[Fetal human myocardium. Proliferation of the myocytes and development of the cardiac interstitium in the last two gestational trimesters].

PURPOSE: To determine prenatal myocardial quantitative changes by using stereology. METHODS: Twenty-six human fetuses were studied (16 in the 2nd trimester and 10 in the 3rd trimester). The hearts were dissected, weighted, fixed in the Bouin's solution for 12 h, embedded in paraplast, sectioned and stained by HE and trichrome of Gomori. Ten random microscopic fields were analyzed by heart. The following parameters were studied: Vv[myocyte] and Vv[interstitium] (%) (the volume densities of the cardiac myocyte and interstitium), and Nv[myocyte] (1/mm3) (the numerical density of the cardiac myocytes) by the dissector method. The total number of myocytes (N[myocyte]) and the mean volume of the myocytes (V[myocyte]) were also determined. The differences were tested by the Mann-Whitney non-parametric test. RESULTS: The cardiac weight increased of 1.95 to 9.1 g, the Vv[myocyte] decreased from 85.18 to 77.78% and the Vv[interstitium] increased from 14.83 to 22.22%. The Nv[myocyte] decreased from 68.86 x 10(4) to 57.40 x 10(4)/mm3. The V[myocyte] increased from 1214.38 to 1412.31 microns3 and the N[myocyte] increased from 1.36 x 10(9) to 5.06 x 10(9) myocytes. These differences were statistically significant (p < 0.05). CONCLUSION: These results suggest the development of the myocardium at the end of the fetal human period as being mainly hypertrophic to the myocyte and the cardiac interstitium.