First-degree atrioventricular block

First-degree AV block
Other names	First degree heart block, PR prolongation
An ECG showing a first degree AV block of greater than 300 ms
Specialty	Cardiology
Symptoms	Asymptomatic
Complications	Progression to second or third degree AV block
Causes	Fibrosis in AV node, medication, vagal tone, electrolyte disturbances
Diagnostic method	Electrocardiogram
Treatment	Avoidance of AV-nodal-blocking medication

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 atria to the 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- and third-degree atrioventricular block. It is diagnosed using an electrocardiogram, and is defined as a PR interval greater than 200 milliseconds.^[1] First degree AV block affects 0.65-1.1% of the population with 0.13 new cases per 1000 persons each year.