This is a medical question of type : exams and tests 
 How to diagnose Atrial Fibrillation ? 
 Atrial fibrillation (AF) is diagnosed based on your medical and family histories, a physical exam, and the results from tests and procedures.
                
Sometimes AF doesn't cause signs or symptoms. Thus, it may be found during a physical exam or EKG (electrocardiogram) test done for another purpose.
                
If you have AF, your doctor will want to find out what is causing it. This will help him or her plan the best way to treat the condition.
                
Specialists Involved
                
Primary care doctors often are involved in the diagnosis and treatment of AF. These doctors include family practitioners and internists.
                
Doctors who specialize in the diagnosis and treatment of heart disease also may be involved, such as:
                
Cardiologists. These are doctors who diagnose and treat heart diseases and conditions.
                
Electrophysiologists. These are cardiologists who specialize in arrhythmias.
                
Medical and Family Histories
                
Your doctor will likely ask questions about your:
                
Signs and symptoms. What symptoms are you having? Have you had palpitations? Are you dizzy or short of breath? Are your feet or ankles swollen (a possible sign of heart failure)? Do you have any chest pain?
                
Medical history. Do you have other health problems, such as a history of heart disease, high blood pressure, lung disease, diabetes, or thyroid problems?
                
Family's medical history. Does anyone in your family have a history of AF? Has anyone in your family ever had heart disease or high blood pressure? Has anyone had thyroid problems? Does your family have a history of other illnesses or health problems?
                
Health habits. Do you smoke or use alcohol or caffeine?
                
Physical Exam
                
Your doctor will do a complete cardiac exam. He or she will listen to the rate and rhythm of your heartbeat and take your pulse and blood pressure reading. Your doctor will likely check for any signs of heart muscle or heart valve problems. He or she will listen to your lungs to check for signs of heart failure.
                
Your doctor also will check for swelling in your legs or feet and look for an enlarged thyroid gland or other signs of hyperthyroidism (too much thyroid hormone).
                
Diagnostic Tests and Procedures
                
EKG
                
An EKG is a simple, painless test that records the heart's electrical activity. It's the most useful test for diagnosing AF.
                
An EKG shows how fast your heart is beating and its rhythm (steady or irregular). It also records the strength and timing of electrical signals as they pass through your heart.
                
A standard EKG only records the heartbeat for a few seconds. It won't detect AF that doesn't happen during the test. To diagnose paroxysmal AF, your doctor may ask you to wear a portable EKG monitor that can record your heartbeat for longer periods.
                
The two most common types of portable EKGs are Holter and event monitors.
                
Holter and Event Monitors
                
A Holter monitor records the heart's electrical activity for a full 24- or 48-hour period. You wear small patches called electrodes on your chest. Wires connect these patches to a small, portable recorder. The recorder can be clipped to a belt, kept in a pocket, or hung around your neck.
                
You wear the Holter monitor while you do your normal daily activities. This allows the monitor to record your heart for a longer time than a standard EKG.
                
An event monitor is similar to a Holter monitor. You wear an event monitor while doing your normal activities. However, an event monitor only records your heart's electrical activity at certain times while you're wearing it.
                
For many event monitors, you push a button to start the monitor when you feel symptoms. Other event monitors start automatically when they sense abnormal heart rhythms.
                
You can wear an event monitor for weeks or until symptoms occur.
                
Stress Test
                
Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise to make your heart work hard and beat fast while heart tests are done. If you can't exercise, you may be given medicine to make your heart work hard and beat fast.
                
Echocardiography
                
Echocardiography (echo) uses sound waves to create a moving picture of your heart. The test shows the size and shape of your heart and how well your heart chambers and valves are working.
                
Echo also can identify areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and previous injury to the heart muscle caused by poor blood flow.
                
This test sometimes is called transthoracic (trans-thor-AS-ik) echocardiography. It's painless and noninvasive (no instruments are inserted into the body). For the test, a device called a transducer is moved back and forth over your chest. The device sends special sound waves through your chest wall to your heart.
                
The sound waves bounce off the structures of your heart, and a computer converts them into pictures on a screen.
                
Transesophageal Echocardiography
                
Transesophageal (trans-e-SOF-ah-ge-al) echo, or TEE, uses sound waves to take pictures of your heart through the esophagus. The esophagus is the passage leading from your mouth to your stomach.
                
Your heart's upper chambers, the atria, are deep in your chest. They often can't be seen very well using transthoracic echo. Your doctor can see the atria much better using TEE.
                
During this test, the transducer is attached to the end of a flexible tube. The tube is guided down your throat and into your esophagus. You'll likely be given medicine to help you relax during the procedure.
                
TEE is used to detect blood clots that may be forming in the atria because of AF.
                
Chest X Ray
                
A chest x ray is a painless test that creates pictures of the structures in your chest, such as your heart and lungs. This test can show fluid buildup in the lungs and signs of other AF complications.
                
Blood Tests
                
Blood tests check the level of thyroid hormone in your body and the balance of your body's electrolytes. Electrolytes are minerals that help maintain fluid levels and acid-base balance in the body. They're essential for normal health and functioning of your body's cells and organs.