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Mechanism of Cardiac Arrhythmias

Mechanism of Cardiac Arrhythmias

Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.

Disturbances in Heart Rhythm

Disturbances in Heart Rhythm

Arrhythmia or dysrhythmia refers to an abnormal heart rhythm caused by a defect in the heart's conduction system. It can cause the heart to beat irregularly, too quickly, or too slowly, leading to symptoms like chest pain, shortness of breath, and fainting. Factors such as stress, caffeine, alcohol, nicotine, cocaine, certain drugs, congenital defects, diseases, and electrolyte abnormalities can trigger arrhythmias.
Arrhythmias are categorized by their speed, rhythm, and origin. A slow...

Cardiac Action Potential

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials

ECG Interpretation of Arrhythmias I: Sinus Arrhythmias

ECG Interpretation of Arrhythmias I: Sinus Arrhythmias

Arrhythmias are disturbances in the heart's rhythm that lead to abnormal heartbeats. These irregularities can originate from different parts of the heart and are classified based on their origin and nature.
Types of Arrhythmias
Sinus Node Arrhythmias
Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism,...

Electrocardiogram

Electrocardiogram

An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...

Correlation between ECG and Cardiac Cycle

Correlation between ECG and Cardiac Cycle

The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...

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Related Experiment Video

Updated: Jun 13, 2025

Analyzing Long-Term Electrocardiography Recordings to Detect Arrhythmias in Mice

Analyzing Long-Term Electrocardiography Recordings to Detect Arrhythmias in Mice

Published on: May 23, 2021

Long-Term Risk of Incident Arrhythmias Associated With Early Repolarization Pattern　- The Atherosclerosis Risk in

Qian He¹, Yi-Jian Liao², Jin-Jie Wang¹

¹Department of Guangdong Cardiovascular Institute, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University.

Circulation Journal : Official Journal of the Japanese Circulation Society

|March 25, 2025

Summary

Early repolarization pattern (ERP) is linked to increased risk of ventricular arrhythmias, bradyarrhythmias, and atrial fibrillation in middle-aged adults. New-onset or persistent ERP significantly elevates arrhythmia incidence.

Keywords:

Atrial fibrillation Bradyarrhythmias Early repolarization Electrocardiography Ventricular arrhythmias

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Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation

Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation

Published on: July 20, 2022

Area of Science:

Cardiology
Electrophysiology
Public Health

Background:

Early repolarization pattern (ERP) is a known risk factor for cardiovascular death.
The association between ERP and various arrhythmias remains underexplored.

Purpose of the Study:

To investigate the relationship between ERP and incident arrhythmias.
To evaluate associations with ventricular arrhythmias, bradyarrhythmias, and atrial fibrillation (AF)/flutter (Afl).

Main Methods:

Analysis of 14,679 middle-aged participants from the Atherosclerosis Risk in Communities cohort over 20 years.
Assessment of baseline, time-varying, and time-updated ERP using Cox models.
Adjustment for potential confounders to estimate hazard ratios (HRs).

Main Results:

Time-updated ERP showed increased HRs for ventricular arrhythmias (1.55), bradyarrhythmias (1.76), and AF (1.25).
New-onset or persistent ERP was associated with higher risks of incident arrhythmias compared to normal ECG.
Anterior leads and J wave amplitude ≥0.2 mV in time-updated ERP correlated with higher arrhythmia incidence.

Conclusions:

Various forms of ERP (time-varying, time-updated, new-onset, persistent) are associated with incident arrhythmias.
Findings highlight ERP as a significant predictor of arrhythmias in a middle-aged, biracial population.