MORPHOMETRIC STUDY OF TRABECULA SEPTOMARGINALIS IN DOGS. / Estudo morfométrico da trabécula septomarginal em cães.

Foram estudados 30 coracoes de caes, com idade entre dois e seis anos e sem historico de afeccoes cardiacas as trabeculas septomarginais com o objetivo de caracterizar as relacoes quanto ao numero de insercoes, dimensoes, constituicao e arranjo tecidual, visando fornecer subsidios para estudos da morfofisiologia e entendimento clinico-cirurgico de problemas relacionados com essa estrutura. Os fragmentos das trabeculas foram submetidos a desidratacao crescente em alcool etilico, diafanizacao em xilol, impregnacao e inclusao em parafina. Posteriormente com uso do microtomo manual (Leica RM 2125RT), cortados em espessura de 5µm e corados com Tricromio de Mallory modificado. Fotomicrografias foram obtidas com auxilio de um microscopio optico Axioscopio Zeiss â e as imagens entao analisadas atraves do programa especifico de morfometria KS-400 Zeiss â . Os resultados obtidos foram submetidos ao teste ‘’U’’ de Mann-Whitney (p≤0,05) comparando-se os tecidos constituintes destas trabeculas. As trabeculas septomarginais, macroscopicamente variaram em tres tipos de insercao, sendo do tipo simples (40%), dupla (33,33%) e ramificadas (26,67%). Microscopicamente as trabeculas septomarginais mostraram-se constituidas por tecido muscular, conjuntivo, de conducao e vascular; A proporcao media de tecido muscular estriado cardiaco foi 67,3% ± 6,79, tecido conjuntivo 27,1% ± 6,92 e a de miofibras de conducao cardiaca 5,6% ± 2,77. SUMMARY The trabecula septomarginalis of 30 dog hearts, aged between two and six years, with no history of heart conditions were studied, aiming to characterize the number of insertions, dimensions, constitution and tissue arrangement of trabeculae. The knowledge about this structure is a tool to be used in morphophysiology studies and cardiac clinic-surgical procedures. Trabecula fragments underwent dehydration with ethanol, diaphanization in xylene, impregnation and were embedded in paraffin. Subsequently, prepared tissue fragments were cut into 5-μm-thick slices using the manual microtome (Leica RM 2125RT) and stained with modified Mallory’s trichrome. Photomicrographs were obtained using a digital optical microscope Zeiss Axioscopio â and the images were analyzed by the image analysis software Zeiss KS-400 â . The data were subjected to Mann-Whitney U test. Macroscopically, the trabecula septomarginalis presented three types of insertion: simple (40%), double (33.33%) and ramified (26.67%). Microscopically, the trabeculae septomarginalis consisted of connective and striated muscle tissues, as well as cardiac conduction myofibers. The mean ratios plus standard deviations of connective tissue, striated muscle tissue and cardiac conduction myofibers were 27.1% ± 6.92 , 67.3% ± 6.79 and 5.6% ± 2.47, respectively.