Influence of atrial septal defect on mitral valve growth after repair of coarctation of the aorta or an interrupted aortic arch in infants

Yi-Chia Wang; Heng-Wen Chou; Chi-Hsiang Huang; Hsing-Hao Huang; Yih-Sharng Chen; En-Ting Wu; Shyh-Jye Chen; Ming-Tai Lin; Shuenn-Nan Chiu; Shu-Chien Huang

doi:10.3345/cep.2025.02110

Clin Exp Pediatr > Volume 69(4); 2026

Wang, Chou, Huang, Huang, Chen, Wu, Chen, Lin, Chiu, and Huang: Influence of atrial septal defect on mitral valve growth after repair of coarctation of the aorta or an interrupted aortic arch in infants

Original Article

Cardiology

Influence of atrial septal defect on mitral valve growth after repair of coarctation of the aorta or an interrupted aortic arch in infants

¹Department of Anesthesiology, National Taiwan University Hospital, Taiwan

²Department of Surgery, National Taiwan University Hospital, Taiwan

³Department of Pediatrics, National Taiwan University Hospital, Taiwan

⁴Department of Radiology, National Taiwan University Hospital, Taiwan

Corresponding author: Shu-Chien Huang, MD, PhD. Department of Surgery, National Taiwan University College of Medicine and National University Hospital, 7 Chung-Shan South Road, Taipei, Taiwan, 10002 Email: cvshuang@gmail.com

Received September 8, 2025 Revised November 11, 2025 Accepted November 21, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Clinical and Experimental Pediatrics 2026;69(4):322-329.

Published online: January 13, 2026

DOI: https://doi.org/10.3345/cep.2025.02110

Abstract

Background

Patients with coarctation of the aorta (CoA) and an interrupted aortic arch (IAA) may present with small mitral valves (MVs) and a reduced left ventricular (LV) volume. Biventricular repair (BVR) in these patients is dependent on adequate size of the left cardiac structures.

Purpose

This study evaluated the impact of the hemodynamic characteristics of atrial septal defects (ASDs) on MV growth following surgical repair.

Methods

We retrospectively reviewed the data of patients diagnosed with CoA or IAA between 2007 and 2024. The z score for MV size measured 6 months postoperatively (Z2) was compared with the preoperative MV size (Z1). The factors associated with MV growth were also studied.

Results

A total of 161 patients with CoA or IAA were included. Transthoracic echocardiography was used to assess the MV and LV dimensions preoperatively and 6 months postoperatively. Of the cohort, 155 (96.3%) underwent initial BVR and 6 underwent single-ventricle palliation. MV z scores significantly increased following BVR (mean change: +0.45±1.35; P<0.001) but decreased after single-ventricle repair (-0.56±0.49, P=0.04). Multivariate analysis identified the initial MV z score and ASD pressure gradient as independent predictors of MV growth (R²=0.39).

Conclusion

Annular growth of the MV was not observed in patients who underwent single-ventricle palliation. In contrast, among patients who achieved BVR, those with a small preoperative MV annulus and low ASD pressure gradient demonstrated subsequent catch-up MV growth, suggesting that adequate left-sided preload is essential for MV development.

Key words: Hypoplastic Left Heart Syndrome, Aortic Arch, Interrupted, Mitral valve, Atrial heart septal defects, Aortic coarctation

Key message

Question: Does atrial septal defect (ASD) physiology affect postrepair mitral valve growth in patients with coarctation of the aorta or an interrupted aortic arch?

Finding: Mitral valve growth occurred after biventricular repair but not single-ventricle palliation, particularly in patients with small valves and low ASD pressure gradients.

Meaning: The ASD pressure gradient determines mitral valve growth and should guide surgical strategies in patients with borderline hypoplastic left heart syndrome.

Graphical abstract. Mitral valve growth was observed after repair of coarctation of the aorta in patients with borderline hypoplastic left heart syndrome and unrestricted atrial septal defects. ASD, atrial septal defect; PG, pressure gradient.

