In case of sudden onset of out-of-hospital atrial fibrillation, one should remain calm, rest in a sitting or lying position, and refrain from excessive stress and anxiety. Patients with paroxysmal atrial fibrillation often have sudden episodes of out-of-hospital atrial fibrillation. In the absence of serious underlying cardiac disease, episodes of atrial fibrillation are not immediately life-threatening, so when you feel palpitations, chest tightness, shortness of breath, feel the pulse rate is absolutely uneven, and suspect a recurrence of atrial fibrillation, first of all, do not panic, immediately sit or lie down and rest, breathe deeply to stay calm. Oxygen can be administered if available, and do not be overly nervous and anxious. If the ventricular rate is faster than 100 beats per minute during an episode of atrial fibrillation, patients with no previous history of bradycardia or syncope may take some heart-rate slowing drugs, such as beta-blocker drugs (e.g., metoprolol) in common dosage form, with advance permission from the physician. Since various types of arrhythmias have similar performance, when it is not clear whether the symptoms are caused by atrial fibrillation, it is not recommended to take medication on your own, and you need to go to the hospital to get an electrocardiogram to clarify the diagnosis before treatment. All medications should be taken under the guidance of a physician and should not be taken in a panic or based on the experience of others. When atrial fibrillation persists without remission or is accompanied by worsening cardiac insufficiency, call 120 or 999 for help as soon as possible. It is common for patients with atrial fibrillation to have an out-of-hospital atrial fibrillation episode. Do not overstress during an episode, but rest immediately and take oxygen or deep breaths to stay calm. Medications may be taken to control the rapid ventricular rate with the consent of the physician, but do not adjust the dosage of medications on your own.