Atrial Fibrillation
The Basics of Heart Function
The heart is an electrical machine. It uses an electrical pulse to pump oxygen-rich blood to the various parts of the body. The heart's pump mechanism is composed of four chambers which are respectively called the left and right atrium, and the left and right ventricles. Each chamber of the heart has its own job. The right atrium receives the "processed" blood supply from the body, and pushes this blood into the right ventricle. The right ventricle sends the blood into the lungs, where the blood becomes freshly oxygenated. Once the blood is full of oxygen, it re-enters the heart through the left atrium, which is the doorway to the left ventricle. The left ventricle then returns the oxygen-rich blood back to the body. This entire process occurs during the space of a single heartbeat. A biological mechanism (called a sinus node) triggers each heartbeat and regulates the chambers. The sinus node is attached to the wall of the right atrium. It lets the chambers know it is time to contract (or "beat") by sending out an electrical impulse to both of the atrial chambers. It sends out approximately 60 to 100 impulses every minute. The sinus node sets the rate of the heartbeat in accordance with the body's level of physical activity. When the body is at rest, there is a decrease in the rate of impulses that the sinus node sends out to the atrial chambers. Conversely, when the body is exercising, the rate of heartbeat-stimulating impulses greatly increases.
The Basics of Atrial Fibrillation
Atrial fibrillation is a type of arrhythmia (or abnormal heart rhythm). It is caused by a disruption of the heart's electrical system. When this disorder occurs, the chambers of the heart do not contract in a coordinated manner. Rather, the atrial chambers are over-stimulated and the heart rate becomes irregular, uncontrolled and extremely rapid. The immediate consequence is that the person experiences heart palpitations, which feels like a fast and uncomfortable throbbing sensation in the heart. In some cases, the irregular rate of the heartbeat makes the person feel like their heart is about to stop, or that they cannot breath properly.
Atrial fibrillations happen when the heart chambers do not receive electrical impulses from the sinus node at a consistent tempo. Instead, the atrial chambers receive erratically-timed impulses that often occur at an extremely rapid rate. As a result, the chambers do not contract in an organized manner, and the walls of the atria begin to quiver (or "fibriallate"). At this point, the rate of the heartbeat is completely uncontrollable. The ventricles begin pumping the blood into the various body parts in a very irregular and rapid rhythm. When a person feels their pulse during an episode of atrial fibrillation, they can easily notice that their heart is beating at an inconsistent tempo.
There are several different types of atrial fibrillation. A person has the "paroxysmal" type if they have recurring episodes of atrial fibrillation that end on their own after a short passage of time. The frequency of the episodes vary. Some people with this condition may experience palpitations only a few times a year, while others may experience recurrences several times a week. The onset of this type of atrial fibrillation is very unpredictable. A person has the "persistent" type of atrial fibrillation is the episodes last for long periods of time. It is possible for drugs to counter the irregular heartbeat rhythm. A person has the "chronic" type if they experience atrial fibrillation with great frequency and for long periods of time. Typically, this type of disorder is not responsive to treatment.
The Effects of Atrial Fibrillation
Atrial fibrillation can have several unwanted effects. First, the irregular pulse may mean that less blood enters the ventricles, which means that the ventricles cannot do their job because they cannot send an adequate flow of blood to the body. Eventually, the weak blood circulation causes an excessive amount of blood to build up in the lungs, which leads to shortness of breath and possible heart failure.
Second, because the heart is not circulating blood properly, it is possible for the blood contained in both atrial chambers to stagnate. Although the risk is small, it is possible for this stagnant blood to become a blood clot. When a blood clot develops, there is a risk that the clot will be pumped through the heart and into the bloodstream. Once in the bloodstream, the clot can travel to the brain where it may become stuck in a cerebral artery and lead to a stroke.
Third, atrial fibrillation can cause a condition called "angina". Angina is a term for acute chest pain. The rapid rate of electrical impulses being pushed through the heart produces an extremely fast heartbeat rhythm. As a result, the heart chambers contract too rapidly, and they cut off blood supply to the body. Ironically, increased heart chamber contraction means that the ventricles need extra oxygen in order to perform this extra work. Thus, the inability of the ventricles to receive an adequate amount of oxygenated blood results in angina.
The Symptoms of Atrial Fibrillation
At first, a person with a developing case of atrial fibrillation may not notice any symptoms. In particular, people do not notice this condition when their overall heartrate remains relatively slow. However, as time goes on, either noticeable symptoms will develop, or a doctor will observe signs of this disorder during a routine examination. Unfortunately, it is possible for symptoms to remain nonexistent up until the point when the affected person experiences a stroke.
