Role of Blood Pressure in Mediating Carotid Artery Dilation in Response to Sympathetic Stimulation in Healthy, Middle-Aged Individuals.

Abstract

OBJECTIVES: Carotid artery diameter responses to sympathetic stimulation, i.e., carotid artery reactivity (CAR), represent a novel test of vascular health and relates to cardiovascular disease (CVD)/risk. This study aims to understand the relationship between the increase in blood pressure and carotid artery diameter response during the CAR-test in healthy, middle-aged men. METHODS: Sample consisted of 40 normotensive men (aged 31-59 years) with no history of CVD of currently taking medication. Noninvasive ultrasound was used to measure carotid artery diameter during the cold pressor test (CPT), with CAR% being calculated as the relative change from baseline (%). Mean arterial pressure (MAP) was measured with beat-to-beat blood pressure recording. RESULTS: CAR% was 4.4 +/- 5.4%, peaking at 92 +/- 43 seconds. MAP increased from 88 +/- 9 mmHg to 110 +/- 15 mmHg, peaked at 112 +/- 38 seconds, which was significantly later than the diameter peak (P = 0.04). The correlation between resting MAP and CAR% was weak (r = 0.209 P = 0.197). Tertiles based on resting MAP or MAP-increase revealed no significant differences between groups in subject characteristics including age, body mass index, or CAR% (all P > 0.05). Subgroup analysis of individuals with carotid constriction (n = 6) vs. dilation (n = 34), revealed no significant difference in resting MAP or increase in MAP (P = 0.209 and 0.272, respectively). CONCLUSION: Our data suggest that the characteristic increase in MAP during the CPT does not mediate carotid artery vasomotion.