The possible diagnostic value of an enlarged left atrial appendage (LAA) on the posterior-anterior or right anterior oblique chest film as a means of implicating a rheumatic etiology for mitral valve disease in children was investigated. Chest films were examined without prior knowledge of clinical or laboratory data, and the results were later correlated with this information in 113 children and adolescents. The clinical and laboratory data included application of the modified Jones criteria

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... r the diagnosis of acute OVER THE PAST SEVERAL YEARS, it has been noted that a dilated left atrial appendage on the posterior-anterior (PA) chest film was frequently associated with rheumatic endocarditis of the mitral valve.' 2 This observation was based on experience with numerous cases of rheumatic and nonrheumatic disease of the mitral valve in both children and adults.3 Although the body of the left atrium often showed enlargement in patients with nonrheumatic mitral valve disease, the left atrial appendage (LAA) was rarely enlarged. This finding raised the possibility of using an enlarged LAA on radiologic examination as an adjunct in the diagnosis of rheumatic heart disease. Supporting data to validate this impression were therefore sought. Recently, the use of certain streptococcal antibody tests [anti-streptolysin 0 (ASO), anti-desoxyribonuclease B (anti-DNAse B), and anti-group A carbohydrate (A-antibody)] in distinguishing rheumatic from nonrheumatic mitral valve disease in children was refined.6"8 The presence of an elevated A-antibody with normal ASO and anti-DNAse B was recently reported in patients with rheumatic valvular disease but not in congenital mitral insufficiency.6 The importance of correctly identifying those patients with mitral valve disease of rheumatic origin relates to the success of anti-streptococcal antibiotic prophylaxis in the prevention of recurrent rheumatic attacks. However, there is little advantage and significant risk in treating patients with mitral valve disease of nonrheumatic etiology in the same fashion. The risk includes both the potential hazard of anaphylactic reactions and the possible higher incidence of bacterial endocar-From the