From Wikipedia, the free encyclopedia
In human
anatomy, the carotid sinus is a localized
dilation of the internal carotid artery at its
origin, the common carotid artery bifurcation. A synonym
for the carotid sinus is the carotid bulb.
Functions
The carotid sinus contains numerous baroreceptors, which
function as a "sampling area" for many homeostatic mechanisms for maintaining blood pressure.
The carotid sinus baroreceptors are innervated by the sinus nerve
of Hering, which is a branch of IX (glossopharyngeal nerve). The
glossopharyngeal nerve synapses in the nucleus tractus solitarius (NTS)
located in the medulla of the brainstem. The NTS indirectly
modulates the activity of sympathetic and parasympathetic (vagal)
neurons in the medulla and pons through the hypothalamus. These
neurons then regulate the autonomic control of the heart and blood
vessels. The aortic arch baroreceptors are innervated by the aortic
nerve (Nerve of Cyon), which combines with CN X (vagus nerve) and
travels to the NTS.
Disease of the carotid
sinus
The carotid sinus often has atherosclerotic
plaques because of disturbed hemodynamics (low wall shear stress, flow
reversal/recirculation).[1] 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 syndrome is a temporary loss of
consciousness that sometimes accompanies convulsive seizures
because of the intensity of the carotid sinus reflex when pressure
builds in one or both carotid sinuses.
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. Like
the valsalva
maneuver, it is a therapy for SVT.[2] It is
less effective than pharmaceutical management of SVT with verapamil or adenosine[3] though
is still the preferred first-line of treatment in a hemodynamically
stable patient[4]
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, hanging and Erotic
asphyxiation[5], but
such deductions remain controversial. Studies have however
suggested 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. A carotid massage can also possibly
dislodge a thrombus, or some plaque. This could lead to any number
of life threatening effects, including stroke. [6]
See also
References
- ^
Glagov S, Zarins C, Giddens DP, Ku DN. Hemodynamics and
atherosclerosis. Insights and perspectives gained from studies of
human arteries. biod degradable Arch Pathol Lab Med. 1988
Oct;112(10):1018-31. PMID 3052352
- ^
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
- ^
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
- ^
American Heart Association. Tachycardia algorithm. Advanced Cardiac
Life Support Provider Manual (2007).
- ^
http://www.altpenis.com/penis_news/autoerotic_asphyxia.shtml
- ^
Passig, K. Carotid sinus reflex death - a
theory and its history. URL last accessed February 28,
2006.
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