Electrocardiographic Tracings Research Articles

Teachable Moments in ECG: The Physiology Behind the Pattern

The electrocardiographic analysis of heart blocks provides great opportunities for the discussion of mechanisms of electrical cardiac conduction, serving as “teachable moments” in medicine. Recognition of heart blocks can sometimes be a challenge as they can present in many forms, different severities and levels of blocks that present as varied patterns on electrocardiographic tracing. The ultimate key to correct diagnosis rests on adequate understanding of normal electrophysiology of the electrical system of the heart. While it is vital to recognize the pattern, we should always know and understand the physiology behind the pattern. This article presents a detailed analysis of a case of heart block which can easily be misinterpreted on first look. The case is featured not for its rarity but for the interesting concepts in cardiac electrophysiology that are highlighted. Navigation of the different elements of tracing can be an adventure and a great learning experience enjoyed by both students and experts. Keywords: Heart block, ECG, electrocardiography

The Use of Animations Depicting Cardiac Electrical Activity to Improve Confidence in Understanding of Cardiac Pathology and Electrocardiography Traces Among Final-Year Medical Students: Nonrandomized Controlled Trial.

Electrocardiography (ECG) interpretation is a fundamental skill for medical students and practicing medical professionals. Recognizing ECG pathologies promptly allows for quick intervention, especially in acute settings where urgent care is needed. However, many medical students find ECG interpretation and understanding of the underlying pathology challenging, with teaching methods varying greatly. This study involved the development of novel animations demonstrating the passage of electrical activity for well-described cardiac pathologies and showcased them alongside the corresponding live ECG traces during a web-based tutorial for final-year medical students. We aimed to assess whether the animations improved medical students' confidence in visualizing cardiac electrical activity and ECG interpretation, compared to standard ECG teaching methods. Final-year medical students at Imperial College London attended a web-based tutorial demonstrating the 7 animations depicting cardiac electrical activity and the corresponding ECG trace. Another tutorial without the animations was held to act as a control. Students completed a questionnaire assessing their confidence in interpreting ECGs and visualizing cardiovascular electrical transmission before and after the tutorial. Intervention-arm participants were also invited to a web-based focus group to explore their experiences of past ECG teaching and the tutorial, particularly on aspects they found helpful and what could be further improved in the tutorial and animations. Wilcoxon signed-rank tests and Mann-Whitney U tests were used to assess the statistical significance of any changes in confidence. Focus group transcripts were analyzed using inductive thematic analysis. Overall, 19 students attended the intervention arm, with 15 (79%) completing both the pre- and posttutorial questionnaires and 15 (79%) participating in focus groups, whereas 14 students attended the control arm, with 13 (93%) completing both questionnaires. Median confidence in interpreting ECGs in the intervention arm increased after the tutorial (2, IQR 1.5-3.0 vs 3, IQR 3-4.5; P<.001). Improvement was seen in both confidence in reviewing or diagnosing cardiac rhythms and the visualization of cardiac electrical activity. However, there was no significant difference between the intervention and control arms, for all pathologies (all P>.05). The main themes from the thematic analysis were that ECGs are a complex topic and past ECG teaching has focused on memorizing traces; the visualizations enabled deeper understanding of cardiac pathology; and ECG learning requires repetition, and clinical links remain essential. This study highlights the value of providing concise explanations of the meaning and pathophysiology behind ECG traces, both visually and verbally. ECG teaching that incorporates relevant pathophysiology, alongside vignettes with discussions regarding investigations and management options, is likely more helpful to students than practices based solely on pattern recognition. Although the animations supported student learning, the key element was the tutor's explanations. These animations may be more helpful as a supplement to teaching, for instance, as open-access videos.

