背景

儿童心肌病的外科治疗技术多样，针对儿童肥厚性心肌病的外科治疗主要以室间隔肥厚心肌切除术为主，但部分患儿术后发生复发性左室流出道梗阻，导致治疗效果不佳。儿童的遗传背景因素影响比成人更高，术后流出道梗阻复发是否与遗传因素、手术切除方式因素有关系尚不清楚。此外，终末期儿童心肌病外科治疗主要以心脏移植为主，部分患儿从确诊至终末期进展较快，遗传因素是否影响了病程进展未知。儿童作为家庭的重要成员，家庭经济教育水平对其影响巨大。家庭社会经济地位低下是导致心血管疾病患者死亡率增加的一个已知因素。不同社会经济教育水平的家庭对终末期心肌病儿童移植预后的管理、看护等表现出较大差异，两者之间的相关性既往尚无报道。

目的

本研究目的是探讨如何提高儿童心肌病外科的诊断和治疗效果。通过调查遗传因素、构建三维心室模型方法探索影响外科治疗肥厚型心肌病的不良预后因素，对高危不良预后患者进行早期风险分层诊断，并指导外科手术进行更为精准的方案。此外，通过调查终末期心肌病患儿的遗传背景、家庭经济教育水平探索影响终末期儿童心肌病预后因素，为提高整体儿童心肌病预后提供建议。

方法

第一部分：本研究回顾性分析了2015年4月至2023年5月期间56名确诊为肥厚型心肌病患儿并接受了室间隔心肌切除术。利用术前心脏CT检查通过标准的17段方法建立了左心室的三维模型。我们将心衰、心律失常事件和复发性左心室流出道梗阻事件定义为不良事件。分析左心室不同肥厚与预后相关性。

第二部分：本研究利用第一部分儿童队列对患儿进行基因测序。并针对PTPN11阳性和阴性患儿的组织进行了相关病理染色分析。分析PTPN11突变是否影响患儿预后。

第三部分：本研究回顾性分析了2004年9月至2023年7月期间在我中心因儿童心肌病进入终末期心衰并且接受心脏移植手术的18岁以下患者共76名，并对这些患者进行了全外显子测序和标准病理学检查，比较了儿童和成人心脏移植患者的致病基因及其在同类型心肌中的发生率。

第四部分：本研究利用第三部分儿童移植队列评估家庭社会经济地位对患儿预后的影响。

结果

第一部分：多因素Cox分析显示左心室中部梗阻(HR: 4.763, 95%CI: 1.53814.754, p=0.007)是高危因素，提示左心室肥大程度与患者预后不良相关。用三维模型分析心脏CT，预后不良的患儿左室后壁心肌更加肥厚(p=0.014)。

第二部分：与其他组相比，PTPN11突变儿童中有6名(54.5%)发生了左心室流出道梗阻复发事件(p=0.015)，术后复发性梗阻的平均时间为227个月。PTPN11突变儿童发生复发性梗阻相关风险的可能性是其他儿童的9倍(95%CI: 1.7745.81, p=0.001)。H&E、Masson和WGA病理染色也显示PTPN11突变组织中心肌细胞肥大更明显。

第三部分：不同类型的心肌病中基因突变比例差异有统计学意义(p0.003)。在扩张型心肌病中，儿童携带TNNT2突变的可能性高于成人(p0.001)，并且携带此突变的儿童进展到终末期心衰阶段更快(19个月 VS. 189个月, p0.002)。

第四部分：低社会经济地位与高社会经济地位的家庭的患儿全因死亡风险比分别为5.99(95%CI：2.2810.64，p=0.003)，中等社会经济地位与高社会经济地位的家庭患儿全因死亡风险比分别为2.53(95%CI：1.049.43，p=0.029)。

结论

通过心脏CT结合三维重建技术，可知左心室后壁肥厚程度与术后预后也有相关性，为术前评估及制定治疗方案提供指导。携带PTPN11突变相关肥厚型心肌病的儿童发生左心室流出道梗阻复发的风险更大，需要对于肥厚型心肌病患儿术前积极进行基因筛选并对于复发高危患儿进行风险分层。TNNT2突变尤其提示扩张型心肌病中的心衰快速进展类型患者。识别这种突变可能有助于指导患者管理和风险分层。家庭社会经济地位对于儿童心肌病移植后预后也有影响。

