Electrocardiography-Derived Predictors for Therapeutic Response to Treatment in Children with Postural Tachycardia Syndrome

Acceleration index predicts efficacy of orthostatic training on postural orthostatic tachycardia syndrome in children

The objective of this study was to examine the utility of the acceleration index observed in an electrocardiogram (ECG) for the prediction of the effectiveness of orthostatic training in pediatric patients diagnosed with postural orthostatic tachycardia syndrome (POTS). This investigation focused on children diagnosed with POTS and undergoing orthostatic training at the Department of Pediatrics of Peking University First Hospital from January 2012 to October 2022. Specifically, patients hospitalized from January 2012 to December 2019 were included in the training set (54 cases), while those hospitalized from January 2020 to October 2022 were included in the external validation set (37 cases). All children received a 3-month orthostatic training, and the baseline symptom score (SS) was calculated in agreement with the pretreatment orthostatic intolerance symptom frequency. Additionally, we determined post-treatment SS during follow-up via telephone after the 3-month treatment. Children with a decrease in post-treatment SS by ≥ 50% of the baseline were considered as responders; otherwise, they were considered as non-responders. Demographic data (age, sex, and body mass index), hemodynamic parameters (supine blood pressure, time to achieve a positive standing test, maximum increase in heart rate during the standing test, maximal heart rate reached during the standing test, and blood pressure at the point of maximal heart rate during the standing test), and electrocardiographic parameters (RR interval in the supine position, shortest RR interval in the upright position, and acceleration index) were collected from all the children prior to treatment. Univariate and multivariate regression analysis were conducted to investigate factors associated with the efficacy of orthostatic training. The predictive value of these indicators for the therapeutic effectiveness of orthostatic training in children with POTS was evaluated using receiver operating characteristic (ROC) analysis, and the indicators were validated using the validation set. Among the 54 children in the training set, 28 responded to orthostatic training, and 26 were nonresponsive. Compared with the non-responders, the responders demonstrated a significant reduction in acceleration index (P < 0.01). The ROC curve for the predictive value of the acceleration index exhibited an area under the curve = 0.81 (95% confidence interval: 0.685-0.926). With the acceleration index threshold < 27.93%, the sensitivity and specificity in the prediction of orthostatic training efficacy among children with POTS were 85.7% and 69.2%, respectively. The external validation results demonstrated that using acceleration index < 27.93% as the threshold, the sensitivity, specificity, and accuracy of predicting orthostatic training efficacy among children with POTS were 89.5%, 77.8%, and 83.8%, respectively.

CONCLUSIONS

Electrocardiographic acceleration index can be used to predict the effectiveness of orthostatic training in treating children with POTS.

WHAT IS KNOWN

• Postural orthostatic tachycardia syndrome (POTS) is a chronic orthostatic intolerance involving multiple mechanisms. Autonomic dysfunction is one of the main mechanisms of POTS in children and could be treated with orthostatic training. • In order to improve the efficacy of orthostatic training in children with POTS, it is particularly important to identify the patients with autonomic dysfunction as the main mechanism before the treatment.

WHAT IS NEW

• We found acceleration index of the electrocardiogram (ECG) can be used as a satisfactory index to predict the efficacy of orthostatic training in the treatment of POTS in children. • Using the acceleration index to predict the efficacy of orthostatic training on POTS in children is easy to be popularized in hospitals at all levels because it is non-invasive, convenient, and not expensive.

Research progress on the predictive value of electrocardiographic indicators in the diagnosis and prognosis of children with vasovagal syncope

Neurally mediated syncope (NMS) is a common type of syncope in children in clinical practice, among which vasovagal syncope (VVS) is the most frequent. In recent years, more and more studies have been carried out to assess the diagnosis and prognosis of VVS. The electrocardiographic indicators such as heart rate variability (HRV), QT dispersion (QTd), P-wave dispersion (Pd), ventricular late potentials (VLP), deceleration ability of heart rate (DC), etc., are easy to obtain and inexpensive. With the help of electrocardiographic indicators, the diagnostic procedure and individualized treatment strategies of pediatric VVS can be optimized. This article reviews the value of electrocardiographic indicators in the diagnosis and prognosis of children with VVS.