Introduction

Patients with coarctation of aorta (CoA) and interrupted aortic arch (IAA) have a higher chance of small mitral valve (MV) and reduced left ventricular (LV) volume. The success of biventricular repair (BVR) in these patients depends on the adequacy of left-sided structures, with MV size playing an important role in determining the feasibility of BVR [1]. There were several criteria to decide the feasibility of BVR in patients with borderline left ventricles and/or critical aortic stenosis [2-5]. However, these scores are not applicable to the whole group of patients and are not uniformly accepted. A key limitation of these criteria is that LV structures, particularly the MV, can grow following surgical interventions and ultimately succeed in BVR. However, the potential for such growth is less studied.

Recently, LV recruitment strategies following initial single-ventricle palliation was introduced [6-8]. These strategies include atrial septal defect (ASD) restriction, atrioventricular valve repair, and relief of LV outflow tract (LVOT) obstruction [1,9]. Notably, ASD closure has been shown to enhance LV loading following relief of LVOT obstruction, leading to observable increases in left heart dimensions [6]. Given the significant impact of flow through the MV on the growth of left heart structures, we hypothesize that preoperative ASD status could influence the blood flow dynamics through the MV and affect postsurgical MV growth in patients with CoA or IAA.

Methods

1. Patient population

We included patients with CoA or IAA in National Taiwan University Hospital between April 2007 to July 2024. Individuals with intrinsic MV conditions, including parachute MV and common atrioventricular valve anomalies, were excluded. Patients with aortic atresia or mitral atresia were also excluded.

Ethical approval for this study (Ethical Committee N°202310048RIND) was provided by the Ethical Committee of the National Taiwan University Hospital, Taiwan, and the requirement for individual consent was waived for this retrospective observational study.

2. Measurements

We reviewed the transthoracic echocardiographic data before initial operation (t1) and 6 months after the operation (t2). The mitral and tricuspid valve annuli were measured at their maximum in diastole from the apical 4-chamber view. LV end-diastolic dimension (LVEDD) was measured by M-mode in the long-axis view. The following morphologic features were collected: aortic valve annulus and morphology, LV length and right ventricular length in apical 4-chamber view, main pulmonary artery diameter, aortic root diameter, mid-aortic arch diameter, apex-forming ventricle, and presence of an ASD and its pressure gradient (PG). Valve annulus diameter z score were obtained using the formula derived from echocardiography-based normal valve measurements adjusted for body surface area [10,11]. The ASD PG was measured preoperatively using Doppler transthoracic echocardiography. ASD status was categorized as no ASD (intact atrial septum), restrictive ASD, or nonrestrictive ASD based on echocardiographic assessment of interatrial communication and Doppler-derived pressure gradients.

3. Surgical technique

1) Biventricular repair

One-stage BVR was performed with application of selective antegrade selective cerebral perfusion [12]. The aortic arch was reconstructed by resection of the isthmus and extended end-to-end anastomosis. The ventricular septal defect (VSD) and ASD were repaired at the same time if present. However, in patients with small MV or LV size, a small fenestration or PFO may be left for easily monitoring Left atrium pressure by echo during wearing off cardiopulmonary bypass support.

2) Single-ventricle repair

A standard Norwood stage I reconstruction (Norwood S1P) was performed [13]. Cardiopulmonary bypass was initiated with arterial cannulation through a 3.5-mm expanded polytetrafluoroethylene (ePTFE) graft to the innominate artery and ductus arteriosus. Antegrade selective cerebral perfusion was performed during aortic arch reconstruction. A 5-mm ePTFE graft was used for the right ventricle-to-pulmonary artery shunt. The interatrial septum was resected if the ASD was restrictive.

4. Scoring system

To evaluate suitability for BVR, we retrospectively applied 5 published prediction models—Rhodes score [14], Congenital Heart Surgeons' Society Study (CHSS)-1 score [15], Discriminant score [2], CHSS-2 score [16], and 2V score [17]—to our study cohort. The patients’ final clinical outcomes (successful BVR, single-ventricle palliation, or failed BVR) were compared with the predictions generated by each model based on their respective cutoff values for BVR recommendation [18].

5. Statistical analysis

We compared the z values of the MV and LVEDD before operation (Z1) and 6 months after the operation (Z2) to assess their growth after surgery. MV growth was defined as the difference between Z2 and Z1.

