Autonomic dysfunction in different subtypes of post-acute ischemic stroke

The Impact of Stimulation Parameters on Cardiovascular Outcomes in Chronic Stroke Patients Following Transcranial Direct Current Stimulation-A Pilot Controlled, Randomized, Double-Blind Crossover Trial

BACKGROUND

Stroke survivors often experience autonomic nervous system (ANS) dysfunction. While Transcranial Direct Current Stimulation (tDCS) has been shown to modulate the ANS when applied to the left hemisphere, its effects on the right hemisphere remain unexplored.

OBJECTIVE

We aimed to compare the effects of tDCS applied to both the injured and the contralateral hemispheres on heart rate variability (HRV) and functional capacity in individuals post-stroke.

METHODS

Twenty individuals with cerebral hemisphere lesions (ten with right-hemisphere lesions and ten with left-hemisphere lesions) were randomized into four groups: anodal and sham tDCS on the left temporal cortex (T3) and anodal and sham tDCS on the right temporal cortex (T4). HRV was assessed before the intervention, after the six-minute walk test (6MWT), and following tDCS. HRV data were categorized into frequency ranges: low frequency (LF), high frequency (HF), and sympathovagal balance. The 6MWT (meters) was conducted both pre- and post-tDCS.

RESULTS

In individuals with right-hemisphere lesions, a higher global LF value was observed (right side: 71.4 ± 16.8 nu vs. left side: 65.7 ± 17.3 nu; p = 0.008), as well as lower values of the HF component (right side: 29.5 ± 18.9 nu vs. left side: 34.0 ± 17.4 nu; p = 0.047), consequently exhibiting higher global values of the low/high-frequency ratio (right side: 3.9 ± 2.8 vs. left side: 2.9 ± 2.4). Regarding the stimulation site, tDCS over T3 led to a lower overall value of the low/high-frequency ratio (left hemisphere: 3.0 ± 2.2 vs. right hemisphere: 3.7 ± 2.9; p = 0.040) regardless of the lesion location. A significant increase in the distance covered in the 6MWT was observed for individuals with lesions in both hemispheres after tDCS at T3.

CONCLUSIONS

Participants with right-hemisphere lesions exhibited superior global sympathetic autonomic nervous system activity. When the tDCS was applied on the left hemisphere, it maintained lower sympathovagal balance values and improved functional capacity regardless of the hemisphere affected by the stroke.

Changes in heart rate variability over time from symptom onset of transient global amnesia

Transient global amnesia (TGA) often involves precipitating events associated with changes in autonomic nervous system (ANS), and heart rate variability (HRV) reflects the ANS state. This study aimed to investigate HRV changes after TGA. A retrospective analysis of HRV included patients diagnosed with TGA between January 2015 and May 2020. The time and frequency domains of HRV were compared among three groups: early (< 1 week after TGA, n = 19), late (1-4 weeks after TGA, n = 38), and healthy control (HC, n = 19). The Pearson's correlation between time and time-domain HRV was also examined. The standard deviation of NN intervals (SDNN) (early, 47.2; late, 35.5; HC, 41.5; p = 0.033) and root mean square of successive RR interval differences (RMSSD) (early, 38.5; late, 21.3; HC, 31.0; p = 0.006) differed significantly among the three groups. Post-hoc analysis showed statistically significant differences only in the early and late groups in both SDNN (p = 0.032) and RMSSD (p = 0.006) values. However, the frequency domain with total power, low-frequency and high-frequency powers, and low-frequency/high-frequency ratio did not differ. SDNN (Pearson correlation coefficient =- 0.396, p = 0.002) and RMSSD (Pearson correlation coefficient =- 0.406, p = 0.002) were negatively correlated with time after TGA. Changes in HRV occurred over time after the onset of TGA, with the pattern showing an increase in the first week and then a decrease within 4 weeks.

Autonomic nervous system imbalance during aging contributes to impair endogenous anti-inflammaging strategies

Inflammaging refers to the age-related low grade, sterile, chronic, systemic, and long-lasting subclinical, proinflammatory status, currently recognized as the main risk factor for development and progression of the most common age-related diseases (ARDs). Extensive investigations were focused on a plethora of proinflammatory stimuli that can fuel inflammaging, underestimating and partly neglecting important endogenous anti-inflammaging mechanisms that could play a crucial role in such age-related proinflammatory state. Studies on autonomic nervous system (ANS) functions during aging highlighted an imbalance toward an overactive sympathetic nervous system (SNS) tone, promoting proinflammatory conditions, and a diminished parasympathetic nervous system (PNS) activity, playing anti-inflammatory effects mediated by the so called cholinergic anti-inflammatory pathway (CAP). At the molecular level, CAP is characterized by signals communicated via the vagus nerve (with the possible involvement of the splenic nerves) through acetylcholine release to downregulate the inflammatory actions of macrophages, key players of inflammaging. Notably, decreased vagal function and increased burden of activated/senescent macrophages (macrophaging) probably precede the development of several age-related risk factors and diseases, while increased vagal function and reduced macrophaging could be associated with relevant reduction of risk profiles. Hypothalamic-pituitary-adrenal axis (HPA axis) is another pathway related to ANS promoting some anti-inflammatory response mainly through increased cortisol levels. In this perspective review, we highlighted that CAP and HPA, representing broadly "anti-inflammaging" mechanisms, have a reduced efficacy and lose effectiveness in aged people, a phenomenon that could contribute to fuel inflammaging. In this framework, strategies aimed to re-balance PNS/SNS activities could be explored to modulate systemic inflammaging especially at an early subclinical stage, thus increasing the chances to reach the extreme limit of human lifespan in healthy status.

