Age changes in the structure of human atrioventricular annuli

Abstract

Atrioventricular annuli are important in hemodynamic stability and support to tricuspid and mitral valves. Anatomical features of the annuli such as circumference, organization of connective tissue fibers, myocardium and cellularity may predispose to annular insufficiency and valvular incompetence. These pathologies increase with age and are more common in females, although the anatomical basis for this disparity remains unclear. This study therefore aimed to investigate age-related changes in the structure of human atrioventricular annuli. One hundred and one hearts (48males, 53 females) from subjects (15 to 60 years) were studied in three age groups (≤ 20 yrs, 21-39 yrs and 40-60 yrs). Annular circumferences were measured and corrected for heart weight. Routine histology was carried out on 21 hearts. Differences in annular circumference between the age groups were determined using one-way ANOVA while gender differences were determined using independent Students’t-test. Overall, females had significantly larger annular circumference than males after correcting for heart weight (p ≤0.05). The annular circumference generally increased with age however there was a significant increase in the 21-39 year age group (p ≤0.05). Microscopically, myocardium was consistently present in males but absent in females except in one specimen. The collagen fiber density increased with age in both gender as the fibers became more irregular. The annular cellularity, elasticity and myocardial content also declined with increasing age. The significantly wider annular circumference in the 21-39 year age group is clinically important as wider circumference is associated with decreased heart valve co-aptation and valvular incompetence. This may suggest an earlier predisposition to this pathology in the study population. The age-related decrease in annular cellularity, elasticity and myocardial content may explain the higher incidence of valvular incompetence with increasing age.