Hypersensitive carotid sinus syndrome

Hypersensitive carotid sinus syndrome

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:

  1. Cardioinhibitory
  2. Vasodepressor
  3. 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. ESC 2013 guidelines recommend 10s massage. Recent stroke, transient ischemic attacks and myocardial infarction are reasons to avoid a carotid sinus massage. In cardioinhibitory response, there is 3 second asystole and in vasodepressor response there is a fall in blood pressure of 50 mm Hg or more [1].

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. Dose of antihypertensive agents may have to be reduced in hypertensives. If the cardioinhibitory variety is symptomatic with recurrent syncope, permanent pacemaker implantation is a Class I indication as per American Heart Association guidelines. According 2013 European Society of cardiology recommendation, 6s asystole with reproduction of syncope is the criteria for pacing [2]. It is mentioned that 40 new patients/million population require pacing for hypersensitive carotid sinus syndrome. This represents about 9% of those presenting with syncope to a specialist facility [1]. Interestingly, syncope can recur in up to 20% patients over 5 years even with pacing and could be due to vasodepressive component [2]. Optimal pacing mode recommended is dual chamber, with ventricular pacing reserved for those with atrial fibrillation [2].

References

  1. Sutton R. Carotid sinus syndrome: Progress in understanding and management. Glob Cardiol Sci Pract. 2014 Jun 18;2014(2):1-8. 
  2. European Society of Cardiology (ESC); European Heart Rhythm Association (EHRA), Brignole M, Auricchio A, Baron-Esquivias G, Bordachar P, Boriani G, Breithardt OA, Cleland J, Deharo JC, Delgado V, Elliott PM, Gorenek B, Israel CW, Leclercq C, Linde C, Mont L, Padeletti L, Sutton R, Vardas PE. 2013 ESC guidelines on cardiac pacing and cardiac resynchronization therapy: the task force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA). Europace. 2013 Aug;15(8):1070-118.