Raised Prevalence of Isolated Atrial Amyloidosis in Chronic Heart Disease

Abstract

Congo red screening of 211 consecutive cardiac biopsies obtained during cardiac surgery from 167 patients revealed 26 (16%) instances of isolated atrial amyloidosis (IAA). IAA-positive patients ranged from 25 to 52 years in age with a mean of 39 years. Controls consisted of 247 healthy adults autopsied for traumatic deaths, with an age range of 18 to 89 years and a mean of 38 years. Only 7 (3%) control subjects were IAA-positive, all above 40 years of age. 23 (88%) IAA-positive biopsies were from patients with chronic rheumatic heart disease (CRHD) and 3 (11%) atrial septal defect (ASD). The prevalence of IAA in CRHD was 23%, appreciably higher than that in ASD (15%) and other patients with atrial biopsies. The prevalence in both CRHD and ASD was significantly higher (P>0.001) than in the controls. IAA deposits were permanganate-resistant and immunohistochemically negative for AA protein. They were observed in intramyocardial vessel walls, along the myocardial sarcolemma and the subendocardium. There was associated myocyte hypertrophy but no atrophy. Electron microscopy demonstrated typical non-branching amyloid fibrils. It is postulated that mechanical and physiological stress to the atria results in a raised prevalence of IAA. The association of atrial natriuretic peptides with IAA would support this view.