Decreased fractal dimension of heart rate variability is associated with early neurological deterioration and recurrent ischemic stroke after acute ischemic stroke

Dysautonomia and activity in the early stroke recovery period

Maintaining cerebral perfusion in the early stages of recovery after stroke is paramount. Autoregulatory function may be impaired during this period leaving cerebral perfusion directly reliant on intravascular volume and blood pressure (BP) with increased risk for expanding cerebral infarction during periods of low BP and hemorrhagic transformation during BP elevations. We suspected that dysautonomia is common during the acute period related to both pre-existing vascular risk factors and potentially independent of such conditions. Thus, we sought to understand the state of the science specific to dysautonomia and acute stroke. The scoping review search included multiple databases and key terms related to acute stroke and dysautonomia. The team employed a rigorous review process to identify, evaluate, and summarize relevant literature. We additionally summarized common clinical approaches used to detect dysautonomia at the bedside. The purpose of this scoping review is to understand the state of the science for the identification, treatment, and impact of dysautonomia on acute stroke patient outcomes. There is a high prevalence of dysautonomia among persons with stroke, though there is significant variability in the type of measures and definitions used to diagnose dysautonomia. While dysautonomia appears to be associated with poor functional outcome and post-stroke complications, there is a paucity of high-quality evidence, and generalizability is limited by heterogenous approaches to these studies. There is a need to establish common definitions, standard measurement tools, and a roadmap for incorporating these measures into clinical practice so that larger studies can be conducted.

Effect of heart rate on poor outcome in stroke patients treated with intra-arterial thrombectomy

BACKGROUND AND PURPOSE

The relationship between heart rate and the prognosis of patients with large vessel occlusion strokes treated with mechanical thrombectomy (MT) is not well established. This study aimed to evaluate the association of mean heart rate and heart rate variability (HRV) with the clinical outcomes after MT therapy.

METHODS

Acute ischemic stroke patients undergoing MT therapy were prospectively recruited from March 2020 to November 2022. Their heart rate was collected every hour for the initial 72 h after MT procedure, and the variability of heart rate was measured by standard deviation (SD) and coefficient of variation (CV). All-cause mortality and worsening of functional outcome (change in modified Rankin Scale (mRS) score) at 3-month were captured. Binary logistic regression was used to evaluate the association between heart rate indicators and all-cause mortality. Ordinal logistic regression was used to evaluate the association between heart rate indicators and worsening of functional outcome.

RESULTS

Among 191 MT-treated patients, 51(26.7%) patients died at 3-month after stroke. Increased mean heart rate per 10-bpm, heart rate SD and CV per 5-unit were all associated with the increased risk of mortality (adjusted hazard ratio [aHR] with 95% CI: 1.29 [1.09-1.51], 1.19 [1.07-1.32], 1.14 [1.03-1.27]; respectively). Patients in the highest tertile of heart rate SD had an increased risk of mortality (4.62, 1.70-12.52). After using mRS as a continuous variable, we found increased mean heart rate per 10-bpm, heart rate SD and CV per 5-unit were associated with the worsening of functional outcome (adjusted odds ratio [aOR] with 95% CI: 1.35 [1.11-1.64], 1.27 [1.05-1.53], 1.19 [1.02-1.40]; respectively). A linear relationship was observed between mean heart rate or heart rate SD and mortality; while all of the heart rate measures in this study showed a linear relationship with the worsening of functional outcome.

CONCLUSIONS

Higher mean heart rate and HRV were associated with the increased risk of 3-month all-cause mortality and worse functional outcome after MT therapy for AIS patients.

Biomarkers and the outcomes of ischemic stroke

Biomarkers are measurable substances that could be used as objective indicators for disease diagnosis, responses to treatments, and outcomes predictions. In this review, we summarized the data on a number of important biomarkers including glutamate, S100B, glial fibrillary acidic protein, receptor for advanced glycation end-products, intercellular adhesion molecule-1, von willebrand factor, matrix metalloproteinase-9, interleukin-6, tumor necrosis factor-a, activated protein C, copeptin, neuron-specific enolase, tau protein, gamma aminobutyric acid, blood glucose, endothelial progenitor cells, and circulating CD34-positive cells that could be potentially used to indicate the disease burden and/or predict clinical outcome of ischemic stroke. We examined the relationship between specific biomarkers and disease burden and outcomes and discussed the potential mechanisms underlying the relationship. The clinical significance and implications of these biomarkers were also discussed.

