Long-Term Effects of Ischemic Stroke on Autonomic Regulation

Impaired autonomic reflex is associated with orthostatic hypotension and falls in ischemic stroke patients. Understanding post-stroke temporal characteristics of autonomic reflex can assist in development of optimal therapy for improving autonomic function and patients’ quality of life. To this end, autonomic reflex 6± 2 years post-stroke was characterized during orthostatic challenge induced by sit-to-stand test. RR intervals (RR), heart rate (HR), systolic blood pressure (SBP), mean arterial pressure (MAP), and diastolic blood pressure (DBP) were extracted from simultaneously recorded electrocardiogram (ECG) and blood pressure waveform from stroke patients and age-matched controls. Shock index (SI), modified shock index (MSI), spectral power of RR in low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, 0.15-0.4 Hz) bands and LF baroreflex (SBP
$\to $
RR) gain were calculated. We observed higher HR, SI, and MSI during both phases in stroke patients compared to controls. Standing caused an increase (
$\text{p} < 0.05$
) in DBP and MAP in stroke patients but blood pressure did not change (
$\text{p}>0.10$
) in controls during standing compared to sitting. Stroke patients had lower (
$\text{p} < 0.05$
) SBP
$\to $
RR gain during both phases of the study compared to controls. Lastly, standing shifted the sympathovagal balance to sympathetic activity (elevated LF/HF ratio,
$\text{p}=0.03$
) in controls but not in patients. The study findings highlight the long-term effects of ischemic stroke on autonomic reflex and underscore the need for novel rehabilitation schemes to mitigate its adverse effect on autonomic reflex. Furthermore, the method proposed in this manuscript can be utilized to evaluate autonomic reflex continuously during rehabilitation, which could assist clinicians in customizing therapy for optimal recovery of autonomic function.