Conduction system abnormalities in rat embryos induced by maternal hyperthermia.

Maternal hyperthermia induces severe malformations in the central nervous system (CNS) in both humans and laboratory animals. These phenomena are accompanied by apoptotic cell death, especially in the developing CNS. Cardiovascular malformations in conjunction with skeletal and CNS abnormalities have been reported in embryos of laboratory animals. In rats, hyperthermic treatment at 43 degrees C for 15 min at day 9 of pregnancy induced various severe external malformations in embryos, such as exencephaly, spina bifida, microphthalmia, anophthalmia, facial cleft or defect, generalized edema, and cardiovascular abnormalities. Examination of the embryonic heart revealed abnormal formation of the conduction system. Although hyperthermia causes marked hemodynamic defects, we could not obtain direct proof of a link between hemodynamic alteration by hyperthermia and malformations of the conduction system.