Atrioventricular block First degree atrioventricular block 2012-04-11T07:17:18Z UMLS:C0085614 The conduction of the cardiac impulse through the atrioventricular node is manifested in the EKG by the PR interval, which is normally less that 200 milliseconds in adults. Normal values are age-dependent in children, but normal values are less that 160 milliseconds in young children. Delay of conduction through the atrioventricular node, which is manifested as prolongation of the PR interval in the electrocardiogram (EKG). All atrial impulses reach the ventricles. SNOMEDCT_US:270492004 HP:0011705