Exploring the Utility of Autonomic Nervous System Evaluation for Stroke Prognosis

Stroke is a major cause of functional disability and is increasing in frequency. Therefore, stroke prognosis must be both accurate and timely. Among other biomarkers, heart rate variability (HRV) is investigated in terms of prognostic accuracy within stroke patients. The literature research of two databases (MEDLINE and Scopus) is performed to trace all relevant studies published within the last decade addressing the potential utility of HRV for stroke prognosis. Only the full-text articles published in English are included. In total, forty-five articles have been traced and are included in the present review. The prognostic value of biomarkers of autonomic dysfunction (AD) in terms of mortality, neurological deterioration, and functional outcome appears to be within the range of known clinical variables, highlighting their utility as prognostic tools. Moreover, they may provide additional information regarding poststroke infections, depression, and cardiac adverse events. AD biomarkers have demonstrated their utility not only in the setting of acute ischemic stroke but also in transient ischemic attack, intracerebral hemorrhage, and traumatic brain injury, thus representing a promising prognostic tool whose clinical application may greatly facilitate individualized stroke care.

Nonpharmacological Treatments for Hospitalized Patients with Stroke: A Nuanced Approach to Prescribing Early Activity

Stroke remains a leading cause of adult disability. To date, hyperacute revascularization procedures reach 5-10% of stroke patients even in high resource health systems. There is a limited time window for brain repair after stroke, and therefore, the activities such as prescribed exercise in the earliest period will likely have long-term significant consequences. Clinicians who provide care for hospitalized stroke patients make treatment decisions specific to activity often without guidelines to direct these prescriptions. This requires a balanced understanding of the available evidence for early post-stroke exercise and physiological principles after stroke that drive the safety of prescribed exercise. Here, we provide a summary of these relevant concepts, identify gaps, and recommend an approach to prescribing safe and meaningful activity for all patients with stroke. The population of thrombectomy-eligible stroke patients can be used as the exemplar for conceptualization.

The combination of heart rate variability and ABCD2 score portends adverse outcomes after minor stroke or transient ischemic attack

BACKGROUND AND PURPOSE

The residual recurrent risk of stroke, which cannot be entirely explained by the traditional ABCD2 score, still existed. Heart rate variability (HRV), a method for reflecting the function of automatic nervous system (ANS), was a novel predictor of secondary stroke events. We aimed to investigate the relationships of combined HRV and ABCD² score with adverse outcomes after acute minor stroke (MS) or transient ischemic attack (TIA), and further investigate the independent associations between HRV and adverse outcomes after MS/TIA stratified by ABCD² score.

METHODS

Data were obtained from the Third China National Stroke Registry (CNSR-III) study. We assessed the activity of ANS using standard deviation of NN intervals (SDNN), a time domain index of HRV. Trained investigators collected clinical characteristics and estimated ABCD² score for each participant. All enrolled patients were categorized into different risk groups based on SDNN level and ABCD² score. The clinial outcomes included recurrent stroke, recurrent ischemic stroke, and disability within 1-year follow-up. We evaluated whether combined SDNN and ABCD² score were associated with recurrent events using multivariable Cox regression models, and those with disability using multivariable logistic regression models. The independent associations between SDNN and diverse outcomes stratified by ABCD² score were explored using multivariable Cox and logistic regression analyses.

RESULTS

A total of 5,743 participants [3,316 (70.02) males, 62.0 (54.0-69.0) years] were included. Patients with low SDNN and ABCD² ≥ 4 were associated with higher risk of recurrent stroke within 1 year (10.8% versus 4.9%; [HR] 1.31, 95% [CI] 0.92-1.88, P = 0.14) compared to patients with high SDNN with ABCD² < 4. Lower SDNN was associated with higher recurrent stroke in patients with ABCD² 0-3 score ([HR] 0.73, 95% [CI] 0.57-0.947, P = 0.01) and ABCD² 4-5 score ([HR] 0.85, 95% [CI] 0.74-0.97, P = 0.02), but not in patients with ABCD² 6-7 score.

CONCLUSION

The combination of HRV and ABCD² score might efficiently stratify the risk of 1-year recurrent stroke after MS/TIA. Moreover, lower SDNN was independently related to recurrent stroke in patients with MS/TIA, especially for those with low-to-moderate traditional vascular risk factors.