Background

Hypertrophic obstruction cardiomyopathy is a cardiomyopathy characterized by left ventricular outflow tract obstruction and inhomogeneous hypertrophy of the interventricular septum. About three-quarters of patients with hypertrophic cardiomyopathy develop left ventricular outflow tract obstruction. Most children with hypertrophic cardiomyopathy develop left ventricular outflow tract obstruction, which can even further lead to heart failure or sudden cardiac death. The modified Morrow operation for hypertrophic obstructive cardiomyopathy in children has a favorable outcome, but some children still have a poor prognosis after the procedure. Even after successful septal myocardial resection, some children may still experience recurrent left ventricular outflow tract obstruction events postoperatively. In addition, left ventricular outflow tract obstruction is strongly associated with an increased risk of hypertrophic cardiomyopathy-related death, heart failure, or malignant arrhythmias. Cardiac computed tomography is an adjunctive test that enables a comprehensive assessment of the anatomy and function of the cardiac chambers. It is a promising imaging tool to characterize left ventricular myocardial disease based on the overall morphology, function, and enhancement of the left ventricular myocardium, as well as the Extracellular Volume fraction. In this study, the authors aimed to investigate the application of cardiac computed tomography to construct a three-dimensional model of the left ventricle and analyze the association between hypertrophy in different parts of the left ventricular and poor prognosis.

In the previous part, we addressed surgical fine resection, constructing a three-dimensional model based on computed tomography to guide surgeons to accurately resect hypertrophic myocardium, thereby improving overall prognosis. Since hypertrophic cardiomyopathy is a disease with a strong genetic correlation, it is unclear whether there is an effect of genetic mutation in children with poor postoperative prognosis, and in this part, we will focus on the correlation between the postoperative prognosis of hypertrophic cardiomyopathy in children and genetic mutation. Hypertrophic cardiomyopathy is an inherited heart disease with different clinical features and prognostic outcome. The prevalence of hypertrophic cardiomyopathy in children due to inborn metabolic anomalies or malformation syndromes is high. Approximately 80％ of children with Noonan Syndrome with Multiple Lentigines are diagnosed with hypertrophic cardiomyopathy. Pathogenic genetic variants in exons 7, 12, and 13 of the PTPN11 gene have been characterized in 70％-90％ of patients with Noonan syndrome with multiple lentigines presenting with hypertrophic obstructive cardiomyopathy. The Heart-Related RASopathies Network reported that patients with mutations in the PTPN11 gene are at higher risk of cardiac death. In another cohort study of 47 children with RAS disease combined with hypertrophic cardiomyopathy, three deaths from heart failure were reported, all of which were associated with mutations in exon 13 of PTNP11. Several studies have shown that PTPN11 encodes the non-receptor-type protein tyrosine phosphatase SHP-2. SHP-2 tyrosine phosphatase activity controls cardiomyocyte size through down-regulation of FAK/Src and mammalian rapamycin-targeted signaling pathway pathways. Left ventricular septal myotomy provides a favorable prognosis for children with hypertrophic obstructive cardiomyopathy. However, some children still suffer from recurrent left ventricular outflow tract obstruction after surgery. Poor prognosis exists for hypertrophic obstructive cardiomyopathy caused by PTPN11 mutation. Therefore, the aim of this study was to determine the clinical features of recurrent obstruction in children with hypertrophic obstructive cardiomyopathy caused by pathogenic mutations in the PTPN11 gene.

In the previous part, we focused on the effect of gene mutations on the postoperative prognosis of childhood hypertrophic cardiomyopathy, which provides an important theoretical basis for the precise treatment of childhood cardiomyopathy. The treatment of early childhood cardiomyopathy is mainly carried out by drugs and surgery. For end-stage pediatric cardiomyopathies, heart transplantation is the main treatment, and the prognostic outcomes of children's heart transplantation treatment vary widely, with a variety of related influencing factors. This section will focus on the influence of genetic factors on end-stage cardiomyopathy in children. Heart transplantation remains the most effective treatment for end-stage heart failure. The International Society for Heart and Lung Transplantation registry has reported nearly 14,000 pediatric heart transplant cases. Given the unique nature of pediatric growth and life expectancy, it is critical to improve the prognosis of this population. Studies have shown that children with hypertrophic cardiomyopathy face twice the risk of heart transplantation as adults. In addition, there are significant differences in clinical characteristics, genotyping, and cardiovascular outcomes among pediatric hypertrophic cardiomyopathy patients. Heart failure resulting from cardiomyopathy in children is usually more severe and fatal compared to adults. Children with mitochondrial cardiomyopathies also have a higher risk of recurrent heart failure after heart transplantation, and therefore, more careful postoperative management is needed in this patient population. Although the genetic causes of cardiomyopathies are well documented, their specific impact on the progression of end-stage heart failure requiring heart transplantation remains unknown. The role of genetic mutations on heart failure progression in pediatric cardiomyopathy has not been fully elucidated. Genetic mutations play an important role in pediatric cardiomyopathy. Some children with cardiomyopathy progress to end-stage heart failure. However, whether different genetic factors contribute to the rate of disease progression remains unclear.