The most common symtoms of an atrial fibrillation include the following:
- heart palpitations (a fluttering or throbbing sensation in the heart
- feeling of anxiety
- weakness or fatigue
- swelling in various parts of the body as fluids begin to accumulate due to poor circulation
- dizziness or disorientation
- acute chest pain or pressure
- shortness of breath
- decreased endurance during physical activity
Diagnosis of Atrial Fibrillation
The medical evaluation of patients who are suspected to have an atrial fibrillation includes a physical examination and a medical history investigation. During the medical examination, the doctor will listen to the heart and lungs through a stethoscope. The doctor will be able to detect any sounds that may indicate a leaky heart valve or fluid congestion in the lungs. Other diagnostic methods that a doctor may utilize during a physical examination include feeling the chest region to tell if the heart is enlarged, feeling the thyroid gland to tell if it is enlarged, and testing the reflexes to look for signs of an overactive thyroid gland. An example of a reflex test is when the doctor taps the knee with a rubber hammer.
A doctor may also order an electrocardiogram (ECG). An electrocardiogram produces a graph print-out that depicts the person's heart activity. If the person has an atrial fibrillation, their print-out will show erratic squiggly lines that do not resemble the consistent wave-like lines of a person who has a normal heartbeat. An ECG can also indicate if the person is in danger of having a stroke due to a moving blood clot.
In some cases, a doctor will put a person on an ambulatory monitor. This device is a small box that records the heart's electrocardiographic activity for a prolonged period of time. The box is attached to the person's chest with wires that have electrodes on their terminal ends. During the time of monitoring, the person is asked to make periodic journal entries regarding their activities. The doctor will look at this journal and compare the recorded activities to the monitor's analysis of the person's heart function.
A doctor may also order an echocardiogram. During an echocardiogram, a sound is sent through the chest wall to the heart, where it bounces back and is picked up by a sound receptor. The reflected sound waves are then converted into an image of the person's heart. The doctor can use this image to determine if the person has an atrial fibrillation.
Other tests that may be used during a diagnosis of an atrial fibrillation include a thyroid-stimulating hormone stimulation test, a chest x-ray, a leg scan, blood tests and a cardiac catheterization.
Treatment
Treating an atrial fibrillation is difficult. One of things that makes it difficult is that there are several different types of this condition. The other thing is that people experience such a wide range of symptoms, from mild to severe.
If the person does not have an advanced form of atrial fibrillation, there are medications that can help them. Palpitations can be treated with medications that actually decrease the rate of electrical pulses that pass into the ventricles. The following medications are all used for this purpose: beta-blockers, calcium channel blockers and digoxin. Digoxin is also used to treat people who are at risk of having heart failure.
People who are at risk of developing a blood clot will often be prescribed blood thinners. At the same time, there are special blood thinners that can be used to help people who have already developed a blood clot. The most common medication that serves this purpose is called heparin. This medication is injected into the skin twice a day. There are other medications that are used for long-term blood thinning. Warfarin is one of these medications. Warfarin is particularly helpful with decreasing the chances that the affected person will have a stroke.
Another treatment technique is called "cardioversion". During cardioversion, a doctor will attempt to convert the heartbeat rhythm from atrial fibrillation to a normal sinus rhythm. This treatment option is not available to every person with atrial fibrillation. For instance, people who have had atrial fibrillations for a long period of time, and people who have extremely enlarged atria, are not able to undergo cardioversion. There are two ways that cardioversion takes place. First, certain medications can cause cardioversion to take place. Second, an electric jolt can be used to "shock" the heart back into a normal rhythm.
If a person has an advanced case of atrial fibrillation, they may require other treatment methods. Severe atrial fibrillation includes any case where the person experiences chest pain, shortness of breath or lightheadedness. In most cases of severe atrial fibrillation, the body will not respond to medications. Instead, the doctor will have to attempt cardioversion through applying an electric shock to the heart. During this procedure, the patient is typically sedated. The doctor then places pads to the chest that carry an electric charge. Greater levels of electric charge are applied until the heart reverts to a normal rhythm.
An additional treatment technique for people who have severe atrial fibrillation is called a transesophageal echo. During this process, a microphone device is passed down the throat into the esophagus, which is located near the heart. The device releases sound waves that can be deflected off the heart, and then picked up by a sound receptor. This technique works like an echocardiogram. Thus, using the received sound waves to make a clear image of the heart, the doctor can tell if the patient has any developing blood clots. This information is particularly useful for situations when the person is about to undergo a cardioversion.