Autonomic dysfunction in multiple sclerosis is better detected by heart rate variability and is not correlated with central autonomic network damage

Morphological and functional assessment of the vagus nerve in multiple sclerosis

PURPOSE

The aim of this work is to determine the relationship between the cross-sectional area (CSA) of the vagus nerve and cardiovagal function in people with multiple sclerosis (pwMS) and healthy controls (HC).

METHODS

We enrolled 50 pwMS and 50 HC. All participants underwent an ultrasound of the vagus nerve and autonomic nervous system testing. The Croatian version of the COMPASS-31 questionnaire was used as a measure of autonomic symptom burden. Cardiovagal function was evaluated with the respiratory sinus arrhythmia (RSA), Valsalva ratio (VR), and heart rate variability.

RESULTS

The mean vagus CSA in pwMS was 2.03 ± 0.49 mm2 on the right side and 1.72 ± 0.38 mm2 on the left side. The mean vagus CSA in HC was 2.08 ± 0.50 mm2 on the right side and 1.74 ± 0.37 mm2 on the left side. There was no statistically significant difference between the two groups in right (p = 0.615) or left (p = 0.866) vagus CSA. In the HC, there was a statistically significant positive correlation between the mean right CSA and both RSA (rp = 0.331, p = 0.019) and VR (rp = 0.327, p = 0.020). On univariable linear regression analysis in the HC group, the mean right CSA was a predictor of both RSA (B = 5.599, 95% CI 0.974-10.224, p = 0.019) and VR (B = 0.253, 95% CI 0.041-0.466, p = 0.020). These findings were not present in pwMS.

CONCLUSIONS

The loss of correlation between vagus nerve CSA and parameters of parasympathetic nervous system function in pwMS corroborates the presence of cardiovagal dysfunction in multiple sclerosis.

Biofluid, Imaging, Physiological, and Functional Biomarkers of Mild Traumatic Brain Injury and Subconcussive Head Impacts

Post-concussive symptoms are frequently reported by individuals who sustain mild traumatic brain injuries (mTBIs) and subconcussive head impacts, even when evidence of intracranial pathology is lacking. Current strategies used to evaluate head injuries, which primarily rely on self-report, have a limited ability to predict the incidence, severity, and duration of post-concussive symptoms that will develop in an individual patient. In addition, these self-report measures have little association with the underlying mechanisms of pathology that may contribute to persisting symptoms, impeding advancement in precision treatment for TBI. Emerging evidence suggests that biofluid, imaging, physiological, and functional biomarkers associated with mTBI and subconcussive head impacts may address these shortcomings by providing more objective measures of injury severity and underlying pathology. Interest in the use of biomarker data has rapidly accelerated, which is reflected by the recent efforts of organizations such as the National Institute of Neurological Disorders and Stroke and the National Academies of Sciences, Engineering, and Medicine to prioritize the collection of biomarker data during TBI characterization in acute-care settings. Thus, this review aims to describe recent progress in the identification and development of biomarkers of mTBI and subconcussive head impacts and to discuss important considerations for the implementation of these biomarkers in clinical practice.

Heart Rate Variability (HRV) serves as an objective correlate of distress and symptom burden in multiple sclerosis

Background

Autonomic nervous system (ANS) dysfunction is frequently seen in people living with multiple sclerosis (MS). Heart rate variability (HRV) is an easy and objective index for evaluating ANS functioning, and it has been previously used to explore the association between ANS and the experience of symptom burden in other chronic diseases. Given ANS functioning can be influenced by physical and psychological factors, this study investigated whether emotional distress and/or the presence of ANS dysfunction is associated with symptom severity in people living with MS.

Methods

Participants with MS and healthy controls (HC) with no history of cardiac conditions were recruited to self-collect HR data sampled from a chest strap HR monitor (PolarH10). Short-term HR signal was collected for five minutes, and time and frequency HRV analyses were performed and compared between groups. HRV values were then compared to self-reported distress (Kessler Psychological Distress Scale) and MS participants' self-reported measures of symptom burden (SymptoMScreen).

