# Step 4 PR interval (PRi) - Cardiac Rhythms

## Description

• Measurement of the PR interval reflects the amount of time from the beginning of atrial depolarization to the beginning of ventricular depolarization.
• Plainly stated, PR interval measurement is from the beginning of the P wave to the beginning of the QRS complex.
• The normal range for PR interval is: 0.12 – 0.20 seconds (3 to 5 small boxes)
• It is important that you measure each PR interval on the rhythm strip.
• Some tracings do not have the same PRi measurement from one cardiac complex to the next. Sometimes there is a prolonging pattern, sometimes not.
• If the PR intervals are variable, report them as variable, but note if a pattern is present or not.

## Measuring PR Interval Practice 1

Analyze this tracing. What is the PR interval Measurement?

Reveal Answer 4 small boxes (4 X 0.04 second) = 0.16 second

## PR Interval Practice 2

Analyze this tracing. What is the PR interval Measurement?

Reveal Answer Variable – inverted P wave has shorter PR, plus one complex has no P wave

Authors and Sources

## Sources

? v:3 | cc: | tar: False | onAr:0 | onPs:2 | tLb:3 | tLbJs:0
| pv: 1 uStat: False | db:0 | shouldInvoke:False | pu:False | em: | refreshTime: 1/1/0001 12:00:00 AM || now: 7/13/2024 6:37:24 PM | firstPage: True
| statusStg: | cDbLookup# 0