The algorithm for analysis of cable reversals relies on scoring of inter-lead correlations estimated over 4s snapshots with time-coherent data from multiple ECG leads. Peripheral cable reversals are detected by assessment of nine correlation coefficients, comparing V6 to limb leads: (I, II, III, -I, -II, -III, -aVR, -aVL, -aVF). Precordial lead reversals are detected by analysis of the ECG pattern cross-correlation progression within lead sets (V1-V6), (V4R, V3R, V3, V4), and (V4, V5, V6, V8, V9). Disturbed progression identifies the swapped leads.

RESULTS

A test-set, including 2239 ECGs from three independent sources-public 12-lead (PTB, CSE) and proprietary 16-lead (Basel University Hospital) databases-is used for algorithm validation, reporting specificity (Sp) and sensitivity (Se) as true negative and true positive detection of simulated lead swaps. Reversals of limb leads are detected with Se = 95.5-96.9% and 100% when right leg is involved in the reversal. Among all 15 possible pairwise reversals in standard precordial leads, adjacent lead reversals are detected with Se = 93.8% (V5-V6), 95.6% (V2-V3), 95.9% (V3-V4), 97.1% (V1-V2), and 97.8% (V4-V5), increasing to 97.8-99.8% for reversals of anatomically more distant electrodes. The pairwise reversals in the four extra precordial leads are detected with Se = 74.7% (right-sided V4R-V3R), 91.4% (posterior V8-V9), 93.7% (V4R-V9), and 97.7% (V4R-V8, V3R-V9, V3R-V8). Higher true negative rate is achieved with Sp > 99% (standard 12-lead ECG), 81.9% (V4R-V3R), 91.4% (V8-V9), and 100% (V4R-V9, V4R-V8, V3R-V9, V3R-V8), which is reasonable considering the low prevalence of lead swaps in clinical environment.

CONCLUSIONS

Inter-lead correlation analysis is able to provide robust detection of cable reversals in standard 12-lead ECG, effectively extended to 16-lead ECG applications that have not previously been addressed.

Pseudo-double T wave ECG artifact

In the ECG of a diabetic patient without coronary artery disease, a double T wave was observed. The ECG was normal the next day. This finding was interpreted as representing repolarization abnormalities (e. g., myocardial ischemia) by many health care workers. However, it represents an artifact called "pseudo double T wave". The cause is unknown but most likely due to abnormalities at the interface between surface electrodes and skin tissue. The diagnosis of ECG artifacts requires meticulous examination of the tracings coupled with a thorough knowledge of normal patterns.

Brugada Syndrome: Clinical, Genetic, Molecular, Cellular, and Ionic Aspects

Brugada syndrome (BrS) is an inherited cardiac arrhythmia syndrome first described as a new clinical entity in 1992. Electrocardiographically characterized by distinct coved type ST segment elevation in the right-precordial leads, the syndrome is associated with a high risk for sudden cardiac death in young adults, and less frequently in infants and children. The electrocardiographic manifestations of BrS are often concealed and may be unmasked or aggravated by sodium channel blockers, a febrile state, vagotonic agents, as well as by tricyclic and tetracyclic antidepressants. An implantable cardioverter defibrillator is the most widely accepted approach to therapy. Pharmacologic therapy is designed to produce an inward shift in the balance of currents active during the early phases of the right ventricular action potential (AP) and can be used to abort electrical storms or as an adjunct or alternative to device therapy when use of an implantable cardioverter defibrillator is not possible. Isoproterenol, cilostazol, and milrinone boost calcium channel current and drugs like quinidine, bepridil, and the Chinese herb extract Wenxin Keli inhibit the transient outward current, acting to diminish the AP notch and thus to suppress the substrate and trigger for ventricular tachycardia or fibrillation. Radiofrequency ablation of the right ventricular outflow tract epicardium of patients with BrS has recently been shown to reduce arrhythmia vulnerability and the electrocardiographic manifestation of the disease, presumably by destroying the cells with more prominent AP notch. This review provides an overview of the clinical, genetic, molecular, and cellular aspects of BrS as well as the approach to therapy.

Identification of 4th intercostal space using sternal notch to xiphoid length for accurate electrocardiogram lead placement

OBJECTIVE

Precordial ECG lead placement is difficult in obese patients with increased chest wall soft tissues due to inaccurate palpation of the intercostal spaces. We investigated whether the length of the sternum (distance between the sternal notch and xiphoid process) can accurately predict the location of the 4th intercostal space, which is the traditional location for V1 lead position.

MATERIALS AND METHODS

Fifty-five consecutive adult chest computed tomography examinations were reviewed for measurements.

RESULTS

The sternal notch to right 4th intercostal space distance was 67% of the sternal notch to xiphoid process length with an overall correlation of r=0.600 (p<0.001).

CONCLUSION

The above measurement may be utilized to locate the 4th intercostal space for accurate placement of the precordial electrodes in adults in whom the 4th intercostal space cannot be found by physical exam.

Brugada ECG patterns in athletes

Brugada syndrome is responsible for up to 4% of all sudden cardiac deaths worldwide and up to 20% of sudden cardiac deaths in patients with structurally normal hearts. Heterogeneity of repolarization and depolarization, particularly over the right ventricle and the outflow tract, is responsible for the arrhythmogenic substrate. The coved Type I ECG pattern is considered diagnostic of the syndrome but its prevalence is very low. Distinguishing between a saddle back Type 2 Brugada pattern and one of many "Brugada-like" patterns presents challenges especially in athletes. A number of criteria have been proposed to assess Brugada ECG patterns. Proper precordial ECG lead placement is paramount. This paper reviews Brugada syndrome, Brugada ECG patterns, and recently proposed criteria. Recommendations for evaluating a Brugada ECG pattern are provided.

