Prenatal hypoxia of early organogenesis period influence on heart rate variability in rats of prepubescent and pubertal age

Risk factors associated with environmental exposure, especially during critical periods of intrauterine development, affect fetal development and increase the risk of certain diseases in adulthood including cardiovascular diseases (CVD). Hypoxia is considered the most common and clinically significant form of intrauterine stress that causes systemic pathological changes, in 78% of cases associated with cardiovascular system disorders. The purpose of this study was to evaluate the effects of acute hypoxia on the 10th day of gestation on heart rate and its regulation in rats’ offspring of prepubescent and pubertal age, as well as to analyze the dependence of resulting disorders on gender. By the beginning of puberty the heart rate of rats survived prenatal hypoxia was significantly higher than in control accompanied by significant decrease in heart rate variability (dX) which naturally leads to stress index (SI) increase indicating growing sympathetic activity in heart rhythm regulation. At the same time the base heart rate in animals suffered intrauterine hypoxia turned out to be lower than in control. The fact that matured animals of both sexes, survived intrauterine hypoxia in early organogenesis, also show changes in dX and SI indicates long-term and irreversible disorders in heart rhythm regulation. Thus hypoxia during early organogenesis is of a programming nature potentially increasing the risk of developing CVD in adult animals. Moreover the autonomic system balance shift towards the activation of sympathetic tone was more pronounced in females making them more vulnerable to the risk of developing cardiac pathology in puberty.