Bradycardia pathophysiology: Difference between revisions
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Pathologic bradycardias are caused by disorders of impulse generation (impaired automaticity at [[SA node]]), impulse conduction ([[heart block]]) or [[escape pacemaker]]s and rhythms. Bradycardia can be underlain by several causes, which are best divided into cardiac and non-cardiac causes. Non-cardiac causes are usually secondary, and can involve recreational drug use, [[endocrine]] disorders ([[hypothyroid]]); [[electrolyte]] imbalance ([[hyperkalemia]]); autonomic reflexes; situational factors (prolonged [[bed rest]]); infections [[lyme disease]], medications, and [[autoimmune|autoimmunity]] disorders. Cardiac causes include acute or chronic [[ischemic heart disease]], vascular [[heart disease]], [[valvular heart disease]], or degenerative primary electrical disease (fibrosis and calcification of the [[sinus node]] and [[conduction system]]). | Pathologic bradycardias are caused by disorders of impulse generation (impaired automaticity at [[SA node]]), impulse conduction ([[heart block]]) or [[escape pacemaker]]s and rhythms. Bradycardia can be underlain by several causes, which are best divided into cardiac and non-cardiac causes. Non-cardiac causes are usually secondary, and can involve recreational drug use, [[endocrine]] disorders ([[hypothyroid]]); [[electrolyte]] imbalance ([[hyperkalemia]]); autonomic reflexes; situational factors (prolonged [[bed rest]]); infections [[lyme disease]], medications, and [[autoimmune|autoimmunity]] disorders. Cardiac causes include acute or chronic [[ischemic heart disease]], vascular [[heart disease]], [[valvular heart disease]], or degenerative primary electrical disease (fibrosis and calcification of the [[sinus node]] and [[conduction system]]). | ||
It is difficult and sometimes impossible to assign a mechanism to any particular bradycardia. However, the underlying mechanism is not clinically relevant to treatment, which is the same in both cases of sick sinus syndrome: a permanent [[artificial pacemaker|pacemaker]]. | |||
There are generally two types of problems that result in bradycardias: | |||
===Disorders of the [[sinus node]] === | |||
* Impaired automaticity - Sinus node dysfunction/[[sick sinus syndrome]]) | |||
* Exit block - Impaired conduction of the impulse from the sinus node into the surrounding atrial tissue | |||
===Disorders of the [[atrioventricular node]] (AV node)=== | |||
* Atrioventricular conduction disturbances ([[First degree AV block|1<sup>o</sup> AV block]], [[Second degree AV block|2<sup>o</sup> type I AV block]], [[Second degree AV block|2<sup>o</sup> type II AV block]], [[Third degree AV block|3<sup>o</sup> AV block]]) may result from impaired conduction in the AV node, or anywhere below it, such as in the bundle of HIS. | |||
==References== | ==References== | ||
Revision as of 03:57, 27 August 2012
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: M.Umer Tariq [2]
Overview
Pathophysiology
Pathologic bradycardias are caused by disorders of impulse generation (impaired automaticity at SA node), impulse conduction (heart block) or escape pacemakers and rhythms. Bradycardia can be underlain by several causes, which are best divided into cardiac and non-cardiac causes. Non-cardiac causes are usually secondary, and can involve recreational drug use, endocrine disorders (hypothyroid); electrolyte imbalance (hyperkalemia); autonomic reflexes; situational factors (prolonged bed rest); infections lyme disease, medications, and autoimmunity disorders. Cardiac causes include acute or chronic ischemic heart disease, vascular heart disease, valvular heart disease, or degenerative primary electrical disease (fibrosis and calcification of the sinus node and conduction system).
It is difficult and sometimes impossible to assign a mechanism to any particular bradycardia. However, the underlying mechanism is not clinically relevant to treatment, which is the same in both cases of sick sinus syndrome: a permanent pacemaker.
There are generally two types of problems that result in bradycardias:
Disorders of the sinus node
- Impaired automaticity - Sinus node dysfunction/sick sinus syndrome)
- Exit block - Impaired conduction of the impulse from the sinus node into the surrounding atrial tissue
Disorders of the atrioventricular node (AV node)
- Atrioventricular conduction disturbances (1o AV block, 2o type I AV block, 2o type II AV block, 3o AV block) may result from impaired conduction in the AV node, or anywhere below it, such as in the bundle of HIS.