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Related Concept Videos

Mechanism of Cardiac Arrhythmias01:28

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.
Cardiac Action Potential01:30

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 II: Atrial, Junctional and Ventricular Arrhythmias01:25

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...
Disturbances in Heart Rhythm01:29

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...
Electrophysiology of Normal Cardiac Rhythm01:19

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...
Dysrhythmias III: Characteristics of Dysrhythmias01:29

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.

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Related Experiment Video

Updated: Jun 2, 2026

A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts
07:56

A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts

Published on: February 17, 2023

Ventricular ectopy and long-term cardiac function.

Andrew T Kwa1, Zhongmin Li, Ezra A Amsterdam

  • 1Division of Cardiology, University of California, Davis, USA.

Critical Pathways in Cardiology
|May 13, 2011
PubMed
Summary
This summary is machine-generated.

Frequent premature ventricular complexes (PVCs) in patients with normal or mildly reduced systolic function did not significantly impact left ventricular ejection fraction (LVEF) over a mean follow-up of 40 months. This suggests PVC burden may not impair cardiac function in this population.

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Isolation and Functional Characterization of Human Ventricular Cardiomyocytes from Fresh Surgical Samples
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Isolation and Functional Characterization of Human Ventricular Cardiomyocytes from Fresh Surgical Samples

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A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts
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A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts

Published on: February 17, 2023

Isolation and Functional Characterization of Human Ventricular Cardiomyocytes from Fresh Surgical Samples
14:39

Isolation and Functional Characterization of Human Ventricular Cardiomyocytes from Fresh Surgical Samples

Published on: April 21, 2014

Area of Science:

  • Cardiology
  • Electrophysiology
  • Cardiac Imaging

Background:

  • Premature ventricular complexes (PVCs) can be associated with structural heart disease and ventricular arrhythmias.
  • While PVCs can trigger arrhythmias, their long-term impact on cardiac systolic function remains incompletely understood.
  • Previous reports suggest improved cardiac function with PVC reduction, prompting further investigation.

Purpose of the Study:

  • To investigate the association between frequent PVCs and left ventricular systolic function.
  • To determine if a high burden of PVCs impacts left ventricular ejection fraction (LVEF) over long-term follow-up.
  • To analyze the relationship between PVC frequency and changes in LVEF, adjusting for potential confounders.

Main Methods:

  • Retrospective analysis of ambulatory electrocardiographic monitoring data.
  • Inclusion criteria: ≥1000 PVCs/24 hours and 2 echocardiograms >3 months apart.
  • Primary endpoint: Change in LVEF in relation to PVC frequency, with adjustments for covariates.

Main Results:

  • Thirty-seven patients with frequent PVCs (≥1000/24 hours) and baseline normal/mildly reduced LVEF were analyzed.
  • Mean follow-up was 40 months, with a mean PVC frequency of 8559/24 hours.
  • PVC frequency was not significantly associated with changes in LVEF over the follow-up period. Confounders showed no correlation.

Conclusions:

  • High PVC burden over approximately 3 years is not associated with a reduction in LVEF in patients with baseline normal or mildly reduced systolic function.
  • These findings suggest that frequent PVCs may not impair left ventricular systolic function in the absence of significant underlying structural heart disease or severely reduced baseline function.
  • Further research may explore specific patient subgroups or different metrics of cardiac function.