Evaluation of a digital stethoscope for electrocardiographic recording in donkeys: Preliminary results

The digital stethoscope (DS) is a cost-effective single-lead digital stethoscope that allows simultaneous electrocardiographic (ECG) and phonocardiographic recordings on a smartphone. Despite its application in small animals and horses, there are currently no studies on its use in donkeys. The aim of this study was to evaluate the use of a new smartphone-based DS device in recording ECG tracings in donkeys. Standard base-apex lead ECG (sECG) and single-lead DS ECG (dECG) were simultaneously recorded for at least 30 s. Both sECG and dECG tracings were analysed by the same operator, recording heart rate, ECG waves and intervals, and the presence and duration of artefacts. Thirty-seven donkeys were included. The dECG tracings were interpretable in all the animals (100 %). The results showed perfect agreement between the sECG and dECG data for the classification of heart rhythm and P-wave polarity. Strong agreement was found in the evaluation of heart rate calculated manually and automatically by the smartphone app, QRS complex polarity, T wave polarity, and duration of the PR interval. However, no agreement was found in the evaluation of P wave duration, QRS complex duration and amplitude, and T wave duration and amplitude. In conclusion, although this is only a preliminary study, the DS was a valid, practical, and easy to use electrocardiographic tool for recording good-quality ECG tracings to assess the ECGs of donkeys in the field.

Qualitative and Quantitative Electrocardiogram Parameters in a Large Cohort of Children with Duchenne Muscle Dystrophy in Comparison with Age-Matched Healthy Subjects: A Study from South India.

Electrocardiography (ECG) remains an excellent screening tool for cardiac assessment in Duchenne muscular dystrophy (DMD), but an accurate interpretation requires comparison with age-matched healthy controls. We examined various ECG parameters in children with DMD, in comparison with age-matched controls. Standard 12-lead ECG tracings of serial patients were screened for quality and selected. Controls were healthy, age-matched school-going children. Both quantitative and qualitative ECG parameters were analyzed. After screening, ECGs from 252 patients with DMD (8.32 ± 3.12 years, 2-21 years) and ECGs from 151 age-matched healthy controls (9.72 ± 2.23, 4-19 years) were included. A significantly higher heart rate, shorter R-R interval, and taller R wave in V1 were seen across all age group of DMD in comparison to controls, with the difference increasing with age. While QT prolongation was seen in all age groups of DMD, QTc prolongation was seen only at 10 years or more. Incomplete right bundle branch block (RBBB) and pathological Q waves in inferolateral leads were exclusive in DMD, with the latter declining with age. Evidence for left ventricular (LV) pathology, such as tall R in V5/V6, increase in SV1 + RV6 height, and QRS complex duration, were seen only in the age group of 10 years or more. Stratification based on age and comparison with age-matched healthy subjects showed that several ECG parameters were influenced by age, and it also identified age-dependent evidence for LV pathology and QTc prolongation in DMD.

A cross-sectional study of the clinical profile of children admitted with yellow phosphorous poisoning in a tertiary care hospital

Background: Yellow phosphorous (YP) is a protoplasmic poison that is mainly used as a rodenticide. Aims and Objectives: The aim of the study is to describe the clinical profile of YP poisoning in children in a tertiary care hospital. Materials and Methods: This is a cross-sectional study done in a tertiary care hospital in Tamil Nadu. A convenience sample of all the cases admitted during the year 2022 was done. Demographic and clinical data were collected and analyzed. Results: The male: female ratio was 1.16:1 (n=13). The mean age of the children was 4.0769±1.373 years. About 84.61% of the children reported to the hospital within 6 h. On admission, fever (30.76%), vomiting (30.76%), abdominal pain (30.76%), bleeding (15.38%), and altered sensorium (15.38%) were the common symptoms. All the children ingested YP accidentally. Leukocytosis was observed in about 30.76%. The mean peak serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were 516.9231±685.976 IU/L and 161.9231±215.107 IU/L, respectively. There were no alterations in the Electrocardiographic tracings, levels of serum electrolytes, blood glucose, and serum creatinine in children with YP poisoning. Significant differences were observed between children who survived and children who died in the levels of mean peak AST, mean peak ALT, INR, and in the presence of encephalopathy and bleeding manifestations. Conclusion: YP is an uncommon but lethal poison in children. Creating awareness among parents about the dangers of YP and nationwide prohibition of the sale of YP will be an important step in eliminating deaths in children who are accidental victims.