Heart rate variability as a predictor of stroke course, functional outcome, and medical complications: A systematic review

Background: Heart rate variability (HRV) is a non-invasive marker of autonomic nervous system function that is based on the analysis of length differences between subsequent RR intervals of the electrocardiogram. The aim of this systematic review was to assess the current knowledge gap in the utility of HRV parameters and their value as predictors of the acute stroke course. Methods: A systematic review was performed in accordance with the PRISMA guidelines. Relevant articles published between 1 January 2016 and 1 November 2022 available in the PubMed, Web of Science, Scopus, and Cochrane Library databases were obtained using a systematic search strategy. The following keywords were used to screen the publications: "heart rate variability" AND/OR "HRV" AND "stroke." The eligibility criteria that clearly identified and described outcomes and outlined restrictions on HRV measurement were pre-established by the authors. Articles assessing the relationship between HRV measured in the acute phase of stroke and at least one stroke outcome were considered. The observation period did not exceed 12 months. Studies that included patients with medical conditions influencing HRV with no established stroke etiology and non-human subjects were excluded from the analysis. To minimize the risk of bias, disagreements throughout the search and analysis were resolved by two independent supervisors. Results: Of the 1,305 records obtained from the systematic search based on keywords, 36 were included in the final review. These publications provided insight into the usability of linear and non-linear HRV analysis in predicting the course, complications, and mortality of stroke. Furthermore, some modern techniques, such as HRV biofeedback, for the improvement of cognition performance after a stroke are discussed. Discussion: The present study showed that HRV could be considered a promising biomarker of a stroke outcome and its complications. However, further research is needed to establish a methodology for appropriate quantification and interpretation of HRV-derived parameters.

Circular RNA FUNDC1 for Prediction of Acute Phase Outcome and Long-Term Survival of Acute Ischemic Stroke

Circular RNAs (CircRNAs) have shown promising potential in the diagnosis and the prediction of outcomes of stroke. This study aimed to explore the potential value of circRNAs for identifying acute neurological deterioration and estimating long-term survival for acute ischemic stroke (AIS). One hundred healthy controls and 200 patients with AIS within 72 h were recruited, 140 of whom were admitted within 24 h after onset. CircRNA levels in peripheral blood were measured by quantitative polymerase chain reaction (qPCR). Compared to the controls, the levels of three circRNAs were significantly increased in three subgroups of patients, including large artery atherosclerosis (LAA) stroke, small artery occlusion (SAO) stroke, and cardioembolism (CE) stroke (all P < 0.001). Among, LAA stroke patients had higher levels of circular RNA FUNDC1 (circFUNDC1) compared to SAO stroke patients (P = 0.015). CircFUNDC1 levels were positively correlated with National Institutes of Health Stroke Scale (NIHSS) scores on the 7th day only in LAA patients (P = 0.048, r = 0.226). It should be noted that the levels of circFUNDC1 in patients with early neurological deterioration (END), admitted within 24 h after onset, were significantly higher than those without END (P = 0.013). In addition, circFUNDC1 levels positively correlated with baseline NIHSS scores (P = 0.016, r = 0.203) or the 7th day NIHSS scores (P = 0.001, r = 0.289) in patients within 24 h after onset. Importantly, after 18 months of follow-up, a significant difference was observed on survival Kaplan-Meier curves (P = 0.042) between AIS patients with low (below cut-off) or high circFUNDC1 levels (above cut-off). Circulating circFUNDC1 could be a potential biomarker for predicting acute-phase outcome and long-term survival in AIS.

Leveraging Continuous Vital Sign Measurements for Real-Time Assessment of Autonomic Nervous System Dysfunction After Brain Injury: A Narrative Review of Current and Future Applications

Subtle and profound changes in autonomic nervous system (ANS) function affecting sympathetic and parasympathetic homeostasis occur as a result of critical illness. Changes in ANS function are particularly salient in neurocritical illness, when direct structural and functional perturbations to autonomic network pathways occur and may herald impending clinical deterioration or intervenable evolving mechanisms of secondary injury. Sympathetic and parasympathetic balance can be measured quantitatively at the bedside using multiple methods, most readily by extracting data from electrocardiographic or photoplethysmography waveforms. Work from our group and others has demonstrated that data-analytic techniques can identify quantitative physiologic changes that precede clinical detection of meaningful events, and therefore may provide an important window for time-sensitive therapies. Here, we review data-analytic approaches to measuring ANS dysfunction from routine bedside physiologic data streams and integrating this data into multimodal machine learning-based model development to better understand phenotypical expression of pathophysiologic mechanisms and perhaps even serve as early detection signals. Attention will be given to examples from our work in acute traumatic brain injury on detection and monitoring of paroxysmal sympathetic hyperactivity and prediction of neurologic deterioration, and in large hemispheric infarction on prediction of malignant cerebral edema. We also discuss future clinical applications and data-analytic challenges and future directions.

Effects of focus training on heart rate variability in post-stroke fatigue patients

Objective

This study discusses the effects of focus training on heart rate variability (HRV) in post-stroke fatigue (PoSF) patients.