Brain connectivity networks underlying resting heart rate variability in acute ischemic stroke

Acute strokes can affect heart rate variability (HRV), the mechanisms how are not well understood. We included 42 acute stroke patients (2-7 days after ischemic stroke, mean age 66 years, 16 women). For analysis of HRV, 20 matched controls (mean age 60.7, 10 women) were recruited. HRV was assessed at rest, in a supine position and individual breathing rhythmus for 5 min. The coefficient of variation (VC), the root mean square of successive differences (RMSSD), the powers of low (LF, 0.04-0.14 Hz) and high (HF, 0.15-0.50 Hz) frequency bands were extracted. HRV parameters were z-transformed related to age- and sex-matched normal subjects. Z-values < -1 indicate reduced HRV. Acute stroke lesions were marked on diffusion-weighted images employing MRIcroN and co-registered to a T1-weighted structural volume-dataset. Using independent component analysis (ICA), stroke lesions were related to HRV. Subsequently, we used the ICA-derived lesion pattern as a seed and estimated the connectivity between these brain regions and seven common functional networks, which were obtained from 50 age-matched healthy subjects (mean age 68.9, 27 women). Especially, LF and VC were frequently reduced in patients. ICA revealed one covarying lesion pattern for LF and one similar for VC, predominantly affecting the right hemisphere. Activity in brain areas corresponding to these lesions mainly impact on limbic (r = 0.55 ± 0.08) and salience ventral attention networks (0.61 ± 0.10) in the group with reduced LF power (z-score < -1), but on control and default mode networks in the group with physiological LF power (z-score > -1). No different connectivity could be found for the respective VC groups. Our results suggest that HRV alteration after acute stroke might be due to affecting resting-state brain networks.

Changes in beat-to-beat blood pressure and pulse rate variability following stroke

Associations between cerebrovascular disease and impaired autonomic function and cerebrovascular reactivity have led to increased interest in variability of heart rate (HRV) and blood pressure (BPV) following stroke. In this study, beat-to-beat pulse rate variability (PRV) and BPV were measured in clinically stable stroke patients (6 ischemic, 2 hemorrhagic) at least one year after their last cerebrovascular event. Beat-to-beat blood pressure (BP) measurements were collected from subjects while resting in the sitting position for one hour. Compared with healthy controls, stroke patients exhibited significantly greater time-domain (standard deviation, coefficient of variation, average real variability) and normalized high-frequency BPV (all p < 0.05). Stroke patients also exhibited lower LF:HF ratios than control subjects (p = 0.003). No significant differences were observed in PRV between the two groups, suggesting that BPV may be a more sensitive biomarker of cerebrovascular function in long-term post-stroke patients. Given a paucity of existing literature investigating beat-to-beat BPV in clinically stable post-stroke patients long (> 1 year) after their cerebrovascular events, this pilot study can help inform future studies investigating the mechanisms and effects of BPV in stroke. Elucidating this physiology may facilitate long-term patient monitoring and pharmacological management to mitigate the risk for recurrent stroke.

Gastrointestinal Dysfunction in Stroke

Gastrointestinal (GI) complications are seen in over 50% of ischemic stroke survivors; the most common complications are dysphagia, constipation, and GI bleeding. The bidirectional relationship of the gut-brain axis and stroke has recently gained traction, wherein stroke contributes to gut dysbiosis (alterations in the normal host intestinal microbiome) and gut dysbiosis perpetuates poor functional neurologic outcomes in stroke. It is postulated that the propagation of proinflammatory cells and gut metabolites (including trimethylamine N-oxide and short-chain fatty acids) from the GI tract to the central nervous system play a central role in gut-brain axis dysfunction. In this review, we discuss the known GI complications in acute ischemic stroke, our current knowledge from experimental stroke models for gut-brain axis dysfunction in stroke, and emerging therapeutics that target the gut-brain axis.

Heart Rate Variability: A Measure of Cardiovascular Health and Possible Therapeutic Target in Dysautonomic Mental and Neurological Disorders

Mental illness such as depression and anxiety as well as cerebrovascular disease are linked to impairment of neurocardiac function mediated by changes to the autonomic nervous system with increased sympathetic and decreased parasympathetic activity. Autonomic neurocardiac function can be evaluated by computing heart rate variability (HRV). Over the past decades, research has demonstrated the diagnostic value of HRV as independent predictor of cardiovascular mortality and as disease marker in progressive autonomic nervous system disorders such as Parkinson’s disease. Here we summarize our studies on HRV and its therapeutic modulation in the context of psychopharmacology as well as psychiatric and neurological disorders to honor the life of Professor Evgeny Vaschillo, the true pioneer of HRV research who sadly passed away on November 21st, 2020.

Role of CRF and the hypothalamic-pituitary-adrenal axis in stroke: revisiting temporal considerations and targeting a new generation of therapeutics

Ischaemic neurovascular stroke represents a leading cause of death in the developed world. Preclinical and human epidemiological evidence implicates the corticotropin-releasing factor (CRF) family of neuropeptides as mediators of acute neurovascular injury pathology. Preclinical investigations of the role of CRF, CRF receptors and CRF-dependent activation of the hypothalamic-pituitary-adrenal (HPA) axis have pointed toward a tissue-specific and temporal relationship between activation of these pathways and physiological outcomes. Based on the literature, the major phases of ischaemic stroke aetiology may be separated into an acute phase in which CRF and anti-inflammatory stress signalling are beneficial and a chronic phase in which these contribute to neural degeneration, toxicity and apoptotic signalling. Significant gaps in knowledge remain regarding the pathway, temporality and systemic impact of CRF signalling and stress biology in neurovascular injury progression. Heterogeneity among experimental designs poses a challenge to defining the apparent reciprocal relationship between neurological injury and stress metabolism. Despite these challenges, it is our opinion that the elucidated temporality may be best matched with an antibody against CRF with a half-life of days to weeks as opposed to minutes to hours as with small-molecule CRF receptor antagonists. This state-of-the-art review will take a multipronged approach to explore the expected potential benefit of a CRF antibody by modulating CRF and corticotropin-releasing factor receptor 1 signalling, glucocorticoids and autonomic nervous system activity. Additionally, this review compares the modulation of CRF and HPA axis activity in neuropsychiatric diseases and their counterpart outcomes post-stroke and assess lessons learned from antibody therapies in neurodegenerative diseases.

