[Estimation of head-up tilt test in diagnosis of syncope of unknown origin. Can we come up with better results?].Pol Arch Med Wewn. 2002 Jul; 108(1):639-46.PA
Optimal conditions in assessment of diagnostic head-up tilt test (TT) value required classification, which identified reactions with syncope and discreet disturbance of consciousness. The aim of the study was to assess of usefulness TT in diagnosis of syncope of unknown origin investigated by classification, which take into consideration vasovagal and nonvasovagal types of neurocardiogenic reactions. We studied 218 pts (115M, 103F), mean age 39.7 +/- 16.1 and 35.2 +/- 17.7 years (adequately for male and female), with 2 or more syncope on unknown origin in last 6 months. Control group was 84 healthy volunteers (43M, 41F), mean age 37.41 +/- 2.6 years, range 18 to 73 years, with no syncope in anamnesis. All patients and controls underwent a TT in Westminster protocol. In case of negative TT, we performed next 20 min TT with 0.25 mg NTG sublinqualis (TT with NTG). Type of vasovagal syncope was defined according to American Experts Classification described in official guidelines of American College of Cardiology (ACC). In the case of vasovagal syncope, detailed specification of syncope was performed according to VASIS classification (the vasovagal Syncope International Study). Passive TT was positive in 51 (23%) pts. In control group passive TT was positive in 6 (7%) pts. TT with NTG generates syncope in additional 99 (45%) pts resulting in number of diagnosed group to 150 (68%) pts. In control group TT with NTG was positive in additional 21 (25%) pts. False positive TT with NTG was diagnosed in 19 (9%) pts in study group and 11 (13%) in control group. Subpopulation of study group with vasovagal syncope was larger than subpopulation with other, nonvasovagal type of reaction (108 vs. 23; p < 0.0001). Taking into consideration this dual types of reaction (vaso- and nonvasovagal) allowed to reveal that there were no statistical significance between sex, age, type of syncope provocation and defined types of vasovagal reactions. ACC classification in comparison to VASIS criteria, was more sensitive (60% vs. 49%), have better diagnostic value to positive (89% vs. 84%) and negative (44% vs. 39%) result of TT and accuracy of diagnosis (66% vs. 47%) with slightly worse specificity of TT (81% vs. 83%).
1. TT results assessment according to ACC classification is more sensitive and almost the same specificity method in diagnosing patients with syncope of unknown origin than VASIS classification. 2. Improvement in diagnostic values of TT concerns passive TT and NTG TT. 3. Nonvasovagal types of reaction of cardiovascular system to orthostatic stress defined in ACC classification are, as the symptomatically syncope, significant clinical indicator of vegetative system instability.