Objective: The use of left internal thoracic artery (LITA) in coronary artery bypass surgery is currently recognized as the best option, providing lower incidences of cardiovascular events and superior long-term survival. Now, incremental utilization of these grafts makes a reassessment of its histological structure necessary. Therefore, the purpose of this study was to examine and compare the sequential histological structure of LITA.Method: Specimens of LITA harvested from 18 cadavers, divided into nine proportional segments, were studied. Cuts of each segment were stained by the Verhoeff-Van Gieson technique. The following parameters were analyzed: perimeter of the arterial lumen, thickness of the intima, thickness of the media layer, amount of elastic fiber in the media layer and the elastic fiber density.Results: The collected data showed that perimeter of the LITA decreases downstream on its course, the thickness of the intima is increased in the proximal segments, the thickness of the media layer diminishes throughout its extension, the number of elastic fibers is concentrated in the intermediate segments and the density of elastic fibers is reduced in the proximal and distal segments. Conclusion:Therefore, the findings of the present study validate the heterogeneity of the LITA sequential histological structure. Descriptors

Objective: The use of left internal thoracic artery (LITA) in coronary artery bypass surgery is currently recognized as the best option, providing lower incidences of cardiovascular events and superior long-term survival. Now, incremental utilization of these grafts makes a reassessment of its histological structure necessary. Therefore, the purpose of this study was to examine and compare the sequential histological structure of LITA. Method: Specimens of LITA harvested from 18 cadavers, divided into nine proportional segments, were studied. Cuts of each segment were stained by the Verhoeff-Van Gieson technique. The following parameters were analyzed: perimeter of the arterial lumen, thickness of the intima, thickness of the media layer, amount of elastic fiber in the media layer and the elastic fiber density. Results: The collected data showed that perimeter of the LITA decreases downstream on its course, the thickness of the intima is increased in the proximal segments, the thickness of the media layer diminishes throughout its extension, the number of elastic fibers is concentrated in the intermediate segments and the density of elastic fibers is reduced in the proximal and distal segments. Conclusion: Therefore, the findings of the present study validate the heterogeneity of the LITA sequential histological structure. Descriptors: Internal thoracic artery. Internal mammary artery. Coronary artery bypass surgery. Histology, comparative. Resumo Objetivo: O uso de enxertos de artéria torácica interna esquerda (ATIE) é atualmente reconhecido como a melhor opção na cirurgia de revascularização miocárdica, proporcionando menor incidência de eventos cardiovasculares e maior sobrevida. Entretanto, com a expansão do uso dos enxertos arteriais, faz se necessário melhor entendimento da estrutura histológica da ATIE. Portanto, o objetivo deste trabalho foi estudar a estrutura histológica da ATIE e a análise histomorfométrica seqüencial e comparativa entre os diferentes segmentos. Método: Foram estudados espécimes de ATIE retirados de 18 cadáveres, divididos em nove segmentos proporcionais. Cortes de cada segmento foram corados com técnica de Verhoeff-Van Gieson. Foram analisados os seguintes 372 KNEUBIL, MC ET AL-Sequential histomorphometric study of the left internal thoracic artery Braz J