In the previous part, we examined the impact of genetic mutations on the prognosis of end-stage heart transplantation in pediatric cardiomyopathy. As a group of minors, the family has a great influence on children, and parental attitudes and the level of family economy have a profound impact on children's health. Therefore, this part will analyze the correlation between the prognosis of children with heart transplantation from a socioeconomic perspective. Lower socioeconomic status is associated with an increased risk of complications and death in patients with cardiovascular disease. Furthermore, socioeconomic status can significantly influence the diagnosis and treatment of heart failure. This effect is particularly important in children who require long-term treatment (including anti-rejection therapy and regular check-ups). Clearly, the impact of low socioeconomic status can lead to delays in the timing of diagnosis and limited therapeutic options, which can lead to the occurrence of adverse events and even death of the patient. Particularly in developing countries, where the distribution of healthcare resources is often imbalanced, only a few experienced cardiac centers are able to perform heart transplantation in children. Low family socio-economic status is a known factor that can contribute to increased mortality for patients with cardiovascular disease. However, in developing countries, the prognostic impact of socio-economic level on pediatric heart transplantation is also unclear.

Objective

The purpose of this study was to explore how to improve the diagnosis and treatment outcome of pediatric cardiomyopathy surgery. We explored the poor prognostic factors affecting surgical treatment of HOCM by investigating genetic factors and constructing a three-dimensional ventricular modeling method to provide early risk stratification diagnosis of patients with high-risk poor prognosis and to guide surgical procedures for a more precise protocol. In addition, we explored the prognostic factors affecting end-stage pediatric cardiomyopathy by investigating the genetic background of children with end-stage cardiomyopathy and the economic and educational level of their families, and provided suggestions for improving the overall pediatric cardiomyopathy prognosis.

Methods

Part I: The authors retrospectively analyzed 57 children with hypertrophic obstructive cardiomyopathy from April 2015 to October 2022, among whom 16 underwent preoperative cardiac computed tomography examination. All children underwent the modified Morrow surgery in our center. Follow-up visits were conducted by a specialized team. They collected relevant data on death, heart failure, ventricular arrhythmic events, and recurrent left ventricular outflow tract obstruction events through a comprehensive review of electronic medical records and telephone contact with patients. The end date of follow-up was set for November 1, 2023. The authors defined heart failure, malignant ventricular arrhythmia, and recurrent left ventricular outflow tract obstruction as adverse events. The authors performed a retrospective Cox analysis and conducted genetic testing. A three-dimensional model of the left ventricular was built through the standard 17-segment method and analyzing the high-risk factors. We carefully measured the thickness of each left ventricular segment and calculated the average thickness of the basal, middle, and apical regions. We then compared these specific ventricular thicknesses with the corresponding segments to objectively assess the severity of hypertrophy in the different regions. Through cluster analysis, we associated poor prognosis with segments, identified prognostically relevant hypertrophied segments, and determined thresholds for high- and low-risk poor prognosis.

Part II: Fifty-six children who were diagnosed with hypertrophic obstructive cardiomyopathy underwent septal myectomies. All children with hypertrophic obstructive cardiomyopathy underwent septal myotomy (also known as the Morrow procedure) performed by the same surgeon. The surgery was performed using a standard median sternotomy. Follow-up data on death, heart failure, ventricular arrhythmias, and recurrent left ventricular outflow tract obstruction events were collected through clinic notes and telephone contact with physicians. The end date of follow-up was November 1, 2023. Echocardiography was performed including transthoracic and intraoperative transesophageal approaches. Measurement of maximal left ventricular outflow tract gradient using continuous Doppler at rest and Valsava test if necessary. Whole-exome sequencing of 49 pediatric cardiomyopathy–associated genes (including PTPN11) was performed. The site of pathologic tissue collection in each child was the hypertrophied septal myocardium. Two pathologists performed pathologic examination of the hypertrophied myocardium removed during surgery without knowledge of the clinical and genetic background. We performed hematoxylin eosin, Masson, and wheat germ agglutinin staining of those tissues positive and negative for PTPN11.

