Related Experiment Video
Updated: Jan 12, 2026
09:36
Dual-Dye Optical Mapping of Hearts from RyR2R2474S Knock-In Mice of Catecholaminergic Polymorphic Ventricular Tachycardia
Published on: December 22, 2023
1.7K
APD restitution controls arrhythmia emergence in cardiac tissue with RyR2 dysfunction
D'Artagnan Greene1, Yohannes Shiferaw1
1Department of Physics and Astronomy, California State University, Northridge, CA, USA.
The Journal of Physiology
|November 4, 2025
Summary
Molecular defects in cardiac RyR2 channels can cause arrhythmias by altering calcium release. Computational models reveal two distinct cellular mechanisms, dependent on subcellular structure, that prolong action potentials and trigger afterdepolarizations, leading to synchronized tissue events and conduction block.
Area of Science:
- Cardiovascular Physiology
- Computational Biology
- Molecular Cardiology
Background:
- Cardiac arrhythmias are linked to molecular defects in the cardiac ryanodine receptor (RyR2).
- The precise mechanisms connecting RyR2 dysfunction to tissue-level electrical disturbances remain unclear.
- Understanding these links is crucial for developing targeted arrhythmia therapies.
Purpose of the Study:
- To investigate the link between RyR2 molecular defects and cardiac arrhythmias.
- To develop a multiscale computational model integrating RyR2 gating and cardiac electrical propagation.
- To elucidate the cellular and tissue-level mechanisms underlying RyR2-associated arrhythmias.
Main Methods:
- Developed a multiscale computational model of cardiac tissue.
- Integrated RyR2 gating dynamics with electrical propagation.
- Simulated calcium release and its impact on action potential duration (APD) and intracellular calcium handling.
- Analyzed the role of subcellular structure (t-tubules) in arrhythmogenesis.
- Investigated the effect of APD restitution slope on synchrony of cellular events in tissue.
Main Results:
- Increased RyR2 open probability enhances calcium release, triggering arrhythmogenic mechanisms dependent on subcellular structure.
- In cells with dense t-tubules, leaky RyR2s amplify calcium spark recruitment, prolonging APD and causing early afterdepolarizations.
- In cells lacking t-tubules, leaky RyR2s initiate regenerative calcium waves, also prolonging APD and causing early afterdepolarizations.
- Synchronization of cellular calcium disturbances in tissue depends on the APD restitution slope; slopes > 1 lead to alternans, conduction block, and arrhythmia.
- APD restitution slopes < 1 prevent synchronization and have no effect on tissue electrical activity.
Conclusions:
- RyR2 dysfunction can lead to arrhythmias through distinct cellular calcium handling abnormalities based on subcellular structure.
- The slope of the APD restitution curve is a critical determinant of whether cellular events synchronize to produce organ-level arrhythmias.
- This study provides a mechanistic link between RyR2 molecular defects and the development of cardiac arrhythmias at the organ scale.
Related Concept Videos
01:29Disturbances in Heart Rhythm
2.5K
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...
2.5K
01:28Mechanism of Cardiac Arrhythmias
1.6K
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.
1.6K
01:25Dysrhythmias VI: Management of Dysrhythmias
424
Dysrhythmia management involves a multifaceted approach, incorporating pharmacological treatments, medical procedures, surgical interventions, lifestyle modifications, and patient education.Pharmacological ManagementAntiarrhythmic Drugs:Class I (Sodium Channel Blockers): This class includes quinidine and procainamide, which reduce the speed of impulse conduction in the heart, stabilize the cardiac membrane, and control arrhythmias. Quinidine and procainamide are Class IA agents that prolong the...
424
01:19Electrophysiology of Normal Cardiac Rhythm
8.7K
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...
8.7K
01:18Dysrhythmias IV: Characteristics of Bradyarrhythmias
487
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...
487
01:24Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers
1.4K
Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which...
1.4K