Cardiac and Musculoskeletal Responses to the Effects of Passive and Active Tilt Test in Healthy Subjects

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.

摘要
背景：直立姿势的维持需要自主神经与肌肉反应协同作用，以实现高效的姿势控制，最小化身体晃动并促进静脉回流，这在神经心源性晕厥（neurocardiogenic syncope, NCS）这类常见晕厥类型中尤为关键。站立位的肌肉活动可通过表面肌电图（surface electromyography）进行记录，而身体晃动可通过测力台（force platform）上的压力中心（center of pressure, COP）位移得以确认。上述外周指标可反映主动直立倾斜试验中肌肉在维持直立姿势中的作用；相较于被动试验（头高位倾斜试验，head-up tilt test）中的肌肉活动，该指标可用于分析相关肌肉的肌电活动，从而预判中枢神经系统（central nervous system, CNS）在这类试验中的临床效应。
目的：评估并对比用于诊断NCS的标准化主动与被动试验方案的效果，以及瓦氏动作（Valsalva maneuver, VM）的相关影响。
方法：招募23名临床状态稳定的女性志愿者，使其完成两类试验。将肌电图（electromyography, EMG）电极安置于参与姿势维持的肌肉上。在主动试验中，受试者站立于测力台上。除肌电图与测力台检测外，所有试验过程中均同步记录心率。试验期间共完成3次瓦氏动作。
结果：两类试验过程中均观察到进行性外周指标变化，其中主动试验中的变化更为显著。
结论：主动试验可检测到肌肉与心血管反应的变化，且该变化会因瓦氏动作而加剧。