<Tr> <Th> eMedicine </Th> <Td> emerg / 233 </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> First - degree atrioventricular block (AV block), or PR prolongation, is a disease of the electrical conduction system of the heart in which the PR interval is lengthened beyond 0.20 seconds . </P> <P> In first - degree AV block, the impulse conducting from atria to ventricles through the atrioventricular node (AV node) is delayed and travels slower than normal . It has a prevalence in the normal (young adult) population of 0.65 - 1.1% and the incidence is 0.13 per 1000 persons . </P>

What is first degree av block in ecg