Results

A total of n = 23 adults with MS (51 ± 12 years, 65 % female, median Patient Determined Disease Steps [PDDS]: 3.0) and n = 23 HCs (43 ± 18 years, 40 % female) completed the study procedures. All participants were able to complete the chest strap placement and HR data capture independently. Participants with MS, compared to the HC participants, had a significantly lower parasympathetic activation as shown by lower values of the root mean square of successive differences between normal heartbeats (RMSSD: 21.86 ± 9.84 vs. 43.13 ± 20.98 ms, p = 0.002) and of high-frequency (HF) power band (HF-HRV: 32.69 ± 12.01 vs. 42.39 ± 7.96 nu, p = 0.016), indicating an overall lower HRV in the MS group. Among individuals with MS, HF-HRV was significantly correlated with the severity of self-reported MS symptoms (r = -0.548, p = 0.010). Participants with MS also reported higher levels of distress compared to HC participants (18.32 ± 6.05 vs. 15.00 ± 4.61, p = 0.050), and HRV correlated with the severity of distress in MS participants (r = -0.569, p = 0.007). A significant mediation effect was also observed, with emotional distress fully mediating the association between HRV and symptom burden.

Conclusions

These findings suggest the potential for ANS dysfunction, as measured by HRV (i.e., lower value of HF power), to be utilized as an objective marker of symptom burden in people living with MS. Moreover, it is apparent that the relationship between HRV and symptom burden is mediated by emotional distress.

How to explore and explain autonomic changes in multiple sclerosis

Autonomic dysfunction (AD) in people with MS (pwMS) is a frequent finding. This narrative review will present an overview of central neural mechanisms involved in the control of cardiovascular and thermoregulatory systems, and methods of autonomic nervous system testing will be discussed thereafter. Since the need for standardization of autonomic nervous system (ANS) testing, we will focus on the standard battery of tests (blood pressure and heart rate response to Valsalva maneuver and head-up tilt, and heart rate response to deep breathing test plus one of the tests for sudomotor function), which can detect ANS pathology in the majority of pwMS. The review will briefly discuss the other types of AD in pwMS and the use of appropriate tests. While performing ANS testing in pwMS one has to consider the multiple sclerosis phenotypes, disease duration, and its activity, the degree of clinical disability of patients included in the study, and the disease-modifying therapies taken, as these factors may have a great influence on the results of ANS testing. In other words, detailed patient characteristics presentation and patient stratification are beneficial when reporting results of ANS testing in pwMS.

Autoimmune autonomic nervous system imbalance and conditions: Chronic fatigue syndrome, fibromyalgia, silicone breast implants, COVID and post-COVID syndrome, sick building syndrome, post-orthostatic tachycardia syndrome, autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants

Chronic fatigue syndrome (CFS), fibromyalgia, silicone breast implants syndrome (SBIs), COVID and post-COVID syndrome (PCS), sick building syndrome (SBS), post-orthostatic tachycardia syndrome (POTS), autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants (ASIA) are frequently accompanied by clinical symptoms characteristic for dysautonomia: severe fatigue, dizziness, fogginess, memory loss, dry mouth and eyes, hearing dysfunction, tachycardia etc. The recent discovery of an imbalance of autoantibodies against G protein-coupled receptors (GPCR) in some autoimmune diseases, post-COVID syndrome, SBIs allowed researchers to assume the novel mechanism in these conditions - autoimmune autonomic nervous system imbalance. In this review, all data published on an imbalance of autoantibodies against GPCR, clinical symptoms and pathogenic mechanisms in CFS, Fibromyalgia, SBIs, COVID and PCS, SBS, POTS, and some autoimmune diseases were analyzed. Possible criteria to diagnose the autoimmune autonomic nervous system imbalance were created.

Heart rate variability and fatigue in MS: two parallel pathways representing disseminated inflammatory processes?

BACKGROUND

Fatigue is a disabling symptom of multiple sclerosis. Its biological causes are still poorly understood. Several years ago, we proposed that fatigue might be the subjective representation of inflammatory processes. An important step for a straight-forward evaluation of our model would be to show that the level of fatigue is associated with vagal activation. The heart rate is under partial control of the vagus nerve. Using power spectrum analysis allows to separate, at least partly, sympathetic and parasympathetic impact on heart rate variability.

