A study was conducted in Al-Assad University Hospital in Lattakia during the period February 2012 and February 2013 the study included a random sample of 97 patients (males and females) divided into three groups: the first group consisted of 16 patients with left atrial enlargement with no atrial fibrillation, the second group included 70 patients who had left atrial enlargement with atrial fibrillation, and the third group of 11 patients had atrial fibrillation with no left atrial enlargement. In the study the ECHO Doppler was used for measuring left atrial volume index (LAVI) through the Simpson method, this is in order to assess the role and relationship with the occurrence of atrial fibrillation. It was found out that three patients out of (16) from the first group about 18.75% developed an atrial fibrillation after one year of follow-up, which means that the left atrial enlargement gave a predication of the occurrence of atrial fibrillation. The continuation of atrial fibrillation was also noticed together with its lifetime with an increase in the size of left atrial after one year of following-up the patients of the second group. 3 out of (11) patients from the third group had an increase in the left atrial volume index at the end of the study 45.45% (P<0.001), Accordingly the atrial fibrillation could cause left atrial enlargement.Even though the left atrial enlargement may cause atrial fibrillation and vice versa according to thisstudy, the study shows the possibilities of existence of other variable factors related to atrial fibrillation whichplay a role in the occurrence.