Clinical signs and haemodynamic patterns before and during head-up tilt-evoked NMS

Background: The links between circulatory pathophysiology and clinical expressions of reflex syncope are imperfectly known. Aim: To improve knowledge of these links. Methods: By adding video-EEG recording to tilt-table-testing (TTT) we recorded clinical, circulatory and EEG changes at a one-second resolution. Results: We explored 69 cases with complete records of tilt-induced syncope. The two EEG patterns, slow (S) or slow-flat-slow (SFS), represented moderate and profound cerebral hypoperfusion. The S and SFS patterns are associated with four types of signs and symptoms. One starts and ends during slowing, e.g. loss of consciousness (LOC). One occurs during slowing only, implicating some degree of cortical activity, such as myoclonic jerks. One occurs during flattening only, such as roving eye movements and stertorous breathing. Finally, one occurred regardless of the EEG phase. Although the SFS pattern has been associated with asystole it could occur without asystole, without an appreciably lower mean arterial pressure (MAP) than when it did not. The point in time when pacemakers conventionally start, three seconds since the last heart beat, were compared with the timing of clinical LOC. In 6 of 22 asystolic cases without nitroglycerin, asystole occurred after LOC (27%). Conclusions: Some clinical signs help identify severe hypoperfusion due to arrhythmia or cardioinhibitory reflex syncope. Unidentified factors other than MAP and heart rate must influence the degree of cerebral hypoperfusion. The time of asystole must be compared to that of LOC when decisions are made concerning pacing in reflex syncope.