METHODS

This narrative review summarizes the evidence for heart rate variability changes in MS patients, their relationship with fatigue and disease course. To do this, we conducted a literature search, including 45 articles relevant to the topic treated in this review.

RESULTS

We illustrate that (1) inflammation leads to a change in cardiac behavior during acute and chronic phases, both in animals and in humans; (2) MS patients show changes of heart rate variability (HRV) that resemble those during acute and chronic inflammation due to multiple causes; (3) existing evidence favors a set of specific predictions about fatigue and parallel HRV changes; and (4) that MS-related brainstem lesions or neurological impairments do not completely explain HRV changes, leaving enough place for an explanatory relation between HRV and fatigue.

DISCUSSION

We discuss the results of this review in relation to our model of fatigue and propose several observational and experimental studies that could be conducted to gain a better insight into whether fatigue and HRV can be interpreted as a common pathway, both reflecting activated autoimmune processes in MS patients.

WITHDRAWN: Autoimmune autonomic nervous system imbalance and conditions: Chronic fatigue syndrome, fibromyalgia, silicone breast implants, COVID and post-COVID syndrome, sick building syndrome, post-orthostatic tachycardia syndrome, autoimmune diseases and autoimmune/inflammatory syndrome induced by adjuvants

The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.autrev.2022.103230. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Analysis of the extent of limbic system changes in multiple sclerosis using FreeSurfer and voxel-based morphometry approaches

Background and purpose

The limbic brain is involved in diverse cognitive, emotional, and autonomic functions. Injury of the various parts of the limbic system have been correlated with clinical deficits in MS. The purpose of this study was to comprehensively examine different regions of the subcortical limbic system to assess the extent of damage within this entire system as it may be pertinent in correlating with specific aspects of cognitive and behavioral dysfunction in MS by using a fully automated, unbiased segmentation approach.

Methods

Sixty-seven subjects were included in this study, including 52 with multiple sclerosis (MS) and 15 healthy controls. Only patients with stable MS disease, without any relapses, MRI activity, or disability progression were included. Subcortical limbic system segmentation was performed using the FreeSurfer pipeline ScLimbic, which provides volumes for fornix, mammillary bodies, hypothalamus, septal nuclei, nucleus accumbens, and basal forebrain. Hippocampus and anterior thalamic nuclei were added as additional components of the limbic circuitry, also segmented through FreeSurfer. Whole limbic region mask was generated by combining these structures and used for Voxel-based morphometry (VBM) analysis.

Results

The mean [95% confidence interval] of the total limbic system volume was lower (0.22% [0.21–0.23]) in MS compared to healthy controls (0.27%, [0.25–0.29], p < .001). Pairwise comparisons of individual limbic regions between MS and controls was significant in the nucleus accumbens (0.046%, [0.043–0.050] vs. 0.059%, [0.051–0.066], p = .005), hypothalamus (0.062%, [0.059–0.065] vs. 0.074%, [0.068–0.081], p = .001), basal forebrain (0.038%, [0.036–0.040] vs. 0.047%, [0.042–0.051], p = .001), hippocampus (0.47%, [0.45–0.49] vs. 0.53%, [0.49–0.57], p = .004), and anterior thalamus (0.077%, [0.072–0.082] vs. 0.093%, [0.084–0.10], p = .001) after Bonferroni correction. Volume of several limbic regions was significantly correlated with T2 lesion burden and brain parenchymal fraction (BPF). Multiple regression model showed minimal influence of BPF on limbic brain volume and no influence of other demographic and disease state variables. VBM analysis showed cluster differences in the fornix and anterior thalamic nuclei at threshold p < 0.05 after adjusting for covariates but the results were insignificant after family-wise error corrections.

Conclusions

The results show evidence that brain volume loss is fairly extensive in the limbic brain. Given the significance of the limbic system in many disease states including MS, such volumetric analyses can be expanded to studying cognitive and emotional disturbances in larger clinical trials. FreeSurfer ScLimbic pipeline provided an efficient and reliable methodology for examining many of the subcortical structures related to the limbic brain.

Blood pressure variability is altered in secondary progressive multiple sclerosis but not in patients with a clinically isolated syndrome

OBJECTIVES

To investigate differences in beat-to-beat systolic blood pressure variability (SBPV) in people with secondary progressive MS (pwSPMS), clinically isolated syndrome (pwCIS) and healthy controls (HC).

