A first degree AV block (also commonly refered to as a first degree heart block) is when there is a minor conduction blockage, that causes the time between the SA node firing and the AV node receiving an impulse to be longer in duration. It is a common dysrhythmia and occurs naturally in very fit people.
First Degree AV Block ECG
Heart Rate: usually mildly slower than normal.
Rhythm: Essentially regular
Pacemaker Site: SA Node
PR Interval: prolonged duration (greater than 0.20 seconds)
QRS Complex: normal.
First Degree Heart Block Signs and Symptoms
These patients are usually asymptomatic.