The Use of Cardiac Autonomic Responses to Aerobic Exercise in Elderly Stroke Patients: Functional Rehabilitation as a Public Health Policy

BACKGROUND AND PURPOSE

The development of public policies must be guided by full knowledge of the health-disease process of the population. Aerobic exercises are recommended for rehabilitation in stroke patients, and have been shown to improve heart rate variability (HRV). Our aim was to compare the cardiac autonomic modulation of elderly stroke patients with that of healthy elderly people during and after an acute bout of aerobic exercise.

METHODS

A total of 60 elderly people participated in the study (30 in the control group, mean age of 67 ± 4 years; 30 in the stroke group, mean age of 69 ± 3 years). HRV was analyzed in rest-10 min of rest in supine position; exercise-the 30 min of peak exercise; and recovery-30 min in supine position post-exercise.

RESULTS

Taking rest and exercises together, for SDNN, RMSSD, pNN50, RRTri, and TINN, there was no difference between the stroke and control groups (p = 0.062; p = 0.601; p = 0.166; p = 0.224, and p = 0.059, respectively). The HF (ms2) was higher and the LF/HF ratio was lower for the stroke group than the control group (p < 0.001 and p = 0.007, respectively). The SD2 was lower for the stroke group than for the control group (p = 0.041).

CONCLUSION

Stroke patients present reduced variability at rest, sympathetic predominance during exercise, and do not return to baseline after the 30 min of recovery, with similar responses found in the healthy elderly group.

Brain to periphery in acute ischemic stroke: Mechanisms and clinical significance

The social and public health burdens of ischemic stroke have been increasing worldwide. In addition to focal brain damage, acute ischemic stroke (AIS) provokes systemic abnormalities across peripheral organs. AIS profoundly alters the autonomic nervous system, hypothalamic-pituitary-adrenal axis, and immune system, which further yield deleterious organ-specific consequences. Poststroke systemic pathological alterations in turn considerably contribute to the progression of ischemic brain injury, which accounts for the substantial impact of systemic complications on stroke outcomes. This review provides a comprehensive and updated pathophysiological model elucidating the systemic effects of AIS. To address their clinical significance and inform stroke management, we also outline the resulting systemic complications at particular stages of AIS and highlight the mechanisms. Future therapeutic strategies should attempt to integrate the treatment of primary brain lesions with interventions for secondary systemic complications, and should be tailored to patient individualized characteristics to optimize stroke outcomes.

Randomized Sham-Controlled Pilot Study of Neurocardiac Function in Patients With Acute Ischaemic Stroke Undergoing Heart Rate Variability Biofeedback

Background: Neurocardiac dysfunction worsens clinical outcome and increases mortality in stroke survivors. We hypothesized that heart rate variability (HRV) biofeedback improves neurocardiac function by modulating autonomic nervous system activity after acute ischaemic stroke (AIS).

Methods: We randomly allocated (1:1) 48 acute ischaemic stroke patients to receive nine sessions of HRV- or sham biofeedback over 3 days in addition to comprehensive stroke unit care. Before and after the intervention patients were evaluated for HRV via standard deviation of normal-to-normal intervals (SDNN, primary outcome), root mean square of successive differences between normal heartbeats (RMSSD), a predominantly parasympathetic measure, and for sympathetic vasomotor and sudomotor function. Severity of autonomic symptoms was assessed via survey of autonomic symptom scale total impact score (TIS) at baseline and after 3 months.

Results: We included 48 patients with acute ischaemic stroke [19 females, ages 65 (4.4), median (interquartile range)]. Treatment with HRV biofeedback increased HRV post intervention [SDNN: 43.5 (79.0) ms vs. 34.1 (45.0) ms baseline, p = 0.015; RMSSD: 46.0 (140.6) ms vs. 29.1 (52.2) ms baseline, p = 0.015] and alleviated autonomic symptoms after 3 months [TIS 3.5 (8.0) vs. 7.5 (7.0) baseline, p = 0.029], which was not seen after sham biofeedback (SDNN: p = 0.63, RMSSD: p = 0.65, TIS: 0.06). There were no changes in sympathetic vasomotor and sudomotor function (p = ns).

Conclusions: Adding HRV biofeedback to standard stroke unit care led to improved neurocardiac function and sustained alleviation of autonomic symptoms after acute ischaemic stroke, which was likely mediated by a predominantly parasympathetic mechanism.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03865225.

Increased One-Year Recurrent Ischemic Stroke after First-Ever Ischemic Stroke in Males with Benign Prostatic Hyperplasia

(1) Background: Patients with benign prostatic hyperplasia (BPH) were questioned about quality of life and sleep. Most BPH patients were treated with alpha-1 adrenergic receptor antagonists, which could improve cerebral blood flow for 1–2 months. Patients with ischemic stroke (IS) could experience cerebral autoregulation impairment for six months. The relationship between BPH and recurrent IS remains unclear. The aim of this study was to determine the risk of one-year recurrent IS conferred by BPH. (2) Methods: We used data from the Taiwanese National Health Insurance Database to identify newly diagnosed IS cases entered from 1 January 2008 to 31 December 2008. Patients were followed until the recurrent IS event or 365 days after the first hospitalization. The risk factors associated with one-year recurrent IS were assessed using Cox proportional hazards regression. (3) Results: Patients with BPH had a higher risk of recurrent IS (12.11% versus 8.15%) (adjusted hazard ratio (HR): 1.352; 95% confidence interval (CI): 1.028–1.78, p = 0.031). Other risk factors included hyperlipidemia (adjusted HR: 1.338; 95% CI: 1.022–1.751, p = 0.034), coronary artery disease (adjusted HR: 1.487; 95% CI: 1.128–1.961, p = 0.005), chronic obstructive pulmonary disease (adjusted HR: 1.499; 95% CI: 1.075–2.091, p = 0.017), and chronic kidney disease (adjusted HR: 1.523; 95% CI: 1.033–2.244, p = 0.033). (4) Conclusion: Patients with BPH who had these risk factors had an increased risk of one-year recurrent IS. The modification of risk factors may prevent recurrent IS.

