The prevalence of isolated atrial amyloid.

The frequency of isolated atrial amyloid (IAA), a form of 'senile' cardiac amyloidosis, was determined in younger age groups. For the detection of amyloid the Sirius red staining technique was used. IAA first appears in the fourth decade; its prevalence increases roughly linearly by 15-20 per cent with each subsequent decade, reaching 95 per cent in the 81-90 years age group. The prevalence is higher in females than in males.