Objective: To analyze the hemodynamic response, cerebral blood flow, and the sympathovagal balance between patients with structurally healthy hearts who have a history of syncope and presyncope that exhibited signs or symptoms of presyncope without progressing to syncope during the tilt-table test, and a healthy group. Methodology: A retrospective study was conducted on patients attending the dysautonomia clinic of a tertiary care center. Individuals of both sexes aged 15 to 50 years were included. Patients with positive tests for VVS, OH, or POTS, and those with negative results were excluded. As a healthy group, healthy volunteers without a personal history of syncope or presyncope and with a negative tilt-table test were included. Statistical Analysis: Categorical variables were expressed as percentages and quantitative variables as mean ± standard deviation. Repeated measures ANOVA, the χ2 test, and effect size using Glass's Δ were used for group comparisons. A P-value < 0.05 was considered statistically significant. The R software, RStudio, and the effsize package were used for analysis. Results: The main finding was a significant decrease in cerebral blood flow secondary to an increase in cerebral vascular resistance in patients from a supine position at the start and throughout the test, compared to the control group. Conclusion: The analysis of cerebral hemodynamics allows for the identification of a subpopulation of patients who exhibit decreased cerebral blood flow from a supine position during the tilt-table test while maintaining cardiovascular stability without progressing to syncope.

中文翻译：

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有晕厥史和晕厥先兆史的患者在倾斜台试验中仰卧位时脑血流量减少

目的：分析具有晕厥病史和在倾斜试验中表现出晕厥先兆体征或症状但未进展为晕厥的心脏结构健康的患者的血流动力学反应、脑血流量和交感迷走神经平衡，以及健康组。方法：对三级护理中心自主神经功能障碍门诊就诊的患者进行回顾性研究。年龄在 15 岁至 50 岁之间的男女个体均包括在内。 VVS、OH 或 POTS 检测呈阳性的患者以及结果呈阴性的患者被排除在外。作为一个健康组，包括没有晕厥或先兆晕厥个人病史且倾斜台测试呈阴性的健康志愿者。统计分析：分类变量表示为百分比，定量变量表示为平均值±标准差。使用重复测量方差分析、χ2 检验和使用 Glass Δ 的效应大小进行组间比较。 P 值 < 0.05 被认为具有统计显着性。使用R软件、RStudio和effsize包进行分析。结果：主要发现是，与对照组相比，在测试开始时和整个测试过程中，患者从仰卧位开始，脑血管阻力增加，导致脑血流量显着减少。结论：脑血流动力学分析可以识别在倾斜台试验期间从仰卧位表现出脑血流量减少同时保持心血管稳定性而不进展为晕厥的患者亚群。