METHODS

This retrospective case-control study included 46 pwSPMS, 46 pwCIS and 44 HC. A semi-automated software made with MATLAB R2019b (The MathWorks, Inc.) was used for the evaluation of SBPV. The frequency domain characteristics observed were the power spectrum in the LF and HF bands and the LF/HF ratio. Data is expressed in absolute power (mmHg²) of LF and HF and ratio (LF/HF) during both supine and tilt-up phases of testing.

RESULTS

There were no significant differences in mean systolic (sBP) or diastolic blood pressure (dBP) values during supine and tilt-up phases of testing between groups. During the supine phase of testing LF and LF/HF were significantly lower in the SPMS group (4.17±5.38 and 3.52±2.34, respectively) compared to the CIS (5.42±3.59, p = 0.015 and 5.92±4.63, p = 0.029, respectively) and HC group (6.03±4.55, p = 0.011 and 6.52 ± 5.09, p = 0.010, respectively), while during the tilt-up phase, LF was significantly lower compared to both the CIS and HC group, and HF was significantly lower only compared to the CIS group.

CONCLUSION

SBPV is altered in pwSPMS compared to pwCIS and normal controls. Further research in the field of MS related dysautonomia is warranted not only because of its relevance to comorbidities and MS symptoms, but also because of its likely involvement in the pathophysiology of MS.

The pathophysiology of motor fatigue and fatigability in multiple sclerosis

Multiple Sclerosis (MS) is a heterogeneous immune mediated disease of the central nervous system (CNS). Fatigue is one of the most common and disabling symptom of MS. It interferes with daily activities on the level of cognition and motor endurance. Motor fatigue can either result from lesions in cortical networks or motor pathways (“primary fatigue”) or it may be a consequence of detraining with subsequent adaptions of muscle and autonomic function. Programmed exercise interventions are used frequently to increase physical fitness in MS-patients. Studies investigating the effects of training on aerobic capacity, objective endurance and perceived fatigability have yielded heterogenous results, most likely due to the heterogeneity of interventions and patients, but probably also due to the non-uniform pathophysiology of fatigability among MS-patients. The aim of this review is to summarize the current knowledge on the pathophysiology of motor fatigability with special reference to the basic exercise physiology that underlies our understanding of both pathogenesis and treatment interventions.

Autonomic Nervous System Function in Newly Diagnosed Multiple Sclerosis: Association With Lipid Levels and Insulin Resistance

Autonomic nervous system (ANS) disorders are common in multiple sclerosis (MS). Previous studies showed differences in insulin resistance (IR) and lipoprotein levels in MS subjects compared to controls. Lipolysis caused by increased sympathetic activity could be one of the possible linking mechanisms leading to dyslipidemia in MS. Our study aimed to evaluate ANS activity in the context of glucose and lipid metabolism in people with MS. We prospectively measured short-term heart rate variability (HRV), fasting lipoprotein concentrations, and calculated IR indices based on plasma glucose and insulin levels during oral glucose tolerance test (oGTT) in 32 patients with MS and 29 healthy controls matched for age, sex and body mass index in our study. There was no significant difference in HRV parameters and lipoprotein levels between MS and controls. A significant positive correlation was found between low/high-frequency power ratio (LF/HF) and triglycerides (r=0.413, p=0.021) in MS subjects but not in controls. A significantly lower whole-body insulin sensitivity index (ISIMat) was found in patients with MS compared to the control group (7.3±3.7 vs. 9.8±5.6, p=0.041). No significant correlations were found between LF/HF and IR parameters. In MS subjects, the positive correlation of LF/HF with triglycerides could reflect the effects of sympathetic activity on lipolysis. Positive correlations of sympathetic activity with increased lipoprotein levels could rather reflect processes associated with immune system activation/inflammation, than processes involved in glucose homeostasis maintenance.

Unveiling the relationship between autonomic involvement, fatigue, and cognitive dysfunction in early relapsing-remitting multiple sclerosis

BACKGROUND

Fatigue is a common, yet disabling, symptom in patients with multiple sclerosis (PwMS). Fatigue has shown to be associated with self-reported autonomic nervous system (ANS) symptoms, particularly for cognitive fatigue; however, the question whether ANS involvement is related to cognitive impairment has never been addressed. We performed a study to unveil the complex relationship between fatigue, ANS symptoms, and cognitive impairment.