Pediatric Postural Orthostatic Tachycardia Syndrome: Where We Stand

Postural orthostatic tachycardia syndrome (POTS), first described in 1992, remains an enigmatic, yet severely and variably debilitating, disorder. The pathophysiology of this syndrome is still not understood, and there remains no biomarker indicating the presence of POTS. Although research interest has increased in recent years, there are relatively fewer clinical and research studies addressing POTS in children and adolescents compared with adults. Yet, adolescence is when a large number of cases of POTS begin, even among adult patients who are subsequently studied. This article summarizes reported research in POTS, specifically in pediatric patients, including discussion of aspects of diagnostic criteria, risk factors and outcomes, neurohormonal and hemodynamic abnormalities, clinical assessment, and treatment. The goals of this review are increased recognition and acknowledgment of POTS among pediatric and adolescent providers, as well as to provide an understanding of reported abnormalities of homeostasis, such that symptomatic patients will be able to be recognized and appropriately managed, enabling them to return to their activities of daily living.

Biomarkers and Hemodynamic Parameters in the Diagnosis and Treatment of Children with Postural Tachycardia Syndrome and Vasovagal Syncope

In children, vasovagal syncope and postural tachycardia syndrome constitute the major types of orthostatic intolerance. The clinical characteristics of postural tachycardia syndrome and vasovagal syncope are similar but their treatments differ. Therefore, their differential diagnosis is important to guide the correct treatment. Therapeutic methods vary in patients with the same diagnosis because of different pathomechanisms. Hence, in patients with vasovagal syncope or postural tachycardia syndrome, routine treatments have an unsatisfactory efficacy. However, biomarkers could increase the therapeutic efficacy significantly, allowing for an accurate and detailed assessment of patients and leading to improved therapeutic effects. In the present review, we aimed to summarize the current state of research into biomarkers for distinguishing the diagnosis of pediatric vasovagal syncope from that of postural tachycardia syndrome. We also discuss the biomarkers that predict treatment outcomes during personalized therapy for each subtype.

Baseline Corrected QT Interval Dispersion Is Useful to Predict Effectiveness of Metoprolol on Pediatric Postural Tachycardia Syndrome

OBJECTIVES

The study was designed to explore the role of baseline-corrected QT interval dispersion (QTcd) in predicting the effectiveness of metoprolol on pediatric postural tachycardia syndrome (POTS).

METHODS

There were two groups in the study, the discovery group and the validation group. The children with POTS in the discovery group were treated with oral metoprolol, with the completed necessary medical records, head-up tilt test (HUTT), blood chemistry, and 12-lead ECG before treatment at the pediatrics of Peking University First Hospital, China. According to whether the symptom score (SS) was reduced by more than 2 points after administration with oral metoprolol as compared with that before treatment, the children with POTS were separated into responders and non-responders. The demographic characteristics, hemodynamic indicators, and the QTcd of the two groups were compared, and the estimate of the baseline QTcd in predicting the treatment response to metoprolol was tested through a receiver operating characteristic (ROC) analysis. Other 24 children suffering from POTS who were, administrated with metoprolol at the pediatrics of Peking University First Hospital were included in the validation group. The sensitivity, specificity, and accuracy of the baseline QTcd in the prediction of the effectiveness of metoprolol on POTS were validated in children.

RESULTS

The pre-treatment baseline QTcd in responders treated with metoprolol was longer than that of the non-responders in the discovery group [(66.3 ± 20.3) ms vs. (45.7 ± 19.9) ms, p = 0.001]. The baseline QTcd was negatively correlated with SS after metoprolol treatment (r = -0.406, p = 0.003). The cut-off value of baseline QTcd for the prediction of the effectiveness of metoprolol on pediatric POTS was 47.9 ms, yielding a sensitivity of 78.9% and a specificity of 83.3%, respectively. The validation group showed that the sensitivity, specificity, and accuracy of the baseline QTcd ≥ 47.9 ms before treatment for estimating the effectiveness of metoprolol on POTS in children were 73.7, 80.0, and 75.0%, respectively.

