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:
* 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.
Evaluation of bradycardia includes assessment of the heart rhythm, symptoms, medications, and associated medical conditions (reversible and irreversible). Symptomatic bradycardias are treated by removal of the underlying causes, medications (atropine) or insertion of a temporary or permanent pacemaker. 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.
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)
There are two main reasons for treating brandycardia:
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.
↑Pagon RA, Bird TD, Dolan CR; et al. PMID20301600. Missing or empty |title= (help)CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)
