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Heart block
 
 
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A heart block is a disease in the electrical system
Electrical conduction system of the heart

The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node of the heart to be propagated to the myocardium ....
 of the heart
Heart

The heart is a muscle organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods....
. This is opposed to coronary artery disease, which is disease of the blood vessels of the heart. While coronary artery disease can cause angina (chest pain) or myocardial infarction
Myocardial infarction

Myocardial infarction , commonly known as a heart attack, occurs when the Blood flow to part of the heart is interrupted. This is most commonly due to occlusion of a coronary artery following the rupture of a Vulnerable plaque, which is an unstable collection of lipids and white blood cells in the wall of an artery....
 (heart attack), heart block can cause lightheadedness, syncope (fainting), and palpitation
Palpitation

A palpitation is an abnormal awareness of the heart rate of the heart, whether it is too slow, too fast, irregular, or at its normal frequency. It should not be confused with ectopic beat....
s.

art block can be a blockage at any level of the electrical conduction system of the heart
Electrical conduction system of the heart

The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node of the heart to be propagated to the myocardium ....
.



Clinically speaking, most of the important heart blocks are AV nodal blocks and infra-Hisian blocks.

SA nodal blocks rarely give symptoms. This is because if an individual had complete block at this level of the conduction system (which is uncommon), the secondary pacemaker of the heart would be at the AV node, which would fire at 40 to 60 beats a minute, which is enough to retain consciousness
Consciousness

Consciousness is a difficult term to define, because the word is used and understood in a wide variety of ways, so that it frequently happens that what one person sees as a definition of consciousness is seen by others as about something else altogether....
 in the resting state.

Types of SA nodal blocks include:

In addition to the above blocks, the SA node can be suppressed by any other arrhythmia that reaches it.






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Encyclopedia


A heart block is a disease in the electrical system
Electrical conduction system of the heart

The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node of the heart to be propagated to the myocardium ....
 of the heart
Heart

The heart is a muscle organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods....
. This is opposed to coronary artery disease, which is disease of the blood vessels of the heart. While coronary artery disease can cause angina (chest pain) or myocardial infarction
Myocardial infarction

Myocardial infarction , commonly known as a heart attack, occurs when the Blood flow to part of the heart is interrupted. This is most commonly due to occlusion of a coronary artery following the rupture of a Vulnerable plaque, which is an unstable collection of lipids and white blood cells in the wall of an artery....
 (heart attack), heart block can cause lightheadedness, syncope (fainting), and palpitation
Palpitation

A palpitation is an abnormal awareness of the heart rate of the heart, whether it is too slow, too fast, irregular, or at its normal frequency. It should not be confused with ectopic beat....
s.

Types of heart block

A heart block can be a blockage at any level of the electrical conduction system of the heart
Electrical conduction system of the heart

The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node of the heart to be propagated to the myocardium ....
.

  • Blocks that occur within the sinoatrial node
    Sinoatrial node

    The sinoatrial node is the impulse generating tissue located in the right atrium of the heart, and thus the generator of sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava....
     (SA node) are described as SA nodal blocks.
  • Blocks that occur within the atrioventricular node
    Atrioventricular node

    The atrioventricular node is a part of electrical control system of the heart that co-ordinates heart rate. It electrically connects atrial and ventricular chambers....
     (AV node) are described as AV nodal blocks.
  • Blocks that occur below the AV node are known as infra-Hisian blocks (named after the bundle of His
    Bundle of His

    The bundle of His, also known as the AV bundle or atrioventricular bundle, is a collection of heart muscle cells specialized for electrical conduction that transmits the action potential from the AV node to the point of the apex of the fascicular branches....
    ).
  • Blocks that occur within the left or right bundle branches are known as bundle branch blocks.
  • Blocks that occur within the fascicles of the left bundle branch are known as hemiblocks.


Clinically speaking, most of the important heart blocks are AV nodal blocks and infra-Hisian blocks.

Types of SA nodal blocks

The SA nodal blocks rarely give symptoms. This is because if an individual had complete block at this level of the conduction system (which is uncommon), the secondary pacemaker of the heart would be at the AV node, which would fire at 40 to 60 beats a minute, which is enough to retain consciousness
Consciousness

Consciousness is a difficult term to define, because the word is used and understood in a wide variety of ways, so that it frequently happens that what one person sees as a definition of consciousness is seen by others as about something else altogether....
 in the resting state.

Types of SA nodal blocks include:
  • SA node Wenckebach (Mobitz I)
  • SA node Mobitz II
  • SA node exit block


In addition to the above blocks, the SA node can be suppressed by any other arrhythmia that reaches it. This includes retrograde conduction from the ventricles, ectopic
Cardiac ectopy

Ectopic beat is a disturbance of the electrical conduction system of the heart in which beats arise from the wrong part of the myocardium.It is a form of cardiac arrhythmia in which Ectopic pacemaker in the cardiac ventricle myocardium, or from finer branches of the electric transduction system, cause additional beats of the heart....
 atrial beats, atrial fibrillation, and atrial flutter.

The difference between SA node block and SA node suppression is that in SA node block an electrical impulse is generated by the SA node that doesn't make the atria contract. In SA node suppression, on the other hand, the SA node doesn't generate an electrical impulse because it is reset by the electrical impulse that enters the SA node.

Types of AV nodal blocks

There are four basic types of AV nodal block
Atrioventricular block

An atrioventricular block is a type of heart block involving impairment of the conduction between the atria and ventricles of the heart. It usually involves the atrioventricular node, but it can involve other structures....
:
  • First degree AV block
  • Second degree AV block
    • Type 1 second degree AV block (Mobitz I) (also known as Wenckebach phenomenon)
  • Third degree AV block (Complete heart block)


Types of infra-Hisian block

Infrahisian block describes block of the distal conduction system. Types of infrahisian block include:
  • Type 2 second degree heart block (Mobitz II)
  • Left bundle branch block
    Left bundle branch block

    Left bundle branch block is a cardiac conduction abnormality seen on the electrocardiogram . In this condition, activation of the left ventricle is delayed, which results in the left ventricle contracting later than the right ventricle....
    • Left anterior fascicular block
    • Left posterior fascicular block
  • Right bundle branch block
    Right bundle branch block

    A right bundle branch block is a defect in the heart's electrical conduction system. During a right bundle branch block, the right ventricle is not directly activated by impulses travelling through the right bundle branch....


Of these types of infrahisian block, Mobitz II heart block is considered most important because of the possible progression to complete heart block.

See also

  • Electrical conduction system of the heart
    Electrical conduction system of the heart

    The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node of the heart to be propagated to the myocardium ....
    • Sinoatrial node
      Sinoatrial node

      The sinoatrial node is the impulse generating tissue located in the right atrium of the heart, and thus the generator of sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava....
       (SA node)
    • Atrioventricular node
      Atrioventricular node

      The atrioventricular node is a part of electrical control system of the heart that co-ordinates heart rate. It electrically connects atrial and ventricular chambers....
       (AV node)


  • Trifascicular heart block
    Trifascicular heart block

    Trifascicular block is a problem with the Electrical conduction system of the heart of the heart. It is diagnosed on an electrocardiogram and has three features: ...


  • Lev's disease
    Lev's disease

    Lev's disease is an acquired complete heart block due to idiopathic fibrosis and calcification of the electrical conduction system of the heart of the heart....