Individuals with Atrial Fibrillation are at Higher Risk for Stroke?

Prepared by: John A. Sawdon, Public Education & Special Projects Director

Atrial Fibrillation (AF) is a condition involving an irregular heart rhythm that is known as arrhythmia. Approximately 350,000 Canadians are living with AF. The risk of developing A-Fib increases with age, diabetes, high blood pressure and underlying heart disease among other causes. Individuals with Atrial Fibrillation have a 3 to 5 time’s greater risk for stroke than people without Atrial Fibrillation. (1)

During an arrhythmia, the heart can beat too fast called tachycardia, too slow called bradycardia or with an irregular rhythm. Most arrhythmias can be managed; however the heart may not be able to pump enough blood to the body. Lack of blood flow can damage the brain, heart and other organs.
Atrial Fibrillation is a supraventricular arrhythmias which is tachycardia that starts in the atria or atrioventricular (AV) node. The AV node is a group of cells located between the atria and the ventriculars. Atrial Fibrillation is the most common type of serious arrhythmia. It involves a very fast and irregular contraction of the atria. To understand arrhythmia we need to understand the heart’s internal electrical system which controls the rate and rhythm of the heartbeat. With each heartbeat, an electrical signal spreads from the top of the heart to the bottom. As the signal travels it causes the heart to contract and pump blood. Each electrical signal begins in a group of cells called the sinus node or sinoatrial (SA) node. The SA node is located in the upper right chamber of the heart called the right Atria. In a healthy adult the SA node fires off an electrical signal to begin a new heartbeat 60 to 100 times a minute. From the SA node, the electrical signal travels through special pathways in the right and left atria. This causes the atria to contract and pump blood into the heart’s lower chambers, the ventricles.

The signal then moves down to a group of cells called atrioventricular (AV) node, located between the atria and ventricles. Here the signal slows down slightly allowing the ventricles time to fill with blood. The electrical signal leaves the AV node along a pathway that divides into a right bundle and a left bundle branch. The signal goes down these branches and causes the ventricles to contract and pump blood to the lungs and rest of the body. The ventricles then relax and the heartbeat process starts all over again in the SA node. If a problem occurs with any part of this process, it can cause arrhythmia. Atrial Fibrillation occurs when the electrical signal travels through the atria in a fast and disorganized way. This causes the atria to quiver instead of contract.
In AF, the heart’s electrical signals don’t begin in the SA node; they instead begin in another part of the atria or the pulmonary veins. These signals spread throughout the atria in a rapid and disorganized way. This causes the walls of the atria to quiver very fast. As a result the atria are not able to pump blood to ventricles as it should. In atrial fibrillation electrical signals can travel through the atria at a rate of more than 300 beats per minute. Some of these signals can travel to ventricles causing them to beat too fast and with an irregular rhythm. Atrial Fibrillation can lead to strokes or heart failure. Blood can pool in the atria, causing blood clots to form. If a clot breaks off and travels to the brain, it can cause a stroke. The origin of 90 to 95% of A-Fib related strokes is in the left atria appendage (LAA). Blood thinners such as Coumadin or Pradaxa reduce risk of stroke by 60 to 70%. The only way to achieve 100% risk reduction is to eliminate A-Fib altogether.

If you have A-Fib, the upper parts of the heart (the atria) aren’t pumping enough blood into the lower chambers of your heart (the ventricles). It’s estimated this reduces by 15% to 30% the amount of blood flowing to the rest of your body. This reduced oxygen causes weakness, fainting, dizziness and shortness of breathe. It also diminishes brain function with 44% of individuals with A-Fib likely to develop dementia.

Insufficient pumping places pressure on ventricles. Prolonged A-Fib episodes stretch and weaken the heart muscle. Individuals with A-Fib have a 20% to 50% risk of heart failure. It is Important to treat A-Fib as soon as possible, A-Fib begets A-Fib. Your heart actually changes as a result of remodelling. The fast, abnormal rhythm enlarges your atria, your heart then develops fibrosis. This enlargement of the heart leads to persistent A-Fib resulting in increased risks for stroke and death.

