Abnormal heart rate and blood pressure responses to baroreflex stimulation in multiple sclerosis patients

Abstract

Cardiovascular autonomic neuropathy has been previously reported in patients with multiple sclerosis (MS) using standard reflex tests. However, no study has separately evaluated both parasympathetic and sympathetic cardiovascular autonomic regulation. We therefore assessed the baroreflex-mediated vagal and sympathetic control of the heart rate and sympathetic control of the blood vessels in MS patients using sinusoidal neck stimulation. We studied 13 multiple sclerosis patients aged 28-58 years and 18 healthy controls aged 26-58 years. The carotid baroreflex was stimulated by sinusoidal neck suction (0 to -30 mmHg) at 0.1 Hz to assess the autonomic control of the heart and blood vessels, and at 0.2 Hz to assess the vagal control of the heart. Continuous recordings were made of blood pressure, electrocardiographic RR-interval and respiration, with breathing paced at 0.25 Hz. Spectral analysis was used to evaluate the magnitude of the low frequency (LF, 0.03-0.14 Hz) and high frequency (HF, 0.15-0.50 Hz) oscillations in RR-interval and blood pressure in response to the sinusoidal baroreceptor stimulation. Responses to the applied stimulus were assessed as the change in the spectral power of the RR-interval and blood pressure fluctuations at the stimulating frequency from the baseline values. The increase in the power of 0.1 Hz RR-interval oscillations during the 0.1 Hz neck suction was significantly smaller (p<0.01) in the MS patients (4.47+/-0.27 to 5.62+/-0.25 ln ms(2)) than in the controls (4.12+/-0.37 to 6.82+/-0.33 ln ms(2)). The increase in the power of 0.1 Hz systolic BP oscillations during 0.1 Hz neck suction was also significantly smaller (p<0.01) in the MS patients (0.99+/-0.19 to 1.96+/-0.39 mmHg(2)) than in the healthy controls (1.27+/-0.34 to 9.01+/-4.10 mmHg(2)). Neck suction at 0.2 Hz induced RR-interval oscillations at 0.2 Hz that were significantly smaller (p<0.05) in the patients (3.22+/-0.45 ln ms(2)) than in the controls (5.27+/-0.29 ln ms(2)). These results indicate that in MS patients, baroreflex dysfunction is not only restricted to the cardiovagal limb of the baroreflex, but that the sympathetic modulation of the blood vessels is also affected.

Autonomic dysfunction in multiple sclerosis

“…Sanya et al used baroreflex stimulation to demonstrate that MS patients have impairment of both the vagal mediated heart rate variability, as well as sympathetic control of blood vessel tone [16].…”

New Markers of Early Cardiovascular Risk in Multiple Sclerosis Patients: Oxidized-LDL Correlates with Clinical Staging

“…Despite data are still scarce, studies point to an increased cardiovascular risk (CVR) in patients with MS, at least when compared with individuals of similar age [3][4][5]. MS patients exhibit autonomic dysfunc-tion [6], increased blood pressure and tachycardia [7], ventricular disturbances [8] and impairment of the balance between vasoconstrictors and vasodilators, such as prostaglandins and nitric oxide (NO) [9,10]. However, there is still no clear explanation for all the aspects that may underlie these findings.…”

Postural Orthostatic Tachycardia Syndrome (POTS) and Vitamin B12 Deficiency in Adolescents

“…12 In vitamin B 12 deficiency, myelin synthesis is disrupted and may lead to baroreflex dysfunction, affecting the sympathetic regulation of blood vessels and the autonomic nervous system, as observed in demyelinating disorders. 13,14 Furthermore, the blood level of noradrenaline is particularly increased because of the dysfunction of enzymes requiring vitamin B 12 , such as phenylethanolamine n-methyltransferase (involved in the conversion of noradrenaline to adrenaline) and COMT (involved in adrenaline-noradrenalinedopamine degradation).…”