Relationship between ischemic stroke locations, etiology subtypes, neurological outcomes, and autonomic cardiac function

BACKGROUND

Post-stroke autonomic nervous dysfunction measured with heart rate variability (HRV) is correlated with the traditional risk factors and poor outcome. This study aimed to investigate the association between HRV and infarct locations, etiology subtypes, and neurological functional outcomes in patients with acute ischemic stroke (AIS).

METHODS

In this prospective observational study, 186 consecutive patients were assigned to four major stroke severity categories based on the National Institutes of Health Stroke Scale score (NIHSS) and the modified Rankin Scale score (mRS): mild (NIHSS 0-4) stroke, moderate (NIHSS 5-14) stroke, 'favorable' (mRS 0-2) group, and 'unfavorable' (mRS 3-5) group. HRV time domain parameters were applied to evaluate the autonomic function of patients within 1 week after admission. All patients were classified into different etiology subtypes based on the TOAST (modified Trial of ORG 10172 in Acute Stroke Treatment) classification. The association of HRV with stroke location, etiology subtypes, neurological outcome was explored for all participants. Univariate and multivariate analyses were applied to explore the prediction value of HRV.

RESULTS

160 participants had large artery atherosclerotic infarction (LAA), 61 had right internal carotid artery system infarction (R-ICA), and 61 had vertebrobasilar artery system infarction (VB). Root-mean-square of differences (RMSSD) of adjacent RR intervals and the proportion calculated by dividing the interbeat interval differences >50 ms (pNN50) in patients of VB group was significantly lower than those of patients in R-ICA group (P < 0.01).  HRV parameters in the LAA group was significantly lower than non-LAA group (P < 0.01). At discharge, significant lower HRV presented in the unfavorable group and moderate group (P < 0.05). After logistic univariate and multivariate analysis, lower SDNN (OR = 1.019; 95% CI = 1.003-1.035; p= 0.021) was independently associated with unfavorable mRS and higher NIHSS at discharge (OR = 1.013; 95%CI = 1.003-1.024; p= 0.015). Only SDNN showed predictive value for mRS≥3 (OR = 1.012; 95%CI = 1.002-1.022; p= 0.016) at 1 year.

CONCLUSIONS

HRV measured after admission is related to the AIS infarction basin, TOAST subtypes, and neurological outcomes at discharge suggesting a possible role for HRV in evaluating AIS and identifying high-risk patients.

Lesion configuration effect on stroke-related cardiac autonomic dysfunction

BACKGROUND

Autonomic nervous system (ANS) malfunction is a common sequel of stroke. The impact of lesion configuration on the expression of stroke-related ANS malfunction is largely unknown.

OBJECTIVE

To examine the relationship between stroke location and ANS malfunction, as reflected in cardiac rhythm control.

METHODS

25 patients in the subacute phase post first-ever ischemic stroke were recruited for the study. Heart rate monitor (RS800CX) was used to record RR intervals analyzed as heart rate variability (HRV) parameters. Lesion data derived from follow-up CT scans of the brain was used for voxel-based lesion symptom mapping (VLSM) analysis (MEDx software, Medical Numerics) to identify voxels of the normalized brain where damage exerts a significant impact on the HRV scores.

RESULTS AND CONCLUSION

ANS control of the cardiac rhythm, as expressed in the HRV, was affected by damage to a large array of cortical and subcortical structures in the right hemisphere. In the left hemisphere only damage confined to a small set of subcortical structures was shown to exert a significant impact on the recorded HRV measures. In addition, VLSM analysis disclosed a different pattern of cerebral control over two widely used standard time-dependent measures of the HRV - SDNN and RMSSD, with the former being sensitive to damage in a much larger array of structures in both hemispheres.

The Relationship Between Blood Flow and Motor Unit Firing Rates in Response to Fatiguing Exercise Post-stroke

We quantified the relationship between the change in post-contraction blood flow with motor unit firing rates and metrics of fatigue during intermittent, sub-maximal fatiguing contractions of the knee extensor muscles after stroke. Ten chronic stroke survivors (>1-year post-stroke) and nine controls participated. Throughout fatiguing contractions, the discharge timings of individual motor units were identified by decomposition of high-density surface EMG signals. After five consecutive contractions, a blood flow measurement through the femoral artery was obtained using an ultrasound machine and probe designed for vascular measurements. There was a greater increase of motor unit firing rates from the beginning of the fatigue protocol to the end of the fatigue protocol for the control group compared to the stroke group (14.97 ± 3.78% vs. 1.99 ± 11.90%, p = 0.023). While blood flow increased with fatigue for both groups (p = 0.003), the magnitude of post-contraction blood flow was significantly greater for the control group compared to the stroke group (p = 0.004). We found that despite the lower magnitude of muscle perfusion through the femoral artery in the stroke group, blood flow has a greater impact on peripheral fatigue for the control group; however, we observed a significant correlation between change in blood flow and motor unit firing rate modulation (r² = 0.654, p = 0.004) during fatigue in the stroke group and not the control group (r² = 0.024, p < 0.768). Taken together, this data showed a disruption between motor unit firing rates and post-contraction blood flow in the stroke group, suggesting that there may be a disruption to common inputs to both the reticular system and the corticospinal tract. This study provides novel insights in the relationship between the hyperemic response to exercise and motor unit firing behavior for post-stroke force production and may provide new approaches for recovery by improving both blood flow and muscle activation simultaneously.

