First degree AV block is a rhythm that is not really a block at all, but more of a slowing down at the junction from the top of the heart to the lower part of the heart, known as the AV node. You can think of it more of a traffic slow up that a lot of traffic being funneled through a small opening tends to slow down. It is not a dangerous rhythm by any means. What I mean is that it doesn’t usually cause any symptoms and people usually don’t know they have it until they get a check up by their family doctor and he/she does an ECG. Some medications can cause slow down of the AV node, but most commonly it is caused by a damaged electrical system.
As I have said it is not a dangerous rhythm but doctors still want to watch it because it can lead to more serious blocks that are life threatening. Usually people that have this block can live a normal happy life and just changing medications can help. The rhythm is regular and as you can see below the P wave is slightly further from the QRS complex than normal indicating a slowing of the signal.
The block is a transitional rhythm which means that it can lead to 2nd degree AV block and lasting the 3rd degree AV block 90% of the people don’t have symptoms until they reach the 3rd degree AV block which is also known as the complete heart block. Each part of the heart has its own intrinsic heart pacing that enables the heart to continue beating, albeit a slower rhythm, but it still beats. It is at this point that some people need a pace maker, but not always probably around 40% as I have seen in my practice.
So in summary most people do not need treatment with this type of rhythm and it is not life threatening. Careful monitoring by your family doctor needs to be done just by visiting regularly and if you develop symptoms like dizziness, passing out or chest pain go to the emergency.