Hemodynamics and Heart Rate Variability Under Orthostatic Challenge Test in Young Caucasian Men: Part 1

Aim: To study hemodynamics and heart rate variability in response to an orthostatic challenge test among young Caucasian men born in the Russian Far North. Methods: Altogether, 172 healthy young men born in the Russian Far North comprised the sample. Cardiohemodynamic parameters in response to an active orthostatic test were studied using "Varicard" device and a tonometer. Results: A significant increase in heart rate, diastolic pressure, blood flow volume per minute, and reduction in systolic flow were observed among residents of the coastal areas as compared to the subjects from the continental areas. Young men of the coastal zone did not show any changes in the total peripheral vascular resistance during the test while the participants of the continental area showed a significant decrease in this indicator, which was most likely a compensatory reaction aimed at maintaining a sufficiently high stroke volume of blood as one of the mechanisms that proved to not allow the development of vasovagal syncope on the background of inadequate activation of the parasympathetic component and a decrease of the sympathetic regulation. It was revealed that the residents of the coastal zone demonstrated more adequate autonomic provision of hemodynamics in response to the orthostatic challenge test by reducing the activity of the parasympathetic link and the relative increase of the sympathetic regulation. The subjects of the intracontinental area tended to develop postural hypotension in response to the test, with a vagotonic type of reactivity and fewer correlations of cardiac hemodynamics with heart rate variability. Conclusion: Our results suggest that young men from the ontinental area develop a negative effect of synergistic amplification of dysregulatory manifestations of hemodynamic changes, autonomous and central contours of autonomic regulation, which can be considered a consequence of the allostatic adaptive tension caused by the particular area of residence.