The Effect of Stroke Subtypes on Baroreceptor Sensitivity, a Predict for Acute Stroke Outcome

Background

Reduced baroreflex sensitivity (BRS) has been reported in patients with acute cardiovascular events. We tested the hypothesis that BRS varies in different subtypes of acute ischemic stroke (AIS) and that BRS is a predictor of clinical outcomes.

Methods

We examined autonomic parameters in 34 patients with AIS, including the small deep hemisphere infarction, the large hemisphere infarction, and the brainstem infarction groups on Day 1, Day 7, and Day 30 after AIS. Autonomic parameters were also evaluated in 18 age- and sex-matched healthy volunteers as a control group. The clinical outcomes were analyzed using the modified Rankin scale at 30 days after stroke.

Results

The BRS, Valsalva ratio, and heart rate response to deep breathing (HR-DB) were significantly lower in patients after AIS on admission than in controls (p<0.01). The frequency domain of HRV (LF/HF ratio) was significantly increased in patients after AIS compared to controls (p<0.05). BRS was significantly reduced in patients with large hemisphere infarction or brainstem infarction compared to patients with small deep hemisphere infarction on Day 1 after AIS (p<0.01). Stepwise logistic regression showed that the levels of BRS and NIHSS are prognostic factors of 1-month outcomes in patients with AIS.

Conclusion

Beside NIHSS score on admission, BRS is a potential prognostic factor of 1-month outcomes in patients with AIS. Patients with large hemisphere infarction or brainstem infarction have more blunting BRS than do those with lacunar infarction, which provides some insight into which patients may be expected to have a poor outcome.

Preventive effects of transcutaneous electrical acustimulation on ischemic stroke-induced constipation mediated via the autonomic pathway

The aim of this study was to explore the preventive effect and possible mechanisms of transcutaneous electrical acustimulation (TEA) on stroke-induced constipation. A total of 86 ischemic stroke patients were randomly allocated to 2-wk TEA or sham-TEA group. Bowel dairy and Bristol Stool Form Scale were recorded daily. Constipation and dyspeptic symptom assessment was performed at the end of the 14-day treatment. Electrocardiogram was recorded for the assessment of autonomic function. The correlation between autonomic function at admission and stroke severity was assessed. The univariate and multivariate regression analyses were performed to investigate the risk factors for stroke-induced constipation. The cumulative incidence of stroke-induced constipation was 68.2% at the acute stage. Sympathetic nerve activity at admission was positively correlated with stroke severity ( R = 0.47, P < 0.001). Sympathetic nerve activity and stroke severity were independent risk factors for stroke-induced constipation. TEA decreased cumulative incidence of stroke-induced constipation (42.9 vs. 68.2%, P = 0.029). TEA significantly increased frequency of bowel movements (4.5 vs. 5.5, P = 0.001) and spontaneous bowel movements (3.0 vs. 4.5, P = 0.003) per week. TEA decreased straining defecations (0.2 vs. 0, P < 0.001) and laxative use (1 vs. 0, P < 0.001). TEA improved stool consistency and patients' quality of life ( P < 0.05, resp.). TEA increased vagal activity ( P < 0.001 vs. baseline) and decreased sympathetic activity ( P < 0.001 vs. baseline). Ischemic stroke patients are predisposed to autonomic function imbalance. TEA was effective in the prevention of stroke-induced constipation, and the effect was possibly mediated via the autonomic function. NEW & NOTEWORTHY This study illustrated that the brain-gut dysfunction, primarily autonomic function imbalance, was correlated with the stroke-induced constipation. This was the first study to report that transcutaneous electrical acustimulation had a preventive effect on stroke-induced constipation, suggesting a potential novel therapy for bowel problem management. The effect was possibly mediated via the autonomic function.

Autonomic function test in progressive lacunar infarction

OBJECTIVE

Neurological progression is a major problem in managing the patients with acute lacunar infarction. The purpose of this was to investigate whether autonomic dysfunction is associated with neurological progression in patients with acute lacunar infarction.

MATERIALS AND METHODS

The study comprised 60 patients with acute lacunar infarction. All enrolled subjects underwent autonomic function tests including the 30° head-up tilt test, Valsalva test, heart rate response to deep breathing, and sympathetic skin response. The primary endpoint is the neurological progression, and the secondary endpoint is the 3-month outcome.

RESULTS

Increased initial National Institute of Health stroke scale (NIHSS), decreased time to admission from onset, decreased rise of heart rate in the 30° head-up tilt test, abnormal blood pressure response in the Valsalva test, and decreased rise of systolic blood pressure in stage IV of the Valsalva test are associated with neurological progression of acute lacunar infarction; an abnormal blood pressure response in the Valsalva test is significant in logistic regression analysis of neurological progression. Advanced age, increased initial NIHSS and modified Rankin scale, decreased expiration/inspiration ratio of heart rate to deep breathing, decreased rise of systolic blood pressure in stage IV of the Valsalva test, and neurological progression were associated with an unfavorable 3-month outcome; neurological progression was significant in logistic regression analysis of 3-month outcome.

CONCLUSIONS

An abnormal blood pressure change in the Valsalva test is associated with neurological progression in patients with acute lacunar infarction, and neurological progression can induce an unfavorable 3-month outcome.

