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Histological Study of Age-Related Changes of Internal Thoracic Artery – A Cross-Sectional Study from Calicut, India

BACKGROUND Internal thoracic artery (ITA) is the ideal graft material for coronary artery bypass grafting (CABG). It’s structural characteristics and resistance to atherosclerotic changes make it ideal for this. It is in this scenario that we attempted to study the histological characteristics and age-related changes. METHODS This cross-sectional study was done on stained slides of segments of ITAs obtained from 100 fresh cadavers during autopsy. Age range was between 20 – 80 years. The segments were collected at various rib levels constituting proximal, middle and distal segments. The wall parameters were measured and recorded. The specimens were grouped according to age into six groups with intervals of 10 years and analysis of variance (ANOVA) test were conducted on the samples using Statistical Package for Social Science (SPSS) software. RESULTS The mean thickness of tunica intima in the proximal segment of 100 specimens was 26.792 µm, tunica media was 171.437µm and the thickness increased significantly with age with (F = 33.038, P = 0.00), (F = 87.910, P = 0.00) respectively. In one specimen, the intimal thickening increased to 96.325 µm. The mean thickness of tunica intima in the middle segment was 19.665 µm, tunica media was 172.302 µm and it increased significantly with age with (F = 71.885, P = 0.00), (F = 85.481, P = 0.00) respectively. The mean thickness of tunica intima in the distal segment was 18.157 µm, tunica media was 146.278 µm and it increased significantly with age (F = 58.847, P = 0.00), (F = 66.137, P = 0.00) respectively. The intima media ratio (IMR) increased significantly with age. The IMR of proximal segment of 2 % specimens were found to be greater than 0.25 indicating atherosclerosis. The vessel wall parameters decreased from proximal to distal segments. CONCLUSIONS The vessel wall thickness and IMR was found to increase with age. The incidence of atherosclerosis was 2 % and in old age. It is clear that the ITA is the ideal graft for CABG in younger individuals. An understanding of these attributes of ITA will be helpful to the cardiothoracic surgeons. Moreover, the results of this study throw light on the vessel wall changes in the population of present times. Further clinical study is needed to assess the effect of other risk factors. KEY WORDS Internal Thoracic Artery, Tunica Intima, Tunica Media, Intima Media Ratio, Atherosclerosis