Complications may occur immediately following the heart attack (in the acute phase), or may need time to develop (a chronic problem). Acute complications may include heart failure if the damaged heart is no longer able to pump blood adequately around the body; aneurysm of the left ventricle myocardium; ventricular septal rupture or free wall rupture; mitral regurgitation, in particular if the infarction causes dysfunction of the papillary muscle; Dressler's syndrome; and abnormal heart rhythms, such as ventricular fibrillation, ventricular tachycardia, atrial fibrillation, and heart block. Longer-term complications include heart failure, atrial fibrillation, and an increased risk of a second MI.

Atrial fibrillation can only be what kind of problem?