Heart Rate Variability in Patients with Acute Ischemic Stroke at Different Stages of Renal Dysfunction: A Cross-sectional Observational Study

Background:

Renal function is associated with mortality and functional disabilities in stroke patients, and impaired autonomic function is common in stroke, but little is known regarding its effects on stroke patients with renal dysfunction. This study sought to evaluate the association between autonomic function and stroke in patients with renal dysfunction.

Methods:

This study comprised 232 patients with acute ischemic stroke consecutively enrolled from February 2013 to November 2014 at Guangdong Provincial Hospital of Chinese Medicine in China. All patients recruited underwent laboratory evaluation and 24 h Holter electrocardiography (ECG). Autonomic function was measured based on the heart rate variability (HRV) using 24 h Holter ECG. Renal damage was assessed through the estimated glomerular filtration rate (eGFR), and stroke severity was rated according to the National Institutes of Health Stroke Scale (NIHSS). The Barthel index and modified Rankin score were also determined following admission. All the clinical covariates that could potentially affect autonomic outcome variables were adjusted with linear regression.

Results:

In the patients with a mild or moderate decreased eGFR, the values for the standard deviation of the averaged normal-to-normal RR interval (SDANN) index (P = 0.022), very low frequency (VLF) (P = 0.043), low frequency (LF) (P = 0.023), and ratio of low-to-high frequency power (LF/HF) (P = 0.001) were significantly lower than those in the patients with a normal eGFR. A multinomial linear regression indicated that eGFR (t = 2.47, P = 0.014), gender (t = −3.60, P < 0.001), and a history of hypertension (t = −2.65, P = 0.008) were the risk factors of LF/HF; the NIHSS score (SDANN index: t = −3.83, P < 0.001; VLF: t = −3.07, P = 0.002; LF: t = −2.79, P = 0.006) and a history of diabetes (SDANN index: t = −3.58, P < 0.001; VLF: t = −2.54, P = 0.012; LF: t = −2.87, P = 0.004) were independent factors for the SDANN index, VLF, and LF; the Oxfordshire Community Stroke Project (t = −2.38, P = 0.018) was related to the SDANN index.

Conclusions:

Autonomic dysfunction is aggravated with the progression of eGFR stage in patients with acute ischemic stroke; the eGFR is an independent factor of LF/HF in the adjusted models. Stroke severity and a history of diabetes are more significantly associated with HRV in patients with acute ischemic stroke at different stages of renal dysfunction.

Autonomic dysfunction in first ever ischemic stroke: Prevalence, predictors and short term neurovascular outcome

OBJECTIVES

Central autonomic dysfunction(AD) is reported post-stroke. Very few studies have looked at its impact on neurovascular outcome. We sought to study the prevalence and predictors of autonomic dysfunction in patients with first ever acute ischemic stroke and its impact on discharge and short term outcome.

PATIENTS AND METHODS

Consecutive patients who presented between 2-4 weeks post stroke were prospectively recruited. Study period was April 2012-March 2014 (2 years). Subjects underwent clinical autonomic function testing using Ewing's battery at bedside and 24h Holter analysis for heart rate variability(HRV). HRV parameters studied included both time domain and frequency domain measures. Neurological and cardiovascular outcomes were assessed at discharge,3 months and 1year.

RESULTS

Of 101 patients of mean age 63yrs, 72% were men.Majority had moderate to severe strokes at onset (Mean NIHSS-13.9,MRS-3.1). Clinical bedside autonomic testing criteria were comparable to Holter detected dysautonomia in our study population (p value 0.3). Clinical autonomic dysfunction had a positive association with male gender whereas onset stroke severity and Insular involvement were associated with significantly higher incidence of autonomic dysfunction with both methodology. Those with autonomic dysfunction had more stroke severity at discharge, which was independent of onset severity. Increasing age, hemispheric laterality or presence of comorbidities had no impact on post-stroke dysautonomia.

CONCLUSIONS

Insular involvement and higher disability at onset are associated with greater incidence of autonomic dysfunction post-stroke. Those with AD had higher chance of infarct expansion and in hospital cardiovascular complications and poorer outcome at 1year, independent of onset stroke severity.

Impaired Hyperemic Response to Exercise Post Stroke

Individuals with chronic stroke have reduced perfusion of the paretic lower limb at rest; however, the hyperemic response to graded muscle contractions in this patient population has not been examined. This study quantified blood flow to the paretic and non-paretic lower limbs of subjects with chronic stroke after submaximal contractions of the knee extensor muscles and correlated those measures with limb function and activity. Ten subjects with chronic stroke and ten controls had blood flow through the superficial femoral artery quantified with ultrasonography before and immediately after 10 second contractions of the knee extensor muscles at 20, 40, 60, and 80% of the maximal voluntary contraction (MVC) of the test limb. Blood flow to the paretic and non-paretic limb of stroke subjects was significantly reduced at all load levels compared to control subjects even after normalization to lean muscle mass. Of variables measured, increased blood flow after an 80% MVC was the single best predictor of paretic limb strength, the symmetry of strength between the paretic and non-paretic limbs, coordination of the paretic limb, and physical activity. The impaired hemodynamic response to high intensity contractions was a better predictor of lower limb function than resting perfusion measures. Stroke-dependent weakness and atrophy of the paretic limb do not explain the reduced hyperemic response to muscle contraction alone as the response is similarly reduced in the non-paretic limb when compared to controls. These data may suggest a role for perfusion therapies to optimize rehabilitation post stroke.

Autonomic symptoms in hypertensive patients with post-acute minor ischemic stroke

BACKGROUND

Most studies regarding autonomic dysfunction in ischemic stroke are limited to heart rate and blood pressure changes during the acute phase. However, there are few data on quantitative assessment of autonomic symptoms. We sought to assess autonomic symptoms in hypertensive ischemic stroke patients.

