Background: Although often referred to as “the forgotten chamber", compared with left ventricle (LV), especially in the past years, the left atrium (LA) plays a critical role in the clinical expression and prognosis of patients with heart and cerebrovascular disease, as demonstrated by several studies. Objective: The aim of the work was to assess the left atrium functional and volume changes during atrial fibrillation (AF) and after sinus rhythm cardioversion in patients with paroxysmal AF, to detect recovery of effective mechanical atrial function (EMAF) after cardioversion with preserved bioelectrical function. Patients and methods: This prospective observational study included a total of 75 subjects divided on two groups: Group 1 (control) consisted of 25 apparently normal people with normal sinus rhythm, and Group 2 (patients) consisted of 50 patients with paroxysmal atrial fibrillation, attending at Damanhur Medical National Institute, for cardioversion. 25 (50%) of patients were cardioverted pharmacologically either by amiodarone or propafenone and 25 (50%) of patients were cardioverted by DC shock. Results: Mean age of controls involved in the study was 44.60 ± 9.82 years. 56% of them were males. Mean age of patients was 51.40 ± 7.23, 54% of them were males. Left Anterior Descending Artery (LAD) showed a significant decreased after cardioversion and after one month. It showed insignificant decrease after 2 months. Number of patients who did not recovered effective mechanical atrial function (EMAF) after one month were 6 (12%). Conclusion: Left atrial diameters and left atrial volumes increase in AF and showed significant reduction by the time after successfully cardioversion. Patients who were underwent DC shock had a slower recovery of atrial function and of LA volumes reduction, implying a greater degree of atrial dysfunction.