Modern standards of ECG interpretation in young athletes: yield and effectiveness

Although cardiovascular screening is recommended before participating in competitive sports, the role of the 12-lead electrocardiogram (ECG) has been debated. When added to the medical history and physical examination, an ECG used during the pre-participation screening (PPS) of young athletes can greatly enhance the ability to detect underlying cardiovascular pathology. Concerns over false positive rates, however, have posed an obstacle to large-scale implementation. The recent development of modern athlete-specific ECG interpretation criteria has dramatically reduced false positive rates to levels below other commonly used screening tests (e.g. breast cancer, prostate cancer) and subsequently improved cost effectiveness. There are also emerging data that certain sub-groups have a higher prevalence of ECG abnormalities, including males, athletes of Afro-Caribbean descent, basketball players, and endurance athletes. While false positive rates from a number of studies are reduced with the improved standards, there may be room for continued improvements. Future efforts should focus on refining criteria based on age, race, gender, ethnicity, and sport, while also clearly delineating the appropriate work-up strategies for those with abnormal findings, as this can lead to improved resource utilization.

Differential diagnosis of rSr' pattern in leads V1 -V2. Comprehensive review and proposed algorithm

One of the more frequent dilemmas in ECG interpretation is the differential diagnosis of an rSr' pattern in leads V1 -V2 . We often face this finding in asymptomatic and otherwise healthy individuals and the causes may vary from benign nonpathological variants to severe or life-threatening heart diseases, such as Brugada syndrome or arrhythmogenic right ventricular dysplasia. In other cases, a normal variant of rSr' pattern can be misinterpreted as pathological after the occurrence of certain clinical events such as cardiac arrest or syncope of unknown cause. In this review we analyze in detail all the possible conditions, both benign and pathological that may explain the presence of this electrocardiographic pattern. We also propose a simple electrocardiographic algorithm for differential diagnosis.

Brugada electrocardiographic pattern: reality or fiction?

In many cases, failure to perform an electrocardiogram according to established standards can lead to incorrect diagnosis. When this error involves a disease that can result in sudden death such as Brugada syndrome, diagnostic procedures are not without risk for the patient. A 20 year-old man visited his family doctor for atypical chest pain some time before. Electrocardiography (ECG) showed sinus rhythm of 47 bpm with striking ST-elevation in V1-V3 suggestive of the Brugada pattern. Sometimes, the different low-frequency components of the ECG, such as the ST segment, may be distorted by high cutoff filters resulting in diagnostic errors [Am J Cardiol 2012;110:318-320]. Faced with an apparent Brugada syndrome pattern on ECG, clinicians should ensure the recording was correctly made.

Effect of ECG filter settings on J-waves

BACKGROUND

While J-waves were observed in healthy populations, variations in their reported incidence may be partly explicable by the ECG filter setting.

METHODS

We obtained resting 12-lead ECG recordings in 665 consecutive patients and enrolled 112 (56 men, 56 women, mean age 59.3±16.1years) who manifested J-waves on ECGs acquired with a 150-Hz low-pass filter. We then studied the J-waves on individual ECGs to look for morphological changes when 25-, 35-, 75-, 100-, and 150Hz filters were used.

RESULTS

The notching observed with the 150-Hz filter changed to slurring (42%) or was eliminated (28%) with the 25-Hz filter. Similarly, the slurring seen with the 150-Hz filter was eliminated on 71% of ECGs recorded with the 25-Hz filter. The amplitude of J-waves was significantly lower with 25- and 35-Hz than 75-, 100-, and 150-Hz filters (p<0.0001).

CONCLUSIONS

The ECG filter setting significantly affects the J-wave morphology.

Current electrocardiographic criteria for diagnosis of Brugada pattern: a consensus report

Brugada syndrome is an inherited heart disease without structural abnormalities that is thought to arise as a result of accelerated inactivation of Na channels and predominance of transient outward K current (I(to)) to generate a voltage gradient in the right ventricular layers. This gradient triggers ventricular tachycardia/ventricular fibrillation possibly through a phase 2 reentrant mechanism. The Brugada electrocardiographic (ECG) pattern, which can be dynamic and is sometimes concealed, being only recorded in upper precordial leads, is the hallmark of Brugada syndrome. Because of limitations of previous consensus documents describing the Brugada ECG pattern, especially in relation to the differences between types 2 and 3, a new consensus report to establish a set of new ECG criteria with higher accuracy has been considered necessary. In the new ECG criteria, only 2 ECG patterns are considered: pattern 1 identical to classic type 1 of other consensus (coved pattern) and pattern 2 that joins patterns 2 and 3 of previous consensus (saddle-back pattern). This consensus document describes the most important characteristics of 2 patterns and also the key points of differential diagnosis with different conditions that lead to Brugada-like pattern in the right precordial leads, especially right bundle-branch block, athletes, pectus excavatum, and arrhythmogenic right ventricular dysplasia/cardiomyopathy. Also discussed is the concept of Brugada phenocopies that are ECG patterns characteristic of Brugada pattern that may appear and disappear in relation with multiple causes but are not related with Brugada syndrome.

Electrocardiogram acquisition errors or myocardial infarct

Incorrect lead placement may result in unnecessary therapeutic interventions. We present a case report of 53-year-old man with new inferior T-wave inversions in the 12-lead electrocardiogram (ECG) noted during routine followup of hypertension without any cardiovascular symptoms.