Atrial fibrillation—Afib, or simply AF—is the most common form of heart arrhythmia, affecting more than two million people in the United States and over four million people in Europe. If detected early, it can be successfully treated and, in some cases, cured. If left to linger, however, it can be deadly.
What is atrial fibrillation (AF)?
A quick look at the heart shows it is composed of four chambers. The lower two chambers are the left and right ventricles that do most of the work to pump blood through the body. The upper chambers are the left and right atria (the plural of “atrium”), which assist the ventricles.
The right atrium contains what is known as the “sinoatrial” or “SA” node. This group of special cells is the heart’s “natural pacemaker” and initiates each heartbeat. As you might imagine, the SA node normally “pulses” 60 to 100 times per minute, producing a normal “sinus rhythm” or heart rate.
During AF, additional abnormal electrical excitations generated in or near the atria—as many as 500 per minute—disrupt the heart’s normally stable and rhythmic cycle of electrical activity. The atria beat irregularly, rapidly, and out of sequence with the ventricles.
There are four different classifications of AF based on frequency and length of episodes.
First detection: Only one diagnosed AF episode
Paroxysmal AF: Recurring AF episodes that end by themselves in less than seven days
Persistent AF: Recurring AF episodes that last more than seven days
Permanent AF: Ongoing long-term AF episodes
What causes atrial fibrillation?
There are many theories and observations about what may cause AF. These include:
- Age (approximately eight percent of people over age 80 develop AF)
- Alcohol consumption (excessive, more than two to three drinks per day)
- Carbon monoxide poisoning
- Congenital heart disease and defects
- Coronary artery disease (CAD)
- Genetic mutations (e.g. Friedreich's ataxia) or family history of atrial fibrillation
- Heart attacks
- Heart surgery
- Heart valve abnormalities
- Hypertension (High blood pressure)
- Hypertrophic cardiomyopathy (HCM)
- Lung disease (e.g. pneumonia, emphysema, cancer, sarcoidosis, pulmonary embolism)
- Pericarditis (infection of the lining around the heart)
- Rheumatoid arthritis
- Sleep apnea
- Stimulants (e.g. certain medications, caffeine, tobacco, etc.)
- Viral infections
All of these conditions are associated with higher rates of atrial fibrillation. Essentially, anything that affects the structure of the heart or its electrical function can potentially trigger atrial fibrillation.
How do I know if I have atrial fibrillation?
While many people have no symptoms at all, the classic symptoms include:
- Chest pain
- Decreased blood pressure
- Heart palpitations (sensations of a racing, uncomfortable, or irregular heartbeat)
- Lightheadedness or confused state
- Shortness of breath
If you notice these symptoms, call your doctor as soon as possible to schedule an appointment for a thorough examination to determine the cause. Symptoms such as chest pain or shortness of breath should always be checked out immediately by a trip to the emergency room as they may also be a sign of an impending heart attack.
Types of tests
AF can be detected by several different tests your doctor may perform either routinely or as part of a specialized examination to confirm the presence of AF regardless of the appearance of noticeable symptoms. These tests include:
Electrocardiogram (ECG). This is the standard test of heart electrical activity. Electrodes are attached to various parts of your chest. During the test, a waveform known as a PQRST wave is generated and charted.
If the “P” portion of the wave (the electrical signal from your SA node) is missing or irregular, it may indicate atrial fibrillation.
Holter monitor. Episodes of AF frequently will not occur in a doctor’s office while taking a standard ECG test. A Holter monitor is essentially a portable ECG you wear on your belt that records your heart’s electrical activity for an extended period of time (typically 24 hours). You go to your doctor’s office to be “wired up” and then go about your normal daily activity (exercise included, but no showers). You return to your doctor’s office after a specified time period to remove the wires and have the recording interpreted (often by a computer). Once again, a missing or irregular “P” wave suggests AF.
Echocardiogram. Sound waves from a probe a technician will maneuver along your chest are used to produce a video image of your heart. It is painless (well, except perhaps for that cold gel they use to aid conduction of the sound waves and help slide the probe along your chest). Echocardiograms allow your doctor to visualize the movement and structure of your heart chambers and valves. Irregular movement of the atria could indicate the presence of AF.
There are numerous other tests your doctor may perform to try to determine the source of your AF (such as thyroid and electrolyte blood tests) if any of the above tests are positive for AF.
Why is atrial fibrillation dangerous?
Since electrical signals from your atria typically determine your heart rate, one might think that the greatest danger from AF would be sudden cardiac death (SCD) due to ventricular fibrillation (an extremely deadly condition). But fortunately, nature has given us a built-in safeguard. Electrical signals from the atria must first pass through the atrioventricular (AV) node on their way to the ventricles. The AV node typically limits the number of electrical impulses allowed to pass through to no more than 175 per minute. The ventricles may beat irregularly (producing all the symptoms mentioned earlier) but rarely produce life-threatening ventricular fibrillation.
The most frequent, life-threatening complication of AF is stroke. In fact, AF is thought to account for approximately 17 percent of all strokes. Because the atria beat erratically, blood does not flow in and out of the atria as efficiently. Small quantities of blood can begin to coagulate and form clots within the atria. This is particularly true of the left atrium. It has a structure called the left atrial appendage (LAA), best described as a small sac near the top of the atrium. Blood easily pools and “stagnates” within this sac, sharply increasing the risk of a clot forming. That clot can break free and lodge in an artery, starving any part of the body of oxygen. However, they frequently travel to the brain, causing a stroke.
How is atrial fibrillation treated?
AF can be successfully treated using many techniques. Drug treatments that focus on controlling the rate and rhythm of the heartbeat as well as drugs that thin the blood to inhibit the formation of blood clots are common. This is a complex area of treatment. The most troublesome aspect of drug treatment involves therapy to prevent clots. This is potentially a lifetime commitment and often requires weekly blood tests to properly manage drug dosage.
Some of the most interesting AF treatment developments involve using minimally invasive surgical procedures that attempt to eliminate or “disconnect” the source of the erratic atrial electrical impulses. This procedure is generically known as “catheter ablation.” Tissues in the heart suspected of generating or conducting abnormal electrical impulses can be destroyed using either high heat from lasers or radio-frequency energy or using extreme cold (cryogenic freezing).
The surgery is not always successful but, when it is, it can provide a temporary or complete cure. This is both exciting and important because a recent study suggests that it may be safe to stop oral anticoagulation (blood thinning) therapy after three to six months in patients who undergo successful catheter ablation for AF. Several AF treatment centers have already begun to implement a protocol for discontinuing blood thinners based on a standardized risk assessment.
Since AF often arises out of damage and other “insults” to the heart, there are also common health and lifestyle changes that can help prevent or reduce episodes of AF. These include:
- Avoiding alcohol
- Avoiding stimulants (e.g. caffeine, cold medications containing pseudoephedrine)
- Adopting a heart-healthy diet
- Using less salt in order to lower blood pressure (if you are salt sensitive)
- Exercising as much as possible up to the limits set by your doctor
- Quitting smoking
What are the take-away concepts on atrial fibrillation?
- Pay attention to AF symptoms and contact your doctor for further testing if you notice any.
- If your symptoms include chest pain or shortness of breath, go to the emergency room.
- Don’t neglect your symptoms. AF is often benign but can be deadly if not properly treated.
- AF can be successfully treated, perhaps even cured.
This article was written to help you understand AF and work effectively to detect and treat AF in partnership with your doctor. As always, be certain to consult with your doctor before making any changes to your health regimen or treatment.