The myocardium in tetralogy of Fallot: a histological and morphometric study.
BACKGROUND
Patients with Tetralogy of Fallot frequently develop ventricular dysfunction in the postoperative period. The histological basis of this functional alteration has been scarcely studied.


OBJECTIVE
To evaluate myocardial remodeling in anatomical specimens, comparing the subepicardial and subendocardial regions, especially because the subendocardial region is easily approached by means of endomyocardial biopsy.


METHODS
Transmural sections of myocardium from the right ventricular (RV) inflow tract, anterior wall and infundibulum, and from the left ventricular (LV) free wall were evaluated regarding the degree of cardiomyocyte hypertrophy, vascularization and interstitial fibrosis were analyzed.


RESULTS
The mean diameter of subendocardial cardiomyocytes is similar to that of subepicardial cardiomyocytes in all regions, except for the RV infundibulum, in which subendocardial cardiomyocytes are significantly larger in relation to those of the subepicardium (p=0.007). The amount of interstitial collagen is in the upper limits of normal and was similar in the subendocardial layers in comparison with the subpericardial layer of each region; however, it was greater in the inflow tract and RV anterior wall than in the LV lateral wall. The numerical density of subendocardial capillaries was similar to that of the subepicardium and was lower than the mean minus two standard deviations of normal in all regions and layers, except for the infundibulum, in which the subepicardium showed normal values and the subendocardium showed values lower than the mean minus two standard deviations.


CONCLUSIONS
The postnatal myocardial changes in Tetralogy of Fallot are homogeneously distributed in the subepicardial and subendocardial halves of the ventricular walls, except for the infundibulum, which has peculiar remodeling characteristics and, therefore, is not representative of the other ventricular regions and layers for morphometric studies.
Farah
Maria Cecília Knoll
MC
Centro de Ciências Biológicas da Saúde, Faculdade de Medicina, Universidade Federal de Mato Grosso, Cuiabá, MT, Brasil.
Castro
Cláudia Regina Pinheiro de
CR
Moreira
Valéria Mello
VM
Riso
Arlindo de Almeida
Ade A
Lopes
Antonio Augusto Barbosa
AA
Aiello
Vera Demarchi
VD
D002196:Capillaries / Q000473:pathology; D016009:Chi-Square Distribution; D002648:Child; D003094:Collagen / Q000032:analysis; D005260:Female; D005355:Fibrosis / Q000473:pathology; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000473:pathology*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D032383:Myocytes, Cardiac / Q000648:ultrastructure*; D013194:Staining and Labeling; D013771:Tetralogy of Fallot / Q000473:pathology*; D020257:Ventricular Remodeling / Q000502:physiology
D003094:Collagen