“…The aim of our study was to identify the best early noninvasive hemodynamic predictor of nitroglycerin-potentiated HUTT outcome in healthy patients with recurrent unexplained syncope. Clinical and experimental previous studies evaluated many parameters as possible predictors of positive HUTT response, such as clinical characteristics of the patients, 23,24 HR, 25,26 HR variability, [27][28][29][30][31] BP oscillations, 32 HR/BP ratio, 33 and other hemodynamic changes during the test [34][35][36] ; however, none of them is routinely used in the clinical evaluation of patients with recurrent unexplained syncope. Fucà et al, 37 by examining during HUTT the noninvasive hemodynamic parameters of 63 healthy patients with history of syncope, showed SV and CO decrease and TPR increase, two minutes after the nitroglycerin administration, among the groups of study patients with recurrent unexplained syncope (subjects with a history of syncope and positive passive TT, subjects with a history of syncope and TT positive after nitroglycerin, subjects with a history of syncope and negative TT); however, the percent changes in the hemodynamic variables did not show significant differences among the groups.…”