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

Wieling W, Krediet CTP, Solari D, De Lange FJ, van Dijk N, Thijs RD, van Dijk JG, Brignole M, Jardine DL (Academic Medical Centre, University of Amsterdam, the Netherlands; Arrhythmologic Centre, Ospedali del Tigullio, Lavagna, Italy; Academic Medical Centre, University of Amsterdam, the Netherlands; Academic Medical Centre, University of Amsterdam, the Netherlands; SEIN-Epilepsy Institute of the Netherlands Foundation, Heemstede, the Netherlands; Leiden University Medical Centre, Leiden, the Netherlands; Christchurch Hospital, University of Otago, Christchurch, New Zealand). At the heart of the arterial baroreflex: a physiological basis for a new classification of carotid sinus hypersensitivity. (Review). J Intern Med 2013; 273: 345-358. 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.