All the infant patients in this study underwent CTA examination using GE Revolution CT with 256 rows. Scanned image postprocessing was performed using the GE SERVICE AW4.7 intelligent advanced postprocessing workstation. CT aorta scanning protocol: Infant patients were scanned in a sleeping state with calm breathing. The patients who could not cooperate were fasted for 4–6 h before the examination and were orally sedated with 10% chloral hydrate (0.5 ml/kg) 30–60 min before the examination and then scanned after they fell into a deep sleep. Indwelling needles were placed in the antecubital or dorsal hand vein in all patients. The patient was placed in the supine position, and the scanning direction was from head to foot, ranging from the thoracic entrance to the level of the pubic symphysis. The layer thickness of the scanned image was 0.625 mm, and the layer spacing was 0.625 mm. Scanning parameters: tube voltage and current were adjusted according to the patient's body mass index. Tube voltage was 80–100 kV, and tube current was 80–120 mas. The nonionic isotonic agent iodixanol (320 mg/ml) was used, and the injection dose was calculated according to the body weight of 1.5–2 ml/kg. Contrast media was injected through the indwelling needle at a rate of 1.0–2.0 ml/s (according to the patient's age, height, and weight), and then 10–15 ml of normal saline was injected at the same rate. To monitor the CT value, the contrast-tracer method was used to select the region of interest (ROI) at the tracheal carina of the descending aorta. When the CT value in the ROI reached 90–100 HU, the scan was automatically triggered after a 5-second delay. The pitch was adjusted according to the heart rate. The scanning layer thickness was 0.625 mm, and the scanning interval was 0.312 mm.

The infants were placed in the supine position, and preoperative blood pressure of the upper and lower extremities was measured by invasive arterial blood pressure monitoring. Then, the patient was placed in a 90-degree lying position on the right side, and the left surgical field was routinely disinfected and draped. The skin, subcutaneous tissue, and back muscles were sequentially incised, and thoracotomy was performed through the fourth intercostal space. The posterior pleura and adventitia of the descending aorta were longitudinally incised. The lower segment of the aortic arch, branch vessels, and the proximal end of the descending aorta were carefully identified and dissociated, and the position of the coarctation was found. In the case of discrete CoA, simple end-to-end anastomosis was performed by blocking the superior and inferior normal arteries and the corresponding branch arteries with blocking forceps and continuous anastomosis at both ends of the aorta. In cases of combined aortic arch hypoplasia, resection and extended end-to-end anastomosis were performed. The aortic arch was controlled near the left carotid artery. Distal blocking forceps were placed distal to the constricted area. After complete excision of all constricted and conduit tissue, the inferior surface of the transverse aortic arch was dissected until a partial and end-to-end anastomosis between the cephalic brachial artery and the left common carotid artery was made. After completion of the anastomosis, blood pressure was measured by invasive arterial blood pressure monitoring in the upper and lower extremities. Prior to closure a thoracic drainage tube was inserted and the wound was closed in layers. The infants were transferred to the ICU after surgery.

The relevant data needed in this study were collected by searching medical electronic record systems. The aortic coarctation data of all patients measured by preoperative CTA were collected, and patients were divided into the mild CoA group and the severe CoA group according to the degree of coarctation. The sex, prenatal diagnosis, gestational age, age at operation, presurgical weight, surgical duration, aortic cross-clamp time, mechanical ventilation duration, length of ICU stay, and other clinical data of the two groups of patients were collected. All patients were followed up regularly after discharge. Patients typically received initial TTE and further CTA if re-CoA occurred. The relevant clinical information in this cohort was collected for research purposes, and data collection was performed in a strictly confidential manner.

The outcomes evaluated in this study were divided into three categories. (1) We compared the differences in prognosis-related data, such as mechanical ventilation duration and length of ICU stay, between the two groups. (2) We assessed the relationship among sex, gestational age, age at operation, presurgical weight, severity of CoA, aortic cross-clamp time, duration of mechanical ventilation and postoperative ICU length of stay. (3) We assessed the relationship between the degree of CoA and z scores at different levels of the aorta.

Data for this study were analyzed using IBM SPSS Statistics version 23. Qualitative variables were expressed as frequencies and percentage values (%), and quantitative variables were defined as the mean ± standard deviation. This study used Q-Q plots to analyze whether variables were normally distributed. Due to the small sample size of this study, Fisher's exact probability method was used instead of χ2 for analysis. Multiple linear regression models were used to assess independent associations between postoperative ICU stay and relevant demographic and clinical factors. Spearman correlation analysis was used to evaluate the relationship between the degree of coarctation of the aorta and the Z score at different levels of the aorta. A P value less than 0.05 was considered statistically significant.

This study was a retrospective analysis of the effect of the degree of aortic coarctation on the prognosis of infants undergoing surgical correction of simple CoA. The results showed that the duration of postoperative ICU stay was significantly shorter in infants with mild CoA than in infants with severe CoA. Multiple linear regression analysis showed that the severity of aortic coarctation was a significant predictor of postoperative ICU stay. In addition, gestational age and operation age were significant predictors of postoperative ICU stay. Correlation analysis indicated that the degree of aortic coarctation significantly correlated with the Z scores of the ascending aorta and the postcoarctation aorta.

Some limitations in this study should be noted. First, due to the low incidence of simple coarctation of the aorta, the sample size that could be included in this study was limited. The small sample size of our study somewhat limited our ability to determine the association between the degree of aortic coarctation as a predictor and the length of postoperative ICU stay. However, we still believe that our results have some clinical implications. Second, this study was a single district retrospective study, and relevant data were not collected from different areas. Moreover, our postoperative follow-up time was limited; thus, the impact of postoperative recoarctation was potentially not accurately assessed. Further prospective studies are needed in the future to more comprehensively and rationally assess the association between the degree of aortic coarctation and surgical prognosis.

The degree of aortic coarctation is an important predictor of poor surgical outcomes in infants with simple CoA. The degree of aortic coarctation significantly correlates with the Z scores of the ascending aorta and the postcoarctation aorta. Therefore, CTA should be routinely performed before aortic surgery to assess the degree of coarctation and better identify risk factors.

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author/s.

The studies involving human participants were reviewed and approved by the ethics committee of Zhangzhou Affiliated Hospital of Fujian Medical University. Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.

HX designed the study, drafted the article and submitted the manuscript. AZ, QH, RH and WL collected and analyzed data together. All authors contributed to the article and approved the submitted version.

We appreciated all doctors in our center for fruitful advice and discussions. We hope humans eventually defeat COVID-19.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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