The Effect of Multiple Sclerosis on Carotid Baroreflex Latencies of Arterial Blood Pressure and Heart Rate

Abstract

Multiple sclerosis (MS) is marked by conduction abnormalities within the central nervous system that lead to impaired blood pressure regulation. However, the impact of these abnormalities on dynamic blood pressure control, particularly the timing of the responsiveness (i.e., latency), has not been examined. We tested the hypothesis that carotid‐cardiac and carotid‐vasomotor latency would be delayed in individuals with MS (n=5) compared to healthy controls (CON, n=5). Carotid baroreflex function was assessed using 5‐sec trials of neck pressure (NP, +40 Torr, simulated hypotension) and neck suction (NS, ‐60 Torr, simulated hypertension). Latencies (i.e., time‐to‐peak responses) were determined for both carotid‐cardiac (peak HR responses) and carotid‐vasomotor (peak MAP responses) by summing the R‐R intervals from the onset of the respective stimuli to the R wave of the cardiac cycle associated with the respective peak responses. Carotid‐cardiac latency was not different between groups for either NP (MS: 3.7±1.3 sec, CON: 3.7±1.3 sec; p=0.97) or NS (MS: 1.6±1.1 sec, CON: 1.9±0.8 sec; p=0.62). In addition, the carotid‐vasomotor latency to NP (MS: 5.7±1.7 sec, CON: 5.6±1.4 sec; p=0.90), and NS (MS: 4.7±2.3 sec, CON: 6.8±0.6 sec; p=0.08) were not different between groups. It appears MS does not markedly alter the timing of peak carotid‐cardiac and carotid‐vasomotor responses.Supported by NIH R15HL117224 and National MS Society RG4696A