Additional Autonomic Tests

The physiology of postural tachycardia syndrome or PoTS is complex and is poorly understood. The magnitude of tachycardia depends on natural and normal compensatory requirement in response to orthostatic challenges. Other contributions come from the inotropic function of the heart, windkessel vascular resistance and venous vascular capacitance. It would be desirable to quantify all of these four contributions during clinical investigation of PoTS. Laboratory standardised surrogate measures of all the four cardiovascular compensatory factors and their autonomic controls are now available. Some are described here as autonomic target-organs neurophysiological tests and may be offered as an adjunct to active stand/tilt testing in some centres in order to better define PoTS phenotypes/subgroups. In addition, other forms of autonomic testing as undertaken in the National Hospital for Neurology & Neurosurgery tertiary centre are also described in chapter “ A Tertiary Referral Centre for PoTS: The Autonomic Unit at the National Hospital for Neurology and Neurosurgery Experience”.