Haemodynamic indices of the early phase of the tilt test: does measurement predict outcome?

ABSTRACT

INTRODUCTION: Tilt testing (TT) is a well-established tool in the diagnosis of syncope. However, it is time-consuming. Therefore, identification of parameters that could shorten the duration of TT is desirable. AIM: To identify and assess the usefulness of early haemodynamic parameter changes in prediction of the tilt test results in a group of patients with syncope of unknown aetiology. METHODS: The study involved a group of 105 patients, including 61 women and 44 men, with a mean age of 34.2+/-13.7 (from 13 to 82) years, with at least two episodes of syncope in the last 6 months. The head-up tilt test was carried out according to protocol 60/20 min and if necessary was continued after administration of sublingual nitroglycerine in a dose of 250 g. The assessment of haemodynamic indices was performed employing the beat-to-beat method using the Portapres M2 device. Systolic (SBP) and diastolic (DBP) arterial pressure, heart rate (HR), cardiac output (CO) and stroke volume (SV), and total peripheral vascular resistance (TPR) were analysed. The measured values of haemodynamic indices were calculated by means of averaging 10-second intervals within 3-minute studied periods either before or after tilting a patient. Mean baroreceptor sensitivity (BRS) for the same 3-minute-long intervals was evaluated using the xBRS (cross-correlation) method. In the analysis, differences (Rx) of the haemodynamic values between the beginning of tilting a patient and the rest period were also calculated. RESULTS: Loss of consciousness was noted in 47 (46%) of the studied patients - group I. The remaining subjects (58 patients, 54%) did not develop syncope during TT (group II). The univariate and multivariate logistic analyses of regression revealed that the mean vascular resistance difference (meanRTPR) <-10 dyn.s/cm8 was an independent risk factor of syncope (chi2=3.4; p<0.0008). The presence of this risk factor was associated with a significantly higher risk of a positive response during the tilt test (65% vs 39%; RR 1.7, 95% CI 1.2-3.2). In predicting a positive TT result, sensitivity of this parameter was 65%, specificity was 61% and the prognostic value of the positive and negative result was 32% and 86%, respectively. CONCLUSIONS: In patients with syncope of unknown origin, an early (within first 3 minutes of TT) asymptomatic fall in total peripheral vascular resistance is a significant predictor of a positive final result of the test.