Age-related myocardial changes in hearts of healthy individuals

Knowledge of age-related changes is crucial for the conscientious interpretation of myocardial histological findings. To assess the normal values of mononuclear cells, myocyte diameter, capillary density and collagen distribution in uninflamed myocardium, we searched our departmental database for homograft hearts. The study population comprised of 25 cases, including 13 children (median age 15.1 years) and 12 adults (median age 33.6 years). These cases were split into four groups according to age (8 to 12, 13 to 17, 18 to 30 and 37 to 49 years, respectively). Tissue sections from the anterior left ventricular wall of each cardiac specimen were reassessed on conventional histology using a purpose-built software. To highlight certain interstitial components immunohistochemistry (CD3: T-lymphocytes, CD68: macrophages, CD31: capillary network, alpha smooth muscle actin: arteriolar walls) and collagen stain were used. In each explanted heart, we observed at least some discrete to mild chronic inflammatory infiltrates with no substantial differences between the inner and outer half of the ventricular wall, but the differences in macrophage cell counts between adults’ and children’s hearts reached statistical significance (p<0.05 and p<0.005, respectively). While myocyte diameter rose with increasing age, the percentage of capillaries showed a trend to decrease with age. For both parameters the differences between age groups were statistically significant (p<0.05). In three of four age groups the interstitial fibrous tissue accounted for more than 7 vol %, which was calculated as cut-off value. With rising age, the fraction of fibrosis decreased (p=0.066 across all age groups). Our data suggest that there are higher cut-off values for inflammatory infiltrates than defined in the Dallas criteria.