Data are summarized using counts and percentages for nominal or dichotomous variables, and median and interquartile range (IQR) for continuous variables. Continuous variables were analyzed using the Mann-Whitney test, while discrete data were analyzed using the chi-square test or Fisher exact test when categorical variables were absent. The paired Student t test was used for comparing continuous variables for the same patient.

MV growth (Z2–Z1) was analyzed using Pearson correlation and univariate P values to identify factors influencing MV growth. Correlation was analyzed by linear correlation modelling, computing the Pearson correlation coefficient (r) and nonparametric regression analysis (categorical variables), as appropriate. Multivariate analysis was conducted on variables with univariate P values <0.20 using stepwise forward and backward selection methods. A 2-tailed P value<0.05 was considered statistically significant. These analyses were performed with STATA 13.0 MP statistical package (StataCorp, USA). Analyses and construction of graphs of MV growth were performed using the GraphPad prism software (ver. 6.01, USA).

Results

1. Demographic data

We identified 161 patients with CoA or IAA, and CoA and IAA were observed in 141 and 20 patients, respectively. Patient characteristics and echocardiographic parameters are summarized in Table 1.

The median age at the initial operation was 7 (IQR, 4–19) days, with a median body weight of 2.9 (IQR, 2.6–3.3) kg. The median follow-up period was 6 (IQR, 3–9) years after the initial surgery. A VSD was present in 60.2% of patients, while an ASD or PFO was identified in 88.2%. There were 87 patients whose aortic valve z score was less than -2(54%), and 35 patients whose MV z score was less than -2 (21.8%).

2. Survival outcomes

There were 6 patients (3.7%) undergoing single-ventricle repair and 155 (96.3%) undergoing BVR as initial surgical approach. Two mortality (2 of 6) occurred following the Norwood operation. One patient successfully achieved BVR after bidirectional Glenn shunt take-down. Among the patients who underwent BVR, there were 3 mortalities (3 of 155). Two patients for whom BVR through aortoplasty was initially attempted developed severe heart failure and shock, leading to conversion to Norwood S1P. Among the patients who received BVR, 20 patients (13.2%) necessitated 5 surgical reinterventions and 4 catheter-based interventions due to recoarctation (n=5), recurrent LVOT obstruction (n=8), and MV plasty (n=3). None of our patients developed pulmonary hypertension during follow-up.

3. MV growth

There were 150 patients with available z values at both preoperative and 6 months postoperative for analysis. Preoperatively, the mean MV annulus diameter was 8.7±2.4 mm with a z value of -0.9±1.4. Six months postoperatively, the mean MV annulus diameter increased to 12.9±2.3 mm with a z value of -0.4±1.2. The growth in MV size, measured as the change in z value from preoperative to postoperative (Z2–Z1), was statistically significant with an increase of 0.43±1.39 (P<0.001). Additionally, the

LVEDD increased from 15.5±4.6 mm to 23.0±3.1 mm, with the z values increased from -1.8±1.9 at preoperative status to -1.6±1.5 at 6 months after operation.

Among the cohort, 94 patients had complete perioperative transesophageal echocardiography (TEE) imaging available for analysis. The aortic valve annulus and MV annulus dimensions were comparable between preoperative transthoracic echocardiography (TTE), pre-bypass TEE, and intraoperative TEE performed after separation from cardiopulmonary bypass (all P>0.05). In contrast, both the aortic valve and MV annulus dimensions increased significantly on the 6-month postoperative TTE (both P<0.01).

MV annulus z score changes were different between the patients receiving single-ventricle repair and the patients with BVR. After single-ventricle reconstruction, MV z scores decreased in the 6 months following the initial operation (paired test Z2–Z1 = -0.56±0.49; P=0.04). However, in BVR patients, the MV z scores significantly increased (paired test Z2-Z1= 0.45±1.35; P<0.001) (Fig. 1).

4. MV growth in BVR

Echocardiographic measurements at initial operation and 6-month follow-up after BVR (N=144) was shown in Table 2. There was significant increase in MV z score, Aortic valve z score and LVEDD score after BVR.

