Background: The direction of changes in hemodynamic parameters during the tilt test (TT) nin individuals with history of vasovagal syncope (VVS) is a subject of discussion.
Objective: to study changes of volume-impedance hemodynamic indicators in the process of tilt test in somatically healthy young men with history of VVS.
Materials and methods: A total of 102 men aged 18-30 years were divided into 4 groups, taking into account the specific features of fainting history and response to TT. Persons of group 1 (n=14) had history of VVS and positive response to TT (syncope). Subjects of group 2 (n=14) had history of VVS and a pattern of postural tachycardia without fainting during TT. Persons of group 3 (n=42) had history of VVS and negative response to TT. Subjects of group 4 (n=32) had no history of VVS and negative response to TT. During TT, we studied dynamics of some indicators, including cardiac output (CO) and total peripheral vascular resistance (TPVR).
Results: In individuals of all groups in the initial horizontal phase of TT values of CO and TPVR corresponded to the norm. Subjects of group 1 had significantly lower CO compared with subjects of groups 2, 3, 4 (p<0.05, p<0.01, p<0.05, respectively). Values of TPVR in subjects of group 1 were significantly higher than in subjects of groups 2, 3, 4 (p<0.05; p<0.05; p<0.05, respectively). In response to orthostasis CO values increased in groups 1, 2, 4 (by 18%, 10%, 5%, respectively) and did not change in group 3; TPVR values decreased in groups 1, 2 (by 8%, 0.5%, respectively), and increased in groups 3, 4 (by 8%, 4% respectively). In the final horizontal phase of TT, CO values in group 1 were significantly lower than in groups 3, 4 (p<0.05), while TPVR values did not significantly differ between all groups (p>0.05).
Conclusions: In tilt-positive and tilt-negative subjects with history of VVS, standardized postural stress leads to unidirectional changes in cardiac output, but to multidirectional changes in total peripheral vascular resistance.