The ECG is the most common test for diagnosing AF. It records the electrical activity of your heart, showing its rhythm and rate. During an ECG, sensors are placed on your chest and limbs. The test is quick, painless, and can immediately reveal if you're in AF at that moment. However, if your AF comes and goes (paroxysmal AF), a single ECG might miss it.

For intermittent AF, longer-term monitoring might be necessary. A Holter monitor is a portable ECG device worn for 24 to 48 hours. It continuously records your heart's activity as you go about your daily life. Event monitors are similar but can be worn for weeks. You activate them when you feel symptoms, allowing the doctor to see what's happening with your heart during these episodes.

In some cases, more advanced tests might be needed. An echocardiogram uses sound waves to create a moving picture of your heart, helping doctors see its structure and function. This can reveal underlying heart problems that might be causing AF. For very intermittent AF, your doctor might recommend an implantable loop recorder. This tiny device is placed under the skin and can monitor your heart for up to three years.

Diagnosing AF often involves piecing together information from various tests and your symptoms.