- Overview of A-Fib
- Causes of A-Fib
- Find the Right Doctor for You
- Treatments for A-Fib
- Q & A: Coping with A-Fib
- Personal A-Fib Stories of Hope
- Directory Doctors/Facilities
- Patient Resources & Links
- Our A-Fib Support Volunteers
- 2023 AF Symposium: Reports
- A-Fib Videos & Animations
- Bibliography
- Glossary of Terms
- Free Offers & Downloads
- How to Search for Articles
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

Doctors & patients are saying about 'Beat Your A-Fib'...
"If I had [your book] 10 years ago, it would have saved me 8 years of hell.”
Roy Salmon, Patient, A-Fib Free,
Adelaide, Australia
"This book is incredibly complete and easy-to-understand for anybody. I certainly recommend it for patients who want to know more about atrial fibrillation than what they will learn from doctors...."
Pierre Jaïs, M.D. Professor of Cardiology, Haut-Lévêque Hospital, Bordeaux, France
"Dear Steve, I saw a patient this morning with your book [in hand] and highlights throughout. She loves it and finds it very useful to help her in dealing with atrial fibrillation."
Dr. Wilber Su,
Cavanaugh Heart Center, Phoenix, AZ
"...masterful. You managed to combine an encyclopedic compilation of information with the simplicity of presentation that enhances the delivery of the information to the reader. This is not an easy thing to do, but you have been very, very successful at it."
Ira David Levin, heart patient,
Rome, Italy
"Within the pages of Beat Your A-Fib, Dr. Steve Ryan, PhD, provides a comprehensive guide for persons seeking to find a cure for their Atrial Fibrillation."
Walter Kerwin, MD, Cedars-Sinai Medical Center, Los Angeles, CA
Your Heart’s Electrical System & How Clots Form: An Introduction
Basic introduction to how the heart works. Identifies the parts of the heart and illustrates the role of each, and shows how clots form; Detail animation of the heart processes accompanied by narration. Transcript below. (3:50 min.)
Animation from the National Heart Lung and Blood Institute.
TO PLAY VIDEO: Click the PLAY button (on the far left) to start video
(The controls inside the video frame don’t work.)\
Your heart’s electrical system is made up of three main parts:
The sinoatrial (SA) node, located in the right atrium of your heart The atrioventricular (AV) node, located on the interatrial septum close to the tricuspid valve The His-Purkinje system, located along the walls of your heart’s ventricles
A heartbeat is a complex series of events. These events take place inside and around your heart. A heartbeat is a single cycle in which your heart’s chambers relax and contract to pump blood. This cycle includes the opening and closing of the inlet and outlet valves of the right and left ventricles of your heart. Each heartbeat has two basic parts: diastole and systole.
During diastole, the atria and ventricles of your heart relax and begin to fill with blood. At the end of diastole, your heart’s atria contract (atrial systole) and pump blood into the ventricles. The atria then begin to relax.
Your heart’s ventricles then contract (ventricular systole), pumping blood out of your heart. Each beat of your heart is set in motion by an electrical signal from within your heart muscle. In a normal, healthy heart, each beat begins with a signal from the SA node. This is why the SA node sometimes is called your heart’s natural pacemaker.
Your pulse, or heart rate, is the number of signals the SA node produces per minute. The signal is generated as the vena cavae fill your heart’s right atrium with blood from other parts of your body. The signal spreads across the cells of your heart’s right and left atria. This signal causes the atria to contract. This action pushes blood through the open valves from the atria into both ventricles.
The signal arrives at the AV node near the ventricles.
It slows for an instant to allow your heart’s right and left ventricles to fill with blood. The signal is released and moves along a pathway called the bundle of His, which is located in the walls of your heart’s ventricles.
From the bundle of His, the signal fibers divide into left and right bundle branches through the Purkinje fibers. These fibers connect directly to the cells in the walls of your heart’s left and right ventricles (see yellow on the picture in the animation).
The signal spreads across the cells of your ventricle walls, and both ventricles contract. However, this doesn’t happen at exactly the same moment.
The left ventricle contracts an instant before the right ventricle. This pushes blood through the pulmonary valve (for the right ventricle) to your lungs, and through the aortic valve (for the left ventricle) to the rest of your body.
As the signal passes, the walls of the ventricles relax and await the next signal.
This process continues over and over as the atria refill with blood and more electrical signals come from the SA node.
If you find any errors on this page, email us. Y Last updated: Wednesday, August 26, 2020
Return to Instructional A-Fib Videos and Animations