Heart Rate and its Variability Assessed by Spectral Analysis in Elderly Subjects with Orthostatic Hypotension: A Case-Control Study

Abstract Background: The prevalence of orthostatic hypotension (OH) increases with age and is associated with changes in autonomic regulation of blood pressure (BP) and heart rate (HR). Objective: to assess HR and HR variability (HRV) in elderly subjects with OH and determine OH predictors. Methods: a total of 105 patients aged ≥ 60 years, 39 with OH (case group) and 66 without OH (control group) (age-matched) were studied. Patients underwent clinical assessment, electrocardiogram, biochemistry tests and Holter monitoring for spectral analysis of HRV (Fourier transform) in the supine and orthostatism positions to identify low frequency (LF) and high frequency (HF) components, as well as the LF/HF ratio. Results: median age was 73.0 years, 64 patients were women. In all participants, there was a reduction in HF (133.0 versus 76.0 ms2, p = 0.001) and increase in LF/HF (1.6 vs 2.1; p < 0.001) and no change in LF (233.0 versus 218.0 ms2, p = 0.080). Between-group comparisons revealed significant differences in the median values of HR in the supine position (62.0 vs. 69.0 bpm, p = 0.001) and LF in the supine position (157.0 in case group vs. 275.0 ms2 in the control group, p = 0.014). Spearman’s correlation coefficient of 0.27 was found between the groups. Multivariate analysis revealed that HR in the supine position was an independent variable for OH (p = 0.001- 95%CI = -0.022 and -0.006). Using the operating characteristic curve, the best cutoff point was 61 bpm, with a sensitivity of 77.3% and specificity of 51.3%, positive predictive value of 61.3%, and negative predictive value 69.3%. Odds ratio was 3.23 for OH in patients with a HR lower than 61 bpm. Conclusions: lower LF and HR in the supine position were found in patients with OH, regardless of age and gender. The independent predictor for OH was HR in the supine position, with an odds ratio of 3.23 for values lower than 61 bpm.

**背景**：直立性低血压（orthostatic hypotension, OH）的患病率随年龄增长而升高，且与血压（blood pressure, BP）及心率（heart rate, HR）的自主神经调节紊乱密切相关。**目的**：评估合并OH的老年受试者的HR及心率变异性（heart rate variability, HRV），并明确OH的预测因素。**方法**：本研究共纳入105名年龄≥60岁的受试者，其中39名合并OH（病例组），66名未合并OH（对照组，年龄匹配）。所有受试者均接受临床评估、心电图检查、生化检验，并进行动态心电图监测以开展HRV频谱分析：采用傅里叶变换（Fourier transform）分别分析仰卧位与直立位下的HRV，获取低频（low frequency, LF）、高频（high frequency, HF）成分及LF/HF比值。**结果**：受试者的年龄中位数为73.0岁，其中64名为女性。所有受试者的HF成分均出现下降（133.0 vs. 76.0 ms²，P=0.001），LF/HF比值升高（1.6 vs. 2.1；P<0.001），而LF成分无明显变化（233.0 vs. 218.0 ms²，P=0.080）。组间比较显示，仰卧位HR的中位数（62.0 vs. 69.0 次/分钟，P=0.001）及仰卧位LF成分的中位数（病例组157.0 ms² vs. 对照组275.0 ms²，P=0.014）均存在显著差异。组间斯皮尔曼相关系数为0.27。多变量分析显示，仰卧位HR是OH的独立预测因素（P=0.001，95%置信区间：-0.022至-0.006）。采用受试者工作特征曲线分析，最佳截断值为61次/分钟，此时灵敏度为77.3%，特异度为51.3%，阳性预测值为61.3%，阴性预测值为69.3%。心率低于61次/分钟的受试者发生OH的比值比为3.23。**结论**：无论年龄与性别如何，合并OH的受试者仰卧位LF成分及HR均更低。仰卧位HR是OH的独立预测因素，当HR低于61次/分钟时，发生OH的比值比为3.23。