METHODS

We prospectively recruited early PwMS that were tested with Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS), State-Trait Anxiety Inventory (STAI), Beck Depression Inventory (BDI), Modified Fatigue Impact Scale (MFIS) and Composite Autonomic Symptoms Scale-31 (COMPASS-31) scale. We performed a comparison between fatigued and non-fatigued patients and between cognitive unimpaired and impaired patients. We evaluated the association of COMPASS-31, MFIS, BDI, STAI, and BICAMS scores, and the analysis was repeated for each scale's sub-scores. A multivariable analysis was performed to elucidate predictors of fatigue.

RESULTS

Forty-four patients were recruited. Fatigued patients had higher COMPASS-31 total, orthostatic intolerance, secretomotor, and pupillomotor scores. No differences in fatigue and ANS symptoms were found between cognitive impaired and unimpaired patients. MFIS total score correlated with STAI state (p = 0.002) and trait (p < 0.001), BDI (p < 0.001), COMPASS-31 total (p < 0.001), orthostatic intolerance (p < 0.001), pupillomotor scores (p = 0.006). Multivariable analysis showed that BDI (p < 0.001) and COMPASS-31 (p = 0.021) predicted MFIS score. Sub-scores analysis showed that orthostatic intolerance has a relevant role in fatigue.

CONCLUSION

ANS symptoms are closely related with fatigue. Orthostatic intolerance may have a predominant role. Cognitive impairment seems not to be associated with ANS symptoms.

Frequency and characteristics of dysautonomic symptoms in multiple sclerosis: a cross-sectional double-center study with the validated Italian version of the Composite Autonomic Symptom Score-31

BACKGROUND

Dysautonomic symptoms (DS) are frequent but often underrecognized in multiple sclerosis (MS) patients, despite the relevant impact on quality of life and physical performance.

OBJECTIVES

To assess frequency and characteristics of DS in our MS population compared with healthy controls (HC). To investigate the relationship between DS and disease characteristics (MS subtype, disease duration, Expanded Disability Status Scale (EDSS), clinical and/or radiological activity, disability progression).

PATIENTS AND METHODS

Cross-sectional study includes 324 MS patients (mean age 44.9 ± 10.7 years; 66% female) and 190 HC (mean age 40.60 ± 12.83 years; 63% female). DS were assessed using the Italian validated version of the Composite Autonomic Symptom Score-31 (COMPASS-31). Possible confounding factors were considered.

RESULTS

More than 94% of enrolled MS patients reported alterations in ≥ 2 domains of the COMPASS-31 scale (score > 0) and significantly higher COMPASS-31 total and single domain median scores compared with HC, independently from possible confounding factors (orthostatic intolerance: p = 0.001; vasomotor: p = 0.017; secretomotor: p = 0.040; gastrointestinal: p = 0.047; bladder: p < 0.001; pupillomotor: p < 0.001; COMPASS-31 total score: p < 0.001). COMPASS-31 total, secretomotor, gastrointestinal, and bladder domain scores showed weak to moderate correlation with disease duration (Rho = 0.19, p < 0.001; Rho = 0.18, p = 0.01; Rho = 0.25, p = 0.030; Rho = 0.28, p < 0.001, respectively). A moderate correlation between EDSS score, COMPASS-31 total, and bladder domain scores (Rho = 0.32, p < 0.001 and Rho = 0.48, p < 0.001, respectively) was observed. Progressive subtypes showed higher COMPASS-31 total (p = 0.025), gastrointestinal (p = 0.07), and bladder (p < 0.001) domain scores vs relapsing-remitting patients.

CONCLUSIONS

Our findings confirm that MS-related DS are frequent and tend to increase paralleling disease duration and clinical worsening, reaching the highest clinical impact in progressive subtypes.

