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Poststroke alterations in heart rate variability during orthostatic challenge
Joel Rodriguez1, Andrew Philip Blaber, Markus Kneihsl
1Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria Centre of Human and Aerospace Physiological Sciences, King's College London, London, UK Aerospace Physiology Laboratory, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada Department of Neurology, Medical University of Graz, Graz, Austria Centre of Human and Aerospace Physiological Sciences (CHAPS), King's College London, Faculty of Life Sciences and Medicine, Guy's Campus, London, UK KBRwyle, European Astronaut Centre, Linder Höhe, Cologne, Germany.
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] ms; 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.