Cardiac Autonomic Dysfunction in Myasthenia Gravis and Relapsing-Remitting Multiple Sclerosis-A Pilot Study

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.

Keywords: blood pressure variability; cardiac autonomic dysfunction; heart rate variability; myasthenia gravis; relapsing-remitting multiple sclerosis; sympathovagal ratio.

Figure 1

MG, MS, and HC groups mean values (±SD) of CI, cardiac index (A); TFC, thoracic fluid content (B); LVWI, left ventricular work index (C); respectively for compared to healthy controls.

Figure 2

MS and MG groups mean values (±SD) of LFnu-RRI, low frequency R-R interval in normalised units (A); HFnu-RRI, high frequency R-R interval in normalised (B); PSD-RRI, power spectral density of heart rate variability (C); LF/HF-RRI, ratio between low and high band for heart rate variability (D); BRS, baroreflex sensitivity (E); respectively for compared to healthy controls.