Heart rate variability in multiple sclerosis during a stable phase

Objectives - Multiple sclerosis (MS) frequently causes disturbances of autonomic functions. Cardiovascular dysautonomia has been studied by classic autonomic tests and, recently, by heart rate variability analysis in some isolated periods. Multiple authors recommended performing heart rate variability analysis with a 24 h ECG recording to increase its sensitivity. Material and methods - We analyzed the heart rate variability in time and frequency domains in 34 MS patients and 24 age and sex-matched healthy control subjects, in order to evaluate the effects of MS on sympathetic and parasympathetic cardiovascular regulatory functions measured from 24-h electrocardiogram. Results - Low frequency power (0.01) and low frequency/ high frequency power (0.01) were significantly higher in multiple sclerosis patients independently, all together or in subgroups. Very low frequency (0.01) and high frequency (0.001) power were higher in less affected multiple sclerosis patients. Variability in time domain (0.05) were lower in most affected multiple sclerosis patients. Conclusions - These results suggest that multiple sclerosis causes cardiovascular autonomic dysregulation manifesting as impaired heart rate variability. This illness seems to cause an increase in sympathetic cardiovascular tone; the parasympathetic tone is most variable and depends on clinical and paraclinical findings, but the illness progression seems to provoke a decrease in it.