Cardiovascular, autonomic, and plasma catecholamine responses in unilateral and bilateral carotid artery stenosis

Objective-To determine impairment of baroreceptor afferent activity, which may affect cardiovascular autonomic function in patients with unilateral an d bilateral carotid artery stenosis. Comparison was made with normal subjec ts and hypertensive patients. Methods-A series of cardiovascular autonomic function tests along with plas ma noradrenaline (norepinephrine) measurements were performed in 46 patient s with carotid artery stenosis (CAS); 23 had unilateral and 23 had bilatera l stenosis. Comparison was made with 21 hypertensive patients (with a simil ar degree of raised blood pressure), and 27 normal subjects. Results-Over a third of patients with unilateral and bilateral CAS had post ural hypotension. Heart rate did not rise appropriately in CAS despite the postural fall in blood pressure. Presser responses in CAS were preserved. H eart rate responses to respiratory stimuli were attenuated. Plasma noradren aline concentrations rose normally during head up tilt. Conclusion-A substantial proportion with CAS had postural hypotension and a ttenuated heart rate responses. This was not due to sympathetic vasoconstri ctor or cardiac parasympathetic failure, thus suggesting impaired afferent baroreceptor activity, probably secondary to involvement of the carotid sin us. Cardiovascular autonomic testing and assessment of postural hypotension and factors enhancing it may be of clinical relevance in such patients, es pecially as the symptoms of postural hypotension overlap with those. due to thromboembolism.