Left atrial size and atrial fibrillation in mitral stenosis. Factors influencing their relationship.

SUMMARY In a series of 135 patients with mitral valvular stenosis, three groups were identified: those in sinus rhythm, those with intermittent atrial fibrillation, and those with longstanding, established atrial fibrillation. Examination of the relationships between atrial fibrillation, hemodynamic findings and radiologic data in mitral stenosis was undertaken. Analysis of clinical and hemodynamic factors in the three groups revealed that: 1) age is an etiological factor in the production of atrial fibrillation, as suggested by the age distribution among the three groups; 2) left atrial enlargement may be the result, rather than the cause, of atrial fibrillation; and 3) severity of mitral stenosis is not invariably related to the incidence of atrial fibrillation. Hemodynamic measurements were not significantly different among the three groups, with the single exception of lower cardiac outputs found in patients with established atrial fibrillation. Since no single consequence of mitral stenosis always produces atrial fibrillation, it is suggested that several factors in different combinations can initiate the self-perpetuating process of atrial fibrillation and that the classic form of the arrhythmia may lead secondarily to left atrial enlargement. Additional Indexing Words: Mitral valve area Mitral insufficiency ATRIAL FIBRILLATION occurs in clinically normal individuals1' 2 and as a complication of virtually every known form of cardiac disease. It does, however, have a preferential tendency to develop in certain specific cardiac conditions, of which mitral valve disease is the most noteworthy. The incidence of atrial fibrillation in mitral stenosis has been estimated at 4O%,3 and in mitral regurgi-tation at 75%.4 Aside from the obvious fact that the left atrium is the chamber bearing the brunt of the overload in both mitral stenosis and regurgitation, the factors predisposing to the development of atrial fibrillation in mitral valve disease have not been adequately clarified. the relationships among the radiologic evidence and hemodynamic consequences of mitral valve stenosis and the presence of atrial fibrillation. As quantifica-tion of severity of the mitral lesion can be achieved with reasonable accuracy only in pure mitral stenosis, patients with mitral incompetence were not considered in the study. Our investigation differs from earlier reports5-7 in that patients with atrial fibrillation were divided into those with intermittent and those with chronic, established atrial fibrillation. Methods All patients with pure or predominant mitral stenosis who had undergone complete right heart cardiac catheterization including cineangiography performed from the main pulmonary artery were included in the study. Of the 135 patients …