CONCLUSION

Baseline QTcd is effective for predicting the effectiveness of metoprolol on pediatric POTS.

Predictive Value of Heart Rate and Blood Pressure on the Prognosis of Postural Tachycardia Syndrome in Children

BACKGROUND

To investigate the predictive value of heart rate (HR) and blood pressure (BP) on the prognosis of postural tachycardia syndrome (POTS) in children.

MATERIALS AND METHODS

53 cases of children aged 5 to 15 years who visited in the Pediatric Syncope Specialist Clinic of The Second Xiangya Hospital of Central South University for unexplained syncope or syncope precursor were diagnosed with POTS by head-up tilt test (HUTT) as the POTS group. 38 healthy children aged 5 to 16 years who underwent physical examination at the Child Health Care Clinic of the hospital in the same period were matched as controls (control group). The children with POTS were followed up after 3 months of treatment and were divided into good prognosis group (40 cases) and poor prognosis group (13 cases) according to the results of HUTT re-examination and whether the symptoms improved or not. HR and BP indicators were collected from each group at baseline and during HUTT.

RESULTS

There were 91 research subjects, of which 45 are males, with a mean age of 11.52 ± 2.13 years. (1) HR at 5 and 10 min (HR 5 and HR 10, respectively), HR difference at 5 and 10 min (HRD 5 and HRD 10, respectively), and HR and BP product at 5 and 10 min (RPP 5 and RPP 10, respectively) were greater in the POTS group than in the control group (P < 0.01). (2) HR 5, HR 10, HRD 5, HRD 10, and RPP 10 in children with POTS were smaller in the good prognosis group than the poor prognosis group (P < 0.01). (3) The area under curve was 0.925 on the four combined indicators (HR 5, HR 10, HRD 5, and HRD 10), predicting a good prognosis of POTS, sensitivity of 99.99%, and specificity of 75.00%.

CONCLUSIONS

HR 5, HR 10, HRD 5, HRD 10, and RPP 10 and the four combined indicators (HR 5, HR 10, HRD 5, and HRD 10) had predictive value for the POTS prognosis in children. The predictive value of the four combined indicators for the POTS prognosis was better than that of the single HR 5, HRD 5, and RPP 10.

Prognostic Value of Biomarkers in Children and Adolescents With Orthostatic Intolerance

Orthostatic intolerance (OI) refers to a series of symptoms that occur during upright standing, which can be relieved when returned to the supine position. OI is a common cause of syncope in children and adolescents. In recent years, more and more studies have been carried out to assess the prognosis of OI by using biomarkers, among which, flow-mediated vasodilation, left ventricular ejection fraction and fractional shortening, hemodynamic change during head-up tilt test, detection of 24-h urinary sodium excretion, body mass index, midregional pro-adrenomedullin, and erythrocytic H2S producing rate are relatively stable, inexpensive, and easy to obtain. With the help of biomarkers, individualized treatment can be carried out to improve the long-term prognosis of children and adolescents with OI. This article reviews the prognostic value of biomarkers in children and adolescents with OI.

Heart Rate and Heart Rate Difference Predicted the Efficacy of Metoprolol on Postural Tachycardia Syndrome in Children and Adolescents

OBJECTIVE

To evaluate the ability of heart rate (HR) and HR difference during head-up tilt test (HUTT) and to predict clinical improvement related to metoprolol treatment in children and adolescents with postural tachycardia syndrome (POTS).

STUDY DESIGN

This was a retrospective cohort study. A total of 53 subjects (27 male, aged 6-12 years old, mean age 11.79 ± 1.50 years old) with POTS treated with metoprolol were involved from July 2012 to September 2019. In total, 52 subjects who underwent health examination during the same period were matched as the control group. Subjects in both groups underwent HUTT. The HR distance between 5 minutes and 0 minutes (HR difference 5) and between 10 minutes and 0 minutes (HR difference 10) during HUTT was calculated.

