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Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per minute.

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 heart...

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

Arrhythmia is a condition characterized by an irregular heart rhythm, with ECG changes that differ based on its origin and nature. The types of arrhythmias discussed below include atrial, junctional, and ventricular arrhythmias.Atrial ArrhythmiasPremature Atrial Complexes (PACs): PACs are early atrial beats caused by stress, caffeine, alcohol, electrolyte imbalances, hypoxia, hyperthyroidism, or certain medications (e.g., bronchodilators and decongestants). The ECG shows early P waves with an...

Dysrhythmias IV: Characteristics of Bradyarrhythmias

Dysrhythmias IV: Characteristics of Bradyarrhythmias

Bradyarrhythmias are cardiac rhythm disorders characterized by a slower-than-normal heart rate, typically defined as fewer than 60 beats per minute. Some of which are discussed here:Sinus BradycardiaSinus bradycardia presents a heart rate lower than 60 beats per minute, with a regular rhythm originating from the SA node. The ECG typically shows normal P waves preceding each QRS complex, a normal PR interval (0.12 to 0.20 seconds), and a normal QRS duration (0.06 to 0.10 seconds).First-Degree AV...

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 of...

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.

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Related Experiment Video

Updated: Jun 22, 2026

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Published on: July 29, 2011

Regional frequency variation during human ventricular fibrillation.

K Umapathy¹, S Masse, E Sevaptsidis

¹The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, ON, Canada.

Medical Engineering & Physics

|June 30, 2009

Summary

Regional frequency variations in human ventricular fibrillation (VF) were quantified. Findings suggest that while myocardial substrate plays a role, ion channel and physiological factors are crucial in maintaining VF.

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Last Updated: Jun 22, 2026

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

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Published on: July 29, 2011

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Published on: February 17, 2023

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Published on: April 11, 2025

Area of Science:

Cardiology
Electrophysiology
Medical Imaging

Background:

Ventricular fibrillation (VF) is a life-threatening arrhythmia.
Understanding regional frequency variations in VF is key to developing targeted treatments.
The relationship between VF frequency patterns and myocardial substrate requires further investigation.

Purpose of the Study:

To quantify regional frequency variations during human VF.
To investigate the relationship between these frequency variations and the underlying myocardial substrate.
To explore factors contributing to VF maintenance.

Main Methods:

Studied 35 VF episodes in eight myopathic human hearts.
Acquired simultaneous epicardial and endocardial electrograms using high-density electrode arrays.
Analyzed regional characteristics using dominant frequency (DF) analysis and bipolar voltage mapping.

Main Results:

The left ventricle (LV) exhibited a larger dominant frequency (DF) span compared to the right ventricle (RV).
No significant difference in DF span was observed between the LV freewall (FW) and septum (SE).
Correlation between abnormal myocardium and DF features was only 50%, suggesting other factors are involved.

Conclusions:

Quantifiable regional frequency variations exist during human VF.
While myocardial substrate is a factor, ion channel heterogeneity and time-varying physiological factors significantly influence VF maintenance.
Findings may inform the development of focal treatment strategies for human VF.