RESUMO
This study was to investigate the changes of autonomic nerve function and hemodynamics in patients with vasovagal syncope (VVS) during head-up tilt-table testing (HUT).HUT was performed in 68 patients with unexplained syncope and 18 healthy subjects served as control group.According to whether bradycardia,hypotension or both took place during the onset of syncope,the patients were divided during the test into three subgroups:vasodepressor syncope (VD),cardioinhibitory syncope (CI) and mixed syncope (MX) subgroups.Heart rate,blood pressure,heart rate variability (HRV),and deceleration capacity (DC) were continuously analyzed during HUT.For all the subjects with positive responses,the normalized low frequency (LFn) and the LF/HF ratio markedly decreased whereas normalized high frequency (HFn) increased when syncope occurred.Syncopal period also caused more significant increase in the power of the DC in positive groups.These changes were more exaggerated compared to controls.All the patients were indicative of a sympathetic surge in the presence of withdrawal vagal activity before syncope and a sympathetic inhibition with a vagal predominance at the syncopal stage by the frequency-domain analysis of HRV.With the measurements ofDC,a decreased vagal tone before syncope stage and a vagal activation at the syncopal stage were observed.The vagal tone was higher in subjects showing cardioinhibitory responses at the syncopal stage.DC may provide an alternative method to understand the autonomic profile of VVS patients.
RESUMO
Fundamentos: Ambientes com temperatura elevada são considerados facilitadores para o desenvolvimento de síndrome neurocardiogênica. No entanto, existem poucas informações a respeito dos efeitos da sazonalidade nos resultados do teste da mesa de inclinação. Objetivo: Avaliar a influência da sazonalidade na taxa de positividade do teste de inclinação em uma cidade de clima tropival. Métodos: Foram analisados 501 testes consecutivos realizados em duas instituições na cidade do Rio de Janeiro, de junho de 2003 a agosto 2008, em uma população cuja idade variou de 6 anos a 90 anos, sendo 39 por cento homens. A resposta ao teste foi considerada positiva de acordo com os critérios do VASIS. O resultado do exame foi comparado no período de acordo com a taxa de positividade média mensal e sazonal. Após ter sido assumida a normalidade das distribuições e verificada a homocedasticidade através do teste de Bartlett, os achados foram comparados, utilizando-se os testes one-way ANOVA, para medidas não repetidas. Os resultados...
Background: High-temperature environments are rated as triggers for vaso-vagal orthostatic intolerance (VOI). However, there is little information on seasonal fluctuations of head-up tilt table test (HUT) outcomes.Objective: To evaluate seasonal fluctuation in HUT outcomes in a tropical city. Methods: We assessed 501 consecutive HUTs conducted at two institutions in the city of Rio de Janeiro, from June 2003 to August 2008 (6 y.o to 90.y.o, 39% males). The test response was defined as positive by the VASIS criteria. The VOI positive (+) outcome rate was compared during the period with the average monthly andseasonal rates. Having tested normality assumption and homocedasticity through the Bartlett test, the findingswere compared through one-way ANOVA tests for nonrepeatedmeasurements. The outcomes are presented as mean±DP. Results: The VOI was positive in 30.3%. Normality(Std Skewness: 1.5±0.4; Std Kurtosis: -0.4±0.8) and homocedasticity assumptions were accepted in all groups. No significant differences were observed in the monthly or seasonal average rates of VOI+ outcome in all comparisons (respectively, p=NS and p=NS). Conclusions: In the city of Rio de Janeiro, positive outcomes for HUT present uniform distribution throughout the year for months and seasons.