Among patients who underwent BVR, the increase in MV z score was significantly and negatively associated with both the initial MV z score (R²=-0.66; P<0.001) (Fig. 2A) and the ASD PG (R²=-0.27; P=0.003) (Fig. 3A). A similar pattern was observed for changes in LVEDD, which were also negatively correlated with the initial MV z score (R²=-0.40; P<0.001) and the ASD PG (R²=-0.32; P<0.001). (Figs. 2B and 3B)

We further performed multivariate analysis in patients to determine the factors associated with MV growth. 144 patients who had BVR were included, and variables with univariate P value <0.02 were selected by stepwise forward and backward method. Both methods revealed that MV Z1 value (coefficient, -0.61; 95% confidence interval [CI], -0.76 to -0.45; P<0.001) and ASD peak PG (coefficient, -0.05; 95% CI, -0.09 to 0.01; P=0.012) were independent risk factors for MV growth in the BVR population. The R-squared for the model was 0.39.

Patients’ final circulatory outcome (BVR vs. single ventricular repair) and their initial MV z value and ASD PG were plotted as Fig. 4. The patients without ASD were also depicted at the top margin of the figure. Among the population with initial small MV (z value<-2.5), patients with high ASD PG or no-ASD had single-ventricle repair, while low ASD PG patients achieved BVR with good survival outcomes.

5. Results of prediction score application

The Rhodes score, CHSS-1 score, Discriminant score, CHSS-2 score, and Two-Ventricle score were retrospectively calculated. The suggested BVR or single-ventricle palliation by these scores [18] were compared against actual patient outcomes. (Table 3). Among these, the Rhodes score demonstrated the highest discrepancy (50%) between predicted and actual outcomes, with a tendency to favor single-ventricle palliation. In contrast, the CHSS-2 score strongly favored BVR, resulting in low specificity for identifying patients who ultimately failed BVR. The 2V score showed relative lower discrepancy, with 12.5% of cases misclassified relative to their final clinical outcome.

Discussion

In this study, we observed a lack of MV annulus growth in patients undergoing single-ventricle palliation. Conversely, in BVR patients, the presence of a small MV annulus and a low ASD PG correlated with subsequent catch-up MV growth.

The 'no flow, no grow' theory, supported by animal studies, highlights the importance of blood flow in fetal heart development [19]. Studies in mouse models and chick embryos have demonstrated the critical role of blood flow in promoting growth of fetal heart structures [20-22]. A nonrestrictive ASD with CoA or IAA can cause a low-flow status in the fetal and neonatal LV due to left-to-right shunting at the atrial level and lack of forward flow through the LV. This inadequate LV filling can impede the growth of left heart structures [23]. Surgical repair of both the ASD and aortic arch can enhance LV inflow and decrease LV afterload, promoting catch-up growth of left heart structures, including the MV annulus. In patients who underwent the Norwood S1P, the flow through the MV was not increased, and consequently, the MV size did not grow.

Previous studies have shown MV catch-up growth in patients with CoA or IAA after BVR [24]. Corno [25] reported significant LV growth after surgery in neonates with CoA and IAA with borderline LV dimensions. Puchalski et al. [26] found notable increases in mitral and aortic valve z scores following coarctation repair, even with initial z scores as low as -4.0. IJsselhof et al. [27] observed the most rapid LV growth within the first year after BVR for hypoplastic left heart complex (HLHC), i.e., Hypoplastic left heart syndrome (HLHS) without intrinsic valvar stenosis or atresia. Our findings align with these studies, however, none of these studies mentioned the impact of ASD PG on MV growth. In our study, we found that the MV size increased in patients with small MV and low ASD PG, but individuals with a high ASD PG had lower potential for significant MV growth.

A high ASD PG indicates elevated left atrial pressure, which can result from large pulmonary flow (Qp/Qs) through the MV, MV stenosis, increased LV afterload, or poor LV compliance. In this condition, the MV receives much pulmonary venous return, and LV is already fully loaded, so ASD closure did not increase much flow through MV. In the literature about borderline HLHS patients undergoing LV recruitment procedures, ASD closure is crucial for LV development [6,28]. For patients with a high ASD PG through small ASD or with intact atrial septum, the situation mimics “nature LV recruitment”; if the LA pressure is high and the MV remains small under these conditions, it could imply conditions similar to LV recruitment failure [1].

