7.3 ASSESSMENT OF BLOOD PRESSURE AND HEART RATE VARIABILITY IN MULTIPLE SCLEROSIS

Abstract

Background: Reported cardiovascular autonomic dysfunction (CAD) prevalence in Multiple Sclerosis (MS) varies between studies. As CAD lowers quality of life and may contribute to sudden death in MS, early CAD detection may assist treatment and risk identification. Methods: In 23 MS patients and age and gender matched controls (38±12 years, 15 female), continuous electrocardiogram and finger blood pressure were non-invasively acquired during 5 minutes supine rest. Baroreceptor sensitivity (BRS) was quantified through sequence and coherence analysis. Heart rate variability (HRV) was analysed in the standard manner and systolic blood pressure variability (SBPV) quantified in the very low (0.0033–0.04 Hz), low (0.04–0.15 Hz) and high (0.15–0.5 Hz) frequency ranges. Results: HRV did not differ between the groups. BRS in the high frequency band was lower in MS than control (22±13 and 39±25 ms/mmHg, p=0.007) as was normalised low frequency SBPV (0.70±0.19 and 0.82±0.14, p=0.006). Normalised high frequency SBPV was greater in MS subjects (0.31±0.19 and 0.18±0.14, p=0.006). Differences in high frequency SBPV indicate differences in respiratory feedback (not directly measured in this study) and in the low frequency range, differences in baroreceptor and/or chemoreceptor cardiovascular control. High frequency coherence in BRS analysis likely indicates reduced BRS control (as suggested by no difference in BRS by the sequence technique), but also respiration derived control of the sinus node. Conclusions: These results indicate that MS subjects have altered degree of cardiovascular autonomic control compared to healthy subjects and the effect of the respiratory pathway warrants further investigation.