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In human anatomy, the carotid sinus is a localized dilation of the internal carotid artery at its origin, the common carotid artery bifurcation. It contains numerous baroreceptors, which function as a "sampling area" for many homeostatic mechanisms for maintaining blood pressure. Manual stimulation of the carotid sinus can induce the carotid sinus reflex, which may reduce the heart rate and/or blood pressure to some degree.Wijetunga, M; Schatz, I. Carotid Sinus Hypersensitivity. www.emedicine.com. URL last accessed February 28 2006 It receives innervation from cranial nerve IX (glossopharyngeal nerve).
Disease of the carotid sinus
The carotid sinus often has atherosclerotic plaques because of disturbed hemodynamics (low wall shear stress, flow reversal/recirculation).Glagov S, Zarins C, Giddens DP, Ku DN. Hemodynamics and atherosclerosis. Insights and perspectives gained from studies of human arteries. Arch Pathol Lab Med. 1988 Oct;112(10):1018-31. PMID 3052352 Since these plaques, if large and unstable, predispose to ischemic strokes and transient ischemic attacks, carotid endarterectomies are frequently done for prophylaxis.
The carotid sinus can be oversensitive to manual stimulation, a condition known as carotid sinus hypersensitivity, carotid sinus syndrome or carotid sinus syncope, in which manual stimulation causes large changes in heart rate and/or blood pressure.
Carotid sinus massage
Massage of the carotid sinus, carotid sinus massage is used to diagnose carotid sinus syncope and is sometimes useful for differentiating supraventricular tachycardia (SVT) from ventricular tachycardia. It, like the valsalva maneuver, is a therapy for SVT.Lim SH, Anantharaman V, Teo WS, Goh PP, Tan AT. Comparison of treatment of supraventricular tachycardia by Valsalva maneuver and carotid sinus massage. Ann Emerg Med. 1998 Jan;31(1):30-5. PMID 9437338 However, it is less effective than pharmaceutical management of SVT with verapamil or adenosine.Ballo P, Bernabo D, Faraguti SA. Heart rate is a predictor of success in the treatment of adults with symptomatic paroxysmal supraventricular tachycardia. Eur Heart J. 2004 Aug;25(15):1310-7. PMID 15288158
Carotid sinus reflex death
Carotid sinus reflex death is a disputed mechanism of death in which manual stimulation of the carotid sinus allegedly causes strong vagus nerve impulses leading to terminal cardiac arrest. Carotid sinus reflex death has been pointed out as a possible cause of death in cases of strangulation and hanging, but such deductions remain controversial. Studies have however shown that the carotid sinus reflex can be a contributing factor in other mechanisms of death by reducing blood pressure and heart rate, especially in the elderly or in people suffering from carotid sinus hypersensitivity. Passig ,K. Carotid Sinus reflex death - a theory and its history. www.datenschlag.org. URL last accessed February 28 2006.
References
"Carotid sinus"