Neurocardiogenic syncope is also referred to as vasovagal, vasodepressor, neurally mediated, and reflex syncope. As the name implies, neurocardiogenic syncope involves the interaction of various autonomic nervous system reflexes, the central nervous system, and the cardiovascular system..sup.1,4,12-14 The Bezold-Harisch reflex is cited as the mechanism responsible for vasovagal syncope and has two components. There is "cardio-inhibitory syncope" due to a vagal (parasympathetic) mediated reflex causing bradycardia or even asystole, plus "vasodepressor syncope" from withdrawal of sympathetic input leading to a drop in PVR with venous pooling in the periphery leading to hypotension.
Vasovagal syncope can occur in heart transplant patients, suggesting that the Bezold-Harisch reflex or vagal stimulation plus sympathetic withdrawal as the only factor may be a somewhat simplistic explanation, and that other variables may also play a role.
Although there are many causes of cardiovascular syncope, the final common mechanism is a decrease in cardiac output causing a decrease in cerebral perfusion.
Orthostatic syncope can occur after a spinal cord injury or sympathectomy, which eliminates
the vasopressor reflexes, and in patients on certain medications, commonly antihypertensive and
vasodilator drugs.
http://www.thefreelibrary.com/Syncope+in+Pediatric+Patients-a0217945432
