Atrial fibrillation may occur in all the following conditions except

Cardioversion within 48 h of the onset of AF is common practice in patients who have not been anticoagulated, provided that they are not at high risk for stroke due to a prior history of embolic events, rheumatic mitral stenosis, or hyperophic cardiomyopathy with marked left atrial enlargement. Ref Harrison 20th edition pg 1432