Comparison between subgroups
In univariate analysis (Table 2 ), TT positivity was higher
among younger syncope patients <30 years, in patients with
lower SBP defined as baseline SBP below the mean value of 128 mmHg, in
patients with lower HR defined as baseline HR value below the mean value
of 69 bpm, and in patients without history of hypertension. In
multivariable-adjusted logistic regression model (Table 2 ),
younger age, lower blood pressure and heart rate, and absence of
hypertension remained the independent predictors of test positivity. In
particular, in the quantitative analysis, positive response to TT was
predicted by younger age (Odds ratio [per 10 years], OR: 1.04; 95%
confidence interval (CI), 1.01-1.07, p=0.007), lower SBP (OR [per 10
mmHg]: 1.05, 95%CI, 1.01-1.08; p=0.006), and lower heart rate (OR
[per 10 bpm]: 1.17; 95%CI, 1.11-1.22, p<0.001). Absence
of hypertension diagnosis increased the probability of positive TT by
over 50% (OR: 1.58; 95%CI, 1.38-1.81, p<0.001). Exclusion of
one database did not substantially affect the overall results except for
the impact of low SBP on TT positivity, which was attenuated after
exclusion of Lavagna data in the multivariable-adjusted (but not in
univariate) logistic regression model (p=0.083).
Table 2 . Univariable and multivariable analysis of factors
predicting tilt test positivity in patients investigated for unexplained
syncope using the Italian tilt test protocol.