Diagnosis and Treatment
Permanent Pacing in Hypersensitive Carotid Sinus Syndrome
and Neurocardiogenic Syncope
Key Points
����The hypersensitive carotid sinus syndrome is defined as syncope or
presyncope resulting from an extreme reflex response to carotid sinus
stimulation. There are 2 components of the reflex:
������ Cardioinhibitory, which results from increased parasympathetic tone and is
manifested by slowing of the sinus rate or prolongation of the PR interval and
advanced AV block, alone or in combination.
������ Vasodepressor, which is secondary to a reduction in sympathetic activity that
results in loss of vascular tone and hypotension.
This effect is independent of heart rate changes.
����Hyperactive response to carotid sinus stimulation is defined as
asystole due to either sinus arrest or AV block of >3 seconds, a
substantial symptomatic decrease in systolic blood pressure, or both.
����Permanent pacing for patients with an excessive cardioinhibitory
response to carotid stimulation is effective in relieving symptoms.
����Because 10%-20% of patients with this syndrome may have an
important vasodepressive component of their reflex response, it is
desirable that this component be defined before one concludes that all
symptoms are related to asystole alone.
Among patients whose reflex response includes both cardioinhibitory and vasodepressive
components, attention to the latter is essential for effective therapy in patients undergoing
pacing.
Treatment
����Permanent pacing is indicated:
������ for recurrent syncope caused by spontaneously occurring carotid sinus stimulation
and carotid sinus pressure that induces ventricular asystole of >3 seconds. (I-C)
����Permanent pacing is reasonable for:
������ syncope without clear, provocative events and with a hypersensitive
cardioinhibitory response of ���3 seconds. (IIa-C)
����Permanent pacing may be considered for:
������ significantly symptomatic neurocardiogenic syncope associated with bradycardia
documented spontaneously or at the time of tilt-table testing. (IIb-B)
����Permanent pacing is NOT indicated for:
������ a hypersensitive cardioinhibitory response to carotid sinus stimulation without
symptoms or with vague symptoms. (III-C)
������ situational vasovagal syncope in which avoidance behavior is effective and
preferred. (III-C)
6
