Bradycardia pathophysiology: Difference between revisions

	Bradycardia Microchapters
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Revision as of 03:57, 27 August 2012

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: M.Umer Tariq [2]

Overview

Pathophysiology

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 (1^o AV block, 2^o type I AV block, 2^o type II AV block, 3^o AV block) may result from impaired conduction in the AV node, or anywhere below it, such as in the bundle of HIS.

References

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 ==Overview==
 ==Pathophysiology==
-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]].