Sex variation in occurrence of myocardium in human mitral valve cusps / Variación del sexo en la aparición del miocardio en cúspides de la válvula mitral humana

Mitral valve cusps consist mainly of connective tissue and myocardium. Connective tissue fibres within the cusps have been demonstrated to exhibit sex variations in organisation. Mitral prolapse, a disease attributed to defects within the cusps occurs more commonly in females. Sex variations in valvular myocardium however remain to be studied. Possible variations in its organisation may enhance understanding of sex differences in prevalence of mitral prolapse. The aim of this study was to determine anatomical variations of mitral valvular myocardium by sex; by mean a comparative cross-sectional study. A total of 48 (27 male and 21 female) adult heart specimens obtained during autopsy at Nairobi City and Chiromo mortuaries after ethical approval were used. Valvular cusps were then harvested. Four ¡ millimetre sections were made at the area of maximum width for both anterior and posterior cusps. These were processed for paraffin-embedding and sectioning and stained with Masson's trichrome and Weigert's resorcin fuchsin with Van Gieson counterstain to demonstrate cardiac muscle, collagen and elastic fibres. Both anterior and posterior cusps demonstrated three histological laminae, that is, atrialis, fibrosa and ventricularis. Only lamina atrialis contained cardiac muscle. This lamina in males was characterised by a transversely oriented subendothelial myocardial strip while that in females contained compact longitudinal elastic fibres but no muscle. The presence of cardiac muscle in the lamina atrialis may be relatively protective against mitral valve prolapse in males compared to females.

Las cúspides de la valva mitral están constituidas principalmente por tejido conectivo y miocardio. Se ha demostrado que las fibras del tejido conectivo de las cúspides presentan diferencias en la organización según sexo. El prolapso mitral, una enfermedad atribuida a defectos en las cúspides es más frecuente en las mujeres. Las variaciones de sexo en el miocardio valvular sin embargo aún no se han estudiado. Las posibles variaciones en su organización puede mejorar la comprensión de las diferencias de sexo en la prevalencia de prolapso mitral. El objetivo de este estudio fue determinar las variaciones anatómicas del miocardio valvar mitral por sexo, por medio un estudio comparativo de corte transversal. Un total de 48 los especímenes de corazón adulto (se utilizaron 27 hombres y 21 mujeres), obtenidos durante autopsias en la ciudad de Nairobi y desde el depósito de cadáveres Chiromo, después de la aprobación ética. Las cúspides valvares fueron extraídas. Fueron realizadas secciones de cuatro milímetros en el parte más ancha de las cúspides anteriores y posteriores. Estas fueron procesadas por inclusión en parafina, corte y tinción con tricrómico de Masson y fucsina-resorcina de Weigert con contraste Van de Gieson, para demostrar la presencia de músculo cardíaco, fibras colágenas y elásticas. T.

Morphological study of the human mitral-aortic intervalvular fibrosa

The mitral-aortic intervalvular fibrosa of the heart is of great clinical and surgical importance, because of its involvement in the anatomical and functional integrity of these two valves. In this work, we examined the morphology of the mitralaortic intervalvular fibrosa and its relationship to the mitral and aortic valves. Thirty formaldehyde-fixed adult human hearts of both sexes were dissected and the structural organization, dimensions and area of the mitral-aortic intervalvular fibrosa were determined. The mitral-aortic intervalvular fibrosa was a thin, translucent membranous area located between the root of the aortic artery and the left atrioventricular orifice. In most cases (63 por cento), the mitral-aortic intervalvular fibrosa was approximately triangular in shape, with an area of 93.9 ± 47.4 mm². The lower edge was associated with the anterior cusp of the mitral valve and was 18.0 ± 2.2 mm long, whereas the anterior edge was continuos with the left fibrous trigone and was 10.6 ± 3.0 mm long. The posterior edge was associated with the aortic wall and was continuos with the right fibrous trigone. This edge was 11.7 ± 3.4 mm long. These results may be useful for manufacturing protheses to substitute this injured membrane.

Estudo morfológico e histoquímico em nível ultra-estrutural da corda tendínea de coraçöes de rato albino / Morphological and histochemical study in structural pattern of chordae tendinae of hearts from albino rat

Fragmentos de cordas tendíneas dos complexos valores mitral e tricúspide de ratos albinos foram observados ao microscópio eletrônico de transmissäo com o objetivo de estudar os componentes da matriz extracelulair. Foram utilizados dois tipos de fixador, um contendo ácido tânico para demonstrar a presença de fibras dos sistemas colágeno e elástico, e outro contendo vermelho de rutênio para a visualizaçäo de proteuglicans. Alguns fragmentos foram tratados previamente pela colagenase ou pela tripisina antes de serem fixados pelo glutaraldeído com vermelho de rutênio. Foi observado que as cordas tendíneas de rato säo revestidas por um endotélio contínuo que repousa sobre uma camada de conjuntivo contendo fibroblastos e esparsas fibras de colágeno, compondo a zona esponjosa. Tal camada circunda uma zona central (zaza fibrosa) constituída de grossos feixes de colágeno onde se encontram vários fibroblastos. Tanto na zona esponjosa como na fibrosa foram detectadas inúmeras fibras com padräo ultra-estrutural de fibras elaunínicas, os quais, juntamente com o colágeno, desempenham funçöes de resistência mecânica ao transmitirem as forças de traçäo exercidas pelo músculo papilar às bordas das válvulas. Adicionalmente, foram observadas as relaçöes morfológicas entre proteoglicans, fibrilas de colágeno e microfibrilas elaunínicas, tendo sido enfatizada a importância do equilíbrio de funçöes entre os diversos componentes da matriz extracelular concorrendo para o perfeito funcionamento deste complexo morfofuncional na fisiologia da corda tendínea.

[Analysis of rheumatic valvulopathy with scanning electron microscopy]. / Análisis de la valvulopatía reumática por microscopía electrónica de barrido.

There is a high incidence of rheumatic endocarditis in our environment. Therefore it is important to know the structural characteristics of the valvular lesions in order to better understand the physiopathologic pathways of tissue injury. We have chosen a non-conventional method, the scanning electron microscopy. There were very few such reports in the current literature. We analyzed ten mitral valve with rheumatic scarring lesion and five normal, as a control group. We were able to establish three structural patterns. 1) Stone pavement like (endocardium with nuclear bulge cells and marginal folds at the cell boundaries, abundant number of microvillous projections and few areas of endothelial loosening). 2) Cerebroid (subendothelium with wrinkles caused by deformity of the valve with or without endothelial loosening) and 3) Smooth pattern (flattened endothelium with scanty microvillous projections and abundant areas of endothelial denundation and exposition of subendothelium). More damage was noted in the auricular surface of the rheumatic group, characterized by a predominance of the smooth pattern. We found Lambl's excrecences in two mitral leaflets, they were formed by collagen break fascicles of the subendothelium. This technique allowed us to analyze integrity of the endocardial selective barrier and the interactions between the damaged surface of the valve and elements of the peripheral blood and showed more endocardial injury in the rheumatic group. These alterations could play an important role in the pathogenesis of this disease.