Abstract
This study assessed cardiac autonomic response to head-up tilt test (HUTT) in 23 myasthenia gravis (MG) and 23 relapsing-remitting multiple sclerosis (RRMS) patients compared to 30 healthy controls (HC). Task Force® Monitor was used to evaluate cardiac inotropy parameters, baroreflex sensitivity (BRS), heart rate (HRV), and blood pressure variability (BPV) during HUTT. MG patients were characterized by reduced BRS (p < 0.05), post-HUTT decrease in high-frequency component (p < 0.05) and increase in sympathovagal ratio of HRV (p < 0.05) when compared to controls indicating parasympathetic deficiency with a shift of sympathovagal balance toward sympathetic predominance. Compared to HC, MG patients also showed lower cardiac inotropy parameters, specifically, left ventricular work index (LVWI) during supine rest (p < 0.05) as well as LVWI and cardiac index values in response to orthostatic stress (p < 0.01 and p < 0.05, respectively). Compared to controls, RRMS patients were characterized by lower HRV delta power spectral density (p < 0.05) and delta low-frequency HRV (p < 0.05) in response to HUTT suggesting combined sympathetic and parasympathetic dysfunction. There were no differences in cardiac autonomic parameters between MG and MS patients (p > 0.05). Our study highlights the possibility of cardiac and autonomic dysfunction in patients with MG and RRMS which should be considered in the pharmacological and rehabilitation approach to managing these conditions.
Highlights
The predominant myasthenia gravis (MG) manifestation is caused by autoantibodies that bind to the acetylcholine receptors (AChR) or to functionally related postsynaptic membrane molecules of the neuro-muscular junction (NMJ)
Our study shows a different pattern of autonomic nervous system involvement in MG and Multiple sclerosis (MS) patients with a comparable mean disease duration and a stable three-month clinical course
Patients with MG were characterized by more frequent occurrence of autonomic symptoms compared to those with MS and reduced cardiac inotropy parameters as well as parasympathetic insufficiency in response to orthostatic stress when compared to the controls
Summary
Multiple sclerosis (MS) and myasthenia gravis (MG) are the most common acquired autoimmune disorders targeting the central nervous system (CNS) and the neuro-muscular junction (NMJ), respectively [1,2]. Both diseases are caused by dysfunctions in self-tolerance in response to over activity of the immune system. The immune component is the leading cause of clinical deterioration in MG throughout course of the disease, whereas in MS it is mainly seen during the relapsing-remitting phase (RRMS) [3,4,5]. It has been suggested that the cholinergic deficit in MG may affect other regions as well, making the disease a “neurologic chameleon”
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