RESULTS

The POTS group was significantly greater than the control group in HR 5, HR 10, HR difference 5, and HR difference 10 (P < .01). There was no statistical difference in HR 0 between the 2 groups (P > .05). In total, 53 subjects with POTS were followed up for 96.0 (IQR, 40.5, 134.5) days during treatment with metoprolol. HUTT results demonstrated that 58.49% of subjects with POTS had a response and symptom scores were reduced after intervention. HR and HR difference were useful in predicting the efficacy of metoprolol on POTS. When HR 5, HR 10, HR difference 5, and HR difference 10, respectively, were ≥110, 112, 34, and 37 beats/min, the sensitivity and specificity were 82.50% and 69.23%, 84.62% and 69.70%, 85.29% and 89.47%, and 97.56% and 64.86%, respectively.

CONCLUSIONS

HR and HR difference are helpful to predict the efficacy of metoprolol on POTS in children and adolescents.

Postural Tachycardia Syndrome in Children and Adolescents: Pathophysiology and Clinical Management

Postural tachycardia syndrome (POTS), characterized by chronic (≥6 months) orthostatic intolerance symptoms with a sustained and excessive heart rate increase while standing without postural hypotension, is common in children and adolescents. Despite the unclear pathogenesis of POTS, the present opinion is that POTS is a heterogeneous and multifactorial disorder that includes altered central blood volume, abnormal autonomic reflexes, "hyperadrenergic" status, damaged skeletal muscle pump activity, abnormal local vascular tension and vasoactive factor release, mast cell activation, iron insufficiency, and autoimmune dysfunction. A number of pediatric POTS patients are affected by more than one of these pathophysiological mechanisms. Therefore, individualized treatment strategies are initiated in the management of POTS, including basal non-pharmacological approaches (e.g., health education, the avoidance of triggers, exercise, or supplementation with water and salt) and special pharmacological therapies (e.g., oral rehydration salts, midodrine hydrochloride, and metoprolol). As such, the recent progress in the pathogenesis, management strategies, and therapeutic response predictors of pediatric POTS are reviewed here.

Diagnostic and prognostic value of T-wave amplitude difference between supine and orthostatic electrocardiogram in children and adolescents with postural orthostatic tachycardia syndrome

OBJECTIVE

To investigate the diagnostic and prognostic value of T-wave amplitude difference between supine and orthostatic electrocardiogram (ECG) in children and adolescents with postural orthostatic tachycardia syndrome (POTS).

METHODS

A total of 100 children and adolescents (POTS group, 50 males and 50 females, aged at 11.0 ± 2.4 years) diagnosed as POTS were enrolled from August 2013 to July 2016. Seventy-one children were matched as the control group according to age and sex. All cases completed the supine and orthostatic ECG.

RESULTS

(a) Compared with the control group, the T-wave amplitude difference in leads I, II, aVL, V4 , V5, and V6 and the heart rate (HR) difference increased in POTS group. (b) Logistic regression analysis: The T-wave amplitude difference in leads V4 , V5 , and V6 and HR difference have statistical significance for POTS diagnosis. (c) Diagnostic test evaluation: When HR difference was ≥ 15 times/min, T-wave amplitude difference in lead V5 was ≥0.15 mV, T-wave amplitude difference in leads V4 and V6 were ≥0.10 mV, and the sensitivity and specificity of POTS diagnosis were 35.0% and 88.7%. (d) Follow-up: There was no significant difference in HR difference and T-wave amplitude difference in the nonresponse groups. In the response group, the T-wave amplitude difference in lead V4 was reduced than the initial value.

CONCLUSIONS

The HR difference and T-wave amplitude difference in leads V4, V5, and V6 between supine and orthostatic ECG are of help in assisting the diagnosis of POTS but no obviously significance on prognosis estimation of it.