Unsuccessful BVR in CoA and IAA patients, compared to initial single-ventricle palliation, may increase morbidity and mortality [16]. A universal guideline for dichotomizing cases into BVR or single-ventricle cannot be established. The Rhodes and CHSS-1 scoring systems were originally developed for patients with critical aortic stenosis and may not be applicable to broader forms of left heart hypoplasia [18]. The discriminant score was designed to predict survival in neonates with aortic stenosis and a relatively preserved MV (z score >-2) [18], limiting its relevance to patients with more complex anatomical variants. The CHSS-2 score aimed to compare survival outcomes between BVR and single-ventricle palliation in patients with severe LVOT obstruction [18]. However, this model is based on historical data, during which single-ventricle outcomes were significantly worse than current standards. As a result, the CHSS-2 score tends to favor BVR and showed poor specificity in identifying patients who ultimately failed BVR in our cohort. The 2V score was developed specifically for patients with hypoplastic left heart structures without intrinsic aortic or MV stenosis or atresia. While this population resembles our cohort, the scoring system was derived from only 20 patients [17], which limits its external validity and generalizability. We could not reproduce the 100% sensitivity and specificity in the original study [17].

In the study of Plymale et al. [23] a MV z score > -2.5 was identified as a key threshold predictive of BVR success in patients with HLHC.

The minimum MV z score in our successful BVR cohort was -4.32. However, 2 patients with larger MV z score (-2.95 and -3.07) and a high ASD PG underwent BVR but failed and required conversion to Norwood stage 1 palliation (Fig. 4). Our findings indicate that CoA and IAA patients who had normal valve morphology with nonrestrictive preoperative ASDs may have catch-up MV growth with successful BVR with small initial MV annulus. In contrast, patients with elevated ASD PGs and small initial MV annulus may face more challenges after BVR.

The application ‘in-between’ strategies in borderline HLHS have evolved over recent years, with use of the hybrid or Norwood circulation as a bridge to decision, and LV recruitment strategies can be employed to enlarge or ‘grow’ the LV in such cases [29]. These strategies allow more patients an opportunity to potentially undergo BVR whilst also deferring decision making to allow further information about the suitability of the LV to manifest. Nonetheless, uniformly applicable data is lacking. Our finding could help differentiate patients who need Norwood from BVR and narrow the “grey zone” to decrease unnecessary interstage risks.

This study is limited by its retrospective nature, limited case number and single-institution experience. The surgical decision and perioperative care are made by the surgical team. Cases of critical aortic stenosis and those involving endocardial fibroelastosis were not included in our analysis, precluding the generalization of our findings to other subtypes of borderline hypoplastic left heart syndrome. We did not perform magnetic resonance imaging flow studies due to facility limitations, and cardiac catheterization was not performed before operation. Therefore, direct measurement of left atrial pressure and trans mitral flow data are not available.

There is a potential for MV growth in HLHC patients who received BVR. Patients with low PG ASD demonstrated a significant increase in MV size following BVR. Our findings emphasize the relevance of ASD physiology in surgical decision-making for CoA/IAA patients with borderline MV hypoplasia.

Footnotes

Conflicts of interest

No potential conflict of interest relevant to this article was reported.

Funding

This study was funded by a grant from the Ministry of Science and Technology in Taiwan (MOST-112-2314-B-002-180-), (MOST-113-2314-B-002-271-) and (NSTC-113-2314-B-002-150-)

Author Contribution

Conceptualization: YCW, SCH; Formal Analysis: HWC; Investigation: YCW, CHH, MTL; Methodology: HHH, YSC, SNC; Project Administration: ETW, SJC; Writing – Original Draft: YCW; Writing – Review & Editing: SCH

Fig. 1.

Changes in mitral valve annulus z scores among patients with coarctation of the aorta or an interrupted aortic arch undergoing single-ventricle palliation or biventricular repair. The mitral valve annulus z scores increased significantly after biventricular repair. Footnote: z1, preoperative mitral valve annulus z score; z2, 6-month postoperative mitral valve annulus z score.

Fig. 2.

