Atrial Fibrillation (AFib) is the most common sustained heart rhythm disorder, characterized by an irregular and often very rapid heart rate. It is an arrhythmia where the heart’s upper chambers, the atria, beat chaotically and out of sync with the lower chambers. AFib increases the risk of stroke, heart failure, and other heart-related complications. The prevalence of AFib rises significantly with age, affecting approximately 9% of individuals over 75 years old.
How AFib Affects Heart Function
The heart’s normal rhythm originates from the sinoatrial (SA) node, the natural pacemaker located in the right atrium. This node sends a regular electrical impulse that causes the atria to contract, pushing blood into the ventricles before they contract. In AFib, this ordered signaling is overwhelmed by disorganized, rapid impulses, often arising from tissue around the pulmonary veins.
These chaotic electrical signals cause the atria to merely “quiver” or fibrillate instead of contracting effectively. The signals flood the atrioventricular (AV) node, which acts as a gatekeeper between the upper and lower chambers. Since the AV node cannot block all the rapid impulses, it allows many to pass through irregularly, resulting in a fast and disorganized ventricular beat. This irregular rhythm can push the heart rate up to 100 to 175 beats per minute or more.
The quivering means the atria lose their ability to contribute to the heart’s pumping action. This loss of efficient contraction, combined with the rapid ventricular rate, reduces the heart’s overall pumping efficiency and circulation. Furthermore, the lack of complete atrial emptying causes blood to pool, particularly in the left atrial appendage, which significantly increases the risk of blood clot formation.
Identifying the Symptoms and Diagnosis
The symptoms of AFib vary widely; some individuals experience no noticeable signs and the condition is only discovered during routine testing. For those who do experience symptoms, the most common is a sensation of a fluttering, pounding, or racing heartbeat, known as palpitations. Other frequent complaints include fatigue, weakness, and a reduced ability to exercise.
Patients may also experience shortness of breath, dizziness, or lightheadedness, which can sometimes progress to fainting. Chest discomfort or pain can occur, requiring immediate medical attention. AFib is classified based on its pattern: paroxysmal AFib describes episodes that start and stop on their own, usually within seven days.
Persistent AFib lasts longer than seven days and requires medical intervention to restore a normal heart rhythm. Diagnosis begins with a physical examination, including checking the pulse for irregularity. The definitive diagnosis relies on an electrocardiogram (ECG or EKG), which records the heart’s electrical activity and shows the disorganized atrial activity.
Since AFib episodes can be intermittent, a standard ECG may not capture the event. This necessitates the use of portable heart monitoring devices.
Portable Monitoring Devices
- A Holter monitor is a small device worn for 24 to 48 hours to continuously record the heart rhythm during daily activities.
- For less frequent episodes, an event recorder or a mobile cardiac telemetry device may be used to record the heart’s activity over several weeks.
Primary Causes and Risk Factors
AFib often develops as a consequence of underlying health conditions that cause structural or electrical changes within the atria. High blood pressure is one of the most common modifiable risk factors, as it can cause the heart muscle to stiffen and thicken, altering how electrical signals travel. Other forms of heart disease, such as coronary artery disease, heart valve disease, and heart failure, also increase the risk of developing AFib.
Conditions that place chronic stress on the body are strongly associated with AFib. These include obesity and diabetes, which contribute to inflammation and remodeling of the atrial tissue. Obstructive sleep apnea is another recognized risk factor that puts strain on the heart, leading to structural changes that promote AFib.
Lifestyle choices and age also play a role in risk. The risk of AFib increases after age 65, reflecting the cumulative effect of aging and other conditions. Excessive alcohol consumption and the use of stimulants like nicotine and certain drugs can trigger episodes or contribute to the long-term development of the condition.
Treatment Approaches and Management
The management of AFib is centered on two primary goals: controlling the heart rate and restoring a normal rhythm. Rate control aims to slow the ventricular rate to a sustainable level using medications. Beta-blockers, such as metoprolol, and certain calcium channel blockers, like diltiazem, are commonly prescribed to dampen the effect of the chaotic signals reaching the ventricles.
Rhythm control focuses on restoring and maintaining the heart’s normal sinus rhythm. This can be achieved pharmacologically using antiarrhythmic drugs like flecainide or sotalol. A more immediate method is electrical cardioversion, a procedure that uses a controlled electrical shock delivered through the chest to momentarily reset the heart’s electrical system, allowing the SA node to regain control.
For patients who do not respond well to medications, catheter ablation is an interventional procedure. During ablation, thin, flexible wires are guided into the heart to pinpoint and destroy the small areas of tissue, often near the pulmonary veins, that are generating the disorganized electrical impulses.
Stroke prevention is a dedicated strategy. Due to the ineffective contraction of the atria, blood can pool and form clots, which can then travel to the brain. Therefore, treatment includes long-term anticoagulation. Medications such as warfarin or direct oral anticoagulants (DOACs) like apixaban or rivaroxaban are prescribed to reduce the risk of clot formation and subsequent stroke.