Atrial Fibrillation (A Fib) Diagnosis

      The doctor will often begin by asking the patient about their medical history to help determine the severity of symptoms. The doctor will assess if any associated factors (for example, alcohol or caffeine intake) may be contributing to the patient's symptoms. The doctor will also listen to the patient's heartbeat and lungs. The evaluation may include the following tests:
     Electrocardiogram (ECG or EKG): This is the primary test to determine when an arrhythmia is atrial fibrillation. The ECG can help the doctor distinguish A fib from other arrhythmias that may have similar symptoms (atrial flutter, supraventricular tachycardia, or runs of ventricular tachycardia). The test can also sometimes reveal damage (ischemia) to the heart, if there is any.
      The following illustrations show the usual ECG tracing from a patient with A fib; the second figure shows the different appearance between a normal (single lead) ECG tracing and the irregular appearance of an atrial fibrillation (single lead) ECG tracing. The atrial tracing for the A fib tracing shows a slowed irregular heartbeat of A fib, where the irregular waves are easily seen before the heartbeat (Figure 2). These waves can be seen if the heartbeat is slowed; they are difficult to see in patients with a rapid heartbeat shown in Figure 3.

 

Figure 2. Rapid heart rate ECG of a patient with atrial fibrillation. 

 

Figure 3. Picture of atrial fibrillation

   Lab tests: There is no blood test that can confirm that a person has atrial fibrillation. However, blood tests may be done to check for certain underlying causes of atrial fibrillation and to rule out heart damage, as from a heart attack. People already taking medication for atrial fibrillation may need blood tests to make sure there is enough of the drug (usually digoxin) in their system to work effectively. Blood tests that may be done to rule out other conditions include:

• Complete blood cell count (CBC) 

• Markers for heart injury or stress (enzymes such as troponins and creatine kinase [CK] and BNP)

• Digoxin drug level (in patients taking this medication)

•  Prothrombin time (PT) and international normalized ratio (INR) (For those taking warfarin [Coumadin] to prevent blood clotting, these tests show how well the drug is working to lower the risk of a blood clot forming in the heart or elsewhere.) 

• Serum electrolytes to evaluate sodium and potassium levels

• Thyroid function tests for hyperthyroidism 

  Chest x-ray: This imaging test is used to evaluate for complications such as fluid in the lungs or to estimate heart size.
Echocardiogram or transesophageal echocardiogram: This is an ultrasound test that uses sound waves to make a picture of the heart while it is beating.

• This test is done to identify problems in heart valves or ventricular function or to look for blood clots in the atria. 

• This very safe test uses the same technique used to check a fetus in pregnancy.

 Ambulatory electrocardiogram (Holter monitor): This test involves wearing a monitor similar to that used for an ECG for a period of time (usually 24-48 hours) to try to document the arrhythmia while people go about their everyday activities.

• The device is worn for 24-48 hours and is named a Holter monitor. 

• An event monitor is a device that can be worn for 1-2 weeks and records the heart rhythm when it is activated by the patient; it is similar to a Holter monitor but only records heart rhythms when activated by the patient. 

• These tests may be used if symptoms come and go and ECGs do not reveal the arrhythmia or other problems that could lead to similar symptoms of A fib.