Rhythm important for development of baby hearts.

A new study has suggested that baby hearts need rhythm to develop correctly, even before they have blood to pump. "We have discovered that mechanical forces are important when making baby hearts," Scientists and clinicians attempting to grow replacement heart valves from a patient's own cells, said. The team reported that they have taken an important step toward this goal by determining that the mechanical forces generated by the rhythmic expansion and contraction of cardiac muscle cells play an active role in the initial stage of heart valve formation. A heart valve consists of two or three flaps, called leaflets, which open and close to control the flow of blood through the heart. It is designed well enough to cycle two to three billion times in a person's lifetime. The researchers wanted to study how heart valves develop naturally so they can figure out how to duplicate the process. To do so, they designed a series of experiments with chickens, whose hearts develop in a fashion similar to the human heart. "The discovery that the deformations produced by the beating cardiac muscle cells are important provides an entirely new perspective on the process," said Merryman, who directed the three-year study. The study was published in the journal Biomaterials.