[Estimation of autonomic nervous system tension in patients with syncope of unknown origin--traps in clinical interpretation results of heart rate variability]. / Ocena napiecia ukladu autonomicznego u chorych z omdleniami niewyjasnionego pochodzenia--pulapki klinicznej interpretacji wyników analizy zmiennosci rytmu serca.

UNLABELLED: Voluntary character of a choice of statistical methods weakens the reliability of the results of heart rate variability assessment and based on them clinical conclusions. The aim of the study was to estimate reliability of the chosen statistical methods of analysing changes in spectral components during tilt testing (TT). MATERIAL AND METHODS: 62 patients (34 women), the average age 38.8 +/- 12.8 years, with at least 2 syncopes during the last 6 months that had not been diagnosed by other examinations, were enrolled. The control group consisted of 44 age- and sex-matched volunteers (21 women), the average age 37.4 +/- 12.6 years, who had no history of syncope. All subjects underwent tilt testing according to Westminster protocol. If the result of a passive phase was negative, 0.25 mg nitroglycerine was applied sublingually and the examination was continued for the next 20 minutes. The type of syncopal reaction was defined according to VASIS classification (the vasovagal syncope international study). The evaluation of heart rate variability was based on the frequency domain methods. The low frequency (LF), the high frequency (HF) component and the balance (the LF/HF ratio) were estimated. The response of the autonomic nervous system (AUN) to tilting was evaluated by tests comparing mean values of respective components (the quantitative analysis) and by the modulation index (deltaXFm) reflecting, in percentage terms, changes in analyzed variable values. Taking into account the obtained results there was also a qualitative analysis performed. This analysis referred to the modulation index, which reflected increase or decrease in spectral component value. RESULTS: Tilt testing explained vasovagal origin of syncope in 35 (60%) patients with syncope. Patients were divided into 3 groups according to anamnesis data and results of tilt testing. Group I consisted of 42 healthy volunteers who had negative result of TT Group II--35 patients with history of syncopes and positive result of TT, and Group III--23 patients with history of syncopes and negative result of TT. In all study groups the quantitative analysis revealed the decrease in the LF and HF component values, whereas the evaluation of autonomic nervous system reactivity based on deltaXFm showed the increase in LF power, concomitant with strongly marked, nearly uniform decrease in HF power in Group I and II. The results obtained from the qualitative analysis did not reveal statistically significant differences between study groups in distribution of defined types of autonomic nervous system reactions. CONCLUSIONS: 1. The quantitative analysis has limited credibility in clinical interpretation of changes in autonomic nervous system activity (especially in the low frequency component--LF) occurring during tilt testing. 2. The best estimation of autonomic nervous system activity during tilt testing is assured by the modulation index supplemented by the preliminary selection of data, i.e., rejection of extreme values or those rarely occurring qualitative changes in spectral components.

[Usefulness of the tilt test with nitroglycerine application in diagnosing of patients with unexplained syncope: new aspects of the well-known problem]. / Przydatnosc testu pochyleniowego po podaniu nitrogliceryny w diagnozowaniu chorych z utratami przytomnosci niewyjasnionego pochodzenia--nowe spojrzenie na znany problem.

INTRODUCTION: The head-up tilt test (TT) performed after sublingual nitroglycerine application (NTG) is a tool that is commonly accepted and widely used in diagnosing patients with unexplained syncope. Although the results of conducted trials suggest advantages related to the protocol of TT with NTG, but data concerning the special diagnostic value of this protocol and the circumstances when it is superior to the passive TT, have not been established yet. The aim of the study was to analyse the problem whether there is, and if so, what circumstances it is related to, any special value of TT with NTG in diagnosing patients with vasovagal syncope. MATERIAL AND METHODS: 112 subjects were examined, 67 men and 45 women, at the mean age 34.4 +/- 19.1, and 42.6 +/- 17.4 years (p = 0.07), respectively, with at least two events of unexplained syncope. The control group consisted of 35 healthy volunteers matched for age and sex (18 men and 17 women), at the mean age 39.4 +/- 12.6 years (18-77 years) without syncope in anamnesis. All patients underwent a passive tilt test (Westminster protocol- 60 degrees/45 min) and in the case of lacking response to the passive test, the patients received 0.25 mg NTG and the test was continued over the next 20 minutes. The type of syncope reaction was determined based on the ACC classification (1996). If vasovagal syncope occurred, its type was defined according to the VASIS classification. RESULTS: The passive TT defined the reason of syncope in 31 patients (28% of all examined subjects), whereas TT with NTG increased this group by another 37 patients (33%), so that 68 patients (61%) were diagnosed using both protocols. The analysis of the study population that was sensitive to TT revealed that the group of patients who had vasovagal syncope during the test was greater than the group of patients who had other, i.e. non-vasovagal, type of reaction (48 vs 20, p = 0.002). There was a statistically significant relationship between the method of provocation and the type of reaction (chi 2 = 6.8, p = 0.009). The age difference between the groups of patients who developed vasovagal reaction during passive TT and patients who developed this type of reaction during TT with NTG (27.3 +/- 11.5 vs 39.9 +/- 20.3, p = 0.005) was also statistically significant. In the context of these results, concerning the mentioned groups of patients, the dichotomy division index of age was established: which was 30 and 50 years, respectively. A statistically significant relationship was found between the sex of the study population and the type of provocation (passive TT vs TT with NTG) resulting in syncope in sensitive patients (chi 2 = 2.84, p = 0.009). Fourteen (70%) women and only 23 (48%) men required NTG in order to establish the diagnosis, i.e. vasovagal background of syncope. CONCLUSIONS: 1. Vasovagal syncope seems to be a highly specific form of circulatory response to TT and requires application of NTG statistically more often than other types of neurocardiogenic reactions. 2. TT with NTG is especially justified in women and patients of either sex older than 50 years.

