The PR Interval indicates AV conduction time.
In this step you should measure the interval from where the P wave begins until the beginning of the QRS complex. Calipers, marked paper or counting small boxes methods can be used to determine PR Intervals. Normally this interval is 0.12 to 0.20 seconds (3 to 5 small boxes) in adults, longer in elderly people. This interval shortens with increased heart rate.
Also evaluate if PR Intervals are constant or varying across the EKG strip. If they vary, determine if the variations are a steady lengthening until the point where an expected QRS does not appear.
PR Interval questions to address:
- Does the PR-Interval fall within the norm of 0.12-0.20 seconds?
- Is the PR-Interval constant across the ECG tracing?