ABC | Volume 113, Nº6, December 2019

Original Article Elias Neto et al. Great arteries behavior during orthostasis Arq Bras Cardiol. 2019; 113(6):1072-1081 Figure 4 – Hypothesis proposed for the role played by the increase in carotid-femoral pulse wave velocity in the maintenance of circulatory homeostasis in response to orthostatic stress. 309x165 mm (72 x 72 DPI). PP: pulse pressure; PWV: pulse wave velocity; MBP: medium blood pressure; HR: heart rate. Orthostasis Gz + Change in the indifferent hydrostatic point Distensibility pressure – abdominal aorta Early return of the reflected component of the pulse wave “Pulse summation” Maintenance of MBP Appropriate baroreceptor response (HR) Circulatory homeostasis Radius Elastic module PWV PP Sympathetic activation HR Vasoconstriction (arteriolar) New sites of wave reflection the pressure transducer. This aspect is more evident in deeper vessels. 37 These observations become potentiallymore significant when carotid-femoral PWV measurement is considered during the tilt test. The change from supine decubitus to orthostatic position may increase the difficulty in recording femoral pulse, mainly in obese individuals. In some cases, recording femoral pulse is impossible. In this study, we tried to reduce these sources of error by using observers who were very well-trained in measuring PWV in the supine and orthostatic positions. Although this study does not allow comparison of the influence of sex on arterial behavior in orthostatic position, the inclusion of female individuals in this study may not have interfered with the response of PWV increase to postural stress. Considering the greater arterial distensibility in young females, 38 a relatively smaller increase could occur in PWV due to postural stress caused by the tilt test. However, this hypothesis cannot be statistically confirmed with the data from this study. 39 Conclusion In conclusion, our study of healthy individuals and in individuals with untreated mild-to-moderate arterial hypertension demonstrates a rapid increase in PWV during the tilt test and its return to baseline levels when resuming to supine position. We found strong indications that these results may enable a better comprehension of the response of the great arteries to gravitational stress. These results may also elucidate this behavior in the long run, in the presence of inherent degenerative disorders, such as arterial hypertension and aging, and predetermined genetic markers. Acknowledgements To Prof. Dr. Roberto Sá Cunha, for the technical assistance. Author contributions Conception and design of the research: Neto JE, Ferreira A; Acquisition of data: Neto JE, Ferreira A, Futuro G, Santos LC, Gomes F, Heringer Filho N; Analysis and interpretation of the data: Neto JE, Ferreira A; Statistical analysis and Obtaining financing: Neto JE; Writing of the manuscript: Neto JE, Mill JG; Critical revision of the manuscript for intellectual content: Neto JE, Ferreira A, Mill JG. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This article is part of the thesis of master submitted by Jorge Elias Neto, from Universidade Federal do Espírito Santo. Ethics approval and consent to participate This article does not contain any studies with human participants or animals performed by any of the authors. 1079