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 &lt; 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.研究背景：体位性低血压（orthostatic hypotension, OH）的患病率随年龄增长而升高，且与血压（blood pressure, BP）、心率（heart rate, HR）的自主神经调节改变相关。研究目的：旨在评估体位性低血压老年受试者的心率及心率变异性（heart rate variability, HRV），并明确体位性低血压的预测因素。方法：共纳入105名年龄≥60岁的患者，其中39名确诊体位性低血压（病例组），66名无体位性低血压（对照组，年龄匹配）。所有受试者均接受临床评估、心电图（electrocardiogram）检查、生化检测及动态心电图监测（Holter monitoring），采用傅里叶变换（Fourier transform）对仰卧位（supine）与直立位（orthostatism）的心率变异性进行频谱分析，以识别低频（low frequency, LF）、高频（high frequency, HF）成分及LF/HF比值。结果：受试者中位年龄为73.0岁，其中64名为女性。全部受试者的高频成分（HF）水平降低（133.0 vs 76.0 ms²，p=0.001），LF/HF比值升高（1.6 vs 2.1；p<0.001），低频成分（LF）无显著变化（233.0 vs 218.0 ms²，p=0.080）。组间比较显示，仰卧位心率中位值（62.0 vs 69.0 次/分，p=0.001）及仰卧位低频成分中位值（病例组157.0 ms² vs 对照组275.0 ms²，p=0.014）存在显著差异。两组间斯皮尔曼相关系数（Spearman’s correlation coefficient）为0.27。多因素分析表明，仰卧位心率是体位性低血压的独立预测因子（p=0.001，95%置信区间：-0.022~-0.006）。通过受试者工作特征曲线（operating characteristic curve）分析，最佳截断值为61次/分，其灵敏度为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/分的患者发生体位性低血压的优势比（odds ratio）为3.23。结论：无论年龄与性别如何，体位性低血压患者的仰卧位低频成分及心率均更低。体位性低血压的独立预测因子为仰卧位心率，心率低于61次/分的患者发生体位性低血压的优势比为3.23。