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Related Concept Videos

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...
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...
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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.
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...
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Conduction System of the Heart

Autorhythmicity is a term that refers to the heart's inherent ability to generate electrical signals and instigate muscle contractions. This self-regulating conduction system within the heart consists of two key components: the pacemaker cells and specialized conducting cells.
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
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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.
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Related Experiment Video

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Programmed Electrical Stimulation in Mice
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Pacemaker inhibition by myopotentials associated with motion and exercise.

J Gialafos1, A Maillis, J Kandilas

  • 1Department of Cardiology, University of Athens Medical School, Greece.

European Heart Journal
|August 1, 1987
PubMed
Summary

Specialized exercises reveal skeletal muscle myopotentials causing pacemaker inhibition. The rectus abdominis and pectoralis major muscles were identified as common sources of oversensing, particularly in DDD pacemaker patients.

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Area of Science:

  • Biomedical Engineering
  • Cardiology
  • Electrophysiology

Background:

  • Standard exercise tests are insufficient for diagnosing oversensing issues in pacemaker patients.
  • Skeletal muscle myopotentials can interfere with pacemaker function, leading to inhibition.

Purpose of the Study:

  • To evaluate specific exercises for identifying oversensing problems caused by rectus abdominis (RA) and pectoralis major (PM) muscle myopotentials.
  • To assess the incidence of pacemaker inhibition due to these myopotentials in various pacemaker types.

Main Methods:

  • 252 paced patients underwent specialized exercise testing targeting RA and PM muscles.
  • Pacemaker inhibition was recorded during these exercises across VVI, VVI Activitrax, and DDD pacemaker groups.
  • Specific maneuvers were used to isolate PM (arm pull) and RA (head/trunk raise) exertion.

Main Results:

  • Pacemaker inhibition occurred in 34.9% of VVI, 26.6% of VVI Activitrax, and 77.3% of DDD patients.
  • Both RA and PM muscles individually, or in synergy, could cause pacemaker inhibition.
  • The defined exercises provided reproducible results for eliciting myopotential interference.

Conclusions:

  • The rectus abdominis muscle is a significant source of inhibitory myopotentials, regardless of pacemaker location.
  • Specific, reproducible exercises are effective in diagnosing oversensing problems related to skeletal muscle activity.
  • DDD pacemakers appear more susceptible to oversensing-induced inhibition from these muscle groups.