THE POSTURAL ORTHOSTATIC TACHYCARDIA SYNDROME - A NEUROCARDIOGENIC VARIANT IDENTIFIED DURING HEAD-UP TILT-TABLE TESTING

Head upright tilt table testing hers emerged as an accepted modality f or identifying an individual's predisposition to episodes of autonomic ally mediated hypotension and bradycardia that are sufficiently profou nd so that transient loss of consciousness ensues (neurocardiogenic sy ncope). However if has also become apparent that less dramatic falls i n blood pressure, while not sufficient to cause full syncope, may prod uce symptoms such as near syncope, vertigo, dizziness, and TTA-like ep isodes. We have identified a subgroup of individuals with a mild form of autonomic dysfunction with symptoms of postural tachycardia and lig htheadedness, disabling fatigue, exercise intolerance, dizziness, and near syncope. During baseline tilt table testing these patients demons trated a heart rate increase of greater than or equal to 30 beats/min (or a maximum heart rate of 120 beats/min) within the first 10 minutes upright (unassociated with profound hypotension), which reproduced th eir symptom complex. In addition these patients exhibit an exaggerated response to isoproterenol infusions. Similar observations have been m ade by others who have dubbed this entity the Postural Orthostatic Tac hycardia Syndrome (POTS). We conclude that POTS represents a mild (and potentially treatable) form of autonomic dysfunction that can be read ily diagnosed during head upright tilt table testing.