Morphometric Study on the Development of the Human Fetal Heart after Mid-term

A total of 23 human fetal hearts from 18 to 40 weeks of gestation were provided for histologic and morphometric studies. The fetuses were the products of spontaneous or artificial abortions and were found to have no congential anomalies or associated lesions at autopsy. Maxima thickness of the left anterior, left lateral, left posterior, right anterior, right lateral, right posterior ventricular wall, and of the interventricular septal wall were measured and the left / right wall thickness ratio was calculated. The cross-sectional area of each ventricle parallel to the base of the heart at about 3-5mm below from the origin of the aorta was measured under drawing attachment-equipped light microscope with the application of point counting or cut-and-weigh method. Data were analyzed by the Anderson-ell ABSTAT dBASE ll statistical package program. The ventricular wall consisted of endocardium, myocardium and epicardium. The myocardium showed epithelial character by stratification of barrel-shaped myocardial cells, but the epithelial character progressively changed to as in adult myocardial tissue from the myocardial area close to the epicardium with increasing fetal age. However, any significant histologic difference between the left and the right ventricular wall at the same fetal age was not found. The growth pattern of both ventricular wall, the interventricular septal wall, and of the cross sectional area were linear (p<0.01). However, there was no significant difference in the wall thickness between the left and right ventricle at the same fetal age, and the left / right thickness ratio was nearly constant with increasing fetal age. The cross sectional area was greater in the right than in the left ventricle in the fetuses after 18 weeks of gestation (p<0.01), and there was no significant difference in the morphometric values between point counting and cut-and-weigh method (p>0.1).