![]() The reason for the restriction to cardioinhibition reflects selection of patients for treatment by pacing. The only fairly precise estimates of incidence of CSS were made in the 1980s from Lavagna in Italy 11 and from Worthing, Sussex in the United Kingdom 12 which gave that of cardioinhibitory CSS as 35–40 new patients per million population per year. 10 Most patients present syncope without any local trigger but the diagnosis is nevertheless made by addressing the carotid sinus by massage, CSM, as described above.Ĭomprehension of the epidemiology of carotid sinus syndrome is adversely affected by confusion over its definition. ![]() Tight collars and neck movements 8,9 have a particular tendency to trigger the reflex and occasionally neck tumours, neck surgery or irradiation may also act as triggers. 9 Their patients had the so-called spontaneous form of the disease. 7 Carotid sinus syndrome has its name because its initial discovery was by mechanical stimulation of the Carotid sinus as described by Roskam 8 and Weiss and Baker. Both may exist in the same patient, but they appear to be independent of each other. The abnormal reflex has been attributed to disturbance of baroreceptor function 4 and also to degeneration of the medulla. ![]() CSS is an autonomic nervous system disease involving a pathological reflex, the pathophysiology of which has features similar to vasovagal syncope (VVS) with two main elements of its reflex involving cardioinhibition via the vagus nerve and vasodepression, which is thought to be due to sympathetic withdrawal. It presents in older persons, with a mean age ∼75 years, and has a strong male dominance >2:1. Therapy for the vasodepressor component of CSS, as pure vasodepression or mixed, where tilt testing will likely be positive, is often unrewarding: alternative therapeutic measures may be needed including discontinuation/reduction of hypotensive drugs. Syncope recurrence is ∼20% in 5 years in paced patients. Therapy for cardioinhibitory CSS is dual chamber pacing, which is most effective in patients with a negative tilt test. CSM carries a small risk of thromboembolism. ![]() If no cause is revealed by the initial evaluation, CSM should be considered in all patients >40 years. CSS patients present syncope with little or no warning. CSH cannot be assumed to respond to pacing. Carotid sinus hypersensitivity (CSH) is a related condition where CSM is positive in an asymptomatic patient. Assessment of the vasodepressor component implies the ‘method of symptoms’ using atropine to prevent asystole. The methodology of CSM requires correct massage in the supine and upright with continuous ECG and BP. Cardioinhibitory CSS shows 3s asystole on CSM and vasodepressor CSS shows >50 mmHg fall in blood pressure (BP), there are mixed forms. CSS is defined as a response to carotid sinus massage (CSM) that includes reproduction of spontaneous symptoms. Forty new patients/million population have been estimated to require pacing for CSS and these patients represent ∼9% of those presenting syncope to a specialist facility. The aetiology is unknown and epidemiological data is limited. Carotid sinus syndrome (CSS) is a disease of the autonomic nervous system presenting with syncope, especially in older males who often have cardiovascular disease.
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