Atrial fibrillation (AFib) is the most common type of cardiac arrhythmia, a disorder involving the heart’s rate or rhythm. This condition is characterized by an irregular and often rapid heartbeat that originates in the upper chambers of the heart. Understanding AFib, its mechanism, signs, and the serious health complications it can cause is important for early detection and appropriate medical management.
Understanding Atrial Fibrillation
The heart’s rhythm is normally controlled by the sinoatrial (SA) node, a specialized group of cells in the upper right chamber that acts as the natural pacemaker. This node generates an electrical impulse that travels smoothly across the atria, causing them to contract and push blood into the ventricles. This process results in a regular resting heart rate, typically between 60 and 100 beats per minute.
In AFib, the orderly signal from the SA node is disrupted by numerous, chaotic electrical impulses. This electrical overload causes the atria to not contract effectively but rather to simply quiver or fibrillate in a disorganized manner. Because the atria are quivering, they cannot efficiently pump blood into the ventricles.
These chaotic signals flood the atrioventricular (AV) node, which acts as a gatekeeper to the ventricles, resulting in a fast and highly irregular ventricular rhythm. Their rapid and irregular beating compromises the heart’s overall efficiency in moving blood to the lungs and the rest of the body. In people with AFib, the ventricular heart rate can range from 100 to 175 beats per minute, significantly faster than a normal resting rate.
Recognizing the Signs and Risk Factors
Symptoms
AFib symptoms vary significantly, and some people experience no noticeable symptoms at all, a condition sometimes referred to as “silent AFib.” For those who are symptomatic, the most commonly reported feeling is heart palpitations, described as a sensation of the heart racing, fluttering, or pounding in the chest.
Other physical manifestations include fatigue, lightheadedness, or dizziness, which result from the heart’s reduced pumping efficiency. People may also experience shortness of breath, especially during physical activity, or chest pain, which warrants immediate medical attention. Symptoms can fluctuate, with episodes coming and going (paroxysmal AFib) or remaining constant (persistent AFib).
Risk Factors and Triggers
Several conditions and lifestyle factors increase a person’s susceptibility to developing AFib. Advanced age is a significant non-modifiable risk factor, with the risk increasing notably after age 65. Pre-existing cardiovascular conditions, such as high blood pressure and coronary artery disease, are common underlying causes, as they can lead to structural changes in the heart tissue.
Other chronic health conditions that raise the risk include obesity, diabetes, and obstructive sleep apnea. These conditions often put stress on the atria, leading to electrical and structural remodeling. Lifestyle choices like excessive alcohol use and the use of stimulants, such as certain cold medicines or illegal drugs, can also trigger AFib episodes.
Why AFib Requires Medical Attention
The primary dangers of untreated AFib stem from two major complications: a heightened risk of stroke and the potential development of heart failure. During an AFib episode, the atria do not contract properly, causing blood to pool inside the upper chambers, particularly in a small pouch called the left atrial appendage. This pooling creates an environment where blood clots can easily form.
If a clot breaks free and travels out of the heart, it can enter the bloodstream and lodge in an artery supplying the brain, causing an ischemic stroke. People with AFib face a three to five times greater risk of this type of stroke compared to those with a normal heart rhythm, making it the leading cardiac cause of stroke. This increased stroke risk exists even in the absence of noticeable symptoms.
The second serious complication is heart failure, which develops because the prolonged, rapid, and irregular heart rate weakens the ventricles over time. The heart beats so quickly and inefficiently that it cannot properly fill or pump enough oxygenated blood to meet the body’s needs. This sustained strain can lead to tachycardia-mediated cardiomyopathy, where the heart muscle becomes damaged and unable to function effectively.
Methods of Diagnosis and Treatment
Diagnosis
The diagnosis of AFib typically begins with a physical examination and a review of the patient’s medical history and symptoms. The primary tool for confirming AFib is the electrocardiogram (ECG or EKG), which records the heart’s electrical signals and shows the characteristic fast, chaotic pattern. Because AFib episodes can be intermittent, a doctor may order continuous monitoring devices.
These devices include Holter monitors, which record heart activity for 24 to 48 hours, or cardiac event recorders, which can be worn for weeks or months to capture less frequent episodes. Blood tests are performed to check for underlying conditions, such as thyroid disease. An echocardiogram, an ultrasound of the heart, may be used to evaluate the heart’s structure and function.
Treatment Goals and Options
Treatment for AFib focuses on two main goals: managing the heart’s rhythm and rate, and preventing stroke. To reduce the risk of stroke, medications known as anticoagulants, or blood thinners, are prescribed to prevent blood clot formation. Modern direct oral anticoagulants are often used as they are safer and simpler to manage than older medications like warfarin.
For heart rate and rhythm control, physicians use medications such as beta-blockers and calcium channel blockers, which help slow the heart rate and allow the ventricles to fill more completely. Antiarrhythmic drugs are used to restore and maintain a normal heart rhythm. If medication is insufficient, procedural interventions may be considered.
These procedures include cardioversion, which uses an electrical shock or medication to reset the heart to a normal rhythm. Another common procedure is catheter ablation, a minimally invasive technique where a catheter is threaded through a blood vessel to the heart. This procedure uses heat or cold energy to create tiny scars that block the faulty electrical signals causing the AFib.