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Related Concept Videos

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...
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
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.
Imbalances in Cardiac Output01:26

Imbalances in Cardiac Output

The heart's primary function is to pump blood throughout the body, maintaining a balance between blood sent out (cardiac output) and blood returning (venous return). If this balance is disrupted, it can result in congestive heart failure (CHF), a severe condition where the heart becomes an inefficient pump, leading to inadequate blood circulation.
CHF can occur due to the failure of either side of the heart. Left-side failure leads to pulmonary congestion—the right side continues to send blood...
Pathophysiology of Cardiac Performance01:29

Pathophysiology of Cardiac Performance

Typical heart performance is influenced by heart rate, rhythm, myocardial contraction, and metabolism or blood flow. The cardiac muscle exhibits distinct electrophysiological features, including pacemaker activity and calcium channel control, which play a vital role in the heart's response to various drugs. The autonomic nervous system, comprising the sympathetic and parasympathetic branches, regulates heart rate. Sympathetic activation increases heart rate, while parasympathetic activation...
Specialized Characteristics of Cardiac Muscles01:27

Specialized Characteristics of Cardiac Muscles

The primary role of cardiac muscles is to propel blood throughout the cardiovascular system. The cardiac muscle cells, or cardiomyocytes, exhibit specialized characteristics that allow them to perform this function.
Cardiac muscle cells are smaller than skeletal muscles, averaging 10–20 mm in diameter and 50–100 mm in length. However, they have large energy demands for continuous contraction and relaxation. This energy is almost exclusively derived from aerobic metabolism of energy reserves in...

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Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations
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Published on: January 8, 2013

Cardiac electrical dynamics: maximizing dynamical heterogeneity.

Robert F Gilmour1, Anna R Gelzer, Niels F Otani

  • 1Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA. rfg2@cornell.edu

Journal of Electrocardiology
|November 13, 2007
PubMed
Summary

Premature heartbeats disrupt normal rhythm, increasing electrical instability and leading to dangerous ventricular tachyarrhythmias. Understanding these electrical changes can improve therapies for sudden cardiac death.

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Area of Science:

  • Cardiac Electrophysiology
  • Computational Biology
  • Translational Medicine

Background:

  • Ventricular tachyarrhythmias are often triggered by premature beats, not constant rapid pacing.
  • Existing theories don't fully explain arrhythmia induction by premature stimuli.

Purpose of the Study:

  • Develop a theory explaining how premature stimuli induce ventricular tachycardia (VT) and fibrillation (VF).
  • Investigate the role of dynamic repolarization heterogeneity and conduction block.

Main Methods:

  • Developed a general theory linking premature stimuli to conduction block.
  • Tested the theory using computer models of cardiac tissue.
  • Validated findings in a canine model of VT and sudden death.

Main Results:

  • Theory predicts conduction block via spatial diastolic interval gradients and amplified repolarization heterogeneity.
  • Computer models showed premature beats increase repolarization dispersion due to dynamic heterogeneity.
  • Animal model results align with theory, showing highest VF induction probability for predicted conduction block sequences.

Conclusions:

  • Premature stimuli can induce VT/VF by creating dynamic repolarization heterogeneity and conduction block.
  • Understanding these mechanisms is crucial for developing targeted antiarrhythmic therapies.
  • Findings may refine drug and electrical therapies for VT and fibrillation.