ABC | Volume 110, Nº1, January 2018

Original Article Liporaci et al Effects of tilt test in healthy subjects Arq Bras Cardiol. 2018; 110(1):74-83 Surface electromyography during AS and HUT divided into three parts – pre-VM, VM and post-VM EMG analysis of the muscle groups revealed statistically significant differences in all muscle groups during the AS – right (rES) and left ES (lES), right (rMG) and left GM (lMG), left (lRA) and left RA (lRA) and right (rTA) and left TA (lTA) – except for the right RA (rRA). In addition, statistical relevance was found for rES, lES, rMG, lMG, lRA, and rTA between post‑VM and pre-VM. Finally, during the AS, statistically significant differences were found for the rMG, lMG, lRA, rTA and lTA muscle groups between post-VM and VM (Figure 6). During the HUT, statistical relevance was observed for the rES, lES, lMG, rRA, lRA, rTA and lTA muscle groups between VM and pre-VM. Significant difference was found for the rES, lES, lMG, rRA, lRA, rTA and lTA muscle groups between post-VM and pre-VM. Finally, in the comparison between the post-VM and VM periods, statistically relevant differences were found for the rES, lES, rRA, lRA and rTA muscle groups (Figure 7). Comparison of the periods pre-VM, VM and post-VM between HUT and AS reveled statistical relevance for the VM period for all muscle groups, with higher values during the AS than HUT, except for the rES and lES, whose EMG activity was significantly higher during the HUT than AS (Figure 8). Discussion The present study explores an alternative method for the classical HUT used for the diagnosis of NCS. In addition to its long duration, the HUT requires considerable effort and cooperation by the patient, 3 which may contribute for prolonged scheduling period. Our proposal was to better know the effects of prolonged orthostatism on blood pressure, level of consciousness, etc. in healthy individuals. In this sense, AS is faster and, although, in theory, it may be used at patients’ bedside, the test should be better performed under controlled conditions, especially in patients very sensitive to NCS. The comparison betweenHUT and AS is little discussed in the literature. A previous study showed that the cardio‑accelerator effect of AS is more evident than in HUT. 11 However, this study was conducted with children and adolescents only, and different protocols were used for AS and HUT, which make comparisons difficult. In order to define a realistic and optimized study design, we first performed the AS with nine volunteers to establish the optimal duration of the tests for the experimental protocol to detect cardiovascular changes. Three of these volunteers had syncope in minute 15 (mean) and one volunteer syncope prodrome in minute 12, which helped us to define that paired comparisons of the responses between AS and HUT should be performed at minute 15 of the test. VM has been reported to be able to identify orthostatism intolerance. 10 Prakash e Pravitan 14 observed that a series of 3 VMs performed at predetermined intervals during the AS would yield results similar to the use of vasodepressor drugs. This finding motivated us to plan a very conservative protocol, i.e., with no use of any drugs or invasive procedure. In line with Matsushima et al., 11 who proposed the comparison of two active and passive tests, we decided not only to compare these two orthostatic tests, with or without a tilt table, but also to evaluate test the effects of these three VMs. Liu et al. 15 observed that during the passive tilt test, syncope generally occurred after the 10 th minute, whereas during the passive tilt test combined with the use of sublingual nitroglycerin, syncope occurred between 5 and 15 minutes. Our data showed an increase in HR for AS and HUT when compared with resting conditions, which was incremented by the VM during the AS. Such increase in HR with orthostatic change may be a predictor factor for syncope in susceptible patients, 16 as an exacerbated response to hypovolemia caused by postural change. Besides, the combination of VM to these tests can contribute to the cardio-acceleration in response to changes in blood pressure. 17 These postural changes and subsequent hemodynamic changes lead to 0.45 0.55 0.35 0.25 0.15 0.05 0.4 0.6 0.5 0.3 0.2 0.1 0 Minute 1 Minute 2 Minute 3 Minute 4 Minute 5 Minute 6 Minute 7 Minute 8 Minute 9 Minute 10 Minute 11 Minute 12 Minute 13 Minute 14 a b b b Ab Ab Ab ABc c c AC c A cm/s TD Figure 3 – Total displacement on the force platform during the Active Standing Test. A, B, C: significant difference with their corresponding minutes (a,b,c); p < 0.05. TD: Total displacement. 77