Evidence of Autonomic Dysfunction in Patients with Relapsing-Remitting Multiple Sclerosis: Heart Rate Variability and Cardiovascular Parameters

This study was aimed at evaluation of autonomic dysfunction in patients with multiple sclerosis (MS) by means of time- and frequency-domain parameters of heart rate variability (HRV) and conventional cardiovascular tests (deep breathing (DB) and active orthostatic test (AOT)). The study group enrolled 32 patients with the relapsing-remitting MS (17 m, 15 f, aged 29 ± 4.9 years, disease duration 4.2 ± 2.7 years, EDSS scores less than 3.0 and 26 subjects in good health (HC, 15 m, 11 f, aged 30.1 ± 2.7 years). In the MS group, at rest the variability of heart rate was decreased in comparison to the HC group seen by time- (SDNN, RMSSD, pNN50, CV, p < 0.01) and frequency-domain (TP, HF, LF, p < 0.05) parameters, what was indicative of the general decrease of the autonomic neurogenic control of the heart rate, both sympathetic and parasympathetic. The functional tests (DB and AOT) showed reduced cardiovascular reactivity in the MS group. Additionally, the cardio-respiratory synchronization was impaired in the MS group at rest and DB. The severity of HRV deficit in the MS group correlated with the activity of MS. In conclusion, the comprehensive assessment of time- and frequency-domain HRV parameters studied with functional tests provides better insight to understanding autonomic dysfunction in subjects with relapsing-remitting MS.

Cardiac Autonomic Modulation Is Different in Terms of Clinical Variant of Multiple Sclerosis

This study evaluates whether the cardiac autonomic response to head-up tilt test (HUTT) differs between patients with relapsing-remitting multiple sclerosis (RRMS) and those with progressive MS (PMS) as compared to healthy controls (HC). Baroreflex sensitivity, cardiac parameters, heart rate (HRV) and blood pressure variability (BPV) were compared between 28 RRMS, 21PMS and 25 HC during HUTT. At rest, PMS patients had higher values of the sympathovagal ratio, a low-frequency band HRV (LFnu-RRI) and lower values of parasympathetic parameters (HFnu-RRI, HF-RRI) compared to RRMS and HC. Resting values of cardiac parameters were significantly lower in RRMS compared to PMS patients. No intergroup differences were observed for post-tilt cardiac and autonomic parameters, except for delta HF-RRI with lower values in the PMS group. The MS variant corrected for age, sex and Expanded Disability Status Scale (EDSS) score was an independent predictor of changes in the sympathovagal ratio as measured by HRV. Furthermore, a higher overall EDDS score was related to a higher sympathovagal ratio, lower parasympathetic parameters at rest, and decrease post-tilt changes of the sympathovagal ratio of sBP BPV. Autonomic imbalance is markedly altered in the MS patient group compared to control changes were most pronounced in the progressive variant of MS disease. The MS variant appeared to have a potential influence on cardiac autonomic imbalance at rest.

Autonomic function in amnestic and non-amnestic mild cognitive impairment: spectral heart rate variability analysis provides evidence for a brain-heart axis

Mild cognitive impairment (MCI) is a heterogeneous syndrome with two main clinical subtypes, amnestic (aMCI) and non-amnestic (naMCI). The analysis of heart rate variability (HRV) is a tool to assess autonomic function. Cognitive and autonomic processes are linked via the central autonomic network. Autonomic dysfunction entails several adverse outcomes. However, very few studies have investigated autonomic function in MCI and none have considered MCI subtypes or the relationship of HRV indices with different cognitive domains and structural brain damage. We assessed autonomic function during an active orthostatic challenge in 253 oupatients aged ≥ 65, [n = 82 aMCI, n = 93 naMCI, n = 78 cognitively normal (CN), neuropsychologically tested] with power spectral analysis of HRV. We used visual rating scales to grade cerebrovascular burden and hippocampal/insular atrophy (HA/IA) on neuroimaging. Only aMCI showed a blunted response to orthostasis. Postural changes in normalised low frequency (LF) power and in the LF to high frequency ratio correlated with a memory test (positively) and HA/IA (negatively) in aMCI, and with attention/executive function tests (negatively) and cerebrovascular burden (positively) in naMCI. These results substantiate the view that the ANS is differentially impaired in aMCI and naMCI, consistently with the neuroanatomic substrate of Alzheimer's and small-vessel subcortical ischaemic disease.

