During a normal lifetime, the heart may beat over 2 billion times, but the mechanisms by which the heart beats are initiated remain a subject of intense investigation. Since the discovery of a pacemaker current (I(f)) in 1978, multiple studies have shown that rhythmic changes in membrane voltage (the "membrane voltage clock") underlie the mechanisms of automaticity. The I(f) is a depolarization current activated during hyperpolarization. Therefore, when the cardiac cells recover, the I(f) is activated and slowly depolarizes the cell membrane, leading to the onset of action potential. Recent studies, however, suggest that increased intracellular Ca (Ca(i)) induced by spontaneous rhythmic sarcoplasmic reticulum Ca release (the "calcium clock") is also jointly responsible for the initiation of the heart beat. Elevated Ca(i) activates another ionic current (the sodium-calcium exchanger current or I(NCX)), leading to spontaneous phase 4 depolarization. Under normal conditions, both clocks are needed to initiate the heart beat. Malfunction of the clocks is associated with sinus node dysfunction in heart failure and atrial fibrillation. More studies are needed to determine how both clocks work together to initiate heart beat under normal and disease conditions.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1253/circj.cj-09-0712 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
A deep learning modular ECG approach for cardiologist assisted adjudication of atrial fibrillation and atrial flutter episodes.
Heart Rhythm O2
December 2024
Cardiology Department, Bichat Hospital, Paris, France.
Background: Detection of atrial tachyarrhythmias (ATA) on long-term electrocardiogram (ECG) recordings is a prerequisite to reduce ATA-related adverse events. However, the burden of editing massive ECG data is not sustainable. Deep learning (DL) algorithms provide improved performances on resting ECG databases.
View Article and Find Full Text PDFPsychological induction of interoceptive hunger cues and their effect on food desire.
Appetite
January 2025
School of Psychology, Macquarie University, Sydney, NSW, 2109, Australia.
Certain interoceptive hunger cues are caused by gut physiology. These interoceptive cues may have psychological consequences, namely an ability to enhance the desire to eat, which are independent of their physiological cause. Testing this idea is difficult because the physiological processes are normally linked to any consequence.
View Article and Find Full Text PDFDeep Neural Network Analysis of the 12-Lead Electrocardiogram Distinguishes Patients With Congenital Long QT Syndrome From Patients With Acquired QT Prolongation.
Mayo Clin Proc
January 2025
Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN; Department of Molecular Pharmacology and Experimental Therapeutics, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN; Division of Heart Rhythm Services, Department of Cardiovascular Medicine, Windland Smith Rice Genetic Heart Rhythm Clinic, Mayo Clinic, Rochester, MN. Electronic address:
Objective: To test whether an artificial intelligence (AI) deep neural network (DNN)-derived analysis of the 12-lead electrocardiogram (ECG) can distinguish patients with long QT syndrome (LQTS) from those with acquired QT prolongation.
Methods: The study cohort included all patients with genetically confirmed LQTS evaluated in the Windland Smith Rice Genetic Heart Rhythm Clinic and controls from Mayo Clinic's ECG data vault comprising more than 2.5 million patients.
Does early heart rate detection and continuous monitoring have an impact on neonatal resuscitation in newborns with intact cord? - An observational study.
J Family Med Prim Care
December 2024
Department of Neonatology, All India Institute of Medical Science, Jodhpur, Rajasthan, India.
Context: Heart rate (HR) is the most vital parameter to assess hemodynamic transition at birth. ECG is considered a gold standard for HR assessment. New devices with dry electrodes are easy to apply on a wet newborn.
View Article and Find Full Text PDFA Probabilistic Modeling Framework for the Prediction of Spontaneous Premature Beats and Reentry Initiation.
Heart Rhythm
January 2025
Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, USA. Electronic address:
Background: Spontaneously occurring life threatening reentrant arrhythmias result when a propagating premature beat encounters a region with significant dispersion of refractoriness. Although localized structural tissue heterogeneities and prescribed cell functional gradients have been incorporated into computational electrophysiological models, a quantitative framework for the evolution from normal to abnormal behavior that occurs via disease is lacking.
Objective: The purpose of this study was to develop a probabilistic modeling framework that represents the complex interplay of cell function and tissue structure in health and disease which predicts the emergence of premature beats and the initiation of reentry.
Want AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!