The frequency of Aschoff bodies in atrial appendages of patients with mitral stenosis. Relationship to age, atrial thrombosis, and season.

Abstract

Three hundred and sixteen biopsies of atrial appendages obtained at mitral valvotomy were studied histologically. They were divided into those with Aschoff bodies (41 per cent), those with nonspecific granulomas (23 per cent), and those without either lesion. These findings were compared with those of previous investigators. A study of 24 hearts with mitral stenosis and survey of the literature showed that Aschoff bodies in the left atrial appendage are usually accompanied by similar lesions in the rest of the heart. The average age of patients with Aschoff bodies in their atrial biopsy was 4 years less than that of those with "nonspecific granulomas" and more than 7 years less than that of patients without inflammatory foci in the endocardium. The etiology of "nonspecific granulomas" is discussed. Aschoff bodies were rare in patients with organized atrial thrombi, most of whom were fibrillating. Statistical analysis showed that thrombosis rather than fibrillation was the principal factor associated with a lowered incidence of Aschoff bodies. It was concluded that mechanical factors may determine the localization of rheumatic lesions in the heart. Elevated sedimentation rates were recorded as often in patients with negative biopsies as in those with Aschoff bodies. The percentage of positive biopsies fell from 66 per cent in patients aged 15 to 20 years to 14 per cent in patients aged over 55 years. The age incidence of Aschoff bodies has been compared with that of acute rheumatic fever, which is rare after the age of 15 years. It is concluded that in patients with mitral stenosis, histologic activity may continue for 20 years or more in the absence of clinical signs and symptoms. The proportion of positive biopsies was lowest in June and maximal in September. This seasonal change suggests that the histologic process is only intermittently active. The seasonal variation in the percentage of Aschoff bodies is discussed in relation to the seasonal incidence of acute rheumatic fever. Our results appear to establish the concept of a "subclinical" rheumatic process which has been postulated by many previous investigators.