New classification of haemodynamics of vasovagal syncope: beyond the VASISclassification - Analysis of the pre-syncopal phase of the tilt test without and with nitroglycerin challenge

We believe that the pattern of blood pressure response to tilt during the t ime preceding the development of the vasovagal reaction may provide adjunct ive diagnostic information. A group of 101 consecutive patients affected by syncope of uncertain origin underwent passive tilt testing for 45 min at 6 0 degrees followed. if negative, by oral (sublingual) trinitroglycerin (TNC ) 0.4 mu g with continuation of the test for 20 min. Three main patterns we re observed: the classic (vasovagal) syncope pattern was observed in 36 pat ients who, during the preparatory phase, had a rapid and full compensatory reflex adaptation to upright position, resulting in stabilization of their blood pressure values until abrupt onset of the vasovagal reaction; the dys autonomic (vasovagal) syncope pattern was observed in 47 patients in whom s teady-state adaptation to upright position was not possible. There was thus a progressive fall in their blood pressure until the occurrence of a typic al vasovagal reaction; the orthostatic intolerance pattern was observed in 18 patients in whom there was a progressive fail in blood pressure, similar to that of the dysautonomic group, but this was not followed by a clear va sovagal reaction. Compared with the classic, the dysautonomic patients were older, had a higher prevalence of co-morbidities, a very much shorter hist ory of syncopal episodes, and a prevalence of mixed and vasodepressor forms of the VASIS classification. The patients with orthostatic intolerance had clinical characteristics similar to the dysautonmic group but they could n ot be classified according to the VASIS classification. In conclusion, in p atients with syncope, a variety of abnormal responses is observed during ti lt testing, suggesting that different syndromes can be diagnosed by the tes t. A more detailed, although still arbitrary, classification may form the b asis of a number of future drug and pacemaker trials, as well as help towar ds a greater understanding of the different mechanisms of tilt-induced sync ope. (C) 2000 The European Society of Cardiology.