Carotid Sinus Hypersensitivity and Syncope

At the heart of the arterial baroreflex: a physiological basis for a new classification of carotid sinus hypersensitivity

The aim of this review is to provide an update of the current knowledge of the physiological mechanisms underlying reflex syncope. Carotid sinus syncope will be used as the classical example of an autonomic reflex with relatively well-established afferent, central and efferent pathways. These pathways, as well as the pathophysiology of carotid sinus hypersensitivity (CSH) and the haemodynamic effects of cardiac standstill and vasodilatation will be discussed. We will demonstrate that continuous recordings of arterial pressure provide a better understanding of the cardiovascular mechanisms mediating arterial hypotension and cerebral hypoperfusion in patients with reflex syncope. Finally we will demonstrate that the current criteria to diagnose CSH are too lenient and that the conventional classification of carotid sinus syncope as cardioinhibitory, mixed and vasodepressor subtypes should be revised because isolated cardioinhibitory CSH (asystole without a fall in arterial pressure) does not occur. Instead, we suggest that all patients with CSH should be thought of as being 'mixed', between cardioinhibition and vasodepression. The proposed stricter set of criteria for CSH should be evaluated in future studies.

Recurrent syncope in patients with carotid sinus hypersensitivity

Syncope recurrence in pacemaker-implanted subjects for the cardio-inhibitory response to sinus carotid massage (SCM) was investigated. The study-hypothesis was that recurrences had significant vasodepressor responses that could justify the loss of consciousness. Forty-six patients were enrolled (16 patients and 30 controls), followed and revaluated after 5–7 years. At the end of follow-up, significant differences were found between patients and controls in mean SCM SAP (87 versus 106 mmHg) and reduction in mean SCM SAP (59 versus 38 mmHg); in the number of symptomatic subjects soon after SCM (5 versus 1); and in the number of subjects suffering from orthostatic hypotension. A subgroup of 13 patients showed significantly different hypotensive responses to SCM compared with the values observed at study recruitment. The data showed that some subjects with a defined hemodynamic pattern in response to SCM may change their characteristics and have spontaneous and/or provocative symptoms. These data explain the syncopal relapses, and suggest the presence of autonomic dysregulation in individuals with carotid sinus hypersensitivity.

Temporary cardiac arrest in patient under robotically assisted total thyroidectomy causing carotid sinus hypersensitivity -A case report-

Carotid sinus hypersensitivity (CSH) is an exaggerated response to carotid sinus baroreceptor stimulation. Bradycardia, hypotension, and syncope are common manifestations of CSH. A 31-year-old female patient was scheduled for a robotically assisted endoscopic total thyroidectomy. No problems occurred during anesthetic induction. Sudden cardiac arrest occurred near dissection of the diseased thyroid. However, while atropine was administered, the patient soon recovered to normal sinus rhythm. Subsequent bradycardia or hypotension was not followed until the end of surgery.