[Atrail fibrillation and heart failure: a complex relationship].

Atrial fibrillation (AF) and heart failure (HF) often coexist in the same patient, not only because they can result from the same heart disease, but also because each of them can directly lead to the other. In the genesis of AF, structural, electrical and functional factors share a key role, but the importance of any of them is variable, according to the different clinical situations. AF causes atrial changes, electrical, anatomical or both, that can result in maintenance, recurrence and even irreversibility of the arrhythmia.