Atrial fibrillation (AFib) is a heart rhythm disorder characterized by irregular heartbeats in the heart’s upper chambers, called the atria. In AFib, the electrical signals that regulate the heartbeat become abnormal, causing the heart to beat too fast or slow instead of contracting normally. Atrial fibrillation can have detrimental effects such as stroke, heart failure, and blood clots. 

Image Credit: cdc.gov

As a result of the irregular heart beatings, a variety of symptoms can be present such as:

• Palpitations (fluttering, pounding, or rapid sensation)
• Shortness of breath
• Fatigue
• Weakness
• Dizziness / lightheaded
• Chest pain

In some cases, people with AFib may not experience any symptoms, making it difficult for some people to tell whether or not they may have AFib.  

Some broader symptoms can include:

• Abrupt weight gain
• Coughing or wheezing
• Fainting
• Nausea and appetite loss
• Depression

Sometimes even these broader symptoms can not help people determine if they have AFib. The only way for people to know if they have AFib without experiencing any symptoms is to get tested and diagnosed by a doctor. It is strongly recommended that if a person has any of the risk factors below, they get checked, just to be safe, by a doctor. 

AFib is often seen in older adults, with risk factors that include:

• History of heart disease
• High blood pressure
• Advancing age
• Obesity
• Diabetes
• Heart failure
• Hyperthyroidism
• Chronic kidney disease
• Smoking or excessive alcohol use

Some treatments are more effective when delivered in the early stages of AFib, which means that a person should not postpone getting checked by a doctor for AFib. However, symptoms and causes of AFib can often differ between men and women. In women, AFib usually is caused by problems with the heart valves. Compared to men, where AFib usually stems from coronary artery disease (CAD). As a result, women with AFib have a greater chance of having a stroke than men with AFib. Women with AFib also are more likely to have heart attacks and congestive heart failure than men with AFib. As a result, treatments for men and women often differ slightly. 

Treatment for AFib is typically a medication to control heart rhythm and prevent blood clots. However, in some cases, procedures such as electrical cardioversion, ablation, or implantation of a pacemaker or defibrillator may be necessary. Men with AFib are often placed on non-drug therapies such as pacemakers and catheter ablation. Women with AFib are more likely to have a cardioversion and be prescribed antiarrhythmic medications such as dofetilide. However, typical treatments for both men and women include blood-thinning medications, surgery, and lifestyle changes to manage AFib risk factors. 

Written by: Sofia H. Davila, Clinical Researcher

Sources:

Miller, K. (2022, December 27). Atrial fibrillation: The difference between men and women. Healthgrades. Retrieved February 17, 2023, from https://www.healthgrades.com/right-care/atrial-fibrillation/atrial-fibrillation-the-difference-between-men-and-women 

Centers for Disease Control and Prevention. (2022, October 14). Atrial fibrillation. Centers for Disease Control and Prevention. Retrieved February 17, 2023, from https://www.cdc.gov/heartdisease/atrial_fibrillation.htm

Listen to the article here:

The familiar wub-dub of the heart accompanies us throughout our lives, providing a gentle beat that keeps us alive. But for some of us, the beat might not be so steady. For 33 million people worldwide, the heartbeat lacks a rhythm at all. It sounds like shoes in a clothes dryer and gets progressively worse. This is called Atrial Fibrillation, or AFib for short. The risks of AFib increase with age, and there is a genetic component as well. Other risk factors include:

• Heart failure
• Ischemic (low blood flow) heart disease
• High blood pressure
• Diabetes
• Obesity
• Sleep Apnea

In order for AFib to occur, doctors believe there needs to be a trigger and a substrate. A trigger, or driver, is the electric signal that travels to the heart and initiates an arrhythmic event. This can be from several areas, but is frequently from one of the big pulmonary veins that carry oxygen to the heart. A substrate is the underlying condition that makes a sustained event possible and could be structural or electrical. Common substrates include the electrical system of the heart, dilation (or stretching) of the atrium, cellular-molecular changes, and/or an increase in disruptive cells called fibroblasts. In general, many or all of these changes would occur, leading to constant AFib.

AFib is very dangerous. Other than a wonky pulse, there are three major complications: heart failure, stroke, and myocardial infarction (a heart attack). Heart failure is when the heart can’t pump enough blood, while stroke and myocardial infarction can be caused by stray blood clots. Heart failure is both a risk and a symptom, which illustrates one way in which AFib is a progressive disease. Through complicated electric and biocellular mechanisms, long term AFib seems to cause more AFib.

Treating AFib has proven difficult. It is effective to treat the underlying risk factors, such as obesity and diabetes, but this is difficult and the actual cause of AFib isn’t always clear. Controlling the rhythm of the heart is also tough and risky, as messing with heart rhythm can easily lead to big problems. Atrial fibrillation ablation is an effective treatment. It is an intensive surgical procedure where doctors scar problem areas to reduce electrical activity. Even with this method, the risk of resurgence is over 30% after 5 years.

Two of the biggest complications of AFib are related to blood clots. Because of this – and the difficulty of other treatments – major pharmaceuticals often target thromboembolisms, or clots. The clotting system itself is very complicated. A simple version is that platelets activate and produce several enzymes. These enzymes make thrombin, which makes a big mesh-like protein called fibrin. This would be a slow process, except that thrombin also activates amplifier enzymes, which makes this process very fast. The fibrin then catches red blood cells and blocks wounds – or blood vessels. When these clots travel to the brain they can cause a stroke. When they restrict blood flow to the heart they can cause a myocardial infarction – a heart attack.

Classic anticoagulants, such as Warfarin (also called Jantoven and Coumadin) work by stopping the clots before they start. These are Vitamin K dependent anticoagulants and can be effective at reducing clots. Unfortunately, they are occasionally too effective. The biggest side effect of Vitamin K dependent anticoagulants is increased bleeding. This can be a serious problem for several patients, including high-risk older patients. 

Doctors are investigating new classes of medications which do not depend on vitamin K. These are called Non-vitamin K oral anticoagulants (NOACs) and some target the amplification pathway of clotting instead. There are  currently four FDA-approved NOAC drugs on the market; dabigatran (Pradaxa), rivaroxaban (Xarelto), apixaban (Eliquis), and edoxaban (Savaysa). Thrombin and fibrin still get produced and some clotting can occur, but the rapid amplification is shut down. The hope is that this can allow the body to repair trauma and stop external bleeds without building internal clots from AFib. With your help and participation in clinical trials, we can push science without pushing clots.

By Benton Lowey-Ball, BS Behavioral Neuroscience

Sources:

Iwasaki, Y. K., Nishida, K., Kato, T., & Nattel, S. (2011). Atrial fibrillation pathophysiology: implications for management. Circulation, 124(20), 2264-2274. https://doi.org/10.1161/CIRCULATIONAHA.111.019893

Wijesurendra, R. S., & Casadei, B. (2019). Mechanisms of atrial fibrillation. Heart, 105(24), 1860-1867. http://dx.doi.org/10.1136/heartjnl-2018-314267

Vann, M. R. (May 10, 2013) The Sound of an Afib Heartbeat. Everyday Health. https://www.everydayhealth.com/heart-health/sound-of-afib-heartbeat.aspx