Dysautonomia in ‘long COVID’: Case report

Background: The reason for autonomic dysfunction in COVID-19 is yet to get clear, though we tend to notice a few dysautonomia cases during post-COVID-19 manifested most commonly in the form of postural orthostatic tachycardia syndrome (POTS). Case Presentation: A case of autonomic dysregulation is presented in a COVID-19 patient as a post-COVID-19 sequelae. On doing an active stand test and two basic autonomic function tests, dysautonomia was diagnosed in the patient, after going through all routine investigations for six months. Cardiac parasympathetic integrity was assessed by measuring the heart rate response to standing by continuous electrocardiographic tracing. The management of these patients is usually conservative. Conclusion: Family physicians must be aware of such cases in future for early diagnosis and management of the patients.

Right fascicular blocks: A case series and a comprehensive electrocardiographic analysis

The main trunk of the right bundle branch divides into an anterior, middle (lateral) and posterior fascicle. This article describes the right anterior and posterior fascicular block. They present a diagnostic challenge and are often overlooked during diagnostic processes. The studied patients were young adults whose electrocardiographic tracings were registered at the Mexican Faculty of Medicine of La Salle University. The presence of delayed R-peak time in aVR and V1, along with the described ventricular complex morphologies, and a right or left deviation of the cardiac axis exceeding +60°, may be suggestive of right fascicular blocks.

Abstract P3144: A Deep Neural Network Algorithm For Accurate Detection Of Brugada Syndrome Features In Electrocardiograms

Brugada Syndrome (BrS) is a rare but potentially fatal cardiac condition that is difficult to diagnose due to the elusive nature of its characteristic ECG pattern. The diagnosis of BrS requires identification of a specific electrocardiographic (ECG) pattern, which often appears only upon administration of sodium-channel blockers. Here, we present a deep neural network (DNN) algorithm that accurately detects BrS features in ECGs without the need for a drug challenge. We trained and validated the DNN on two independent cohorts of patients who were enrolled in electrophysiological studies for BrS diagnosis. The internal prospective validation cohort included 370 subjects, and the multicenter external validation cohort included 110 subjects from three other medical institutions in Italy. All subjects who did not present a spontaneous type 1 ECG underwent an ajmaline drug challenge to aid in confirming a BrS diagnosis. We found that the DNN approach classified ECGs for BrS with a sensitivity of 79.6%, specificity of 93.6%, accuracy of 88.4%, and area under the curve (AUC) of 0.934±0.027 in the validation cohorts. The DNN model also detected BrS with 100% accuracy in all cases in which a patient presented the spontaneous type 1 pattern. Our results demonstrate that a multivariate machine-learning algorithm can accurately detect the features of BrS in a conventional ECG without the challenge of a sodium-channel blocker. The computer-assisted analysis of digital ECG traces from current electrocardiographs might help physicians recognize patients affected by this disease. In conclusion, we have developed an advanced deep learning algorithm that can accurately detect BrS features in ECGs. Our results demonstrate that the DNN approach could be an effective tool to improve the diagnosis of BrS and potentially prevent sudden cardiac death in affected individuals.

Abnormal transmitral flow: what is the rhythm?

Echocardiography was performed on 78-year-old woman for the follow-up of moderate mitral valve regurgitation (MR). A single-lead electrocardiographic (ECG) tracing showed bradycardia with irregular heart rhythm between 46 and 53 beats per minute. The echocardiographic image of pulsed wave Doppler at mitral inflow is displayed in Panel. There was a progressive shortening of the interval between E (early) and A (late) diastolic filling waves, followed by an absent A wave. A gradual shortening of the A-A wave interval was also noted. The interval between A wave and MR envelope remains constant. This typical pattern is consistent with Wenckebach phenomenon in sinoatrial (SA) exit block. SA exit block is due to failed propagation of pacemaker impulses beyond the SA node. In Type I second-degree SA block (Wenckebach), there is a progressive delay in the conduction from the SA node to the atrium until one impulse is completely blocked, leading to intermittent failure of atrial depolarization and ensuing absence of A wave in the Doppler inflow pattern. Moreover, the A-A wave interval is gradually decreased (i.e. the atrial rate accelerates) as the increment in the conduction delay from the SA node to the atrium becomes progressively smaller.

Yield of diagnosis and risk of stroke with screening strategies for atrial fibrillation: a comprehensive review of current evidence.

