Whether atrial fibrillation of the heart is dangerous or not has a lot to do with its complications. It is generally not life-threatening, but if repeated atrial fibrillation cannot be controlled, there are likely to be some complications, such as atrial fibrillation thrombus dislodgement, malignant arrhythmia, and atrial fibrillation leading to heart failure, leading to adverse consequences. The details are as follows: 1. Atrial fibrillation thrombus dislodgement: when thrombus dislodgement occurs in atrial fibrillation, it can cause cerebral infarction, mesenteric embolism, pulmonary embolism and so on. When the area of cerebral infarction is large, it can cause cerebral ischemia, hypoxia, brain cell damage, necrosis and so on, leading to life-threatening. Mesenteric embolism can lead to life-threatening acute abdominal conditions such as abdominal pain, vomiting, and intestinal necrosis. Pulmonary embolism may cause shortness of breath. 2. Atrial fibrillation leads to malignant arrhythmia: for example, atrial fibrillation combined with rapid ventricular rate reduces cardiac output and sometimes causes acute pulmonary edema, which can be life-threatening. 3. Atrial fibrillation leads to heart failure: for organic heart disease, repeated atrial fibrillation can lead to cardiac insufficiency, heart failure, and a greater risk of sudden death. Therefore, patients with atrial fibrillation should actively treat the primary disease, actively control atrial fibrillation, and use anticoagulant drugs to prevent thrombosis, to prevent life-threatening.