Abstract
BackgroundPostural tachycardia syndrome (POTS) is a heterogeneous disorder that creates challenges for treatment. Beta-blocker was one of the most commonly used drugs, but it is inconsistently effective. The purpose of this study is to explore whether orthostatic plasma norepinephrine level could be an indicator of therapeutic effectiveness of metoprolol for POTS in children.MethodsTwenty-seven children with POTS were enrolled in our study. They received metoprolol treatment, and their orthostatic plasma norepinephrine levels were measured by high-performance liquid chromatography method. Three months after rmetoprolol treatment, 25 patients were followed up. A receiver-operating characteristic (ROC) curve was used to explore the predictive value of orthostatic plasma norepinephrine level.ResultsThe symptom severity and increment of heat rate from supine position to upright of patients positively correlated with their orthostatic plasma norepinephrine level (r = 0.599, P < 0.001; r = 0.633, P <0.001, respectively). Orthostatic plasma norepinephrine level in responders to metoprolol was significantly higher than that of nonresponders (P = 0.028). A ROC curve on the predictive value of orthostatic plasma norepinephrine level showed that the area under the curve was 0.785. Using a cutoff value for orthostatic plasma norepinephrine level of 3.59 pg/ml yielded both sensitivity (76.9%) and specificity (91.7%) in predicting the efficacy of metoprolol therapy for POTS.ConclusionOrthostatic plasma norepinephrine level of > 3.59 pg/ml was an indicator of the effectiveness of metoprolol therapy for POTS in children and adolescents.
Highlights
Postural tachycardia syndrome (POTS) is a heterogeneous disorder that creates challenges for treatment
Our findings showed a clear association between the orthostatic plasma norepinephrine level and symptom severity in patients with POTS
We found that the effectiveness of metoprolol in POTS children was related to the level of orthostatic plasma norepinephrine
Summary
Postural tachycardia syndrome (POTS) is a heterogeneous disorder that creates challenges for treatment. Postural tachycardia syndrome (POTS) is a heterogeneous disorder characterized by sustained tachycardia (≥30 bpm in adults and ≥40 bpm in children) upon standing, and relief of these symptoms with recumbence. Β-blockers have been reported to improve symptoms in case reports and open-label studies [6,7,8,9,10]. It is inconsistently effective [11,12]. Differences in noradrenergic activity between hyperadrenergic and other types of POTS may explain this inconsistency, and previous studies of efficacy of β-blockers in POTS subjects did not stratify participants into POTS subtypes according to their underlying causes.
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