When a person has atrial fibrillation (A-fib), the electrical signals don't conduct like they usually would. As a result, the top portions of the heart may contract several times or out of time with the chambers in the bottom portion of the heart.
One of the ways a doctor will monitor A-fib is by examining an electrocardiogram (EKG). This painless test uses electrodes applied to different locations on the chest to measure the heart's electrical activity.
If a person has A-fib, their EKG will have a few distinct characteristics as highlighted in this article.
A "normal" EKG is one that shows what is known as sinus rhythm. Sinus rhythm may look like a lot of little bumps, but each relays an important action in the heart.
An EKG displays P Waves, T Waves, and the QRS Complex. These may have abnormalities in people with A-fib.
A few key aspects of the EKG exist, and these will often look different when compared to an EKG of a person that has A-fib:
- P Waves: P waves are the first "bump" on the EKG. They represent the time when the atria, the upper chambers of the heart, are squeezing blood through the heart.
- QRS Complex: The QRS complex is when the ventricles, the lower chambers of the heart, contract. This will distribute blood throughout the body.
- T Waves: The T wave comes after each QRS complex and represents the brief moment when the heart relaxes before starting to squeeze again.
An EKG of a person with A-fib is very different in its appearance when compared with sinus rhythm. While there are variations on an A-fib EKG, some examples of these variations include:
- Absence of P waves: The atria typically contract due to a signal, which appears as the "P" wave that an EKG measures. When a person has A-fib, the atria don't usually contract from this signal, so a doctor won't usually view P waves before a QRS.
- Irregular rhythm: People with A-fib sometimes have a rhythm that is described as "irregularly irregular." The rhythm isn't even, like sinus rhythm, but it has a pattern to it. This irregular rhythm is what can lead to heart palpitations and other A-fib symptoms.
- Fibrillatory waves: Some people with A-fib will have fibrillatory waves on their EKG. These waves are a sign of the atria pulsing out of time. Fibrillatory waves can look a lot like P waves, and this can make an A-fib rhythm look like sinus rhythm. However, an A-fib rhythm is usually irregular while sinus rhythm is consistent and even.
When an EKG measures how many beats per minute, the device is measuring how many times the ventricle beats each minute, or the number of QRS complexes. Because an A-fib rhythm can change from beat to beat, an EKG in real time may read varying numbers, such as 72 to 84 to 60 all within the span of several seconds.
Several different subtypes of A-fib exist. Some are determined by their symptoms while others can be detected on an EKG. Examples of some A-fib types a doctor can identify by EKG include:
A doctor can diagnose some types of A-fib by looking at an EKG.
- Ashman's phenomenon: A type of A-fib where there is a long pause between heartbeats, then several beats that are close together. These beats usually display a right bundle branch block (BBB), which indicates the right ventricle may not be conducting electricity through the heart as effectively.
- A-fib with rapid ventricular response: Also known as A-fib with RVR, this type means the heart is beating faster than 100 beats per minute. The heart can range in pace from 100 to 120 to 145 and back again. Beating at this fast rate can weaken the heart and can lead to heart failure.
- Paroxysmal A-fib: Paroxysmal A-fib occurs when a person doesn't consistently have an A-fib rhythm, but instead goes in and out of it.
- Continuous A-fib: When a person has continuous A-fib, they are always in an A-fib rhythm.
There are different ways a doctor can view A-fib on an EKG. An EKG called a 12-lead EKG is usually the most sensitive because the EKG measures the heart from 12 different locations on the body.
When the heart doesn't beat in time, it can create a fluttering in the chest. A person may sometimes get short of breath and feel lightheaded.
A-fib can also increase a person's risk of blood clots in the heart, which can increase a person's risk for stroke.
Common symptoms of A-fib can include:
- heart palpitations, as if the heart is flip-flopping
- lightheadedness or feeling as if one may pass out
- shortness of breath
When the heart beats very rapidly, a person can start to feel very anxious. Because their heart can't pump out blood as effectively, they may become short of breath.
The A-fib symptoms are often the signs of an underlying heart disease that can damage the heart's structure.
Examples of these causes can include:
- abnormalities of the heart valves
- congenital heart defects
- coronary artery disease
- high blood pressure
- history of previous heart surgeries
- overactive thyroid gland
- underlying lung disease
It is also possible that a person can have a condition known as lone A-fib. This is A-fib that occurs without an underlying cause.
Treatments for A-fib can depend upon the severity of person's symptoms, the underlying cause, and how long a person has had the condition.
Because A-fib can lead to the development of blood clots that could possibly cause a stroke, a doctor will often first prescribe anticoagulants to reduce the likelihood that blood clots will form.
Depending on the severity of the A-fib, it may be treated with anticoagulants.
Anticoagulants are drugs that thin the blood. Examples of these anticoagulants could include:
If a person's heart rate is very rapid, a doctor may also prescribe medications to help slow heart rhythm. Examples can include calcium channel blockers, such as diltiazem, or beta-blockers, such as metoprolol.
Sometimes, a doctor may recommend trying to "reset" the heart's rhythm through treating the abnormal electrical patterns. These treatments may include:
- Cardioversion: An electrical shock is delivered to the heart, causing the heart to very briefly stop. After this point, the heart's electrical activity will restart. Ideally, the rhythm after this will be normal sinus rhythm.
- Medication management: A class of medications known as antiarrhythmics may be prescribed to reduce the incidence of A-fib. Examples of these medications include flecainide, dofetilide, amiodarone, or sotalol.
If these medications prove ineffective, a doctor may recommend more invasive procedures to correct A-fib.
An example is a catheter ablation, which involves inserting a catheter through a blood vessel in the groin to access areas of the heart. A doctor will then use extreme cold, extreme heat, or energy radiofrequency to destroy the heart tissue to keep the heart from sending out abnormal electrical signals.