Methods

Self-generate physiological coherence system (SPCS) was used for the focus training of PoSF patients for 12 weeks. Then, fatigue severity scale (FSS), Hamilton depression scale (HAMD), HRV and satisfaction scale (SASC-19) before and after the training were assessed.

Results

Compared with the control group, FSS score, HAMD score, RMSSD, PNN50% were significantly lower in the research group at the end of the intervention (P < 0.05); SDNN, SDANN, LF, HF, LF/HF intervention satisfaction rate increased significantly in the research group at the end of the intervention (P < 0.05).

Conclusion

The use of SPCS software during the focus training of PoSF patients reduced the fatigue and depression, meanwhile improved the HRV of the patients. Therefore, these patients were greatly satisfied with the intervention.

Ethnic Differences on Cardiac Rhythms and Autonomic Nervous System Responses During a High-Altitude Trek: A Pilot Study Comparing Italian Trekkers to Nepalese Porters

Altitude hypoxia exposure results in increased sympathetic activity and heart rate due to several mechanisms. Recent studies have contested the validity of heart rate variability (HRV) analysis on sympathetic activity measurement. But the plethora of HRV metrics may provide meaningful insights, particularly if linked with cardiovascular and autonomic nervous system parameters. However, the population-specific nature of HRV and cardiorespiratory response to altitude hypoxia are still missing. Six Italian trekkers and six Nepalese porters completed 300 km of a Himalayan trek. The ECG analysis was conducted at baseline, and before (bBC) and after (aBC) the high-altitude (HA) circuit. Urine was collected before and after the expedition in Italians, for assessing catecholamines. Heart rate increased with altitude significantly (p < 0.001) in the Italian group; systolic (p = 0.030) and diastolic (p = 0.012) blood pressure, and mean arterial pressure (p = 0.004) increased with altitude. Instead, pulse pressure did not change, although the Nepalese group showed lower baseline values than the Italians. As expected, peripheral oxygen saturation decreased with altitude (p < 0.001), independently of the ethnic groups. Nepalese had a higher respiratory rate (p = 0.007), independent of altitude. The cardiac vagal index increased at altitude, from baseline to bBC (p = 0.008). Higuchi fractal dimension (HFD) showed higher basal values in the Nepalese group (p = 0.041), and a tendency for the highest values at bBC. Regarding the urinary catecholamine response, exposure to HA increased urinary levels, particularly of norepinephrine (p = 0.005, d = 1.623). Our findings suggest a better cardiovascular resilience of the Nepalese group when compared with Italians, which might be due to an intrinsic adaptation to HA, resulting from their job.

Admission Glucose Levels May Increase the Risk for Early Neurological Deterioration in Females With Acute Ischemic Stroke

Background and purpose: Early neurological deterioration (END) is associated with poor outcome for patients with acute ischemic stroke (AIS). Patients with hyperglycemia have increased risk for stroke and tend to have poor outcome with and without diabetes after stroke. The present study aimed to determine if blood glucose was associated with END and if sex difference was present in the development of END in AIS patients.

Methods: A total of 220 consecutive patients (both males and females) with AIS between 2012 and 2015 were screened for this retrospective study. After exclusion, 213 patients were included for analysis. Propensity-score matching was used for normalization of variables including stroke severity, time from symptom onset to treatment, and treatment methods.

Results: END was present in 68 patients (31.9%). Multivariate regression analysis showed that the risk of END was significantly higher in males with AIS than in females (P < 0.001), and admission blood glucose level was independently associated with END (P < 0.001). However, subgroup analysis demonstrated that admission glucose levels were significantly associated with increased risk for END only in females, but not in males (P = 0.008). When the cutoff value of 107.1 mg/dL was used, the admission blood glucose level had a significant predictive value for END prediction with a sensitivity of 100% and a specificity of 53% in female patients.

Conclusions: The data demonstrated that sex difference was present for the development of END in AIS patients with an increased risk for males. The present study also showed that admission glucose level could be an important predicting factor for END in female patients with AIS.

The effect of remote ischemic postconditioning on autonomic function in patients with acute ischemic stroke: A Randomized Controlled Trail

OBJECTIVE

The evidence for the effect of remote ischemic postconditioning(RIpostC) on autonomic function in patients with acute ischemic stroke(AIS) is lacking and the neural mechanism underlying the protection of RIpostC remains speculative. This trial was aimed to evaluated the efficiency of RIpostC on autonomic function in AIS patients.

