Rheumatic lesions in left atrial appendages; pathologic studies of material removed during mitral commissurotomy.

The left atrial appendage removed incidental to mitral valve commissurotomy was studied for rheumatic lesions in 128 cases. Endocardial Aschoff bodies, which are usually considered indicative of active rheumatic disease, were found in 35.9 per cent of the cases.Postoperative follow-up observations were available in only 53 patients. Of these, only eight had clinical evidence of postoperative rheumatic activity. In none of this group of eight cases had Aschoff bodies been observed in pathologic study of the surgically removed left atrial appendage.