Cardiac Autonomic Dysfunction in Multiple Sclerosis: A Systematic Review of Current Knowledge and Impact of Immunotherapies

Cardiac autonomic dysfunction (CAD) has been reported in patients with multiple sclerosis (MS). This systematic review summarizes the evidence for the types and prevalence of CAD in MS patients, as well as its association with MS type, disease characteristics, fatigue and immunotherapies used to treat MS. The analysis revealed that CAD is correlated with pathophysiological processes of MS, can trigger serious cardiovascular complications that may reduce life expectancy, and may have implications for treatment with immunotherapies, especially fingolimod. Numerous mainly small case-control or cohort studies have reported various measures of CAD (particularly heart rate variation) in MS patients, showing higher rates of abnormality versus controls. A smaller number of studies have reported on cardiac autonomic symptoms in MS, including orthostatic intolerance/dizziness in around 50% of patients. CAD also appears to be associated with disease duration and to be more common in progressive than relapsing-remitting MS. However, although a substantial evidence base suggests that assessing CAD in people with MS may be important, standardised methods to evaluate CAD in these patients have not yet been established. In addition, no studies have yet looked at whether treating CAD can reduce the burden of MS symptoms, disease activity or the rate of progression.

Prospects of using cardiovascular magnetic resonance in the identification of arrhythmogenic substrate in autoimmune rheumatic diseases

Sudden cardiac death (SCD) is due to ventricular tachycardia/fibrillation (VT/VF) and may occur with or without any structural or functional heart disease. The presence of myocardial edema, ischemia and/or fibrosis plays a crucial role in the pathogenesis of VT/VF, irrespective of the pathophysiologic background of the disease. Specifically, in autoimmune rheumatic diseases (ARDs), various entities such as myocardial/vascular inflammation, ischemia and fibrosis may lead to VT/VF. Furthermore, autonomic dysfunction, commonly found in ARDs, may also contribute to SCD in these patients. The only non-invasive, radiation-free imaging modality that can perform functional assessment and tissue characterization is cardiovascular magnetic resonance (CMR). Due to its capability to detect and quantify edema, ischemia and fibrosis in parallel with ventricular function assessment, CMR has the great potential to identify ARD patients at high risk for VT/VF, thus influencing both cardiac and anti-rheumatic treatment and modifying perhaps the criteria for implantation of cardioverter defibrillators.

Cardiac autonomic function during postural changes and exercise in people with multiple sclerosis: A cross-sectional study

BACKGROUND

People with multiple sclerosis (PwMS) often develop an autonomic dysfunction (AD), which onset should be assessed early at a subclinical level, as it may interfere with pharmacological treatments and exercise.

OBJECTIVE

To evaluate basal cardiac autonomic tone, its modulations during sit-to-stand, sub-maximal exercise and recovery in PwMS without clinical overt AD and its relationships with fatigue perception.

METHODS

Twenty-three PwMS (55 ± 8 yrs [mean ± SD]; EDSS score 5.7 ± 1.3) and 20 age-matched healthy controls (HC; 55 ± 8yrs) were enrolled. ECG was digitally acquired during:1) sitting at rest (low sympathetic activation); 2) standing (light sympathetic activation); and 3) during light exercise (moderate sympathetic activation) and recovery. Parasympathetic and sympatho-vagal parameters of heart rate (HR) variability in time and frequency domains were calculated from beat series.

RESULTS

HR was slightly but not significantly higher in PwMS compared to HC in all experimental conditions. Parasympathetic indexes were significantly lower (p < 0.05) in PwMS compared to HC during baseline sitting and post-exercise recovery, whereas sympathovagal parameters were similar in both groups. No correlation between autonomic tone and perceived fatigue was observed.

CONCLUSION

Parasympathetic tone appears to be impaired in PwMS basal and post-exercise conditions, but not during postural challenge and exercise. In addition, AD does not affect perceived fatigue.