Association between changes in (A) mitral valve annulus z scores and (B) left ventricular end-diastolic dimension (LVEDD) with the initial mitral valve z score in patients with coarctation of the aorta or an interrupted aortic arch undergoing biventricular repair. Negative correlations were observed (P<0.001). Footnote: z1 = preoperative mitral valve z score; z2, 6-month postoperative mitral valve z score; Δz = z2 – z1 = change in mitral valve z score.

Fig. 3.

Association between the change in (A) mitral valve annulus z scores and (B) left ventricular end-diastolic dimension (LVEDD) with the atrial septal defect (ASD) pressure gradient (PG) in patients with coarctation of the aorta or an interrupted aortic arch undergoing biventricular repair. Negative correlations were observed (P<0.01). Footnote: z2 – z1 = change in mitral valve z score between post- and preoperative measurements.

Fig. 4.

Relationship between initial mitral valve z score and atrial septal defect (ASD) pressure gradient among patients with coarctation of the aorta or an interrupted aortic arch. Each point represents a patient categorized according to the final circulation outcome. Patients without ASD are shown in the top margins. The shaded area represents the region with an ASD pressure gradient <10 mmHg and initial MV z score < -2.5. BiV, biventricle; MV, mitral valve; PG, pressure gradient of the ASD; V, ventricle.

Table 1.

Demographic and clinical characteristics of the enrolled patients (n=161)

Variable	Value
Male sex	92 (57.1)
Age at repair (days after birth)	7 (4–19)
Body weight (kg)	2.9 (2.6–3.3)
Body height (cm)	49 (46–50.6)
CoA/IAA	141/20 (87.6/12.4)
VSD	97 (60.2)
ASD/PFO	142 (88.2)
Echocardiographic measurements
MV annulus (mm)	8.8 (7.5–10.1)
AV annulus (mm)	5.21 (4.9–5.92)
LVEDD (mm)	16 (13.1–18.7)
Apex-forming right ventricle	37 (23)
MV/TV valve ratio	0.87 (0.74–0.99)

Values are presented as number (%) or median (interquartile range).

CoA, coarctation of the aorta; IAA, interrupted aortic arch; VSD, ventricular septal defect; ASD, atrial septal defect; PFO, patent foramen ovale; MV, mitral valve; AV, aortic valve; LVEDD, left ventricular end-diastolic dimension; TV, tricuspid valve.

Table 2.

Echocardiographic measurements preoperatively and at 6-month follow-up

Variable	Initial status	6-Month follow-up
MV annulus (mm)	8.8 (7.4–9.2)	13.00 (11.75–14.00)
MV z score	-1.40 (-1.96 to -0.75)	-0.51 (-1.16 to 0.23)
AV annulus (mm)	5.10 (4.90–5.74)	8.5 (7.9–9.2)
AV z score	-2.12 (-2.58 to -1.26)	-0.94 (-1.66 to -0.21)
LVEDD (mm)	15.2 (13.1–17.0)	20.4 (21.7–25.0)
LVEDD z score	-2.20 (-3.56 to -1.20)	-1.40 (-2.30 to -0.49)
MV/TV valve ratio	0.87 (0.74–0.99)	0.92 (0.83–1.05)

Values are presented as median (interquartile range).

MV, mitral valve; AV, aortic valve; LVEDD, left ventricular end-diastolic dimension; TV, tricuspid valve.

Table 3.

Predictive performance of 5 scoring systems for identifying biventricular repair candidates

Scoring system	Cutoff value [18]	Specificity (%)^a)	PPV (%)^b)	Misclassification rate (%)^c)
Rhodes et al. [14]	≥0.35	100.0	28.1	50.0
CHSS-1 [15]	<0	50.0	82.4	25.0
Discriminant [2]	≥-0.65	50.0	64.7	37.5
CHSS-2 [16]	<0	0.0	66.7	25.0
2V [17]	≤16.2	25.0	83.7	12.5

PPV, positive predictive value; CHSS, Congenital Heart Surgeons' Society Study; BVR, biventricular repair.

^a) Among patients treated with single-ventricle palliation, % correctly predicted as not requiring BVR.

^b) PPV: % of patients predicted to require BVR who underwent it.

^c) Percentage of all patients misclassified by the model

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