Objective: To investigate the value of hemodynamic changes during head-up tilt (HUT) test and predictive value thereof in evaluating the efficacy of metoprolol therapy in children with vasovagal syncope (VSS).
Methods: Twenty-six consecutive children with history of VSS diagnosed by head-up tilt (HUT) or sublingual nitroglycerin potentiated head-up tilt (SNHUT), who were treated with metoprolol for 6 approximately 12 months and followed up for (18 +/- 9) months (12 approximately 36 months), were divided into two groups according to effect of metoprolol: effective treatment group (n = 16, aged 12 +/- 2) without VSS recurrence during treatment and fellow-up, and futile treatment group (n = 10, aged 12 +/- 3). The heart rate changes during HUT or SNHUT were evaluated between the two groups.
Results: There were no significant differences between these 2 groups with regard to the demographic and clinical characteristics including age, gender, history, syncope spells, follow-up time and heart rate, mean blood pressure in supine position and during positive response. For example, the baseline heart rate of the effective treatment group was 81 +/- 12 beats/min, not significantly different from that of the futile treatment group (78 +/- 8 beats/min, P = 0.804). However, during tilt test 16 of the 26 patients in the effective treatment group showed tachycardia before positive response, with the mean heart rate of (123 +/- 15) beats/min, whereas all 10 patients in the futile group did not have tachycardia before positive response, with the mean heart rate of (96 +/- 17) beats/min. If an increase of 30 beats/min was taken as a borderline in heart rate during positive response in HUT compared with that of baseline value, in respect of predicting the metoprolol efficacy in the treatment of VVS, the sensitivity was 81% (13/16), the specificity was 80% (8/10), and the diagnostic value was 81% (21/26).
Conclusion: A marked increase in heart rate in HUT or SNHUT is a better predictor of metoprolol efficacy in the treatment of children with VVS.