Causes of Atrial Fibrillation

  • Often there is no clear reason for A-Fib
  • Other heart problems can lead to diseased tissue which generates extra a-fib pulses such as mitral valve disease, congestive heart failure, hypertension; high blood pressure stretch and put pressure on pulmonary veins where most a-fib originates
  • 40% of patients having open heart surgery develop a-fib
  • Obesity, diabetes, extreme fatigue, emotional stress, severe infections, severe pain and drug abuse can trigger a-fib
  • Low or high concentrations of minerals including potassium, magnesium and calcium can trigger a-fib
  • Thyroid problems(hyperthyroidism), lung disease, reactive hypoglycaemia and viral infections can trigger a-fib
  • Smoking which causes fibrotic damage to the atria can also contribute to a-fib
  • Sleep apnea which causes stress to the pulmonary vein opening can also cause a-fib
  • A-fib is associated with aging, it is rare under 50 years of age, with 2% occurrence in the 60’s, 5% to 6% in the 70’s, 8% to 10% in the 80’s. A-fib is uncommon for children except after surgery
  • Heavy alcohol drinking may trigger A-Fib as well
  • Individual’s risk of atrial fibrillation increases by 40% if a parent or sibling has A-Fib
  • Athletes are more prone to A-fib, usually as a result of a larger atria and pressure placed on the pulmonary veins through aerobic exercise
  • Vagal A-fib occurs in endurance athletes with low pulse rates
  • A-Fib is also more likely to occur in tall people, particularly basketball players
  • Overweight adults are 87% more likely to develop A-Fib than normal weight adults
  • Men are diagnosed more often than women, but women carry more long term risk of premature death
  • A-Fib more likely associated with coronary artery disease in Men
  • A-Fib more likely associated with valve disease in Women
  • A-Fib more common in white populations than Blacks or Hispanics
  • Common triggers for A-Fib include: anti-histamines, bronchial inhalers, local anaesthetics, meds-sumatriptan for headaches, MSG, cold beverages, high altitude, sleeping on left side or stomach, heartburn and stimulants including caffeine and chocolate

The key recommendation for anyone with A-Fib is to create a journal and record when A-fib incidences occur, what you were doing, eating or drinking and the time of day. In this way you can identify the triggers for you personally. It is important to remember that A-Fib is different for everyone.

Treatments and Procedures for controlling Atrial Fibrillation

Diagnostic Testing for A-Fib:

  • Blood Serum tests are usually ordered to check thyroid hormone, balance of body’s electrolytes (potassium, magnesium, calcium, sodium), to look for infection, to measure blood oxygen levels and hormone levels. Blood tests also reveal anemia or problems with kidney function that complicate atrial fibrillation.
  • Electrocardiogram uses up to twelve sensors attached to your body to create a graphical representation of your heart. It only records for a few seconds at a time. If a longer analysis is required then a halter which can continuously record and monitor for 24 to 48 hours is used. Another alternative device that can be used for longer periods of time but is activated by the wearer is called an events monitor. When the individual wearing the monitor feels their heart out of rhythm, they turn on the monitor that then records the beats and rhythm of the heart. There is also an implantable monitor that goes under the skin and is used to monitor for longer periods of time. This procedure is used if the person is fainting or is weak and the episodes have not been identified.
  • Exercise Stress test is completed with the person on the tread mill or a cycle. An ECG is used to monitor the hearts function during increased exercise stress undertaken by the individual being monitored.
  • Electrophysiology study is a catheterization test done to assess irregular heartbeats and is performed by an electrophysiologist. The electrophysiologist records arrhythmia by inserting electrode catheters through a vein in your groin and ultimately up into your heart. This allows the electrophysiologist to examine the electrical activity inside your heart in order to determine if and why the rhythm is abnormal.
  • Echocardiography(Cardiac Ultrasound), the echo uses ultrasound waves to get a picture of your moving heart. This is used to assess blood flow in your heart, assess valve functioning, muscle damage and thickening of heart walls.
  • Transesophageal Echocardiography (TEE): a tube with an ultrasound device is passed down through the esophagus.

Drug therapy strategies are usually the first line of defence for Doctors in treating someone with A-fib. There are three main ways that medication is used to treat A-fib as follows (2):

  • To prevent blood clots and stroke using blood thinners
  • To control the heart rate but leave the heart in A-fib using rate control drugs
  • To stop the A-fib and make your heart beat normally using rhythm control drugs

Mineral Deficiencies

  • Magnesium levels help with co-ordinating activity of the heart muscle and nerves. Low magnesium levels may lead to arrhythmias and heart palpitations
  • Potassium- both high and low levels of potassium can cause irregular heart rhythms
  • Electrolyte imbalance can occur through loss of fluids ( vomiting, diarreaha, high fever), antibiotics, diuretics, stomach or bowel disorders and kidney disease
  • Blood Serum Testing does not adequately test magnesium; instead ask for EX A test for measuring magnesium at the intra cellular level. Red Cell Magnesium Test (RBC) or White Blood Cell Magnesium Test (WBC). Anyone in A-Fib is magnesium deficient, if you take supplements( speak to you Doctor first) build slowly and spread out over the day
  • Calcium Overload is one cause of remodelling of the heart. These may include changes in size, shape and function.
  • Potassium is a key deficiency related to A-Fib. When potassium levels are too low, heart cells become unusually excitable, often leading to premature contraction or A-Fib.