Atrial fibrillation (AF) is the most prevalent arrhythmia worldwide. The presence of AF is associated with increased risk of systemic thromboembolism, but with the uptake of oral anticoagulant (OAC) and implementation of a holistic and integrated care management, this risk is substantially reduced. The diagnosis of AF requires a 30-s-long electrocardiographic (ECG) trace, irrespective of the presence of symptoms, which may represent the main indication for an ECG tracing. However, almost half patients are asymptomatic at the time of incidental AF diagnosis, with similar risk of stroke of those with clinical AF. This has led to a crucial role of screening for AF, to increase the diagnosis of population at risk of clinical events. The aim of this review is to give a comprehensive overview about the epidemiology of asymptomatic AF, the different screening technologies, the yield of diagnosis in asymptomatic population, and the benefit derived from screening in terms of reduction of clinical adverse events, such as stroke, cardiovascular, and all-cause death. We aim to underline the importance of implementing AF screening programmes and reporting about the debate between scientific societies' clinical guidelines recommendations and the concerns expressed by the regulatory authorities, which still do not recommend population-wide screening. This review summarizes data on the ongoing trials specifically designed to investigate the benefit of screening in terms of risk of adverse events which will further elucidate the importance of screening in reducing risk of outcomes and influence and inform clinical practice in the next future.

The electrocardiographic changes generated by centrally applied arachidonic acid in rats

Arachidonic acid (AA) and its metabolites have multifunctional regulatory effects on the central nervous system. Our previous reports disclosed that centrally injected AA organized the cardiovascular system in normal or hypotensive conditions by regulating the central and peripheral mechanism. In the light of the knowledge of the potential cardiovascular effects of AA, the current study aimed to investigate the effects of intracerebroventricular (ICV) injected AA on the electrocardiography (ECG) of the anesthetized rats. The adult Sprague Dawley rats were anesthetized with ketamine and xylazine mixture (50 mg/kg and 20 mg/kg; i.m., respectively). Under the anesthesia, the guide cannula was inserted into the left lateral ventricle of the rats. The ECG traces obtained from the lead II were written by placing electrodes on the limbs of the rats. Centrally injected AA (150 μg; ICV) statistically significantly (p&amp;lt;0.05) caused to the lengthening of the ECG waves and intervals, resulting in a decrease in the heart rate of the rats without changing the ECG waveforms, the amplitude, and also the isoelectric line. The obtained results clearly show that centrally injection of AA caused the deceleration in the heart electrical activity. The deceleration in the electrical activity of the heart caused to show bradycardia in the rats by extending the duration of the ECG waves and intervals.

48 A CASE OF RECURRENT VENTRICULAR TACHYCARDIA IN A PATIENT WITH GRANULOMATOSIS WITH POLYANGIITIS WITH A CHALLEGING IDENTIFICATION OF ARRHYTHMIC SUBSTRATE: THE ROLE OF MULTIMODALITY IMAGING

Abstract Background Granulomatosis with polyangiitis (GPA), previously known as Wegener's granulomatosis, is a pulmonary-renal syndrome affecting small and medium sized blood vessels. Cardiac involvement is rare and generally includes pericarditis, myocarditis and aortic valve disease. We report a case of recurrent sustained ventricular tachycardia (VTs) in a patient with GPA. Case summary A 67-year-old man with past medical history of GPA presented palpitations, chest pain and episodes of presyncope. Electrocardiographic tracing upon ED presentation showed sustained monomorphic VT (fig.1) associated with global hypokinesia of the left ventricle and moderately reduced ejection fraction at transthoracic echocardiography (TTE). As the patient was hemodynamically stable, prompt treatment with amiodarone was adopted with successful recovery of sinus rhythm. After a few hours, TTE was normal. However, as troponin I was markedly elevated, coronarography was performed and coronary disease was ruled out. Contrast-enhanced cardiac magnetic resonance imaging (ceCMR) revealed late gadolinium enhancement in basal anteroseptal mid wall, suggestive of myocardial scar tissue with non-ischemic pattern. No sustained ventricular arrhythmias were induced during electrophysiological study (EPS), even with an aggressive protocol (up to 4 extra stimuli and ventricular refractoriness) and electro-anatomical mapping of both ventricles failed to show any arrhythmic substrate. An implantable cardioverter defibrillator (ICD) was then implanted. After 4 months the patient was admitted for multiple episodes of sustained VT (with cycle length in the ICD monitoring window) refractory to drugs and three external defibrillations. Repeated EPS failed to induce sustained arrhythmias. High-density electroanatomical mapping of the right ventricle, however, showed fragmented potentials in the mid-posterior septal wall (fig. 2-3). After myocardial biopsy of the region of interest, radiofrequency catheter ablation of the area was performed with regression of the potentials. The results of endomyocardial biopsy demonstrated fibrosis. At 5 months of follow-up, the patient didn't relapse. Discussion Multimodality imaging is of paramount importance in identifying arrhythmogenic substrate and in characterizing the specific anatomical–functional components of VT circuits. In our patient high-density electroanatomical mapping was able to identify fragmented potentials and define the ablation target area, despite the mismatch with ceCMR.

