Response of atrial fibrillation to therapy: role of etiology and left atrial diameter.

Left atrial diameter was measured by echocardiography in 107 patients in atrial fibrillation. The etiology of atrial fibrillation was rheumatic heart disease with predominant mitral valve involvement (RHD) in 51 patients and idiopathic atrial fibrillation (IAF) in 56. The left atrial diameter was correlated to the patient's response to therapy. The mean left atrial diameter was 3.4 cm in patients with paroxysmal atrial fibrillation, 3.8 cm in those requiring direct current (DC) cardioversion, and 4.4 cm in patients with persistent atrial fibrillation. However, in each of these therapeutic response groups, the left atrial diameter was signficantly smaller in patients with idiopathic atrial fibrillation. In the group with paroxysmal atrial fibrillation, the mean left atrial diameter was 4.3 +/- .7 cm in patients with RHD, compared to 3.1 +/- .6 cm in those with IAF (p less than .001). In the group requiring DC cardioversion, the left atrial diameter was 4.7 +/- .8 cm in patients with RHD compared to 3.6 +/- .5 cm in those with IAF (p less than .01). In patients with persistent atrial fibrillation, the left atrial diameter was 5.2 +/- .9 cm in patients with RHD and 4.0 +/- 1.0 cm in IAF (p less than .001). Left atrial diameter as well as the etiology of the heart disease are important in determining the response of atrial fibrillation to therapy.