ABC | Volume 110, Nº1, January 2018

Original Article Cardiac and Musculoskeletal Responses to the Effects of Passive and Active Tilt Test in Healthy Subjects Rogerio Ferreira Liporaci, Marcelo Camargo Saad, Julio César Crescêncio, Fabiana Marques, Debora Bevilaqua- Grossi, Lourenço Gallo-Júnior Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo, Ribeirão Preto, SP – Brazil Mailing Address: Rogerio Ferreira Liporaci • Av. Bandeirantes, 3900. Postal Code 14048-900, Monte Alegre, Ribeirão Preto, SP – Brazil E-mail: rogerioliporaci@gmail.com , rogerio.liporaci.fisio@gmail.com Manuscript received October 13, 2016, revised manuscript August 02, 2017, accepted August 21, 2017 DOI: 10.5935/abc.20180003 Abstract Background: Maintenance of orthostatism requires the interaction of autonomic and muscle responses for an efficient postural control, to minimize body motion and facilitate venous return in a common type of syncope called neurocardiogenic syncope (NCS). Muscle activity in standing position may be registered by surface electromyography, and body sway confirmed by displacement of the center of pressure (COP) on a force platform. These peripheral variables reflect the role of muscles in the maintenance of orthostatism during the active tilt test, which, compared with muscle activity during the passive test (head-up tilt test), enables the analyses of electromyographic activity of these muscles that may anticipate the clinical effects of CNS during these tests. Objective: to evaluate and compare the effects of a standardized protocol of active and passive tests for CNS diagnosis associated with the effects of Valsalva maneuver (VM). Methods: twenty-thee clinically stable female volunteers were recruited to undergo both tests. EMG electrodes were placed on muscles involved in postural maintenance. During the active test, subjects stood on a force platform. In addition to electromyography and the platform, heart rate was recorded during all tests. Three VMs were performed during the tests. Results: progressive peripheral changes were observed along both tests, more evidently during the active test. Conclusion: the active test detected changes in muscle and cardiovascular responses, which were exacerbated by the VM. (Arq Bras Cardiol. 2018; 110(1):74-83) Keywords: Syncope, Vasovagal; Heart Rate; Postural Balance; Tilt Table Test. Introduction Maintenance of balance on orthostatic position is associated with small, constant oscillations of the body that cause changes in plantar pressure areas and contribute to adequate venous return. 1 These oscillations may be confirmed by displacement of the center of pressure (COP) on a force platform. Some individuals cannot stay in an upright position for prolonged period of time and have transient loss of consciousness combined with loss of postural tone and spontaneous recovery, the so called neurocardiogenic syncope (NCS). 2-4 NCS is more common among women due to attenuated responsiveness to orthostasis in women than in men. 5,6 Predisposing factors for NCS include an impaired reflex vasoconstriction. 7 NCS can be assessed by two non-invasive tests based on the force of gravity – the Head-Up Tilt test (HUT) or passive tilt test 3,8-11 , and the Active Standing Test (AS) or active tilt test. 11 In the HUT, the change from supine to orthostatic position of the body is performed passively using a special bed (tilt-table). The subject stays in orthostatic position for 45 minutes. 3 In the AS, NCS is assessed by active change to the vertical position, with no consensus on the test duration. 11,12 Positive HUT and AS tests were defined as loss of consciousness. The combined use of forced expiratory maneuvers, such as the Valsalva maneuver (VM), increases the applicability of these tests in the clinical practice. Orthostatic stress causes changes in heart rate (HR) and blood pressure, 13 and these cardiovascular responses affect peripheral muscle groups. Investigation of this muscle response to orthostatism may contribute to the understanding of the systemic physiological stress in attempt to predict cardiovascular reactions and interrupt stop the test before syncope occurs. The aim of the study was to evaluate HUT and AS combined with VM on HR and electromyographic (EMG) activity of muscles involved in postural maintenance, and the relationship of active orthostatic stress with changes in COP displacement on a force platform, in order to better understand the effects of prolonged orthostatism. 74