Procedures and Surgeries

  • The goal of Cardioversion is to return an irregular beating heart and rhythm into normal sinus rhythm. This can be achieved via Chemical cardioversion which is through the use of medications or Electrical cardioversion or a combination of both. The electrical involves the delivery of an electrical shock while the patient is anesthetized and unconscious. A defibrillator is used to deliver a minor shock from 50 to 200 joules which stops your heart for a split second. The hope is that your heart will return to normal sinus rhythm. Electrical cardio-version does have a large risk for clots and possible strokes, therefore individuals are placed on blood thinners prior to the procedure to reduce the risk of a blood clot occurring.
  • Pulmonary Vein Isolation or PVI involves a catheter-based ablation technique designed to remove or disrupt the faulty electrical pathways of the heart which causes A-Fib. Electrically destroying or isolating these signal areas keeps atrial fibrillation from occurring. About 90% of A-Fib signals arise from the pulmonary openings located in the left atrium. The pulmonary veins are large veins that carry bright red oxygenated blood from the lungs to left atrium. There are four pulmonary veins two from each lung. The pulmonary veins most often associated with A-Fib are the two upper veins (left and right). Before the ablation begins, an image of your heart is taken using CT or MRI. This information is imported to a 3D scanner in mapping the electrical circuitry or roadmap of your heart. (3) During the ablation a catheter which is a flexible tube with an electrode tip is inserted through the groin, the wrist or neck and guided into the right atria of the heart. The catheter then pierces the septum wall entering the left atria and on to the pulmonary vein openings. The tip of the catheter delivers energy which burns or ablates the tiny spot of tissue. This process is repeated for each location. If other areas besides the pulmonary veins are causing a-fib, these areas are ablated as well. These ablation scars prevent the abnormal signals which cause atrial fibrillation from reaching the rest of the atrium. Once the scars form, any a-fib impulses are blocked, thereby electrically disconnecting them from the heart. This process allows the Sinus Node to once again control the heart rhythm resulting in Normal Sinus Rhythm.
  • Steven Ryan Ph.D. who is both a health care provider and a consumer who had Atrial Fibrillation has written a book entitled “Beat Your A-Fib: The Essential Guide to Finding Your Cure”. This publication has informed much of this article. This is an excellent resource for individuals with Atrial Fibrillation. It provides a clear understanding of A-Fib and the actions one should take in managing their Atrial Fibrillation. Within this book, Steve identifies other surgeries and procedures in Chapter 7 of his book. This includes AV Node Ablation with Pace Maker, The Cox-Maze and Mini Maze Surgeries and Pacemakers and Internal Cardioverter Defibrillators (ICD).
    Steven Ryan also writes a blog and operates a web site which is an excellent resource for patients www.A-Fib.com . We encourage the reader to access this website in learning more about A-Fib and the potential strategies that may be relevant for your individual situation. The American Heart Association also operates an A-Fib support group and web based discussion group. This can be accessed at www.heart.org and then scrolling down to A-Fib Town www.myafibexperience.org/home. This site also has a blog, community forum and resource information.

If you have signs or symptoms of A-Fib we encourage you to see your Doctor right away. As mentioned in this article A-Fib begets A-Fib and therefore both runs the risk of becoming more frequent but also altering the heart which can lead to heart failure. We hope this article is helpful in providing an introduction to Atrial Fibrillation. We would love to hear your reactions to this article including any outstanding questions you may. Send your comments to jsawdon@cardiachealth.ca


  1. Atrial Fibrillation; http://www.heartandstroke.ca/heart/conditions/atrial-fibrillation
  2. Arrhythmia Arrhythmia http://www.nhlbi.nih.gov/book/export/html/4885
  3. Ryan, Steve S. Ph.D, Ryan Patti J., Beat Your A-Fib: The Essential Guide to Finding your Cure; A-Fib, Inc Malibu CA 2012 ISBN-10:0984951407
  4. Atrial Fibrillation - Who is at Risk for Atrial Fibrillation? http://www.nhlbi.nih.gov/book/export/html/4890
  5. Hooman Kamel MD; Peter M Okin MD; Mitchell S. V. Elkind MD, MS; Costantino Ladecola MD; Atrial Fibrillation and Mechanisms of Stroke: Time for new Model http://stroke.ahajournals.org DOI:10.1161/StrokeAHA.115.012004
  6. Deborah Brauser; Cather Ablation May Be Better Atrial Fibrillation Treatment than Drugs for Serious and Professional Athletes February 5, 2010; StopAfib.org

The articles, on the Cardiac Health Foundation of Canada website, are presented with the understanding that the Foundation is providing information only and not rendering medical advice. Please check with your family physician, specialist or health care professional before implementing any of the ideas expressed in these articles.