How is atrial fibrillation diagnosed ?
In many situations, atrial fibrillation can be detected by simply feeling the pulse in your wrist or by a doctor listening to your heart with a stethoscope. The presence of an irregular and often fast heart beat would suggest that you may have atrial fibrillation. However, the diagnosis of atrial fibrillation needs to be confirmed by an electrocardiogram. In general, additional tests are needed to identify potential underlying causes of atrial fibrillation.
Diagnostic tests and investigations
This is the most important test for diagnosing atrial fibrillation. It is a quick and painless test, which records the electrical activity of your heart from your skin. For this test special stickers (electrodes) are placed on your arms, legs and across the chest (see below). A standard resting ECG only records the heartbeat for a few seconds so if atrial fibrillation is not present during this time a heart monitor is required.
A 12-lead ECG is a quick and painless test, when special stickers (electrodes) are placed on your arms, legs and across the chest to record the heart rhythm (see attached picture). The whole procedure usually takes just a few minutes and it can be done in your GP practice or in a hospital.
Detection of atrial fibrillation may be more difficult in people who develop it only intermittently. It may be necessary to have the ECG tracing recorded for 24 hours or longer (sometimes for 7 days or longer). This test, often called “Holter monitoring”, involves a small recording device attached by wires to 4 special stickers (electrodes) placed on your chest (see above). The device is easy to carry under clothes. You do not need to stay in hospital for this test and can carry on with most of your usual daily activities. A diary of your activities and any symptoms you experience while wearing the device can be useful. This test will provide detailed information on your heart rhythm and important correlations with your symptoms over the period of the recording for your doctor.
An alternative is event monitoring. It only records your heart's electrical activity at certain times while you're wearing it. For many event monitors a button is used to start the recording when you feel symptoms. These wearable event monitors can be used for weeks.
If atrial fibrillation is still not detected but suspected an implantable or insertable cardiac monitor can be used for continuous heart rhythm monitoring. These miniaturized monitors are positioned under the chest skin and can record changes in heart rhythm for up to three years.
Many people now buy their own monitors that can be attached to your smartphone and record just the rhythm of your heart or an ECG tracing. When you experience a symptom you simply pick up your phone and record an ECG (example eg AliveCor).
Once atrial fibrillation is diagnosed you may also be asked to have some blood tests. Although the blood tests are not needed to make the diagnosis of atrial fibrillation, they may help to explain why you have developed atrial fibrillation, for example due to thyroid gland problems and the balance of your body's electrolytes. The blood tests will also help your doctor to choose the best treatment(s) for you.
An echocardiogram, often called an “echo” or an “ultrasound heart scan”, is a test used to check the size and function of your heart. This test is entirely painless and harmless. During this test the healthcare professional (doctor or cardiac technician) will scan your chest using a handheld device with some gel on it in order to characterize the structure and function of the four major chambers of the heart, the heart muscle and valves.
A transesophageal echocardiogram, or TEE, is used to take pictures of your heart through the esophagus (passage leading from your mouth to your stomach). Due to the position of the heart in the chest TEE can give very detailed insights of the most important parts of the heart in patients with atrial fibrillation (the left atrium and its appendage and surrounding heart muscle and valve). TEE is the gold standard to detect blood clots that may be forming because of atrial fibrillation. During this test a flexible tube is introduced through your mouth and positioned in your esophagus. You'll likely be given medicine to help you relax during the procedure.
Additional imaging of the heart
Depending on your medical history additional imaging of the heart can be necessary. Cardiac computer tomography or cardiac magnetic resonance imaging can be used for detailed analysis of the structure and function of the heart. Unlike other imaging tests, magnetic resonance imaging doesn't use radiation or carry any risk of causing cancer. Images from computer tomography or magnetic resonance imaging can be used to guide the treatment of atrial fibrillation. These includes detecting the causes of atrial fibrillation, as well as planning and guidance of catheter ablation procedures. These images can be merged with intracardiac electrograms during an electrophysiological study to form a detailed electrophysiological cardiac landscape.
Some causes or consequences of atrial fibrillation are easier to diagnose when your heart is working hard and beating fast. A stress test can be performed by physical or pharmacological stimulation of the heart. Whether an ECG, echocardiogram, MRI or other method is used to investigate your heart during a stress test depends on your individual situation.