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bradycardia

  (brăd'ĭ-kär'dē-ə) pronunciation
n.

Slowness of the heart rate, usually fewer than 60 beats per minute in an adult human.

[BRADY– + Greek kardiā, heart; see cardia.]

bradycardic brad'y·car'dic (-dĭk) adj.
 
 
World of the Body: bradycardia

Bradycardia describes a heart beat which is either habitually slow, or which drops from its usual rate. In health, bradycardia may be the result of athletic training, which reduces the resting heart rate. Persons with heart block have persistent or intermittent bradycardia. Sudden bradycardia can result in a dramatic fall in cardiac output and hence in arterial blood pressure, depriving the brain of blood flow and causing a ‘black-out’. Fainting (‘syncope’) is one such instance, caused by depression of the heart's pacemaker by the parasympathetic (vagus) nerves; acute exacerbation of heart block is another. From the Greek for ‘slow’ and ‘heart’.

— Stuart Judge

See heart block; syncope; fainting.

 
Food and Nutrition: bradycardia

An unusually slow heartbeat, less than 60 beats/min. Such a low rate may be normal in trained athletes.

 
Food and Fitness: bradycardia

A decreased or slowed heart rate, sometimes taken as being less than 60 beats per minute. The significance of bradycardia depends on a person's history. Those who have suffered a heart attack sometimes develop chronic bradycardia that needs to be treated with a pacemaker. A slow resting heart rate is, however, a normal effect of endurance training and is usually taken as a sign of good aerobic fitness. See also athlete's heart.

 
Dental Dictionary: bradycardia
(brad′i-kär′dē-ə)
n

Abnormal slowness of the heart as evidenced by a slowing of the pulse rate (less than 50 beats per minute).

 

A slow resting heart rate (less than 60 beats min−1). It may be due to a pathological defect in the cardiovascular system. Highly trained endurance athletes, however, often develop low resting heart rates (the resting heart rate of Lance Armstrong, the professional cyclist, was recorded as 32 beats min−1 when he won the Tour de France). This is an advantageous adaptation and does not indicate a pathological defect.

 

Slowness of the heartbeat, in dogs and cats to less than 60 beats per minute.

  • sinus b. — a slow sinus rhythm, characterized by normal electrocardiographic complexes in a normal rhythm or a sinus arrhythmia. A normal finding, most commonly seen in large breeds of dogs or athletic animals.
    Sinus bradycardia in a dog. By permission from Ettinger SJ, Feldman E, Textbook of Veterinary Internal Medicine, Saunders, 2004
  • b.–tachycardia syndrome — see sick sinus syndrome.


 
Wikipedia: bradycardia
Name of Symptom/Sign:
Bradycardia
Classifications and external resources
ICD-10 R00.1
ICD-9 427.81, 659.7, 785.9, 779.81

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
Enlarge
ECG showing Slow heart rate or Bradycardia

There are generally two types of problems that result in bradycardias: disorders of the sinus 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; 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.

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

Management

There are two main reasons for treating any cardiac arrhythmias. With bradycardia, the first is to address the associated symptoms, such as fatigue, limitations on how much an individual 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 in this vein depends on whether any symptoms are present, and what the underlying cause is. Primary or idiopathic bradycardia is treated symptomatically if it is significant, and the underlying cause is treated if the bradycardia is secondary.

Treatment

Drug treatment for bradycardia is typically not indicated for patients who are asymptomatic. In symptomatic patients, underlying electrolyte or acid-base disorders or hypoxia should be corrected first. IV atropine may provide temporary improvement in symptomatic patients, although its use should be balanced by an appreciation of the increase in myocardial oxygen demand this agent causes.

Atropine 0.5-1 mg IV or ET q3-5min up to 3 mg total (0.04 mg/kg)

Image:Lead II rhythm generated sinus bradycardia.JPG

See also

References

  1. ^ Sinus Bradycardia eMedicine

 
 

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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
World of the Body. The Oxford Companion to the Body. Copyright © 2001, 2003 by Oxford University Press. All rights reserved.  Read more
Food and Nutrition. A Dictionary of Food and Nutrition. Copyright © 1995, 2003, 2005 by A. E. Bender and D. A. Bender. All rights reserved.  Read more
Food and Fitness. Food and Fitness: A Dictionary of Diet and Exercise. Copyright © 1997, 2003 by Oxford University Press. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Veterinary Dictionary. The Veterinary Dictionary. Copyright © 2007 by Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bradycardia" Read more

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