The walls of the human heart are a disorganized jumble of tissue until relatively late in pregnancy, despite having the shape of a fully functioning heart, according to a pioneering study.
Although scientists saw four clearly defined chambers in the fetal heart from the eighth week of pregnancy, they did not find organized muscle tissue until the 20th week -much later than expected.
Developing an accurate, computerized simulation of the fetal heart is critical to understanding normal heart development in the womb and, eventually, to opening new ways of detecting and dealing with some functional abnormalities early in pregnancy.
Studies of early heart development have previously been largely based on other mammals such as mice or pigs, adult hearts and dead human samples.
The research team, led by scientists at the University of Leeds is using scans of healthy fetuses in the womb, including one mother who volunteered to have detailed weekly ECG (electrocardiography) scans from 18 weeks until just before deliver. These functional data are incorporated into a 3D computerised model using information about the structure, shape and size of the different components of the heart from two types of MRI (Magnetic Resonance Imaging) scans of fetuses’ hearts.
Early results are already suggesting that the human heart may develop on a different timeline from other mammals. While the tissue in the walls of a pig heart develops a highly organized structure at a relatively early stage of a fetus’ development, a paper published in the Journal of the Royal Society Interface Focus reports that the there is little organisation of the human heart’s cells until 20 weeks into pregnancy.
A pig’s pregnancy lasts about three months and the organized structure of the walls of the heart emerge in the first month of pregnancy. The new study only detected similar organized structures well into the second trimester of the human pregnancy. Human fetuses have a regular heartbeat from about 22 days.