Twenty-four-hour urine NE level as a predictor of the therapeutic response to metoprolol in children with recurrent vasovagal syncope.

Background: Vasovagal syncope (VVS) is a heterogeneous disorder that creates challenges for treatment. Metoprolol is an important therapeutic option for children with VVS.

Aims: The study examined the predictive value of 24-h urine norepinephrine (NE) levels in the assessment of the therapeutic efficacy of metoprolol for recurrent VVS in children.

Methods: Thirty-eight children with recurrent VVS and 20 healthy children were enrolled in our study. Twenty-four-hour urine NE levels were measured by LC-MS-MS. VVS children were diagnosed by BHUTT and/or SNHUTT, and received metoprolol treatment for 3 months. Symptom scoring was utilized to evaluate the therapeutic effect. A ROC curve was used to investigate the predictive value of 24-h urine norepinephrine levels.

Results: There exists significant correlation between 24-h urine NE levels and supine systolic and diastolic blood pressures. The 24-h urine NE levels of responders (40.75 ± 12.86 μg/24 h) were higher than those of nonresponders (21.48 ± 6.49 μg/24 h), and there was a significant difference between the two groups (P < 0.001). A ROC curve of the predictive value of 24 h urine NE levels revealed that the area under the curve was 0.926. A cutoff value for 24-h urine NE level of 34.84 μg/24 h produced both high sensitivity (70%) and specificity (100%) in predicting the efficacy of metoprolol therapy for VVS.

Conclusions: Patients with high 24-h urine NE levels have higher supine systolic and diastolic pressures and more effective responses to metoprolol. A 24-h urine norepinephrine level of > 34.84 μg/24 h was an indicator of the effectiveness of metoprolol therapy for VVS in children.