Mechanisms of heart rate and arterial blood pressure control: implications for the pathophysiology of neurocardiogenic syncope

Neurocardiogenic syncope is a general term that describes syncope resulting from altered autonomic activity, as manifested by abnormal regulation of peripheral vascular resistance and heart rate. Although there has been great interest in the contribution of heart rate to this form of syncope, the peripheral circulation plays the dominant role in the induction of neurocardiogenic syncope in most patients. We review in this brief article the physiology of cardiovascular reflexes, which are important for short-term arterial pressure control, and their potential contribution to the pathophysiology of neurocardiogenic syncope. This type of syncope represents a profound failure of the normal mechanisms for short-term regulation of arterial pressure. Any therapeutic strategies for the management of neurocardiogenic syncope must deal with alterations in vascular control, which contribute to its pathogenesis.