Welcome to the MedLibrary.org Wikipedia Supplement on Bradyarrhythmia -- Please Click to Return to Front Page

Bradycardia, as applied to adult medicine, is defined as a resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. ^[1] Trained athletes tend to have slow resting heart rates, and resting bradycardia in athletes should not be considered abnormal if the individual has no symptoms associated with it.

The term relative bradycardia is used to explain a heart rate that, while not technically below 60 beats per minute, is considered too slow for the individual's current medical condition.

This cardiac arrhythmia 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 drug use or abuse; metabolic or endocrine issues, especially in the thyroid; an electrolyte imbalance; neurologic factors; autonomic reflexes; situational factors such as prolonged bed rest; and autoimmunity. Cardiac causes include acute or chronic ischemic heart disease, vascular heart disease, valvular heart disease, or degenerative primary electrical disease. Ultimately, the causes act by three mechanisms: depressed automaticity of the heart, conduction block, or escape pacemakers and rhythms.

Causes

ECG showing Slow heart rate or Bradycardia

There are generally two types of problems that result in bradycardias: disorders of the sinoatrial node (SA node), and disorders of the atrioventricular node (AV node).

With sinus node dysfunction (sometimes called sick sinus syndrome), there may be disordered automaticity or impaired conduction of the impulse from the sinus node into the surrounding atrial tissue (an "exit block"). It is difficult and sometimes impossible to assign a mechanism to any particular bradycardia, but the underlying mechanism is not clinically relevant to treatment, which is the same in both cases of sick sinus syndrome: a permanent pacemaker.

Atrioventricular conduction disturbances (aka: AV block; 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.

Patients with bradycardia have likely acquired it, as opposed to having it congenitally. Bradycardia is more common in older patients.

Management

There are 2 main reasons for treating any cardiac arrhythmias. With bradycardia, the first is to address the associated symptoms, such as fatigue, limitations on how much a person can physically exert, fainting (syncope), dizziness or lightheadedness, or other vague and non-specific symptoms. The other reason to treat bradycardia is if the person's ultimate outcome (prognosis) will be changed or impacted by the bradycardia. Treatment depends on whether any symptoms are present, and what the underlying cause is.

Treatment

Drug treatment is not needed if the pt is asymptomatic.

In symptomatic pts, draw a chem 12 and abg's to assess electrolytes and blood gases. IV atropine may provide temporary improvement in symptomatic pts.

for symptomatic pts: Atropine 0.5-1 mg IV or ET q3-5min [maximum dose is 3 mg total] (0.04 mg/kg)

See also

• Tachycardia
• Hypotension

References

Wikipedia content modification information:

• This page was last modified on 24 July 2008, at 03:48.

Wikipedia Authorship and Review

Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.

Wikipedia Usage Guidelines

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Bradyarrhythmia".

The URL for this specific entry is:

• http://medlibrary.org/medwiki/Bradyarrhythmia

All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.