Abstract
Percutaneous coronary intervention (PCI) is a common treatment method for patients with coronary artery disease (CAD), but its effect on synchronously measured heart rate variability (HRV) and pulse transit time variability (PTTV) have not been well established. This study aimed to verify whether PCI for CAD patients affects both HRV and PTTV parameters. Sixteen CAD patients were enrolled. Two five-minute ECG and finger photoplethysmography (PPG) signals were recorded, one within 24 h before PCI and another within 24 h after PCI. The changes of RR and pulse transit time (PTT) intervals due to the PCI procedure were first compared. Then, HRV and PTTV were evaluated by a standard short-term time-domain variability index of standard deviation of time series (SDTS) and our previously developed entropy-based index of fuzzy measure entropy (FuzzyMEn). To test the effect of different time series length on HRV and PTTV results, we segmented the RR and PTT time series using four time windows of 200, 100, 50 and 25 beats respectively. The PCI-induced changes in HRV and PTTV, as well as in RR and PTT intervals, are different. PCI procedure significantly decreased RR intervals (before PCI 973 ± 85 vs. after PCI 907 ± 100 ms, p < 0.05) while significantly increasing PTT intervals (207 ± 18 vs. 214 ± 19 ms, p < 0.01). For HRV, SDTS-only output significant lower values after PCI when time windows are 100 and 25 beats while presenting no significant decreases for other two time windows. By contrast, FuzzyMEn gave significant lower values after PCI for all four time windows (all p < 0.05). For PTTV, SDTS hardly changed after PCI at any time window (all p > 0.90) whereas FuzzyMEn still reported significant lower values (p < 0.05 for 25 beats time window and p < 0.01 for other three time windows). For both HRV and PTTV, with the increase of time window values, SDTS decreased while FuzzyMEn increased. This pilot study demonstrated that the RR interval decreased whereas the PTT interval increased after the PCI procedure and that there were significant reductions in both HRV and PTTV immediately after PCI using the FuzzyMEn method, indicating the changes in underlying mechanisms in cardiovascular system.
Highlights
Heart rate variability (HRV) refers to the variability of RR intervals between successive sinus beats, which results from the impact of the autonomic nervous system tone on sinus node function [1].Pulse transit time (PTT) is the interval from the R wave peaks to the feet of the corresponding pulse in the same cardiac cycle [2] and its variability, i.e., pulse transit time variability (PTTV), can provide insight into the inherent mechanisms of the cardiovascular system
HRV reduction after cardiac surgery is not exclusively related to percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG), as it is recorded in patients undergoing valve surgery [14]
This study showed a decrease of parasympathetic tone and autonomic balance shift towards sympathetic domination after the PCI procedure, indicated by the decreased standard deviation of time series (SDTS) in HRV and further confirmed by the FuzzyMEn analysis
Summary
Heart rate variability (HRV) refers to the variability of RR intervals between successive sinus beats, which results from the impact of the autonomic nervous system tone on sinus node function [1]. Pulse transit time (PTT) is the interval from the R wave peaks to the feet of the corresponding pulse in the same cardiac cycle [2] and its variability, i.e., pulse transit time variability (PTTV), can provide insight into the inherent mechanisms of the cardiovascular system. Physiological time series variability has been shown to have the potential to predict cardiovascular diseases [3,4]. Due to either the fact that it is a time-consuming technique associated with long-term physiological signal recordings or a lack of standardization of diagnostic methods as well as some technical difficulties for variability analysis, short-term measures lasting 2 to 15 min have been welcomed in clinical practice [5].
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