How Long Does It Take for the Atria to Depolarize?

The first interval that we'll look at is the PR interval. That's basically the amount of time it takes for the atria to depolarize and how long does it take for the electrical signal to make it through the AV node. If you see a prolongation of the PR interval, that usually indicates that there's something going on with the AV nodes. The other thing that can commonly do it is ectopic atrial rhythm if you have another pacemaker in your heart.