Hypersensitive carotid sinus syndrome is an exaggerated response to stimulation of the baroreceptors in the carotid sinus and leads to bradycardia / hypotension and syncope. Three types of responses have been described: cardioinhibitory, vasodepressor and mixed. In cardioinhibitory type there is only bradycardia, and there is no fall in blood pressure. The cardioinhibitory type is the commonest variety contributing to about three fourth of the cases. In vasodepressor type there is only hypotension, but no bradycardia. It is the least common type. In the mixed variety there is both bradycardia and hypotension. Mixed type occurs in about one fifth to one fourth of cases. Though baroreceptor function decreases with age, the Hypersensitive carotid sinus syndrome is more common in older males. In some even trivial stimuli like a tight collar or shaving the neck may be enough to cause a syncope.
Hypersensitive carotid sinus syndrome can be spontaneous or induced. The former occurs spontaneously while the latter is brought on by carotid sinus massage during the evaluation of a syncope. Spontaneous variety may present with fractures or other injuries, especially in the elderly. Vasovagal syncope and postural hypotension have to be excluded in this setting.
While trying to reproduce carotid sinus syncope, extreme care is needed, especially in the elderly. Careful assessment of carotids for bruit or obstruction on either side is needed to prevent the potential for dislodgement of atherosclerotic plaques and causing embolic stroke. ECG and blood pressure has to be monitored through out. Initial evaluation should be in the supine position and gentle. If negative in the supine position, carotid massage may have to be repeated in the standing position, to improve the sensitivity, if the clinical suspicion is high. But it will be ideal to conduct it with the patient strapped to a tilt table in order to prevent injuries due to a fall. The massage is done for five seconds on each side with a one minute interval. Recent stroke, transient ischemic attacks and myocardial infarction are reasons to avoid a carotid sinus massage.
Treatment of hypersensitive carotid sinus syndrome
Midodrine, fludrocortisone and volume supplementation are the methods tried in the treatment of vasodepressor variety of carotid sinus hypersensitivity. If the cardioinhibitory variety is symptomatic with recurrent syncope, permanent pacemaker implantation is a Class I indication as per American Heart Association guidelines.