MORPHOLOGICAL-CHANGES IN THE NORMAL PATTERN OF VENTRICULAR MYOARCHITECTURE IN THE DEVELOPING HUMAN HEART

Background: The aim of the present study was to describe the morpholog ical changes in the normal pattern of ventricular myoarchitecture in t he prenatal and adult human heart, to understand the three-dimensional organization of the muscle fibers and their active functional role in valvular dynamics. Methods: We used dissection and histological techn iques in 56 human hearts from fetuses and adults of both sexes, Result s: In all hearts, the ventricular wall was arranged in three different layers: superficial (subepicardial), middle, and deep (subendocardial ) myocardium, The superficial and deep layers are present in both vent ricles, whereas the middle layer is found only in the left ventricle, Age-related differences were noted in the pattern of myoarchitecture o f the superficial layer, mainly in the fetal period, and especially in the right ventricle; however, the middle layer always shows a circumf erential pattern, which is specially evident in elderly hearts. The ve ntricular fibers in the superficial and deep layers are anchored in th e ventricular orifices. Conclusions: Our findings reveal that muscle f iber architecture showed age- but not sex-related differences, These v ariations may reflect a mechanism of adaptation of the heart to functi onal demands throughout life. (C) 1995 Wiley-Liss, Inc.