Abstract 13292: Comparison of Outcomes Between Pulseless Electrical Activity by Electrocardiography and Pulseless Myocardial Activity by Echocardiography in Out-of-Hospital Cardiac Arrest

Objective: To measure prevalence of discordance between electrical activity recorded by electrocardiography (ECG) and myocardial activity visualized by echocardiography (echo) in patients presenting after cardiac arrest and to compare survival outcomes in cohorts defined by ECG and echo. Methods: This is a secondary analysis of a previously published prospective study at twenty hospitals. Patients presenting after out-of-hospital arrest were included. The cardiac electrical activity was defined by ECG and contemporaneous myocardial activity was defined by bedside echo. Myocardial activity by echo was classified as myocardial asystole- -the absence of myocardial movement, pulseless myocardial activity (PMA)--visible myocardial movement but no pulse, and myocardial fibrillation- -visualized fibrillation. Primary outcome was the prevalence of discordance between electrical activity and myocardial activity. Secondary outcome was survival to hospital discharge. Results: 793 patients and 1943 pauses in CPR were included. 28.6% of CPR pauses demonstrated a difference in electrical activity (ECG) and myocardial activity (echo), 5.0% with asystole (ECG) and PMA (echo), and 22.1% with PEA (ECG) and myocardial asystole (echo). Survival to hospital admission for patients with PMA (echo) was 29.1% (95%CI-23.9-34.9) compared to those with PEA (ECG) (21.4%, 95%CI-17.7-25.6). Twenty-five percent of the 32 pauses in CPR with a shockable rhythm by echo demonstrated a non-shockable rhythm by ECG and were not defibrillated. One of these patients survived, a patient with asystole on ECG and vfib by echo survived because vfib was identified on ECG during a subsequent pause and was defibrillated. Conclusion: Patients in cardiac arrest commonly demonstrate different electrical (ECG) and myocardial activity (echo). Further research is needed to better define cardiac activity during cardiac arrest and to explore outcome between groups defined by electrical and myocardial activity.

ECG Interpretation: Clinical Relevance, Challenges, and Advances

Since its inception, the electrocardiogram (ECG) has been an essential tool in medicine. The ECG is more than a mere tracing of cardiac electrical activity; it can detect and diagnose various pathologies including arrhythmias, pericardial and myocardial disease, electrolyte disturbances, and pulmonary disease. The ECG is a simple, non-invasive, rapid, and cost-effective diagnostic tool in medicine; however, its clinical utility relies on the accuracy of its interpretation. Computer ECG analysis has become so widespread and relied upon that ECG literacy among clinicians is waning. With recent technological advances, the application of artificial intelligence-augmented ECG (AI-ECG) algorithms has demonstrated the potential to risk stratify, diagnose, and even interpret ECGs—all of which can have a tremendous impact on patient care and clinical workflow. In this review, we examine (i) the utility and importance of the ECG in clinical practice, (ii) the accuracy and limitations of current ECG interpretation methods, (iii) existing challenges in ECG education, and (iv) the potential use of AI-ECG algorithms for comprehensive ECG interpretation.

A review of cardiac autonomics: from pathophysiology to therapy

The effective management of cardiovascular diseases requires knowledge of intrinsic and extrinsic innervation of the heart and an understanding of how perturbations of said components affect cardiac function. The innate cardiac conduction system, which begins with cardiac pacemaker cells and terminates with subendocardial Purkinje fibers, is modulated by said systems. The intrinsic component of the cardiac autonomic nervous system, which remains incompletely elucidated, consists of intracardiac ganglia and interconnecting neurons that tightly regulate cardiac electrical activity. Extrinsic components of the autonomic nervous system, such as carotid baroreceptors and renin-angiotensin-aldosterone system, modulate sympathetic input to the heart through the stellate ganglion and parasympathetic input via the vagus nerve. There remains a need for additional therapies to treat conditions, such as advanced heart failure and refractory arrhythmias, and a better understanding of autonomics may be key to their development.

HIV and Antiretroviral Therapy Are Independently Associated with Cardiometabolic Variables and Cardiac Electrical Activity in Adults from the Western Cape Region of South Africa

Cardiovascular-related complications are on the rise in people with HIV/AIDS (PWH); however, the relationship among HIV and antiretroviral therapy (ART)-related parameters, cardiovascular risk, and cardiac electrical activity in PWH remain poorly studied, especially in sub-Saharan African populations. We investigated whether HIV and ART are associated with cardiometabolic and cardiac electrical activity in PWH from Worcester in the Western Cape Province, South Africa. This was a cross-sectional study with HIV-negative (HIV−, n = 24) and HIV-positive on ART (HIV+/ART+, n = 63) participants. We obtained demographic, lifestyle, and medical history data and performed anthropometric, clinical assessments, and blood/urine biochemistry. We performed multiple stepwise linear regression analyses to determine independent associations among HIV, ART, cardiometabolic, and electrocardiographic (ECG) variables. HIV+/ART+ independently associated with a lower body mass index (p = 0.004), elevated gamma-glutamyl transferase levels (β: 0.333 (0.130–0.573); p = 0.002), and elevated alanine aminotransferase levels (β: 0.427 (0.224–0.629); p < 0.001) compared to HIV−. Use of second-line ART was positively associated with high-sensitivity C-reactive protein (p = 0.002). Although ECG parameters did not differ between HIV− and HIV+/ART+, viral load positively associated with p-wave duration (0.306 (0.018–0.594); p = 0.038), and longer HIV duration (≥5 years) with ST-interval (0.270 (0.003–0.537); p = 0.047) after adjusting for confounding factors. Our findings suggest that HIV and ART are associated with mixed effects on this population’s cardiometabolic profile and cardiac electrical activity, underpinning the importance of cardiovascular risk monitoring in PWH.

