Carotid Sinus Hypersensitivity

Carotid sinus hypersensitivity (CSH) often manifests as syncope and results from an exaggerated response of hypersensitive baroreceptors within the carotid sinus when stimulated. The carotid sinus, located at the bifurcation of the common carotid artery into the internal and external carotid arteries, functions as a neurovascular structure housing pressure-sensitive baroreceptors. These receptors, which respond to stretch or pressure ( originates from the Greek word for pressure), play a central role in blood pressure regulation (see . Pathophysiology of Carotid Sinus Hypersensitivity). Baroreceptor stimulation triggers afferent neural signals via the glossopharyngeal nerve to the solitary nucleus of the medulla. In response to increased pressure or stretch, this neural pathway activates parasympathetic output, resulting in vasodilation, bradycardia, and hypotension. The resulting decline in blood pressure reduces baroreceptor stimulation and ultimately terminates the reflex response. CSH is defined clinically as an exaggerated autonomic reaction to mechanical stimulation of the carotid sinus, leading to transient cerebral hypoperfusion and subsequent presyncope or syncope. Three subtypes are recognized. The cardioinhibitory response involves a pause in cardiac activity (asystole) lasting 3 seconds or longer on continuous monitoring. The vasodepressor response is characterized by a drop in systolic blood pressure of 50 mm Hg or greater without marked bradycardia. The mixed response includes both cardioinhibitory and vasodepressor components (see . Types of Carotid Sinus Hypersensitivity).