Abstract
PurposeTo improve the metoprolol therapeutic effectiveness, we aimed to explore whether baseline heart rate variability (HRV) indicators before metoprolol treatment were useful for predicting its efficacy for postural tachycardia syndrome (POTS).MethodsWe recruited 45 children with POTS who received metoprolol and 17 healthy controls. All children underwent a standing test or basic head-up tilt test and 24-h dynamic electrocardiography before treatment. After 3 months of metoprolol, therapeutic responsiveness was evaluated. The usefulness of baseline HRV parameters in predicting the effectiveness of metoprolol was studied and the long-term cumulative symptom rate was analyzed.ResultsThe baseline HRV frequency domain indicators for power, ultra-low frequency, very-low frequency, low frequency (LF), high frequency (HF), and total power (TP) as well as time domain indicators were significantly lower for responders than non-responders to metoprolol; however, low-frequency normalized units and LF/HF ratio were markedly greater for responders than non-responders. On series-parallel analysis, combined baseline triangular (TR) index ≤ 33.7 and standard deviation of all normal-to-normal intervals (SDNN) index ≤ 79.0 ms as cut-off values yielded sensitivity, specificity and accuracy of 85.3, 81.8, and 84.4%, respectively, to predict therapeutic responsiveness to metoprolol. On long-term follow-up, the cumulative symptom rate was significantly higher with TR index > 33.7 and SDNN index ≤ 79.0 ms, TR index ≤ 33.7 and SDNN index > 79.0 ms or TR index > 33.7 and SDNN index > 79.0 ms than TR index ≤ 33.7 and SDNN index ≤ 79.0 ms (P < 0.05).ConclusionCombined TR index ≤ 33.7 and SDNN index ≤ 79.0 ms were useful preliminary measures to predict therapeutic response to metoprolol in pediatric POTS.
Highlights
Postural tachycardia syndrome (POTS) is a common type of orthostatic intolerance (OI) and is characterized by excessive increase in heart rate (HR) when standing upright (Fedorowski et al, 2017)
To improve the metoprolol therapeutic effectiveness, we aimed to explore whether baseline heart rate variability (HRV) indicators before metoprolol treatment were useful for predicting its efficacy for postural tachycardia syndrome (POTS)
The baseline HRV frequency domain indicators for power, ultra-low frequency, very-low frequency, low frequency (LF), high frequency (HF), and total power (TP) as well as time domain indicators were significantly lower for responders than non-responders to metoprolol; low-frequency normalized units and LF to HF (LF/HF) ratio were markedly greater for responders than non-responders
Summary
Postural tachycardia syndrome (POTS) is a common type of orthostatic intolerance (OI) and is characterized by excessive increase in heart rate (HR) when standing upright (Fedorowski et al, 2017). POTS is accompanied by symptoms of OI (Fedorowski, 2019) and results in serious physical and psychological problems in children (Bagai et al, 2011; Kizilbash et al, 2014). A beta-adrenoceptor blocker (β-blocker) is commonly used for treating POTS in children (Kernan and Tobias, 2010; Bryarly et al, 2019). It inhibits sympathetic nerve modulation, reducing HR and the stimulation of cardiac baroreceptors, blocking the action of increased catecholamine levels in circulation. Previous studies showed that β-blockers could improve symptoms only in some children with POTS (Lai et al, 2009; Chen et al, 2011). Predicting the therapeutic effect of the β-blocker metoprolol on POTS before treatment is of great clinical importance to improve the effectiveness of the therapy
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