Abstract
Autonomic reflex ascertains cardiovascular homeostasis during standing. Impaired autonomic reflex could lead to dizziness and falls while standing; this is prevalent in stroke survivors. Pulse rate variability (PRV) has been utilized in the literature in lieu of heart rate variability (HRV) for ambulatory and portable monitoring of autonomic reflex predominantly in young, healthy individuals. Here, we compared the PRV with gold standard HRV for monitoring autonomic reflex in ischemic stroke survivors. Continuous blood pressure and electrocardiography were acquired from ischemic stroke survivors (64 ± 1 years) and age-matched controls (65 ± 2 years) during a 10-minute sit-to-stand test. Beat-by-beat heart period (represented by RR and peak-to-peak (PP) intervals), systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse arrival time (PAT), an indicator of arterial stiffness, were derived. Time and frequency domain HRV (from RR intervals) and PRV (from PP intervals) metrics were extracted. PAT was lower (248 ± 7 ms vs. 270 ± 8 ms, p < 0.05) suggesting higher arterial stiffness in stroke survivors compared to controls during standing. Further, compared to controls, the agreement between HRV and PRV was impaired in stroke survivors while standing. The study outcomes suggest that caution should be exercised when considering PRV as a surrogate of HRV for monitoring autonomic cardiovascular control while standing in stroke survivors.
Highlights
Impairment in autonomic function is commonly observed following ischemic stroke [1,2,3].Autonomic cardiovascular control is a vital mechanism which regulates blood pressure during standing [4,5,6], the failure of which could cause dizziness and unexpected falls [7]
We observed disagreement between heart rate variability (HRV) and pulse rate variability (PRV) in the stroke survivors during the sitting phase as well as during the standing phase compared to controls. This finding leads us to conclude that PRV may not be a reliable surrogate of HRV for monitoring autonomic cardiovascular control while standing, in people with a history of ischemic stroke
A tremendous amount of literature is focused on quantifying the relationship (HRV vs. PRV) in young, healthy participants during resting conditions, while when the same comparative relationship was studied in an unhealthy population, unfavorable outcomes were observed [36,37,38]
Summary
Autonomic cardiovascular control is a vital mechanism which regulates blood pressure during standing [4,5,6], the failure of which could cause dizziness and unexpected falls [7]. Falls that are associated with the failure to regulate blood pressure during a standing position (orthostatic intolerance), due to autonomic dysfunction, are prevalent in stroke survivors, which adversely affect their quality of life [8,9,10,11]. The development of a portable and cost-effective technology for the continuous monitoring of the autonomic reflex in an ambulatory fashion can play a consequential role in the management of untoward effects of a stroke to improve the quality of life of affected persons. Beat-to-beat reduction in blood pressure is sensed by the baroreceptors localized in the aortic arch and carotid
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