Vectocardiographic analysis of right ventricular electrical conduction delay

Introduction: The electrocardiographic interpretation of end conduction delay (ECD) in the right ventricular branch of the heart has already generated some hypotheses that this right branch is not single, as anatomically demonstrated, and can be divided into distinct terminal branches when we analyze tracings through the vectorcardiogram. Methods: There were 227 electrocardiograms selected, with typical characteristics defined as ECD of patients from the electrocardiography service of the Centro Universitário Saúde ABC, of both sexes, in the age range of 18 to 87 years, with varied ethnicities, weight and height, with cardiovascular risk factors or without them. We performed vectorcardiograms in these patients to observe the behavior of the final portion of electrical conduction. Results: Analyzing the vectorcardiographic tracings of patients who presented ECD in electrocardiogram, we confirmed in the recording by the frontal plane, the presence of ECD but recorded in three distinct regions; 103 patients in the right upper quadrant between -120° and -150°, 45 patients in the right lower quadrant between +170° and -170°, and medial, and 79 patients in the right lower quadrant between +110° and + 140°. Conclusion: Electrical depolarization of the heart in the right ventricle in electrocardiographic tracings apparently records typical alterations that we can diagnose as depolarization of a single bundle; but when we performed vectorcardiograms, we recorded three distinct zones of right ventricular depolarization with delay; i.e., three distinct sectors of right ventricle free wall delay, such as type I (upper), type II (lower) and type III (medial).

Cardiovascular Health and Atrial Fibrillation or Flutter: A Cross-Sectional Study from ELSA-Brasil.

The association between ideal cardiovascular health (ICVH) status and atrial fibrillation or flutter (AFF) diagnosis has been less studied compared to other cardiovascular diseases. To analyze the association between AFF diagnosis and ICVH metrics and scores in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). This study analyzed data from 13,141 participants with complete data. Electrocardiographic tracings were coded according to the Minnesota Coding System, in a centralized reading center. ICVH metrics (diet, physical activity, body mass index, smoking, blood pressure, fasting plasma glucose, and total cholesterol) and scores were calculated as proposed by the American Heart Association. Crude and adjusted binary logistic regression models were built to analyze the association of ICVH metrics and scores with AFF diagnosis. Significance level was set at 0.05. The sample had a median age of 55 years and 54.4% were women. In adjusted models, ICVH scores were not significantly associated with prevalent AFF diagnosis (odds ratio [OR]:0.96; 95% confidence interval [95% CI]:0.80-1.16; p=0.70). Ideal blood pressure (OR:0.33; 95% CI:0.15-0.74; p=0.007) and total cholesterol (OR:1.88; 95% CI:1.19-2.98; p=0.007) profiles were significantly associated with AFF diagnosis. No significant associations were identified between global ICVH scores and AFF diagnosis after multivariable adjustment in our analyses, at least partially due to the antagonistic associations of AFF with blood pressure and total cholesterol ICVH metrics. Our results suggest that estimating the prevention of AFF burden using global ICVH scores may not be adequate, and ICVH metrics should be considered in separate.

Reduced coronary flow velocity reserve and blunted heart rate reserve identify a higher risk group in patients with chest pain and negative emergency department evaluation.