METHODS

In 100 hypertensive patients (45 with symptomatic ischemic stroke (6 months after stroke onset) and 55 without stroke), we assessed autonomic symptoms using the Scale for Outcomes in Parkinson disease-Autonomic (SCOPA-AUT).

RESULTS

The age (mean ± standard deviation) for the stroke group was 66 ± 12 and 63 ± 15 for the without stroke group (P=0.8). Orthostatic hypotension occurred in 3.6% of the stroke group and 4.4% in the group without stroke. The total SCOPA-AUT score was higher in the stroke group compared with the group without stroke (P=0.001). Domain scores for gastrointestinal (P=0.001), urinary (P=0.005) and cardiovascular (P=0.001) were higher in the stroke group. No differences were found when comparing the total SCOPA-AUT scores for stroke subtypes (P=0.168) and for lateralization (P=0.6). SCOPA AUT scores were correlated with depression scores (P=0.001) but not with stroke severity (P=0.2).

CONCLUSION

Autonomic symptoms, especially, gastrointestinal, urinary and cardiovascular function, were significantly increased in hypertensive patients with minor ischemic stroke. Symptoms were associated with depression but not with the characteristic of the stroke.

Cardiac autonomic dysfunction in chronic stroke women is attenuated after submaximal exercise test, as evaluated by linear and nonlinear analysis

Background

We evaluated cardiac autonomic modulation in women with chronic ischemic stroke (at least 4 years post-stroke) at rest and in response to submaximal exercise test.

Methods

Fourteen post-stroke women (S group) and 10 healthy women (C group) participated in this study. Autonomic modulation (using linear and nonlinear analysis), blood pressure and metabolic variables at rest were evaluated immediately after the exercise test and during the recovery period (20 min). All participants underwent submaximal exercise test on cycle ergometer with gas analysis.

Results

At rest, the S group displayed higher lactate concentration, systolic (SBP) and diastolic blood pressure (DBP) values when compared to C group. Furthermore, the S group had lower heart rate variability (HRV) in time domain (SDNN: S = 30 ± 5 vs. 40 ± 8 ms; rMSSD: S = 14 ± 2 vs. C = 34 ± 3 ms), decreased high frequency band of pulse interval (S = 8.4 ± 2 vs. 33.1 ± 9 %) and 2V pattern of symbolic analysis (S = 17.3 ± 1 vs. 30 ± 3 %) (both indicators of cardiac vagal modulation) when compared to C group. Immediately after exercise, S group presented higher values of lactate, SBP, DBP and double product when compared to C group, as well as decreased heart rate recovery (HRR) measured at the first, second and third minutes. At recovery time, all HRV parameters in time and frequency domains improved in the S group; however, HF band remained lower when compared to C group.

Conclusions

After the exercise test, women with chronic stroke presented reduced heart rate variability, reduced cardiac vagal modulation, as well as reduced HRR, while displayed an improvement of heart rate variability and cardiac vagal modulation when compared to their baseline. These results reinforce the importance of a physically active lifestyle for cardiovascular autonomic disorders observed in chronic stroke women.

Association between non-alcoholic fatty liver disease and autonomic dysfunction in a Chinese population

BACKGROUND

Autonomic dysfunction (AD) accompanying with chronic liver disorders led to an increased risk of mortality. However, researches that investigated the association between non-alcoholic fatty liver disease (NAFLD) and AD were insufficient.

AIMS

To study the association of NAFLD with AD in middle-aged and elderly Chinese adults.

DESIGN

Four thousand nine hundred seventy-four adults aged 40 years or older were enrolled in this cross-sectional study. NAFLD was diagnosed by hepatic B-mode ultrasonography. Autonomic function was assessed using a simple EZSCAN test by measuring sudomotor function, with an AD index > 50% defined as a manifestation of AD.

METHODS

Pearson correlation, multiple stepwise linear regression, univariate and multivariate logistic regression was employed to examine the relationship between NAFLD and AD, controlling for potential confounders.

RESULTS

The prevalence of AD was significantly higher in participants with NAFLD than those without (40.75 vs. 26.86%, P < 0.0001). Age, body mass index, status of diabetes, sex, diastolic blood pressure and prevalent NAFLD, were positively correlated with AD index in multiple stepwise linear regression analysis (all P < 0.05), whereas total cholesterol was negatively related to it (P = 0.0043). Compared with the participants without NAFLD, those with NAFLD had an increased odds of the prevalent AD (odds ratio 1.38; 95% confidence interval 1.15-1.64; P = 0.0004) after controlling for multiple confounders.

CONCLUSIONS

The presence of NAFLD was significantly associated with AD, as indicated by abnormal sudomotor function. The association was independent from various conventional risk factors.

Predictors and Proarrhythmic Consequences of Inappropriate Implantable Cardioverter-Defibrillator Therapy

BACKGROUND

Despite the benefits of implantable cardioverter-defibrillator (ICD) therapy, inappropriate shocks can lead to multiple adverse effects. The aim of this study was to clarify the predictors of inappropriate ICD shocks and their proarrhythmic consequences.

METHODS AND RESULTS

We retrospectively studied 316 consecutive patients who underwent ICD implantation from December 2000 to December 2011. Of them, 70 (22%) experienced inappropriate ICD shocks without proarrhythmia requiring some intervention; 2 patients (0.6%) had proarrhythmic inappropriate ICD therapy by antitachycardia pacing (ATP), thereby calculated to be 0.18% of patients per year. However, they did not have syncope from this inappropriate ATP. Multivariate analysis identified younger age (≤56 years: hazard ratio [HR] 1.68, 95% confidence interval [CI] 1.02-2.77, P=0.043), paroxysmal atrial fibrillation (HR 3.00, 95% CI 1.64-5.31, P=0.0002), stroke (HR 2.23, 95% CI 1.11-4.47, P=0.024), and no diuretic use (HR 1.72, 95% CI 1.03-2.93, P=0.039) as independent predictors of the occurrence of inappropriate ICD shocks.

