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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...

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.

Conduction System of the Heart

Conduction System of the Heart

Autorhythmicity is a term that refers to the heart's inherent ability to generate electrical signals and instigate muscle contractions. This self-regulating conduction system within the heart consists of two key components: the pacemaker cells and specialized conducting cells.
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...

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

Electrophysiology of Normal Cardiac Rhythm

Electrophysiology of Normal Cardiac Rhythm

The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase...

Electrocardiogram Fundamentals

Electrocardiogram Fundamentals

Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin...

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Related Experiment Video

Updated: Jun 25, 2025

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

Published on: December 11, 2017

Infra-Hisian Conduction Disturbance and Alternating Left Anterior/Posterior Fascicular Block.

Anne-Sophie Lacharite-Roberge¹, Gregory M Petersen², Kavisha Patel¹

¹Section of Electrophysiology, Division of Cardiology, Department of Medicine, University of California-San Diego, La Jolla, California, USA.

JACC. Case Reports

|May 23, 2024

Summary

This case study details alternating fascicular block, a rare heart rhythm condition. Electrophysiological study confirmed infra-Hisian disease, leading to pacemaker implantation for patient safety.

Keywords:

cardiac pacemaker electrocardiogram electrophysiology

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Last Updated: Jun 25, 2025

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

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Published on: July 29, 2011

Area of Science:

Cardiology
Electrophysiology
Cardiac Electrophysiology

Background:

Alternating bundle branch blocks indicate significant conduction system disease.
Fascicular blocks, particularly alternating types, are uncommon and may signal underlying cardiac pathology.

Observation:

The patient presented with an unusual pattern of alternating left anterior and left posterior fascicular block.
This specific presentation raised concerns due to its association with potential progression to complete atrioventricular block.

Findings:

Electrophysiological study was conducted to assess the severity of the conduction abnormality.
Results were consistent with infra-Hisian disease, indicating a block below the His bundle in the cardiac conduction system.

Implications:

Infra-Hisian disease necessitates intervention to prevent complete heart block.
Pacemaker implantation was performed, establishing a treatment strategy for this rare fascicular block presentation.