Part III: We collected basic clinical data on 76 children and 166 adults who underwent heart transplantation for cardiomyopathy, and conducted whole-exome sequencing and standard pathology examinations on these patients. To improve the prediction of the hazard of genetic variants, we used a classification system developed by the American College of Medical Genetics and Genomics. This system classifies variants into the following categories: pathogenicity, possible pathogenicity, variants of unknown significance, and possibly benign or benign. A result was considered positive if the pre-certified person carried a mutation categorized as Pathogenicity or Likely Pathogenicity. We collected six representative specimens from the ventricular area for histologic examination. Two pathologists, unaware of the clinical and genetic data, examined the specimens microscopically. We then compared the prevalence of pathogenic genes and their occurring in the same type of myocardium between children and adult transplant recipients, with a focus on the age of onset and duration of disease.

Part IV: We conducted a retrospective cohort analysis of children younger than 18 years who underwent heart transplantation at our center from October 1, 2005, to May 31, 2023. To assess the impact of socio-economic status, we followed up with the discharged children until September 30, 2023, monitoring for all-cause mortality and unplanned readmission events. Normal discharged heart transplant enrollees receive outpatient appointments at our center at 1-month, 6-month, and 12-month intervals, followed by annual visits. These follow-up visits include routine checkups to assess cardiac function and to gather information about health status and any readmission events. Efforts were made to contact parents or guardians by telephone to contact patients who missed an appointment and to schedule follow-up visits. Questionnaires collected details of survival, general health status, complication status, and any readmissions, including date and reason. Patients who could not be contacted were categorized as lost to follow-up. The cut-off date was 9/30/2023. Lost-to-follow-up patients were considered alive until their last known date of contact. We referred to previous research methods to create a composite family socioeconomic status score that included family income over the past year, as well as the occupation and education level of both parents in the family. All questionnaires were administered simultaneously on the day of discharge and informed consent was obtained from the patient's family. To evaluate the relationship between socio-economic status and prognosis, we assigned a composite score based on an assessment of household income, parental education level, and occupation. The Cox proportional hazards model and the Kaplan-Meier method were utilized for this analysis.

Results

Part I: Seventeen (29.8％) had adverse events during follow-up. Multivariate Cox analysis revealed that genetic mutation (HR: 5.634, 95％CI: 1.663–19.086, p=0.005), Noonan syndrome (HR: 3.770, 95％CI: 1.245–11.419, p=0.019), preoperational systolic anterior motion (HR: 4.596, 95％CI: 1.532–13.792, p=0.007)and mid-ventricular obstruction (HR: 4.763, 95％CI:1.538–14.754, p=0.007) were high-risk factors, suggesting that the degree of hypertrophy in the left ventricular is associated with poor prognosis. By analyzing the cardiac computed tomography with a three-dimensional model, children with poor prognosis have more hypertrophy in basal-inferior (p=0.014), mid-inferoseptal (p=0.044), and mid-inferior (p=0.017). We set critical values for the ratios of three segments (S4: 0.885, S9: 1.000, S10: 1.330) based on the model results. Based on the critical values, we plotted a bull's-eye diagram and localized these 17 segments. From the figure, we could see that these three segments were located in the posterior wall of the left ventricle. Further, when we reduced these 17 segments to a three-dimensional overall left ventricular view, we could visualize more intuitively that the hypertrophied posterior wall, which affects the prognosis, happens to be adjacent to the region of the septal band and is located below the conduction bundle. It suggests that a more hypertrophied posterior left ventricular wall portends a worse prognosis.

Part II: A total of 56 children with hypertrophic obstructive cardiomyopathy were included in this study, of whom 34 (60.7％) were male. The mean age at first diagnosis was 5.6±3.7 years. WES gene sequencing revealed that 25 (44.6％) children carried disease-causing mutant genes. Two of the children carried two disease-causing mutations, RAF1/RBM20 and LMNA/TNNT2, respectively. only one case ran in the family. Ten (17.9％) children had recurrent left ventricular outflow tract obstruction adverse events after surgery. There were no deaths during hospitalization, but two children died during follow-up, one at 12 months postoperatively due to heart failure induced by pulmonary infection and the other at 53 months postoperatively due to sudden cardiac death. Six (10.7％) children had life-threatening malignant arrhythmic events, with ventricular fibrillation as the main symptom, and all returned to normal after treatment with an implantable cardioverter defibrillator. Whole-exome sequencing results showed 11 children with the PTPN11 mutation (19.6％). In long-term follow-up (median 37 months, maximum 9 years), children with the PTPN11 mutation had 6 (54.5％) recurrent left ventricular outflow tract obstruction compared with other groups (p=0.015) but similar survival rates (p=0.514). The mean postoperative time to recurrent obstruction was 22±7 months. Children with PTPN11 mutation were 9-fold more likely to experience the risk associated with recurrent obstruction (95％ confidence interval, 1.77-45.81, p=0.001). Hematoxylin-eosin, Masson, and wheat germ agglutinin staining also revealed more cardiomyocyte hypertrophy in tissues with the PTPN11 mutation.