CONCLUSIONS

Young age, paroxysmal atrial fibrillation, stroke, and no use of diuretics were independently associated with inappropriate ICD shocks. Proarrhythmic inappropriate ICD therapy was observed with an annual incidence of 0.18% by ATP.

Peripheral to central: Organ interactions in stroke pathophysiology

Stroke is associated with a high risk of disability and mortality, and with the exception of recombinant tissue-type plasminogen activator for acute stroke, most treatments have proven ineffective. Clinical translation of promising experimental therapeutics is limited by inadequate stroke models and a lack of understanding of the mechanisms underlying acute stroke and how they affect outcome. Bidirectional communication between the ischemic brain and peripheral immune system modulates stroke progression and tissue repair, while epidemiological studies have provided evidence of an association between organ dysfunction and stroke risk. This crosstalk can determine the fate of stroke patients and must be taken into consideration when investigating the pathophysiological mechanisms and therapeutic options for stroke. This review summarizes the current evidence for interactions between the brain and other organs in stroke pathophysiology in basic and clinic studies, and discusses the role of these interactions in the progression and outcome of stroke and how they can direct the development of more effective treatment strategies.

Link between cerebral blood flow and autonomic function in survivors of internal carotid artery occlusion

PURPOSE

Symptomatic internal carotid artery occlusion (ICAO) is an important cause of cerebral ischemia with poor long-term outcome. Reductions in baroreflex function is reported in carotid atherosclerosis and implicated in increased risk of recurrent cardiovascular events. A distributed network of forebrain regions can exert modulatory influences over the cardio-vagal and baroreflex functions. The successful clinical translation of these approaches offers insights into underlying modulatory mechanisms and to possible therapeutic strategy.

METHODS

This study enrolled 20 symptomatic ICAO survivors, 20 patients with small vessel disease (SVD) as risk control, and 20 healthy controls. All underwent a standardized evaluation of cardiovascular autonomic function testing that included baroreflex sensitivity (BRS), Valsalva ratio (VR), and heart rate response to deep breathing (HR_DB). The regional cerebral blood flow (rCBF) of the central autonomic network (CAN) was obtained from arterial spin-labeling magnetic resonance imaging. Parameters of autonomic function between symptomatic ICAO survivors with and those without recurrent cardiovascular events were compared.

RESULTS

Valsalva ratio and HR_DB levels were significantly higher in the control group, followed by the SVD and ICAO groups (p=0.009 and p=0.007, respectively). Spontaneous BRS and BRS during the early phase II of Valsalva maneuver levels were both significantly higher in the control group, followed by the SVD and ICAO groups (p<0.001 and p=0.042, respectively). The rCBF of CAN inversely correlated with spontaneous BRS.

CONCLUSION

Autonomic dysregulation, including reduced BRS and impaired cardio-vagal function in the convalescent stage ICAO, can persist for a long time. Reduced BRS is inversely correlated with CAN activity.

Beyond BOLD: optimizing functional imaging in stroke populations

Blood oxygenation level-dependent (BOLD) signal changes are often assumed to directly reflect neural activity changes. Yet the real relationship is indirect, reliant on numerous assumptions, and subject to several sources of noise. Deviations from the core assumptions of BOLD contrast functional magnetic resonance imaging (fMRI), and their implications, have been well characterized in healthy populations, but are frequently neglected in stroke populations. In addition to conspicuous local structural and vascular changes after stroke, there are many less obvious challenges in the imaging of stroke populations. Perilesional ischemic changes, remodeling in regions distant to lesion sites, and diffuse perfusion changes all complicate interpretation of BOLD signal changes in standard fMRI protocols. Most stroke patients are also older than the young populations on which assumptions of neurovascular coupling and the typical analysis pipelines are based. We present a review of the evidence to show that the basic assumption of neurovascular coupling on which BOLD-fMRI relies does not capture the complex changes arising from stroke, both pathological and recovery related. As a result, estimating neural activity using the canonical hemodynamic response function is inappropriate in a number of contexts. We review methods designed to better estimate neural activity in stroke populations. One promising alternative to event-related fMRI is a resting-state-derived functional connectivity approach. Resting-state fMRI is well suited to stroke populations because it makes no performance demands on patients and is capable of revealing network-based pathology beyond the lesion site.

CNS-disease affecting the heart: brain-heart disorders

There are a number of hereditary and non-hereditary central nervous system (CNS) disorders, which directly or indirectly affect the heart (brain-heart disorders). The most well-known of these CNS-disorders are epilepsy, stroke, subarachanoid bleeding, bacterial meningitis, and head injury. In addition, a number of hereditary and non-hereditary neurodegenerative disorders may impair cardiac functions. Affection of the heart may manifest as arrhythmias, cardiomyopathy, or autonomic dysfunction. Rarer cardiac complications of CNS disorders include heart failure, systolic or diastolic dysfunction, myocardial infarction, arterial hypertension, or pulmonary hypertension. Cardiomyopathy induced by hereditary CNS disease mainly include stress-induced myocardial dysfunction, known as Takotsubo syndrome (TTS). CNS disease triggering TTS includes epilepsy, ischemic stroke, subarachnoid bleeding, or PRES syndrome. Arrhythmias induced by hereditary CNS disease include supraventricular or ventricular arrhythmias leading to palpitations, dizziness, vertigo, fainting, syncope, (near) sudden cardiac death, or sudden unexplained death in epilepsy (SUDEP). Appropriate management of cardiac involvement in CNS-disorders is essential to improve outcome of affected patients.