Characterisation of cardiac autonomic function in multiple sclerosis based on spontaneous changes of heart rate and blood pressure.

BACKGROUND: Prevalence of cardiovascular autonomic dysfunction (CAD) in multiple sclerosis (MS) varies between studies. Cardiac autonomic function is usually assessed by cardiovascular reflex tests. We hypothesized that MS is associated with CAD, quantifiable by non-invasive means including quantification of baroreceptor sensitivity (BRS) and heart rate variability.

METHODS: In this study a comprehensive suite of cardiovascular autonomic tests based only on the spontaneous changes of heart rate and blood pressure was applied to 23 MS patients and age and gender-matched controls. From 5-min continuous non-invasive recording of the electrocardiogram and blood pressure, heart-rate, blood pressure, and autonomic function variables were calculated. Analysis included heart rate variability in the time domain, heart rate and blood pressure variability in the frequency domain, and baroreceptor sensitivity in both the time and frequency domain.

RESULTS: BRS measured by the frequency technique in high frequency band was found to be significantly lower in MS (16 ± 9 ms/mmHg) compared to controls (29 ± 17 ms/mmHg) (p < 0.05). Also mean of BRS modulus in MS averaged 15 ± 8 ms/mmHg which is significantly lower compared to controls (25 ± 15 ms/mmHg) (p < 0.05). Systolic blood pressure variability in the high frequency band (0.15-0.5 Hz) was found to be significantly higher in the MS compared to controls (5.8 ± 16.7 mmHg2 vs. 1.3 ± 0.8 mmHg2 ) (p < 0.05).

CONCLUSIONS: The results, using techniques novel to MS investigation, showed diminished baroreceptor reflex and impaired sympathetic function using frequency domain systolic blood pressure variability analysis.