Long-Term Outcomes of Children and Adolescents With Postural Tachycardia Syndrome After Conventional Treatment

Objectives: To explore the long-term outcomes of children and adolescents with postural tachycardia syndrome receiving conventional interventions. Materials and Methods: A total of 121 patients were recruited, but 6 (5.0%) of them were lost at follow-up. The detailed clinical data were collected, and the reoccurrence and frequency of orthostatic intolerance symptoms were evaluated with a mean followed-up period of 18.7 months (range, 14-74 months). The Kaplan-Meier curve was used to show the cumulative symptom-free rate of patients over time. Factors influencing the long-term outcomes were examined using the Cox's proportional hazards models. Results: The cumulative symptom-free rate was gradually increased over time. It was 48.4% at the 1-year follow-up and increased to 85.6% at the 6-year follow-up. The duration of symptoms before treatment and the maximum upright heart rate in standing-up test were identified as independent indicators for the long-term outcomes. Each 1-month prolongation in the duration of symptoms before treatment was associated with a 1.2% decrease in the cumulative symptom-free rate. However, each 1-bpm increase in the maximum upright heart rate in standing-up test was associated with a 2.1% increase in the cumulative symptom-free rate. Conclusions: The long-term outcomes of postural tachycardia syndrome patients who received conventional interventions are benign and the cumulative symptom-free rate was gradually increased over time. The prolonged duration of symptoms before treatment and the reduced maximum upright heart rate in standing-up test are the independent risk indicators.

Acceleration Index Predicts Efficacy of Orthostatic Training on Vasovagal Syncope in Children

OBJECTIVE

To explore the value of the acceleration index as a predictor of therapeutic response to orthostatic training in children with vasovagal syncope (VVS).

STUDY DESIGN

Thirty-three children with VVS were recruited and treated with orthostatic training. The therapeutic response of each patient was evaluated after 3 months of treatment. A Pearson correlation was calculated between the acceleration index and the severity of VVS. The value of the acceleration index in predicting the therapeutic response to orthostatic training was assessed by analysis of the receiver operating characteristic curve.

RESULTS

Among the 33 children with VVS, 20 were found to be responders and the remaining were nonresponders. The mean acceleration index was significantly lower in responders compared with nonresponders (21.10 ± 6.61 vs 31.36 ± 9.00; P = .001) and it was negatively correlated with positive response time in the head-up tilt test, with systolic blood pressure and with diastolic blood pressure at positive response time in the head-up tilt test (P < .05). The receiver operating characteristic curve for the predictive value of the acceleration index showed that the area under the curve was 0.827 (95% CI, 0.676-0.978; P = .002), and a cutoff value of the acceleration index of 26.77 yielded a sensitivity of 85.0% and a specificity of 69.2%.

CONCLUSIONS

The acceleration index may be useful for predicting the efficacy of orthostatic training on VVS in children.

2018 Chinese Pediatric Cardiology Society (CPCS) guideline for diagnosis and treatment of syncope in children and adolescents

Syncope belongs to the transient loss of consciousness (TLOC), characterized by a rapid onset, short duration, and spontaneous complete recovery. It is common in children and adolescents, accounting for 1% to 2% of emergency department visits.Recurrent syncope can seriously affect children's physical and mental health, learning ability and quality of life and sometimes cardiac syncope even poses a risk of sudden death. The present guideline for the diagnosis and treatment of syncope in children and adolescents was developed for guiding a better clinical management of pediatric syncope. Based on the globally recent development and the evidence-based data in China, 2018 Chinese Pediatric Cardiology Society (CPCS) guideline for diagnosis and treatment of syncope in children and adolescents was jointly prepared by the Pediatric Cardiology Society, Chinese Pediatric Society, Chinese Medical Association (CMA)/Committee on Pediatric Syncope, Pediatricians Branch, Chinese Medical Doctor Association (CMDA)/Committee on Pediatric Cardiology, Chinese College of Cardiovascular Physicians, Chinese Medical Doctor Association (CMDA)/Pediatric Cardiology Society, Beijing Pediatric Society, Beijing Medical Association (BMA). The present guideline includes the underlying diseases of syncope in children and adolescents, the diagnostic procedures, methodology and clinical significance of standing test and head-up tilt test, the clinical diagnosis vasovagal syncope, postural orthostatic tachycardia syndrome, orthostatic hypotension and orthostatic hypertension, and the treatment of syncope as well as follow-up.