Doctors & patients are saying about 'A-Fib.com'...
"A-Fib.com is a great web site for patients, that is unequaled by anything else out there."
Dr. Douglas L. Packer, MD, FHRS, Mayo Clinic, Rochester, MN
"Jill and I put you and your work in our prayers every night. What you do to help people through this [A-Fib] process is really incredible."
Jill and Steve Douglas, East Troy, WI
“I really appreciate all the information on your website as it allows me to be a better informed patient and to know what questions to ask my EP.
Faye Spencer, Boise, ID, April 2017
“I think your site has helped a lot of patients.”Dr. Hugh G. Calkins, MD Johns Hopkins,
Baltimore, MD
Understanding the EKG Signal
Video: Cardiac Conduction System and its Relationship with ECG. Go to video.
The ECG signal strip is a graphic tracing of the electrical activity of the heart. It measures the length of time it takes for the initial impulse to fire at the Sinus Node and then ends in the contracting of the Ventricles.
The first upward pulse of the EKG signal, the P wave, is formed when the atria (the two upper chambers of the heart) contract to pump blood into the ventricles. In A-Fib you will see many “fibrillation” beats instead of one P wave. A characteristic sign of A-Fib is the absence of a P wave in the EKG signal.
The next large upward spike segment, the QRS Complex, is formed when the ventricles (the two lower chambers of the heart) are contracting to pump out blood. The normal duration (interval) of the QRS complex is between 0.08 and 0.10 seconds.
The next section, the ST segment, measures the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat.
The next slight rising section, the T wave, measures the resting period of the ventricles.
These pulses are caused by the movement of positively and negatively charged ions (sodium, calcium, potassium, magnesium) through proteins called ion channel receptors. (For an excellent discussion and explanation of the science behind the movement of these chemical ions, see Restart Your Heart by Dr. Aseem Desai, p. 21.)
ECG (EKG) Strip: Atrial Fibrillation
In the case of Atrial Fibrillation, the consistent P waves are replaced by fibrillatory waves, which vary in amplitude, shape, and timing (compare the two illustrations below).
© 2012 A-Fib, Inc.
ECG recorder: special graph Paper
The output of an ECG recorder is a graph (or sometimes several graphs, representing each of the leads) with time represented on the x-axis and voltage represented on the y-axis. A dedicated ECG machine would usually print onto graph paper which has a background pattern of 1mm squares (often in red or green), with bold divisions every 5 mm in both vertical and horizontal directions.
Interpreting a ECG strip involves counting the squares of the tracing. For example, by counting the squares of a heart in Normal Sinus Rhythm, you can calculate the heart rate.
Video: Cardiac Conduction System and its Relationship with ECG
Animation with narration about the heart’s conduction system. Schematic diagram and explanation of normal sinus rhythm for a human heart as seen on ECG (3:34 min.) Click on image to go to the video page.
If you find any errors on this page, email us. Y Last updated: Wednesday, August 26, 2020