To estimate the prognostic value of stress echo (SE) with the assessment of coronary flow velocity reserve (CFVR) and heart rate reserve (HRR) in patients admitted for chest pain with non-diagnostic EKG, negative troponin, and without inducible regional wall motion abnormalities (RWMA). 658 patients (age 67 ± 12years) admitted to our Emergency Department with chest pain, non-diagnostic EKG, and negative serial troponin underwent dipyridamole (0.84mg/kg in 6') SE with simultaneous assessment of RWMA, CFVR in the left anterior descending artery, and HRR as peak/rest heart rate. The outcome measure was all-cause mortality. Of the 658 patients initially enrolled, 20 (3%) showed RWMA during SE and were referred to ischemia-driven revascularization. In the remaining 638, CFVR was abnormal (≤ 2.0) in 148 patients (23%). HRR was abnormal (≤ 1.22 in patients in sinus rhythm, or ≤ 1.17 in patients with permanent atrial fibrillation) in 196 patients (31%). During a follow-up of 7.3 ± 4.3years, 151 (24%) patients died. Survival at 8years was 93% in patients with normal CFVR and HRR, 76% in patients with abnormal CFVR only, 73% in patients with abnormal HRR only, and 38% in those with abnormal CFVR and HRR (p < 0.0001). At multivariable analysis, abnormal CFVR (HR 1.49, 95% CI 1.05-2.10, p = 0.02) and abnormal HRR (HR 2.01, 95% CI 1.43-2.84, p < 0.0001) were independent predictors of survival. In admitted patients with non-ischemic EKG, negative serial troponin, and without RWMA during dipyridamole SE, a reduced CFVR and blunted HRR independently identify a subset with worse survival in the long term. Upper panel: Color and pulsed-wave Doppler with the electrocardiographic lead tracing of Four different response patterns (from left to right): normal CFVR and HRR; normal CFVR, abnormal HRR; abnormal CFVR, normal HRR; abnormal CFVR and HRR. Lower panel: The annualized death rate for each of the four groups with negative SE for RWMA and stratified according to the presence of CFVR and HRR: none, one, or two abnormalities.

Catheter Ablation of Atrial Arrhythmias in Patients Post-Fontan.

Atrial arrhythmias are highly prevalent in the aging Fontan population and contribute importantly to morbidity and mortality. Although the most common arrhythmia is scar-based intra-atrial re-entrant tachycardia, various other arrhythmias may occur, including focal atrial tachycardia, atrioventricular node-dependent tachycardias, and atrial fibrillation. The type and prevalence of atrial arrhythmia is determined, in part, by the underlying congenital defect and variant of Fontan surgery. Although the cumulative incidence of atrial tachyarrhythmias has decreased substantially from the atriopulmonary anastomosis to the more recent total cavopulmonary-connection Fontan, the burden of atrial arrhythmias remains substantial. Management is often multifaceted and can include anticoagulation, anti-arrhythmic drug therapy, pacing, and cardioversion. Catheter ablation plays a key role in control of arrhythmia. Risks and benefits must be carefully weighed. Among the important considerations are the clinical burden of arrhythmia, ventricular function, hemodynamic stability in tachycardia, suspected arrhythmia mechanisms, risks associated with anaesthesia, venous access, approaches to reaching the pulmonary venous atrium, and accompanying comorbidities. Careful review of surgical notes, electrocardiographic tracings, and advanced imaging is paramount, with particular attention to anatomic abnormalities such as venous obstructions and displaced conduction systems. Despite numerous challenges, ablation of atrial arrhythmias is effective in improving clinical status. Nevertheless, onset of new arrhythmias is common during long-term follow-up. Advanced technologies, such as high-density mapping catheters and remote magnetic guided ablation, carry the potential to further improve outcomes. Fontan patients with atrial arrhythmias should be referred to centres with dedicated expertise in congenital heart disease including catheter ablation, anaesthesia support, and advanced imaging.

