[Efficiency of heart rate and heart rate difference at different time points during head-up tilt test in the diagnosis of postural tachycardia syndrome in children and adolescents].

OBJECTIVE: To study the efficiency of heart rate (HR) and heart rate difference (HRD) at different time points during head-up tilt test (HUTT) in the diagnosis of postural tachycardia syndrome (POTS) in children and adolescents. METHODS: A total of 217 children and adolescents, aged 6-16 years, who were diagnosed with POTS were enrolled as the POTS group, and 73 healthy children and adolescents, matched for sex and age, were enrolled as the control group. The POTS group was further divided into ≤12 years old group with 127 children/adolescents and >12 years old group with 90 children/adolescents. The two groups were compared in terms of HR at baseline and at 5 and 10 minutes of HUTT (HR0, HR5, and HR10 respectively), difference between HR5/HR10 and HR0 (HRD5 and HRD10 respectively). The efficiency of HR5, HR10, HRD5 and HRD10 in the diagnosis of POTS was assessed. RESULTS: Compared with the control group, the POTS group had significant increases in HR5, HR10, HRD5, and HRD10 (P<0.05). The coincidence rate of HR or HRD for the diagnosis of POTS in males was higher than that in females at 5 minutes of HUTT (P<0.05), while the coincidence rate of HR or HRD for the diagnosis of POTS in males was lower than that in females at 10 minutes of HUTT (P<0.05). The coincidence rate of HR for the diagnosis of POTS was higher in the >12 years old subgroup (P<0.05), while the coincidence rate of HRD for the diagnosis of POTS was higher in the ≤12 years old subgroup (P<0.05). The combination of HR5, HR10, HRD5, and HRD10 for the diagnosis of POTS had a greater area under the curve (0.974; 95%CI: 0.949-0.989) than HR5, HR10, HRD5, or HRD10 alone, with a sensitivity of 87.80% and a specificity of 95.83%. The diagnostic efficacy of HRD for POTS was higher than that of HR (P<0.05). CONCLUSIONS: HR and HRD at different time points during HUTT have a good value in the diagnosis of POTS in children and adolescents, and the accuracy of diagnosis varies with age and gender.

[Association of T-wave amplitude on electrocardiogram with left ventricular ejection fraction in children with dilated cardiomyopathy].

OBJECTIVE: To study the association of T-wave amplitude on electrocardiogram (ECG) with left ventricular ejection fraction (LVEF) in children with dilated cardiomyopathy. METHODS: A retrospective analysis was performed for the clinical data of 44 children who were diagnosed with dilated cardiomyopathy from May 2009 to June 2018. According to LVEF, they were divided into two groups: LVEF ≥50% group (n=26) and LVEF <50% group (n=18). After treatment, 25 children were followed up for 3-42 months (mean 14±9 months). The Guangdong Zhongshan SR-1000A ECG Automatic Analyzer was used to obtain the 12-lead body surface ECG results in the supine position. T-wave amplitude on ECG was evaluated by software and manual measurement. RESULTS: Compared with the LVEF ≥50% group, the LVEF <50% group had a significant reduction in the T-wave amplitude in leads II, V4, V5 and V6 (P<0.05). The increased-LVEF group (an increase in LVEF > 5% after treatment) had a significant increase in the T-wave amplitude in leads aVR, V5, and V6 after treatment (P<0.05), while the unchanged-LVEF group (an increase in LVEF ≤ 5% after treatment) had a significant reduction in the T-wave amplitude in lead aVR after treatment (P<0.05). The receiver operating characteristic curve analysis showed that the T-wave amplitude in leads II, V4, V5 and V6 had a certain value in predicting LVEF <50% in children with dilated cardiomyopathy (P<0.05). A combination of T-wave amplitude of ≤0.20 mV in lead II, ≤0.40 mV in lead V4, and ≤0.30 mV in leads V5 and V6 had a sensitivity of 88.2% and specificity of 76.0% in the predication of LVEF <50% in children with dilated cardiomyopathy. CONCLUSIONS: T-wave amplitude on ECG can be used as the indexes for the evaluation of the left ventricular systolic function in children with dilated cardiomyopathy.

[T wave and ST segment amplitude changes in the supine and standing electrocardiograms of children with orthostatic hypertension and their clinical significance].