Diaphragmatic pacemaker induced ventricular tachycardia leading to cardiac arrest: A case report

Background Diaphragmatic pacemakers are used to assist respiration in ventilator-dependent patients. Electromagnetic interference with intrinsic cardiac electrical activity is a theoretical risk but has never been reported in the literature. This case highlights a serious complication of cardiac arrest as a result of diaphragmatic pacing. Case Summary We report a quadriplegic patient with recent diaphragmatic pacemaker implantation who presented with ventricular tachycardia leading to cardiac arrest. Extensive workup was negative for other etiologies for ventricular arrythmias. Reduction of the left-sided diaphragmatic pacemaker voltage resulted in cessation of ventricular ectopy. Discussion Diaphragmatic pacing at high voltages can cause unwanted transmission of impulses to the cardiac myocytes as a rare complication. This should be noted as a possible complication of intramuscular diaphragmatic pacing, and efforts should be taken to circumvent this risk in the future.

Nucleoporin 50 mediates Kcna4 transcription to regulate cardiac electrical activity

Emerging evidence has demonstrated that nucleoporins (Nups) play a pivotal role in cell-type-specific gene regulation, but how they control the expression and activity of ion channel genes in the heart remains unclear. Nup50, which is localized in the nucleus of cardiomyocytes, selectively induced an increase in the transcription and translation of Kcna4. The Kcna4 gene encodes a K+ voltage gated channel of shaker-related subfamily member 4 and is essential for regulating the action potential in cardiac membranes. Using immunofluorescence imaging, luciferase assays, and chromatin immunoprecipitation assays, we identified that the direct binding of the FG-repeat domain within Nup50 to the proximity of the Kcna4 promoter was required to activate the transcription and subsequent translation of Kcna4. Functionally, Nup50 overexpression increased the currents of KCNA4-encoded Ito,s channels, and reverse knockdown of Nup50 resulted in a remarkable decrease in the amplitude of Ito,s currents in cardiomyocytes. Moreover, a positive correlation between Nup50 and Kcna4 mRNA and protein expression was observed in heart tissues subjected to ischemic insults. These findings provide insights into the homeostatic control of cardiac electrophysiology through Nup-mediated regulation.

Sparse Representation for Cardiac Electrical Activity Imaging in Magnetocardiography

Signal sparsity has been widely discussed in communication system, cloud computing, multimedia processing and computational biology. Reconstructing the sparsely distributed current sources of the heart by means of non-invasive magnetocardiography (MCG) measurement and various optimization methods provides a new way to solve the inverse problem of the cardiac magnetic field. The problem of sparse source location of MCG is in the time series of MCG measurement caused by active sparse current source, can the spatiotemporal source be reconstructed accurately and effectively? For the above problem, the scientific contributions of the paper include: (1) A modified focal underdetermined system solver algorithm is proposed for a sparse solution, by combing with dynamic regularization factor and smoothed sparse constraint; (2) Lead field matrix is reduced by prior information of cardiac magnetic field map to reduce under-determination; (3) Spatiotemporal sources are reconstructed for non-invasive cardiac electrical activity imaging. The results of real MCG data demonstrate the effectiveness of this method for cardiac electrical activity imaging. The temporal and spatial changes of the current sources are similar to the depolarization and repolarization process of the ventricle.

Design of a Wireless Single Arm Electrocardiograph System

Electrocardiograms (ECGs) are a method of assessment of cardiac electrical activity. It is the heart’s electrophysiological activity which occurs by the conduction of electrical impulses from the Sinoatrial (SA) node and the Atrioventricular (AV) node across the cardiac muscles and is displayed as a voltage-time graph. Conventionally, they have been acquired using a system of ten surface electrodes placed in different locations throughout the body in a 12-lead system. Single Arm ECG systems, where the ECG rhythm is obtained from only a single part of the body, replace the need for ten different electrodes to detect the heart's activity. Three pre-gelled electrodes are applied in different locations of the left arm to derive the sinus rhythm signal of a subject. An op-amp based hardware instrument has been developed for this purpose with active filters and amplifiers to perform signal conditioning. This paper demonstrates the implementation of a single arm hardware system of small size to improve portability, used as an ECG detection method and the results from various subjects taken at different gain values to improve the view of the signal, while also presenting a method to transmit the data of the signals wirelessly through an Internet-of-things (IoT) platform.