Cardiac responses in Crassostrea gasar: An experimental approach of how the tidal cycle influences the heart function of the mangrove oyster

Cardiac physiological studies in oysters are scarce and these kinds of responses can be key issues for understanding behavioral and baseline adaptive responses. In this study we characterized the electrocardiogram (ECG) tracing patterns, wave intervals (RR; QT), and complex duration (QRS) of Crassostrea gasar during immersion followed by air exposure, simulating what occurs in a tide cycle. Initially, the ECG was analyzed in the oysters under immersion for 30 min to evaluate the basal recordings (immersion exposure condition). Then, the same animals were removed from the water and the ECG was analyzed for another 30 min to assess cardiac activity under air exposure (air exposure condition). For this, a technique of cardiac recordings was developed, allowing us to analyze, beyond ECG, other cardiac parameters such as the heart rate (HR) in beats per minute, the spectral power of HR, and the amplitude. The basal cardiac parameters analyzed in oysters in the immerse condition clearly show the waves and intervals (R-R: 11.03 ± 0.63 s, P-Q: 2.09 ± 0.06 s), with a normal and regular electrocardiographic tracing and sinus rhythm without alterations. When in the air exposure condition, oysters maintained the ECG tracing of sinus rhythm, but with changes in intervals and a prolonged isoelectric period. Moreover, in this condition, oysters presented a biphasic response: initially (phase I), heart rate increased (9.83 ± 0.98 BPM), and consequently the R-R and P-Q intervals decreased (5.86 ± 2.01 s e 1.91 ± 0.13 s, respectively); in phase II, heart rate (3.68 ± 0.82 BPM) and spectral power (21.26 ± 5.44 mV2/Hz x 10−3) decreased and consequently, the R-R interval increased (14.83 ± 2.92 s). But, the P-Q interval remained (2.45 ± 0.65 s) in phase II. The QRS complex of oysters in both phases decreased (Phase I: 0.57 ± 0.13 s; Phase II: 0.62 ± 0.05 s) compared to the immersion exposure condition (0.79 ± 0.09 s). We conclude that air exposure affected cardiac function in C. gasar leading to arrhythmia in response to the beginning of air exposure, as a means of maintaining oxygen supply, followed by bradycardia to decrease metabolism as a survival strategy. The basal responses of the mangrove oyster in the physiological modulation against the environmental factors of the tidal regime provide information about the species for possible application as model organisms in studies of toxicological evaluation of chemical products and in conservation and sustainability studies.

Comparison of 2 Smart Watch Algorithms for Detection of Atrial Fibrillation and the Benefit of Clinician Interpretation: SMART WARS Study.

Smart watches and wearable technology capable of heart rhythm assessment have increased in use in the general population. The Apple Watch Series 4 (AW4) and KardiaBand (KB) are devices capable of obtaining single-lead electrocardiographic recordings, presenting a novel opportunity for the detection of paroxysmal arrhythmias. The aim of this study was to assess the diagnostic utility of the AW4 and KB in an elderly outpatient population. Consecutive recordings were taken from patients attending cardiology outpatient clinic from the AW4 and KB concurrently with 12-lead electrocardiography. Automated diagnoses and blinded single-lead electrocardiographic tracing interpretations by 2 cardiologists were analyzed. Analysis was also conducted to assess the effect of combined device and clinician interpretation. One hundred twenty-five patients were prospectively recruited (mean age 76 ± 7 years, 62% men). The accuracy of the automated rhythm assessment was higher with the KB than the AW4 (74% vs 65%). For the detection of atrial fibrillation, the sensitivity and negative predictive value of the KB were 89% and 97%, respectively, and of the AW4 were 19% and 82%, respectively. Using hybrid automated and clinician interpretation, the overall accuracy of the KB and AW4 was 91% and 87%, respectively. The KB automated algorithm outperformed the AW4 in its accuracy and sensitivity for detecting atrial fibrillation in the outpatient setting. Clinician assessment of the single-lead electrocardiogram improved accuracy. These findings suggest that although these devices' tracings are of sufficient quality, automated diagnosis alone is not sufficient for making clinical decisions about atrial fibrillation diagnosis and management.

