Editing First-degree atrioventricular block (section)

{{Infobox medical condition (new)
| name            = First-degree AV block
| synonyms        = First degree heart block, PR prolongation
| image           = FirstAVBlock.jpg
| caption         = An ECG showing a first degree AV block of greater than 300 ms
| pronounce       =
| field           = [[Cardiology]]
| symptoms        = Asymptomatic
| complications   = Progression to [[Second-degree atrioventricular block|second]] or [[Third-degree AV block|third degree AV block]]
| onset           =
| duration        =
| types           =
| causes          = Fibrosis in AV node, medication, [[vagal tone]], electrolyte disturbances
| risks           =
| diagnosis       = [[Electrocardiography|Electrocardiogram]]
| differential    =
| prevention      =
| treatment       = Avoidance of AV-nodal-blocking medication
| medication      =
| prognosis       =
| frequency       =
| deaths          =
}}
'''First-degree atrioventricular block''' (AV block) is a disease of the [[electrical conduction system of the heart]] in which electrical impulses conduct from the cardiac [[atrium (heart)|atria]] to the [[ventricle (heart)|ventricles]] through the [[atrioventricular node]] (AV node) more slowly than normal. First degree AV block does not generally cause any symptoms, but may progress to more severe forms of heart block such as [[Second-degree atrioventricular block|second]]- and [[third-degree atrioventricular block]]. It is diagnosed using an [[Electrocardiography|electrocardiogram]], and is defined as a [[PR interval]] greater than 200 milliseconds.<ref name="urlLesson VI - ECG Conduction Abnormalities2">{{cite web|url=http://library.med.utah.edu/kw/ecg/ecg_outline/Lesson6/index.html#First|title=Lesson VI - ECG Conduction Abnormalities|access-date=2009-01-07}}</ref> First degree AV block affects 0.65-1.1% of the population with 0.13 new cases per 1000 persons each year.