Related Experiment Video
Updated: Jul 28, 2026
14:39
Isolation and Functional Characterization of Human Ventricular Cardiomyocytes from Fresh Surgical Samples
Published on: April 21, 2014
Beat-to-beat repolarization variability in ventricular myocytes and its suppression by electrical coupling
M Zaniboni1, A E Pollard, L Yang
1Department of Evolutive and Functional Biology, University of Parma, Parma, Italy 43100.
Summary
Beat-to-beat action potential duration (APD) variability in heart cells is influenced by ion channel behavior. Electrical coupling between myocytes reduces this variability, preventing arrhythmias.
Area of Science:
- Cardiac Electrophysiology
- Computational Biology
- Molecular Cardiology
Background:
- Single ventricular myocytes display beat-to-beat variations in action potential duration (APD) under constant pacing and temperature.
- Understanding the mechanisms of APD variability is crucial for comprehending cardiac rhythm regulation.
Purpose of the Study:
- To quantify beat-to-beat APD variability in single myocytes.
- To investigate the underlying mechanisms of APD variability, including ion channel function and electrotonic interactions.
- To determine the effect of electrotonic coupling on APD variability and arrhythmogenesis.
Main Methods:
- Action potential duration at 90% repolarization (APD90) variability was measured using the coefficient of variability (CV).
- Pharmacological agents like tetrodotoxin (TTX) and EGTA were used to probe ion channel contributions.
- The rapid delayed rectifier potassium current (IKr) was inhibited using L-691,121.
- Electrical coupling between myocytes was simulated using varying junctional resistance (Rj).
Main Results:
- APD90 variability (CV) in normal solution was 2.3 ± 0.9%.
- Extracellular TTX and intracellular EGTA significantly reduced CV by 44% and 26%, respectively, indicating roles for sodium and calcium channels.
- Inhibition of IKr with L-691,121 increased CV by 300%.
- Electrical coupling (Rj = 100 MΩ) reduced CV by 35% and completely abolished early afterdepolarization (EAD) formation in coupled cells.
Conclusions:
- Beat-to-beat APD variability is likely driven by the stochastic behavior of ion channels.
- Electrotonic interactions between myocytes play a significant role in limiting temporal dispersion of refractoriness.
- Reduced APD variability through electrical coupling may serve as a protective mechanism against cardiac arrhythmias.
More Related Videos
06:40Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System
Published on: May 22, 2018
09:35Preclinical Cardiac Electrophysiology Assessment by Dual Voltage and Calcium Optical Mapping of Human Organotypic Cardiac Slices
Published on: June 16, 2020
Related Concept Videos
01:13The Cardiac Cycle
The heart beats rhythmically in a sequence called the cardiac cycle—a rapid coordination of contraction (systole) and relaxation (diastole).
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...
01:19Electrophysiology 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...
01:28Mechanism 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.
01:25Correlation 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...
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...
01:29Disturbances 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...
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
01:30Cardiac 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
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