Analysis of Factors Relevant to the Severity of Symptoms in Children and Adolescents with Postural Orthostatic Tachycardia Syndrome

Abstract

Objectives: The current study aims to investigate the factors associated with the severity of conditions for pediatric cases with postural orthostatic tachycardia syndrome (POTS). Methods: Patients hospitalized and first diagnosed with POTS were retrospectively included and reviewed. The severity of symptoms was evaluated by symptom scores (SSs). Multiple Spearman correlation analyses and multiple linear regression analyses were used to determine factors independently associated with SS. Patients were divided into the mild (SS ≤ P25) and severe (SS ≥ P75) groups to test the distinguishing efficiency of the candidate factors. The efficiency of each independently correlated factor in indicating the condition of children with POTS was assessed by the receiver operating characteristic (ROC) curve. Results: A series of 296 pediatric patients aged 5-17 years suffering from POTS were included. Multiple Spearman correlation analyses and multiple linear regression analyses showed that corrected QT interval dispersion (QTcd) was independently correlated with SS (p < 0.05). QTcd can be used to suggest the severity of POTS symptoms, and the area under the curve (AUC) was 0.986 (95% CI 0.976-0.997). At a threshold of QTcd = 45 ms, the sensitivity and specificity were, respectively, 94.0% and 91.8% for symptom severity indication. Conclusions: In pediatric cases with POTS, QTcd was positively correlated with their symptom severity and exhibited a strong indicative value. A QTcd of 45 ms was a valid cut-off value for indicating symptom severity.

Keywords: children; corrected QT interval dispersion; postural orthostatic tachycardia syndrome; relevant factor; symptom score; symptom severity.

Figure 1

The flow chart of study design. * Patients were divided into the mild (symptom score ≤ the 25th percentile) group and severe (symptom score ≥ the 75th percentile) group.

Figure 2

The heatmap of correlation matrix between quantitative variables. The color bar on the right represents the Spearman correlation coefficient, with darker blue indicating a higher negative correlation and darker red indicating a higher positive correlation. BMI, body mass index; RBC, red blood cell count; HGB, hemoglobin; HCT, hematocrit; MCV, mean corpuscular volume; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; RDW, red cell distribution width; PLT, platelet count; MPV, mean platelet volume; PCT, platelet hematocrit; PDW, platelet distribution width; Urine SG, urine specific gravity; SBP, systolic blood pressure; DBP, diastolic blood pressure; UA, uric acid; HR, heart rate; QTmax, maximum QT interval; QTmin, minimum QT interval; QTcmax, corrected QTmax; QTcmin, corrected QTmin; QTcd, corrected QT interval dispersion; SDNN, standard deviation of NN intervals in 24 h Holter monitoring; LVEF, left ventricular ejection fraction; LVFS, left ventricular Fraction shortening.

Figure 3

The ROC curve of QTcd indicates the symptom severity in children with POTS. The sensitivity and specificity for symptom severity indication were 94.0% and 91.8%, respectively.