Value of propranolol-induced heart rate and blood pressure changes in predicting results of tilt testing.

BACKGROUND: A degree of reduction of heart rate (HR) and blood pressure (BP) values following beta-blocker administration has been shown to indicate beta-blockade effectiveness. Whether this parameter is also useful in the identification of patients with vaso-vagal syncope (VVS) who could benefit from beta-blocker therapy, has not yet been established. AIM: To analyse the usefulness of propranolol-induced acute changes in HR and BP in the prediction of the results of tilt testing (TT) in patients with VVS. METHODS: The study group consisted of 37 patients with a history of at least two syncopal episodes in the past 6 months, in whom syncope was reproduced during TT. After positive baseline TT the patients were returned to supine position and were given intravenous propranolol. After 15 min supine rest the patients were tilted again using the same protocol as during the baseline test. Propranolol was considered effective when the result of the second (on drug) TT was negative or the time to syncope occurrence was longer than during baseline TT. During the whole procedure systolic BP (SBP), mean BP (MBP), diastolic BP (DBP) and HR were measured. These parameters were analysed in four different time-intervals: period I - between 13th and 15th minute of supine rest preceding the passive phase of TT, period II - between first and third minute of the passive TT, period III - following propranolol injection, between 13th and 15th minute of supine rest preceding second TT, and period IV - between first and third minute of second TT, either passive (if positive) or after NTG administration. Both, mean values and differences (Delta) in analysed parameters between various time-intervals (II-I, III-I, IV-II and IV-III) were taken into account. RESULTS: Intravenous propranolol occurred effective in preventing syncope during second TT in 29/37 (78%) patients. The DeltaSBP, DeltaMBP and DeltaDBP values calculated from periods III and IV were significantly different between patients with or without protective effects of propranolol. The cut-off values which were computed to obtain the highest value of total predictive accuracy (the highest value of the sum of sensitivity and specificity) were -5 mmHg for DeltaSBP, -4 mmHg for DeltaMBP and -2 mmHg for DeltaDBP. A stepwise logistic regression analysis revealed that DeltaSBP of -5 mmHg or less had the highest value in the prediction of a positive response to propranolol, reaching a sensitivity of 72%, specificity of 88%, positive predictive value of 95% and negative predictive value of 48%. CONCLUSIONS: Propranolol-induced changes in blood pressure values may predict the effectiveness of beta-blockade in preventing syncope during second TT performed after intravenous infusion of propranolol. A drug-induced reduction in systolic blood pressure of less than 5 mmHg may identify those who will benefit from beta-blocker therapy.

Heart rate variability during head-up tilt test in patients with syncope of unknown origin.

BACKGROUND: Analysis of pathophysiological mechanisms responsible for vaso-vagal reaction reveals a close relationship between neurocardiogenic syncope and the preceding abnormalities of autonomic nervous system (ANS). Therefore, the interest in the assessment of heart rate variability (HRV) for detecting and establishing therapy in patients with syncope due to vaso-vagal mechanism is not surprising. AIM: To assess ANS changes during tilt testing in patients with syncope of unknown origin. METHODS: Forty patients (18 males, mean age 34.8+/-15.8 years) with a history of at least two syncopal episodes during the last 6 months and 24 healthy controls underwent tilt testing. Spectral HRV analysis was performed from ECG recorded 5 min before tilting (period A), 5 min after tilting (period B), and 5 min before syncope (or 20-25 min of tilt test when syncope did not occur) (period C). RESULTS: Tilt test was positive in 23 (58%) patients; 12 (30%) had mixed response, 10 (25%) - vasodepressive, and 1 (3%) - cardioinhibitory reaction. The mean time from tilt to syncope was 22.3 minutes. One (4%) control subject developed syncope. In all groups a decrease of LF and HF power, as well as an increase in the LF/HF ratio in response to tilting were observed. The LF/HF values were significantly different between patients with mixed vaso-vagal reaction and controls (1.9 vs 4.2; p=0.04). In the C-B periods the highest decrease in the HF spectra was found in patients with mixed reaction and was significantly greater than in other patients or controls. Also, patients with mixed reaction had the highest increase in LF values which was significantly more pronounced than in patients with vasodepressive reaction (10139.3 vs 466.9; p=0.003). As a result, the change in LF/HF ratio was positive in patients with mixed reaction, controls and patients with negative result of tilt test, and negative - in patients with vaso-depressive syncope, reaching statistical significance between patients with mixed and vaso-depressive response (2.04 vs -0.51; p=0.03). CONCLUSIONS: The pattern of HRV changes during tilt testing depends on the type of vaso-vagal reaction which leads to syncope. The most accurate HRV parameter for identification of patients with reflex syncope is the LF/HF ratio.