Poststroke alterations in heart rate variability during orthostatic challenge

Abstract

Older adults following recovery from ischemic stroke have a higher incidence of orthostatic hypotension, syncope, and fall risk, which may be related to impaired autonomic responses limiting the ability to maintain cerebral blood flow. Thus, we investigated cerebrovascular and cardiovascular regulation in 23 adults ≥55 years of age, 10 diagnosed with ischemic stroke, and 13 age-matched healthy controls when sitting at rest and upon standing to compare differences of autonomic variables at ∼7 months (218 ± 41 days) poststroke.Arterial blood pressure via finger plethysmography, muscle-pump baroreflex via electromyography, heart rate variability via 3-lead ECG, and cerebral blood flow velocity via transcranial Doppler were analyzed while sitting for 5 minutes and then during quiet standing for 5 minutes.From the seated to standing position, the stroke group had significantly greater decline in the low frequency component of heart rate variability (164 [79] vs 25 [162] ms2; P = 0.043). All other cardiovascular parameters and assessments of autonomic function were not significantly different between the two groups.Our findings support the hypothesis of continued autonomic dysfunction after recovery from ischemic stroke, with potential attenuation of the cardiovascular response to standing. However, further investigation is required to determine the mechanisms underlying the increased risk of orthostatic hypotension, syncope, and falls poststroke.

Orthostatic Intolerance in Older Persons: Etiology and Countermeasures

“…Recently, Rodriguez et al ( 2017 ) reported that there is no difference in spontaneous baroreflex sensitivity between stroke patients and healthy controls during standing up from a sitting posture. However, the gain values from SBP to EMG impulse were attenuated in patients, which suggests a post-stroke impairment of muscle-pump and baroreflex.…”

“…We are only aware of one study that has investigated in older persons the post-stroke relationship in heart rate variability (HRV; Rodriguez et al, 2017 ) at rest and during changes in posture. A greater magnitude of decrease in LF HRV modulation upon standing up for the stroke group—indicating a transition to less sympathetic modulation—on average compared to the control subjects was observed.…”

Impaired baroreflex sensitivity and increased systolic blood pressure variability in chronic post-ischemic stroke

“…Another limitation is the lack of a protocol for challenging the autonomic nervous system. Rodriguez et al 31 evaluated alterations in HRV during orthostatic challenge at approximately 7 months post-stroke and found that the LF component of HRV when moving from a seated to a standing position was lower in the stroke group than in the control group, suggesting that cardiovascular autonomic dysfunction persists after recovery from stroke and that the cardiovascular response to standing may be impaired in these patients.…”

Postural hemodynamic parameters in older persons have a seasonal dependency

“…The selection criteria and the number of participants required to show statistical significance were based on previously published studies regarding hemodynamic responses to orthostatic loading (sit-to-stand test) in patients with stroke [7,10,28,31]. It was estimated that using a sample size calculator with an error probability (a) of 0.05, power (1-β) of 0.80 and an average effect size (d) of 0.5, the number of participants needed to achieve statistical significance was 37.…”