Step 4 PR interval (PRi) ECG Interpretation #318
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 secondPR 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 waveAuthors and Sources
Authors and Reviewers
- ECG heart rhythm modules: Thomas O'Brien.
 - ECG monitor simulation developer: Steve Collmann
 - 
                    12 Lead Course: Dr. Michael Mazzini, MD.
 - Spanish language ECG: Breena R. Taira, MD, MPH
 - Medical review: Dr. Jonathan Keroes, MD
 - Medical review: Dr. Pedro Azevedo, MD, Cardiology
 - Last Update: 11/8/2021 
 
Sources
- 
                        Electrocardiography for Healthcare Professionals, 6th Edition
                    
                    Kathryn Booth and Thomas O'Brien
ISBN10: 1265013470, ISBN13: 9781265013479
McGraw Hill, 2023 - 
                        Rapid Interpretation of EKG's, Sixth Edition
                    
                    
Dale Dublin
Cover Publishing Company - 
                        EKG Reference Guide
EKG.Academy - 
                        12 Lead EKG for Nurses: Simple Steps to Interpret Rhythms, Arrhythmias, Blocks, Hypertrophy, Infarcts, & Cardiac Drugs
                    
                    
Aaron Reed
Create Space Independent Publishing - 
                        Heart Sounds and Murmurs: A Practical Guide with Audio CD-ROM 3rd Edition
                    
                    
Elsevier-Health Sciences Division
Barbara A. Erickson, PhD, RN, CCRN - 
                        The Virtual Cardiac Patient: A Multimedia Guide to Heart Sounds, Murmurs, EKG
                    
                    Jonathan Keroes, David Lieberman
Publisher: Lippincott Williams & Wilkin)
ISBN-10: 0781784425; ISBN-13: 978-0781784429 - Project Semilla, UCLA Emergency Medicine, EKG Training Breena R. Taira, MD, MPH
 - 
                        ECG Reference Guide
PracticalClinicalSkills.com