ABC | Volume 113, Nº6, December 2019

Original Article Influences on the Functional Behavior of Great Arteries during Orthostasis Jorge Elias Neto, 1, 3 Albano Ferreira, 2 G uilherme Futuro, 3 Luiz Carlos dos Santos, 3 Nevelton Heringer Filho, 3 Fernando Gomes, 3 Jose Geraldo Mill 3 Vitória Apart Hospital, 1 Serra, ES – Brazil Universidade Katyavala Bwila Benguela, 2 Luanda – Angola Universidade Federal do Espirito Santo, 3 Vitória, ES – Brazil Mailing Address: Jorge Elias Neto • Vitoria Apart Hospital - Serviço de Eletrofisiologia - Rodovia BR-101 Norte, Km 2,38, s/n. Postal Code: 29161-900, Boa Vista II, Serra, ES – Brazil E-mail: jeliasneto@gmail.com Manuscript received October 15, 2018, revised manuscript December 17, 2018, accepted February 13, 2019. DOI: 10.5935/abc.20190182 Abstract Background: Arterial compliance reduction has been associated with aging and hypertension in supine position. However, the dynamic effects of orthostatism on aortic distensibility has not been defined. Objective: We sought to determine the orthostatic influence and the interference of age, blood pressure (BP) and heart rate (HR) on the great arteries during gravitational stress. Methods: Ninety-three healthy volunteers (age 42 ±  16 years). Carotid-femoral pulse wave velocity (PWV) assumed as aortic stiffness was assessed in supine position (basal phase), during tilt test (TT) (orthostatic phase) and after return to supine position (recovery phase). Simultaneously with PWV acquisition, measures of BP and HR rate were recorded. Results: PWV during TT increased significantly compared to the basal and recovery phases (11.7  ±  2.5 m/s vs. 10.1 ± 2.3 m/s and 9.5 ± 2.0 m/s). Systolic BP (r = 0.55, r = 0.46 and r = 0.39) and age (r = 0.59, r = 0.63 and r = 0.39) correlated with PWV in all phases. The significance level for all tests was established as α = 0.05. Conclusion: We conclude that there is a permanent increase in PWV during orthostatic position that was returned to basal level at the recovery phase. This dynamic pattern of PWV response, during postural changes, can be explained by an increase in hydrostatic pressure at the level of abdominal aorta which with smaller radius and an increased elastic modulus, propagates the pulse in a faster way. Considering that it could increase central pulse reflection during the orthostatic position, we speculate that this mechanism may play a role in the overall adaptation of humans to gravitational stress. (Arq Bras Cardiol. 2019; 113(6):1072-1081) Keywords: Switch Arterial; Hypertension; Aging; Standing Position; Pulse Wave Analysis; Gravitation. Introduction Great arteries are not only seen as mere passive conductors of blood, functioning only in its transportation and distribution, but rather playing a fundamental and complex role in the maintenance of circulatory homeostasis and in the genesis of cardiovascular disease. 1-2 The great arteries may be considered a functional organ with several roles, such as endocrine and paracrine activity, in addition to the capacity for muffling the pulsatile blood flow. The functional behavior of the great arteries in the supine position was assessed noninvasively by measuring the pulse wave velocity (PWV) in several arterial segments. 3-5 Epidemiological and longitudinal studies using that methodology have shown the clinical relevance of this approach for predicting morbid cardiovascular events. 1,6–7 However, due to methodological limitations, the functional response of the great arteries has not been investigated in the orthostatic position. 8 The tilt test has long been used for assessing the influence of gravitational stress on the behavior of hemodynamic parameters. 9–10 Although this technique allows adequate reproducibility of the gravitational action upon individuals in active orthostatic position, only from the end of the 1980s that small studies have been carried out with primates, aiming at assessing the influence of postural changes on the behavior of aortic pulse wave and PWV. 8,11–13 Studying the function of the great arteries in the orthostatic position by noninvasively measuring carotid-femoral PWV may be important for understanding the vascular mechanisms of adaptation to gravity and their implications on cardiocirculatory homeostasis, development or progression of cardiovascular disease and occurrence of unadaptable postural events. This study is the first to assess the effects of orthostatic position on the function of the great arteries in humans, by measuring the carotid-femoral PWV in healthy individuals 1072