Head-to-head comparison of single-lead and six-lead electrocardiography of a wrist-worn device for atrial fibrillation detection

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Funded by the European Regional Development Fund under agreement with the Research Council of Lithuania. Background The increasing numbers of available mHealth tools for electrocardiography (ECG)-based atrial fibrillation (AF) detection promote long-term screening. A common feature of smartwatches is lead-I-like ECG. However, only limited data exists directly comparing the performance of single-lead and six-lead wearable-recorded ECGs. Purpose To compare the accuracy of single-lead and six-lead ECGs of the same wrist-worn device for AF detection. Methods We included patients with AF which represent the main group for testing the diagnostic ability of wearable. In addition, authors selected control groups of stable sinus rhythm (SR) and SR with frequent premature contractions. Cardiac rhythm was monitored using an investigational wrist-worn device which provides six-lead ECG, similar to standard limb leads. To display a single-lead wearable-recorded ECGs, the same six-lead ECG tracings were trimmed to a width of lead-I-like ECGs. A validated Holter ECG device constituted a gold standard test for rhythm verification. Two independent diagnosis-blinded cardiologists evaluated reference, six-lead and single-lead ECGs as "AF", "SR", or "Inconclusive". A third cardiologist evaluated ECGs only in cases of physician disagreement. Results A total of 344 adult patients were enrolled in this study including AF group (121 patients) and control group of SR with or without frequent premature contractions (223 patients). Patients with missing (11/420; 2.62%) or insufficient quality (43/420; 10.24%) of wearable-recorded ECGs were excluded. AF detection based on single-lead and six-lead ECGs yielded sensitivity of 95.73% (95% CI 90.31–98.6%) and 99.16% (95% CI 95.41–99.98%), respectively. Specificity was 100% (95% CI 96.19–100%) for both single-lead and six-lead ECGs when differentiating between AF and stable SR. If patients with frequent premature beats were included in the control group, the specificity of single-lead and six-lead ECGs dropped to 95.81% (95% CI 92.31–98.07%) and 99.1% (95% CI 96.78–99.89%), respectively. False positive cases were more common for single-lead ECG (9/332) compared to six-lead ECG (2/341) (P=0.02). There was a strong association between reference ECGs and wearable-recorded ECGs (P&amp;lt;0.001): Cramer‘s V 0.91, (95% CI 0.82–1.0) for single-lead ECG and 0.98 (95% CI 0.89–1.0) for six-lead ECG. After including a control group of frequent premature contractions, single-lead ECG (12/344) was more frequently labelled "Inconclusive" than six-lead ECG (3/344) (P=0.01). Inter-rater agreement, measured as Cohen’s kappa, indicated great concordance in both methods but was higher for six-lead ECG (0.945, P&amp;lt;0.001) than single-lead ECG (0.887, P&amp;lt;0.001). Conclusions Six-lead ECG of a wearable device demonstrated higher diagnostic accuracy of AF detection than single-lead ECG when controlled by patients with frequent premature contractions. The performance of both methods was equivalent when controlled by patients with stable SR.

P408 CERTIFICATION FOR COMPETITIVE SPORTS ACTIVITY IN A TEENAGER WITH WPW BY VIA INTRAHYSSIAN ACCESSORY PATHWAY

Abstract The case of a 12–year–old male, height 160 cm, weight 46 kg, who practices water polo at a competitive level is reported. Negative family history of cardiovascular pathologies, general and cardiovascular physical examination within the limits of normality. On the electrocardiographic trace (ECG) presence of delta wave from ventricular pre–excitation from intrahyssian accessory pathway (Fig. 1). Echocardiography + color Doppler was normal. The subject underwent a cardiopulmonary stress test with an incremental ramp protocol and steps of 20 watts / min. Shutdown at 190 watts for muscle exhaustion with peak oxygen consumption (VO2) = 43.9 mL / Kg / min, Heart rate = 197 beats / minute, BP = 210/70 mmHg, VE / VCO2 slope = 27.6. Normal course of the cronotropic and pressure curve. The ventricular pre–excitation delta wave persisted for the entire duration of the test and in recovery (Fig. 2, Fig. 3). Secondary disturbances of ventricular repolarization characterized by ST segment sub–leveling and negative T wave appeared at high load and persisted in the first minutes of recovery, delta VO2 / delta WR = 12. Given the non–disappearance of the delta wave from ventricular pre–excitation during the maximal stress test, the subject was sent to an electrophysiological study and subsequent ablation of the accessory pathway. The electrophysiological study was negative for inducibility of atrial fibrillation (AF) and ventricular arrhythmias. Safe ablation was impossible given the intrahyssian position of the accessory pathway. Considering the negativity of the electrophysiological study due to non inducibility of supraventricular and ventricular arrhythmias, eligibility for competitive sports was granted.