OBJECTIVE: To examine the changes in T wave and ST segment amplitude in the supine and standing electrocardiograms (ECG) of children with orthostatic hypertension (OHT) and to determine their clinical significance. METHODS: A total of 49 children with OHT were included in the OHT group. Forty-three age- and sex-matched healthy children were included in the control group. Heart rate and T wave and ST segment amplitude were measured in both groups. T wave amplitude and ST segment amplitude in supine ECG were compared with those in standing ECG within each group. The differences in supine vs standing T wave amplitude and ST segment amplitude were compared between the OHT and control groups. RESULTS: In the control group, T wave amplitude in leads aVR, V1, and V4-V6 were significantly lower in standing ECG than in supine ECG (P<0.05); ST segment amplitude in leads V4 and V5 were significantly higher in standing ECG than in supine ECG (P<0.05). In the OHT group, T wave amplitude in leads II, aVR, aVF, and V4-V6 were significantly lower in standing ECG than in supine ECG (P<0.05); ST segment amplitude in lead II was significantly higher in standing ECG than in supine ECG (P<0.05). The differences in T wave amplitude in lead II and V6 between supine and standing ECG were significantly higher in the OHT group than in the control group (P<0.05). Difference in T wave amplitude in lead V6 between supine and standing ECG was a significant diagnostic marker for OHT (P<0.05). This marker had 72.10% sensitivity and 57.10% specificity for the diagnosis of OHT at the optimal cut-off value of 0.105 mV. CONCLUSIONS: Difference in T wave amplitude in lead V6 between supine and standing ECG has certain diagnostic value for OHT.

[Time-dependent heart rate variability in the head-up tilt test in children with postural orthostatic tachycardia syndrome].

OBJECTIVE: To study the time-dependent heart rate (HR) variability in the head-up tilt test (HUTT) in children with postural orthostatic tachycardia syndrome (POTS) and to explore the HR diagnostic criteria for POTS in children. METHODS: A retrospective analysis was performed on the clinical data of 105 children diagnosed with POTS with HR≥120 beats per minute (bpm) within the first 10 minutes of HUTT between January 2007 and December 2014. Their HR variability within the first 10 minutes of HUTT was analyzed. RESULTS: The HR of children with POTS increased gradually from the supine position to a 60° head-up tilt position, and the increase in HR was 24±12 bpm at the beginning of HUTT, 30±14 bpm at 3 minutes of HUTT, 32±13 bpm at 5 minutes of HUTT, and 38±12 bpm at 10 minutes of HUTT. The average maximal HR increase within the first 10 minutes of HUTT was 43±10 bpm. CONCLUSIONS: In children with POTS, the HR variability gradually increases with time, and therefore, it is suggested that HR increase ≥40 bpm is more suitable for diagnosis of POTS in children.

[Evaluation of psychological fear in children undergoing head-up tilt test].

OBJECTIVE: To investigate the effects of different tilt angles of head-up tilt test (HUTT) and different responses to HUTT on the psychological fear in children undergoing the test. METHODS: HUTT was performed on children with unexplained syncope or pre-syncope (107 cases: 52 males and 55 females), aged 5.5-17.8 years (mean 12.0±2.8 years). All subjects were randomly assigned to undergo HUTT at an angle of 60°, 70° or 80°; the negative cases underwent sublingual nitroglycerin-provocation HUTT at the same tilt angle. The Wong-Baker Faces Pain Rating Scale was used for self-assessment of psychological fear in subjects during HUTT at the end point of the test. RESULTS: The positive rate, hemodynamic changes and distribution of response types showed no significant differences between children at tilt angles of 60°, 70° and 80° (P>0.05). The greater the tilt angle, the higher the degree of psychological fear in children undergoing the test, but there were no significant differences between them (P>0.05). The degree of psychological fear in children who showed a positive response to HUTT (n=76) was significantly higher than that in children who showed a negative response (n=31) (P<0.01). CONCLUSIONS: HUTT can cause psychological fear in children undergoing the test, and the degree of psychological fear increases in children tested at tilt angles from 60° to 80°, but the differences have no statistical significance. A positive response to HUTT can significantly increase the psychological fear in children.