Recurrence quantitative analysis of heart rate variability during intradialytic hypotension

Recurrence quantitative analysis (RQA) of heart rate variability (HRV) is helpful for the non-invasive study of the regulation of the cardiovascular system by the autonomic nervous system. HRV monitoring during hemodialysis (HD) sessions of end-stage renal disease patients reflects a sympathetic hyperactivity that has been proposed as an early marker of intradialytic hypotension (IDH). However, neither intradialytic HRV analysis nor episodes of IDH have been explored from the RQA perspective. We studied the HRV dynamics with linear and RQA indices during intradialytic recordings (N = 38) in which 39.5% of patients presented IDH. Patients with IDH showed a restricted HRV during the whole HD compared to patients with stable blood pressure (p < 0.05). Although the RQA results during HD were heterogeneous, laminarity and the recurrence time of the second type revealed a constricted behavior around the onset of the IDH episodes. RQA analysis complemented the linear HRV measure to reveal a characteristic behavior immediately before and after the IDH episode. We also explored a framework for IDH prediction with a linear HRV index, the standard deviation of the differences between adjacent heartbeats intervals, which was associated in the early moments of HD with the development of IDH throughout HD sessions (sensitivity 80%, specificity 82.6%). The observed differences between groups may be of clinical utility for an early identification of patients prone to IDH.