Objective:To investigate the prognosis and risk factors for children diagnosed with all types of subaortic stenosis(SAS) who developed recurrent left ventricular outflow tract obstruction after surgical treatment.Methods:The study retrospectively included patients aged 0-18 years old who underwent open heart SAS surgery at Fuwai Hospital from 2016-2019. Children with hypertrophic obstructive cardiomyopathy were excluded. Detailed operative notes, medical records and ultrasound information, and follow-ups were extracted. Recurrent SAS was defined as left ventricular outflow tract gradient 30 mmHg(1 mmHg=0.133 kPa) 1 month after SAS surgical treatment.Results:A total of 137 children were included in this study. The medium age of children at the time of SAS surgery was 4.6 years old(3 months-17.8 years old). After a median follow-up of 4.36 years(3.2-5.7 years), a total of 30 patients developed recurrent LVOTO, with a recurrence rate of 21.9%, and 7(5.1%) underwent a second surgery. Compared to the non-recurrent group, children in the recurrent group were younger at the time of surgery( P=0.0443), had a smaller body surface area( P=0.0485), and a longer length of stay( P=0.0380). In Cox analysis, when only considering preoperative variables, the independent risk factor for LVOTO recurrence were a peak left ventricular outflow tract gradient higher than 50 mmHg( HR=5.25, P=0.001), a BSA less than 0.9( HR=2.5, P=0.023), and a length of SAS 5 mm( HR=2.29, P=0.050). When both preoperative and intraoperative variables were considered, preoperative peak left ventricular outflow tract gradient 50 mmHg( HR=4.91, P=0.002) and peeling from the aortic valve( HR=3.23, P=0.010) were independent risk factors for postoperative recurrence. Conclusion:Recurrent LVOTO after SAS surgical repair is common, and regular postoperative follow-up is crucial to evaluate whether a secondary intervention is required. Regular postoperative follow-up is needed for children at high risk.

Objective To acquire the external contour changes and positioning errors during fractionated intensity-modulated radiotherapy for nasopharyngeal carcinoma using kilovoltage cone-beam computed tomography(CBCT),and to analyze their effects on the dose distributions in target areas and organs-at-risk.Methods Twenty-one patients with nasopharyngeal carcinoma were enrolled in the study,and the positioning errors in the left-right,superior-inferior and anterior-posterior directions were obtained by matching 137 CBCT images with the positioning CT images.The transverse width of the external contour was measured at 3 different layers of the neck,and its effects on positioning errors were analyzed using Pearson's coefficient and independent sample t-tests.Additionally,simulation plans based on CBCT images were created to analyze the effects of positioning errors and external contour changes on radiotherapy dose,with Mann-Whitney U tests applied for significance analysis.Results The positioning errors in the left-right,superior-inferior and anterior-posterior directions were(1.04±0.73),(1.13±0.87)and(1.38±0.95)mm,respectively.The rates of external contour changes at the A,B and C layers of the head and neck were 15.36%,14.94%and 14.99%,respectively.Compared with executed plans,simulation plans had lower GTV D98,CTV1 D95 and CTV2 D95(P<0.05),and higher Dmax for the brainstem and spinal cord(P<0.05).Conclusion The simulation plans indicate that the presence of uncertainties such as positioning errors and external contour changes will significantly affect dose distributions in target areas,with the largest decrease observed in GTV D98(11.49%)and the maximum change rates in CTV1 D95 and CTV2 D95 being 12.88%and 21.64%,respectively.Except for the left and right lenses and left parotid gland,significant differences are observed in the doses for the other organs-at-risk and target areas,suggesting that positioning errors and external contour changes in actual radiotherapy will exert significant effects on dose distributions.

At present, traditional methods on statistics have limitations in controlling time- varying confounding. This paper introduces an analysis method, parametric g-formula, which would adjust time-varying confounding, and also exemplifies the steps of its implementation for purpose to provide a new reference for researchers to deal with long-term observational data.

Objective     To summarize the characteristics of children diagnosed with secondary subaortic stenosis after the surgical closure for ventricular septal defect and explore its potential mechanism. Methods     We retrospectively collected patients aged from 0 to 18 years, who underwent ventricular septal defect closure and developed secondary subaortic stenosis, and subsequently received surgical repair from 2008 to 2019 in Fuwai Hospital. Their surgical details, morphological features of the subaortic stenosis, and the follow-up information were analyzed. Results     Six patients, including 2 females and 4 males, underwent the primary ventricular septal defect closure at the median age of 9 months (ranging from 1 month to 3 years). After the first surgery, patients were diagnosed with secondary subaortic stenosis after 2.9 years (ranging from 1 to 137 months). Among them, 2 patients underwent the second surgery immediately after diagnosis, and the other 4 patients waited 1.2 years (ranging from 6 to 45 months) for the second surgery. The most common type of the secondary subaortic stenosis after ventricular septal defect closure was discrete membrane, which located underneath the aortic valve and circles as a ring. In some patients, subaortic membrane grew along with the ventricular septal defect closure patch. During the median follow-up of 8.1 years (ranging from 7.3 to 8.9 years) after the sencond surgery, all patients recovered well without any recurrence of left ventricular outflow tract obstruction. Conclusion     Regular and persistent follow-up after ventricular septal defect closure combining with or without other cardiac malformation is the best way to diagnose left ventricular outflow tract obstruction in an early stage and stop the progression of aortic valve regurgitation.

Artificial chord is a mature mitral valve repair technique, especially in adult mitral valve repair. It is still challenging to repair mitral valve in children with artificial chords because the quality of mitral valve is soft and immature. There are some differences in the methods of suture, the choice of suture size and the number of artificial chords. Although the artificial chords could not grow naturally, we found through the long-term research that most children did not have mitral valve restriction or even chords rupture due to itself can compensate through the growth of the flap and papillary muscle. This article summarizes the recent research progress on the treatment of mitral valve insufficiency in children with artificial chords, providing reference for clinical treatment.