Heart rate variability as predictive factor for sudden cardiac death

Sudden cardiac death (SCD) represents about 25% of deaths in clinical cardiology. The identification of risk factors for SCD is the philosopher's stone of cardiology and the identification of non-invasive markers of risk of SCD remains one of the most important goals for the scientific community.The aim of this review is to analyze the state of the art around the heart rate variability (HRV) as a predictor factor for SCD.HRV is probably the most analyzed index in cardiovascular risk stratification technical literature, therefore an important number of models and methods have been developed.Nowadays, low HRV has been shown to be independently predictive of increased mortality in post- myocardial infarction patients, heart failure patients, in contrast with the data of the general population.Contrariwise, the relationship between HRV and SCD has received scarce attention in low-risk cohorts. Furthermore, in general population the attributable risk is modest and the cost/benefit ratio is not always convenient.The HRV evaluation could become an important tool for health status in risks population, even though the use of HRV alone for risk stratification of SCD is limited and further studies are needed.

Investigation of ischemic and demyelinating lesions by cerebral vasoreactivity based on transcranial Doppler sonography: a comparative study

PURPOSE

Variations of cerebral blood flow in response to hypoxia and hyperoxia in different disease conditions can provide new insights into disease etiopathogenesis. This study aimed to determine the characteristics of cerebral vasoreactivity for ischemia and demyelination.

MATERIALS AND METHODS

This case-control study included: 28 patients with lacunar infarctions verified by history, physical examination, and MRI; 28 age- and sex-matched healthy controls; 28 patients with relapsing-remitting multiple sclerosis (MS), based on McDonald criteria; and 28 age- and sex-matched healthy controls for the MS group. Transcranial Doppler sonography was undertaken in all subjects to calculate the mean flow velocity (MFV) of the right middle cerebral artery (MCA) and, after a breath-holding (BH) maneuver, the breath-holding index (BHI) was determined.

RESULTS

There was no significant difference of BHI and changes of MFV of the MCA in MS patients compared to controls (1.02 ± 0.4 vs 1.02 ± 0.3, p = 0.993; and 16.8 ± 8.1 vs 11.3 ± 10.8, p = 0.057). BHI in patients with lacunar infarctions was significantly lower (0.8 ± 0.4 vs 1.2 ± 0.3, p < 0.001) compared to controls. The BHI (p = 0.040) and variations of MFV of MCA (p = 0.007) in MS patients were significantly higher than in patients with lacunar infarctions. The vasoreactivity of demyelinating lesions was higher than that of ischemic ones.

CONCLUSION

Therefore, cerebral vasoreactivity determined by transcranial Doppler could be utilized for differentiating demyelinating from ischemic lesions.

Cerebral autoregulation is preserved in multiple sclerosis patients

Multiple sclerosis (MS) is an inflammatory disease that may also be associated with vascular dysfunction. One master component of vascular regulation is cerebral autoregulation (CA). We aimed to investigate the integrity of CA in MS patients and study its relationship with autonomic dysfunction (AD), magnetic-resonance-imaging (MRI) lesion load and hemodynamic parameters. We enrolled 20 relapsing-remitting MS and 20 healthy subjects. CA was assessed by transfer function analysis parameters (coherence, gain and phase), as obtained in the very low, low and high-frequency domains (VLF, LF, HF, respectively). We evaluated the autonomic parameters heart rate variability and spontaneous baroreflex sensitivity (BRS). There were no significant differences in CA parameters between MS and controls (p>0.05). Lesion load was not correlated with any CA parameter. LF gain was positively correlated with BRS in both groups (MS: p=0.017; controls: p=0.025). Brainstem lesion load in MS was associated with higher systolic blood pressure (SBP; p=0.009). Our findings suggest that CA is preserved in our MS cohort. On the other hand, AD in MS patients with brainstem lesions could contribute to the increase of supine SBP. Whether this systemic deregulation could contribute to disease burden remains to be investigated.

Wearable biosensors to monitor disability in multiple sclerosis

Purpose of review

Biosensors capable of measuring physiologic and kinetic parameters associated with disability are being applied to the study of people with multiple sclerosis (MS). We review the use of biosensors in people with MS with an emphasis on measuring/monitoring disability and understanding knowledge gaps between biosensor data and clinical care.

Recent findings

Accelerometers are available to the public and may be able to help the clinician understand a patient's degree of disability. Further studies with wearable biosensors capable of measuring other physiologic features, such as vital signs, are needed and are likely to contribute to our understanding of MS.

Summary

Wearable biosensors can improve our understanding of disability, response to treatment, and natural history of MS.