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Encyclopedia > Third degree heart block
Third degree heart block
Classification & external resources
ICD-10 I44.2
ICD-9 426.0
DiseasesDB 10477
eMedicine emerg/235 

Third degree heart block, also known as complete heart block or third degree AV block, is a defect of the electrical system of the heart, in which the impulse generated in the atria (typically the SA node on top of the right atrium) does not propagate to the ventricles. Image File history File linksMetadata Size of this preview: 800 × 160 pixel Image in higher resolution (881 × 176 pixel, file size: 125 KB, MIME type: image/jpeg) Rhythm strip showing third degree heart block. ... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following codes are used with International Statistical Classification of Diseases and Related Health Problems. ... The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify diseases and a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes of injury or disease. ... The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. ... The Disease Bold textDatabase is a free website that provides information about the relationships between medical conditions, symptoms, and medications. ... eMedicine is an online clinical medical knowledge base that was founded in 1996. ... The heart and lungs, from an older edition of Grays Anatomy. ... The sinoatrial node (abbreviated SA node, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the heart. ... This page is about the muscular organ, the Heart. ...


Because the impulse is blocked, an accessory pacemaker below the level of the block will typically activate the ventricles. This is known as an escape rhythm. Since this accessory pacemaker activates independently of the impulse generated at the SA node, two independent rhythms can be noted on the electrocardiogram (EKG). One will activate the atria and create the P waves, typically with a regular P to P interval. The second will activate the ventricles and produce the QRS complex, typically with a regular R to R interval. The PR interval will be variable, as the hallmark of complete heart block is no apparent relationship between P waves and QRS complexes. The sinoatrial node (abbreviated SA node, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the heart. ... Lead II An electrocardiogram (ECG or EKG, abbreviated from the German Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical activity of the heart over time. ...


Etiology

Many conditions can cause third degree heart block, but the most common cause is coronary ischemia. Progressive degeneration of the electrical conduction system of the heart can lead to third degree heart block. This may be preceded by first degree AV block, second degree AV block, bundle branch block, or bifascicular block. In addition, acute myocardial infarction may present with third degree AV block.


An inferior wall myocardial infarction may cause damage to the AV node, causing third degree heart block. In this case, the damage is usually transitory, and the AV node may recover. Studies have shown that third degree heart block in the setting of an inferior wall myocardial infarction typically resolves within 2 weeks. The escape rhythm typically originates in the AV junction, producing a narrow complex escape rhythm.


An anterior wall myocardial infarction may damage the distal conduction system of the heart, causing third degree heart block. This is typically extensive, permanent damage to the conduction system, necessitating a permanent pacemaker to be placed. The escape rhythm typically originates in the ventricles, producing a wide complex escape rhythm. A pacemaker A pacemaker (or artificial pacemaker, so as not to be confused with the hearts natural pacemaker) is a medical device designed to regulate the beating of the heart. ...


Third degree heart block may also be congenital and has been linked to a condition in the mother called Lupus. It is thought that maternal antibodies may cross the placenta and attack the heart tissue during gestation. The cause of congenital third degree heart block in many patients is unknown. Studies suggest that the prevalence of congenital third degree heart block is between 1 in 15,000 and 1 in 22,000 live births.


See also

The contractions of the heart are controlled by electrical impulses, these fire at a rate which controls the beat of the heart. ... The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node (SA node) of the heart to be propagated to (and stimulate) the myocardium (Cardiac muscle). ... Lead II An electrocardiogram (ECG or EKG, abbreviated from the German Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical activity of the heart over time. ...

External links


  Results from FactBites:
 
Third degree heart block - Wikipedia, the free encyclopedia (438 words)
Third degree heart block, also known as complete heart block, is a disease of the electrical system of the heart, in which the impulse generated in the top half of the heart (typically the SA node in the right atrium) does not propagate to the left or right ventricles.
Third degree heart block may also be congenital and has been linked to a condition in the mother called Lupus.
Studies suggest that the prevalence of congeital third degree heart block is between 1 in 15,000 and 1 in 22,000 live births.
Heart block - Wikipedia, the free encyclopedia (405 words)
Blocks that occur within the sinoatrial node (SA node) are described as SA nodal blocks.
Blocks that occur within the atrioventricular node (AV node) are described as AV nodal blocks.
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 in the resting state.
  More results at FactBites »

 
 

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