Cardiac Rhythms

Graph Paper ECG Interpretation

Time 1

The value of time and voltage just discussed is very important to understand, but it must be combined with an understanding of the grid or graph paper the tracing is printing upon that you are analyzing.
The grid is broken down in small boxes (1 X 1 millimeter) and heavier darkened lined boxes.
There are five small boxes going from left to right and bottom to top of each large box (5 X 5 mm).

Time 2

Each small box has a time value of 0.04 second.

If there are five small boxes going across each large box, then the value of time for each large box equals 0.20 second

(5 small boxes X 0.04 second = 0.20 second)

(5 LARGE BOXES X 0.20 SECOND = 1 SECOND)

Voltage 1

Voltage is important when measuring the height or depth of a waveform.
The height or depth provides an indication of the amount of electrical activity occurring within the heart.
Voltage can be affected by a number of different factors to include the amount of viable muscle mass in the heart.
When analyzing cardiac tracings, the question always comes up “where do I measure from”?

Voltage 2

To keep it as clear as possible, it is important to establish the isoelectric line or baseline.

There are times when this can prove to be impossible, but in most cases if you can see the PR segment, ST segment and TP segment, you should have a strong sense that this is where the isoelectric line is located.

However, all three segments are not always on the isoelectric line

Where two out of the three of them are located when analyzing horizontally, this is typically where the isoelectric line is located.

Authors 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