In normal individuals, the AV node slows the conduction of electrical impulse through the heart. This is manifest on a surface EKG as the PR interval. The normal PR interval is from 120 milliseconds (ms) to 200 milliseconds (ms) in duration.  This is measured from the initial deflection of the P wave to the beginning of the QRS complex.
In<unk>  degree heart block, the diseased AV node conducts the electrical activity slower.  This is seen as a PR interval greater than 200 milliseconds (ms) in length on the surface EKG. It is usually an incidental finding on a routine EKG.<unk>  degree heart block does not require any particular evaluation except for electrolyte and drug screens especially if an overdose is suspected.
First degree AV block electrocardiogram
Third degree AV block electrocardiogram
Atrial flutter electrocardiogram
Pacemaker syndrome electrocardiogram
Right bundle branch block electrocardiogram
Junctional tachycardia ECG
AVNRT electrocardiogram
Ventricular fibrillation electrocardiogram