Cardiology CME: EKG Basics

Make no mistake about it, you can learn EKG rhythms from a book.  No problem.  And, you can get hints about a 12 lead from a book.  But, to really know 12 lead EKGs, you have to be mentored.  This blog post kicks off a series on EKG interpretation that is designed to provide you with the answers you need when patients need them most.

Be sure to learn the MUST MEMORIZE portions of these blogs.  These will lay the foundation for other critical information.

The EKG PaperScreen Shot 2014-12-22 at 2.11.41 PM

First and foremost, you have to know the EKG paper.  An EKG is printed on paper covered with a grid of squares.  Notice that five small squares on the paper form a larger square. The width of one small square on EKG paper is 0.04 seconds.

There are 5 small boxes in a big box.  A big box is 0.2 seconds.

A common length of an EKG printout is 6 seconds; this is known as a “six second strip.”

The “height” of an EKG wave is called its amplitude.  The isoelectric line is considered to have an amplitude of zero.  YOU ABSOLUTELY HAVE TO KNOW HOW TO DRAW A BASELINE.  You cannot read a 12 lead EKG without it.  Anything above the isoelectric line is positive; below the line is negative.

So, the horizontal lines measure time.  The vertical lines measure amplitude as represented in millimeters.

Normal EKG Values

For you to learn EKGs, you have to remember these normal values:

PR Segment = 0.12-0.2 seconds  

(If longer the 0.2 seconds = first degree heart block.  If shorter then 0.12 seconds = Wolf Parkinson White Syndrome)

QRS = Less then 0.12 seconds


Small box                = 0.04 seconds

Big box                     = five small boxes or 0.2 seconds

PR Segment            = 0.12-0.2 seconds

QRS                            = less the 0.12 seconds


What EKG questions are on your mind? What would you like to know in future blogs?

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John Bielinski, Jr., MS PAC is a practicing emergency medicine clinician, and has been lecturing nationally for more than ten years, teaching the tactics that have proven invaluable in his career as a medical professional.