Part III: A total of 76 children were included in the final analysis during the study period. Among them, 49 (64.47％) had dilated cardiomyopathy, 4 (5.26％) had hypertrophic cardiomyopathy, 3 (3.95％) had restrictive cardiomyopathy, 11 (14.47％) had arrhythmogenic cardiomyopathy, 5 (6.58％) had valvular heart disease, and 4 (5.26％) had Complex Congenital Heart Disease. There were no significant differences between the different types of cardiomyopathies in terms of age at surgery (p=0.419) or gender (p=0.769). 33(43.4％) children carried mutation genes. The proportion of mutations varied significantly among different types of cardiomyopathies (p=0.003). The time from the first diagnosis to heart transplantation was significantly shorter in children compared to adults in case of dilated cardiomyopathy (15 months VS. 50 months, p=0.001), hypertrophic cardiomyopathy (16 months VS. 35 months, p=0.002) and arrhythmogenic cardiomyopathy (28 months VS. 127 months, p=0.001). In dilated cardiomyopathy, children were more likely to carry the TNNT2 mutation compared to adults (p=0.001), and heart failure progresses more rapidly in children with this mutation (19 months VS. 189 months, p=0.002). The most common mutation site in these children was K220del.

Part IV: 64 children (median age at operation 14 years, IQR:13–15) were enrolled and one case died in hospital due to primary graft dysfunction, 63 (98.4％) children had a median follow-up of 60 months (IQR:5.9-113.9). During the follow-up period, five of these children were lost to follow-up and 10 died during follow-up. The 1-, 2-, and 10-year survival rates of these children were higher than those of the adult cohort during the same time period, with survival rates of 94.7％, 87.9％, and 82.7％, respectively, compared with 93.1％, 85.0％, and 69.7％ for the adults (p=0.042). We also analyzed the socioeconomic factors of the children's families and found that 17 (27.0％) children came from poor areas, 39 (61.9％) had parents with less than high school education, and 43 (68.3％) had parents who were farmers or workers. Despite this difference in socioeconomic background, there were no significant differences in gender, heart transplant waiting time, weight, or age at surgery among children from families with low, medium, or high socioeconomic levels. However, children from families with high socioeconomic status were more likely to be from urban areas (p=0.047) and less likely to be from deprived areas (p=0.025) than children from low or moderate socioeconomic status. The median cost of surgical treatment was 350.87±131.67 thousand yuan. 20 (31.7％) children had 25 unplanned readmissions. Children had higher all-cause mortality and more unplanned readmissions in families with low socio-economic status (n=33) than middle (n=10) or high (n=20) family socio-economic status. Hazard ratios were 5.99 (95％CI:2.28–10.64, p=0.003) for all-cause mortality for low versus high family socio-economic status, and 2.53 (95％CI:1.04–9.43, p=0.029) for middle versus high family socio-economic status.

Conclusions

In ventricular septal myocardiectomy, the degree of left ventricle posterior wall hypertrophy is also correlated with postoperative prognosis through CCT combined with three-dimensional reconstruction. CCT combined with three-dimensional reconstruction provides guidance for preoperative assessment of the overall prognosis and the development of a treatment plan, and the hypertrophy of the posterior wall of the left ventricle should be more aggressively managed in children with HOCM during the operation. Children with PTPN11 mutation-associated hypertrophic cardiomyopathy are at greater risk of LVOTO recurrence. Therefore, we need to actively conduct preoperative genetic screening for children with hypertrophic cardiomyopathy and risk stratify children at high risk of recurrence, and strengthen the frequency of postoperative review and management. Genetic mutations play a critical role in the progression of pediatric cardiomyopathy to end-stage heart failure. the TNNT2 mutation is particularly suggestive of patients with rapidly progressive types of heart failure in DCM. Identification of such mutations may help guide patient management and risk stratification. Family socioeconomic status also has an impact on post-transplant prognosis in pediatric cardiomyopathy, and we suggest that more proactive measures to alleviate economic, educational, and other family disparities are needed to improve the prognosis of HTx for pediatric cardiomyopathy.

In conclusion, we investigated in detail the impact of genetic background, pathology, surgical strategy, and aspects of family socioeconomic and educational background on the diagnosis, treatment, and prognosis of pediatric cardiomyopathy in this study, emphasizing the importance of precise surgical diagnosis and treatment of pediatric cardiomyopathy and highlighting the significance of individualized diagnosis and treatment of pediatric cardiomyopathy.