Histomorphometric analysis of the human internal thoracic artery and relationship with cardiovascular risk factors

Abstract

In this study, we aimed at performing a histomorphometric analysis of human left internal thoracic artery (ITA) samples as well as at correlating the histomorphometric findings with the clinical profile, including risk factors and medication. Distal segments of ITA were obtained from 54 patients undergoing coronary artery bypass grafting. Histological observation was performed in paraffin-embedded transverse sections of ITA through four staining protocols: hematoxylin-eosin, van Gieson, Masson's trichrome and von Kossa. Morphometric analysis included the intimal width (IW), medial width (MW) and intima/media ratio (IMR). No overt atherosclerotic lesions were observed. Mild calcifications were observed across the vascular wall layers in almost all samples. Multivariable linear regression analysis showed associations between IW and IMR and the following clinical variables: age, gender, kidney function expressed as eGFR and myocardial infarction history. Age (odds ratio = 1.16, P = 0.004), female gender (odds ratio = 11.34, P = 0.011), eGFR (odds ratio = 1.03, P = 0.059) and myocardial infarction history (odds ratio = 4.81, P = 0.040) were identified as the main clinical predictors for intimal hyperplasia. Preatherosclerotic lesions in ITA samples from patients undergoing coronary revascularization were associated not only with classical cardiovascular risk factors such as age and gender, but also with other clinical variables, namely kidney function and myocardial infarction history.

Fig 1. Histomorphology of human ITAs.

(A) Histological observation shows the three vascular wall layers, tunica intima (1), tunica media (2) and tunica adventitia (3) by hematoxylin-eosin (left) and van Gieson (right) staining protocols (10x magnification). Scale bar represents 200 μm and arrows represent the internal elastic lamina. (B) Von Kossa (40x magnification) staining revealed predominant adventitial mild calcifications. Scale bar represents 200 μm. (C) Box plots for IW, MW and IMR according to gender. (D) Frequencies of IMR grades across the total population. (E) Representative photomicrographs for the IMR grades by van Gieson (10x magnification for grade 2 and 40x magnification for other grades) staining. Scale bar represents 200 μm in grade 2 and 50 μm for other grades. (F) Scatterplots of the correlation between histomorphometric parameters: IW vs MW and IMR.

Fig 2. Forest plot for odds ratio for intimal hyperplasia (IMR > 0.25) in the total population.

Results represent the odds ratio, 95% confidence intervals and P-value from multivariable logistic regression analysis. Dashed vertical line represents an odds ratio of 1. Abbreviations: CI, confidence interval; eGFR, estimated glomerular filtration rate.