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Bradycardia: Difference between revisions
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==Sinus Node Dysfunction== | ==Sinus Node Dysfunction== | ||
===Sinus Bradycardia=== | ===Sinus Bradycardia=== | ||
Sinus bradycardia is a slow sinus rhythm of <60 beats per minute. | Sinus bradycardia is a slow sinus rhythm of <60 beats per minute. Sinus bradycardia can be physiological, as is athletes or during sleep. Commonly sinus bradycardia is caused by medication, ischemia or neuro-mediated bradycardia, such as in a vasovagal reaction. Furthermore metabolic diseases can cause bradycardia, e.g. hypothermia or hypothyroidism. | ||
===Sinus Node Exit Block=== | ===Sinus Node Exit Block=== | ||
In the case of sinus node exit block, an impulse generated from the sinus node is blocked at one of the exit sides of the sinus node. However impulse formation is not affected, therefore the interval between subsequent beats should be similar to n=x times the P-P interval. | In the case of sinus node exit block, an impulse generated from the sinus node is blocked at one of the exit sides of the sinus node. However impulse formation is not affected, therefore the interval between subsequent beats should be similar to n=x times the P-P interval. On the surface electrocardiogram this is expressed as a pause. | ||
Like AV-nodal conduction disorders (see below) multiple subtypes can be distinguished: | |||
* Second degree Type I (Wenkebach) SA exit block: the P-P interval progressively shortens prior to the pause | |||
* Second degree Type II SA exit block: the pause equals approximately 2-4 times the preceding PP interval | |||
* Third degree SA exit block: absence of P waves (can only be diagnosed with an sinus node electrode, during electrophysiological evaluation) | |||
===Sinus Arrest=== | ===Sinus Arrest=== | ||
If the sinus node has a problem with impulse formation it is defined as a sinus arrest. There can be the appearance of a irregular rhythm, however sinus P-waves are clearly present. In comparison with the sinus node exit block, there is no relation with a previous P-P interval. | If the sinus node has a problem with impulse formation it is defined as a sinus arrest. There can be the appearance of a irregular rhythm, however sinus P-waves are clearly present. In comparison with the sinus node exit block, there is no relation with a previous P-P interval. Often an ectopic pacemaker takes over lower in the conduction system, but the new rate varies slightly from the old one. | ||
===Asystole=== | |||
Asystoly is the lack of cardiac activity eventually leading to immediate death. | |||
===Sick Sinus Syndrome=== | ===Sick Sinus Syndrome=== | ||
Sick sinus syndrome is an denoter of diseases of inappropriate sinus node responses. These encompass for instance | Sick sinus syndrome is an denoter of diseases of inappropriate sinus node responses. These encompass for instance: | ||
* An inappropriate response after tachycardia due to overdrive suppression (which can result in long pauses) | |||
* An inadequate response to exercise. | |||
* Bradycardia-tachycardia syndrome; where alternating bradycardia and tachycardia arise. | |||
==AV-Block== | ==AV-Block== | ||
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=References= | =References= | ||
# ESC Textbook of Cardiovascular Medicine, 2nd Edition | # ESC Textbook of Cardiovascular Medicine, 2nd Edition | ||
# ECGpedia.org | |||