DESIGN

One hundred and six AIS patients were included in this prospective, randomized, placebo-controlled trial. Patients in intervention group (n = 57) received 4 cycles of alternating inflation (cuff inflation to 200 mmHg) and deflation for 5 min on healthy upper arm once a day for 30 days. The control group underwent a sham inflation and deflation cycles. Autonomic function was evaluated by heart rate variability (HRV).

RESULTS

All HRV parameters except for the ratio of low frequency to high frequency (P = 0.101) increased significantly with time (P < 0.001) in the two groups. The value of standard deviation of all normal R-R intervals(SDNN) and high frequency at day7 and day30 and the value of the percent of difference between adjacent normal R-R intervals (pNN50) at day 30 in RIpostC group was significantly higher than that of the sham-RIpostC group(P < 0.05). A significant time-by-group interaction was observed in SDNN、pNN50、and high frequency over time between two groups (P < 0.05).

CONCLUSIONS

30-day RIpostC could improve autonomic function in AIS patients through the enhancement of the total autonomic nerve activity and vagus nerve activity. The mechanism of RIpostC mediating autonomic function needs to be further investigated.

Analysis of autonomic nervous pattern in hypertension based on short-term heart rate variability

Physiological studies have found that the autonomic nervous system plays an important role in controlling blood pressure values. This paper, based on machine learning approaches, analysed short-term heart rate variability to determine differences in autonomic nervous function between hypertensive patients and normal population. The electrocardiogram (ECG) of hypertensive patients are 137 ECG recordings provided by Smart Health for Assessing the Risk of Events via ECG (SHAREE database). The RR intervals of healthy subjects include the data of 18 subjects from the MIT-BIH Normal Sinus Rhythm Database (nsrdb) and 54 subjects from the Normal Sinus Rhythm RR Interval Database (nsr2db). In this paper, each RR segment includes continuous 500 beats. Seventeen features were extracted to distinguish the hypertensive heart beat rhythms from the normal ones, and Kolmogorov-Smirnov test and sequential backward selection (SBS) were applied to get the best feature combinations. In addition, support vector machine (SVM), k-nearest neighbor (KNN) and random forest (RF) were applied as classifiers in the study. The performance of each classifier was evaluated independently using the leave-one-subject-out validation method. The best predictive model was based on RF and enabled to identify hypertensive patients by five features with an accuracy of 86.44%. The best five HRV features are sample entropy (SampEn), very low frequency spectral powers (VLF), root mean square of successful differences (RMSSD), ratio of low frequency spectral powers and high frequency spectral powers (LF/HF) and vector angle index (VAI). The results of the study show sympathetic overactivity and decreased parasympathetic tone in hypertensive patients.

Admission Heart Rate Variability Is Associated With Poststroke Depression in Patients With Acute Mild-Moderate Ischemic Stroke

BACKGROUND

Stroke has been shown to cause cardiac autonomic dysfunction. Depression is common complication after acute ischemic stroke (AIS). The purpose of this study was to investigate whether decreased heart rate variability (HRV) was related to poststroke depression (PSD) in patients with mild-moderate AIS.

METHODS

In this study, we assessed autonomic function of ischemic stroke patients within 72 h from symptom onset by fractal dimension (FD). 503 patients (mean age 65.93 ± 10.19) with mild-moderate AIS underwent FD test after admission. Depressive symptoms were assessed using 17-item Hamilton Depression Rating Scale (HDRS) at baseline (within 7 days) and 3 months. Depression were defined if HDRS >6 points. According to the data of FD, we investigated association with early-onset PSD status and 3-month PSD.

RESULTS

59.24% (293/503) of patients had early-onset PSD status at baseline, and 38.66% (184/476) of patients had PSD at 3 months. ROC curve analysis shown that the optimal cut point of FD for early-onset PSD status and 3-month PSD were FD ≤ 1.27 and FD ≤ 1.19, respectively. In fully adjusted models, higher NIHSS [adjusted odd ratios (OR), 1.15; 95% confidence interval (CI), 1.05-1.27; P=0.005], younger age (adjusted OR, 1.18; 95% CI, 1.01-1.13; P=0.046), and FD ≤ 1.27 (adjusted OR, 3.31; 95% CI, 2.23-4.92; P<0.001) were associated with increased risk of early-onset PSD status. Higher NIHSS (adjusted OR, 1.21; 95% CI, 1.09-1.43; P<0.001) and FD ≤ 1.19 (adjusted OR, 2.68; 95% CI, 1.79-4.03; P=0.000) were associated with increased risk of 3-month PSD.

CONCLUSIONS

PSD is common after mild-moderate AIS and is highly correlated with decreased HRV, FD could serve as an objective tool to help in prediction of PSD.