The impact of multiple sclerosis onset symptom on cardiac repolarization

The Heart–Brain Interplay in Multiple Sclerosis from Pathophysiology to Clinical Practice: A Narrative Review

Multiple sclerosis (MS) is a chronic neurological disorder characterized by inflammation in the central nervous system (CNS) that leads to neurodegeneration. The clinical course is highly variable, but its prevalence is rising worldwide, partly thanks to novel disease-modifying therapies. Additionally, the lifespan of people with MS is increasing, and for this reason, it is fundamental to have a multidisciplinary approach to MS. MS may be associated with cardiovascular diseases (CVD), but there is scarce attention on this issue. In particular, CNS is essential in regulating the autonomic system and heart activity. Moreover, cardiovascular risk factors show a higher prevalence in MS patients. On the other hand, conditions like Takotsubo syndrome are rare complications of MS. The parallelism between MS and myocarditis is also interesting. Finally, cardiac toxicity represents a not infrequent adverse reaction to MS drugs. This narrative review aims to provide an overview of cardiovascular complications in MS and their management to prompt further clinical and pre-clinical research on this topic.

A novel role of cardiac inwardly rectifying potassium channels explaining autonomic cardiovascular dysfunctions in a cuprizone-induced mouse model of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS), believed to have an autoimmune etiology. MS patients showed an increased cardiovascular (CV) risk probably related to an impairment in the autonomic control of CV functions, but the underlying molecular mechanisms are not completely elucidated. Inwardly-rectifying potassium (Kir) channels play a key role in cardiac excitability by contributing to the repolarization phase of action potential and were recently identified as target of the autoantibody response in MS patients. Therefore, we investigated the role of cardiac Kir channels in the CV dysfunctions occurring in MS. Cardiac functions were evaluated by electrocardiographic recordings (ECG) in cuprizone-fed C57BL/6 mice, a classic demyelination animal model. Gene expression profiling of cardiac Kir2.2, Kir4.1 and Kir6.2 channels was performed using real-time PCR in mice. Cuprizone-induced mouse model was confirmed by immunohistochemistry analysis showing demyelination in the corpus callosum. ECG recordings from mice showed a significant decreased duration of the P wave and RR interval as well as an increase of the heart rate in cuprizone-treated mice as compared with the controls. Significant increased relative expression levels of Kcnj11 and Kcnj12, encoding for Kir6.2 and Kir2.2 channels respectively, were observed in mouse heart tissue, whereas no differences were found in mRNA levels of Kir4.1 channel as compared with controls. For the first time, these findings provided valuable insights into the potential role of Kir channels in cardiac problems associated with MS.

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.

The impact of multiple sclerosis onset symptom on cardiac repolarization

INTRODUCTION

Multiple sclerosis is associated with prolonged cardiac repolarization but the underlying physiology has remained unknown. In this study, we compared cardiac repolarization during the relapsing-remitting multiple sclerosis (RRMS) disease course in patients with motor and sensory onset symptom.

METHODS

Twenty-five RRMS patients with motor and 33 RRMS patients with sensory onset symptom having 12-lead electrocardiogram (ECG) recorded at the time of the first demyelinating event (ECG1) as well as at the later disease course (ECG2) were identified from the patient records. The average time interval between ECG1 and ECG2 was 8.6 ± 5.9 y. Heart rate-corrected QT intervals reflecting cardiac repolarization were calculated by Bazett (QTcBaz), Fridericia (QTcFri), and Karjalainen (QTcKar) formulas.

RESULTS

Heart rate-corrected QT intervals as well as heart rate were similar in patients with motor and sensory onset symptom in ECG1. However, QTcBaz (p = .002), QTcFri (p = .019), and QTcKar (p = .026) were longer and heart rate was higher (p = .035) in patients with motor than sensory onset symptom in ECG2. Correspondingly, QTcBaz (p = .002), QTcFri (p = .033), and QTcKar (p = .043) prolonged and heart rate tended to increase (p = .060) during the disease course only in the patients with motor onset symptom.

CONCLUSIONS

Cardiac repolarization prolonged and heart rate increased during the disease course in RRMS patients with motor but not with sensory onset symptom. This suggests different traits in RRMS according to its initial manifestation and also association of motor onset symptom with more unfavorable cardiovascular prognostic determinants.