Left pulmonary artery kinking caused by outflow tract dilatation after transannular patch repair of tetralogy of Fallot

Pulmonary Artery Angioplasty for Improving Ipsilateral Lung Perfusion in Adolescent and Adult Patients: An Analysis Based on Cardiac Magnetic Resonance Imaging and Lung Perfusion Scanning

Background

The left pulmonary artery (LPA) may be kinked and stenotic, especially in tetralogy of Fallot, because of ductal tissue and anterior deviation of the conal septum. If LPA stenosis is not effectively treated during total correction, surgical angioplasty is occasionally performed. However, whether pulmonary artery (PA) angioplasty in adolescents or adults improves perfusion in the ipsilateral lung remains unclear.

Methods

This retrospective review enrolled patients who underwent PA angioplasty for LPA stenosis between 2004 and 2019. Among patients who underwent a lung perfusion scan (LPS) or cardiac magnetic resonance imaging (cMRI) pre- and post-pulmonary angioplasty, those aged >13 years with <40% left lung perfusion (p-left) in the pre-angioplasty study were included. Preoperative and postoperative computed tomography, LPS, and cMRI data were collected. The perfusion ratio was analyzed according to the LPA's anatomical characteristics.

Results

Seventeen adolescents and 16 adults (≥18 years old) were finally included (median age, 17 years). The most common primary diagnosis was tetralogy of Fallot (87.9%). In all patients, LPA angioplasty was performed concomitantly with right ventricular outflow tract reconstruction. No patients died. Preoperative p-left was not significantly different between adolescents and adults; however, adolescents had significantly higher postoperative p-left than adults. P-left significantly increased in adolescents, but not in adults. Seven patients had significant stenosis (z-score <-2.0) confined only to the proximal LPA and demonstrated significantly increased p-left.

Conclusion

PA angioplasty significantly increased ipsilateral lung perfusion in adolescents. If focal stenosis is confined to the proximal LPA, PA angioplasty may improve ipsilateral lung perfusion, regardless of age.

Morphometrics predicts the differential regurgitant fraction in bilateral pulmonary arteries of patients with repaired tetralogy of fallot

In patients with repaired tetralogy of Fallot (rTOF), the regurgitant fraction (RF) in left pulmonary artery (LPA) and right pulmonary artery (RPA) is usually unequal. The morphometrics may play a crucial role in this RF discrepancy. Cardiovascular MR of 79 rTOF patients and 20 healthy controls were retrospectively enrolled. Forty-four from the 79 patients were matched in age, sex and body surface area to the 20 controls and were investigated for: (1) phase-contrast flow of main pulmonary artery (MPA), LPA, and RPA; (2) vascular angles: the angles between the thoracic anterior-posterior line (TAPL) with MPA (θM-AP), MPA with RPA (θM-R), and MPA with LPA (θM-L); (3) cardiac angle, the angle between TAPL and the interventricular septum; (4) area ratio of bilateral lung and hemithorax regions. Compared with the 20 controls, the 44 rTOF patients exhibited wider θM-AP, sharper θM-L angle, and a smaller θM-L/θM-R ratio. In the 79 rTOF patients, LPA showed lower forward, backward, and net flow, and greater RF as compared with RPA. Multivariate analysis showed that the RF of LPA was negatively associated with the θM-L/θM-R ratio and the age at surgery (R2 = 0.255). Conversely, the RF of RPA was negatively associated with the left lung/left hemithorax area ratio and cross-sectional area (CSA) of LPA, and positively associated with CSA of RPA and MPA (R2 = 0.366). In rTOF patients, the RF of LPA is more severe than that of RPA, which may be related to the vascular morphometrics. Different morphometric parameters are independently associated with the RF of LPA or RPA, which may offer potential insights for surgical strategies.

Pulmonary Artery Stenosis in Tetralogy of Fallot

Tetralogy of Fallot (TOF) is the most common cyanotic congenital cardiac defect. The survival rate after primary complete repair is high (98-100%); however, pulmonary artery stenosis (PAS) is not uncommon after TOF repair, and severe PAS aggravates pulmonary regurgitation, resulting in right ventricle dilation, ventricular arrhythmia, and possibly death. PAS in TOF can be congenital due to hypoplasia or coarctation or can be acquired secondary to a surgical procedure. The latter may be caused by an exogenous conduit implant, compression from the adjacent enlarged ascending aorta, or outflow tract dilation after transannular patch repair. PAS can also be caused by the pulmonary artery plasty strategy itself. Here, the intrinsic mechanisms underlying PAS and pulmonary artery plasty techniques and strategies are reviewed to provide guidance for surgeons.

Clinical characteristics of tetralogy of Fallot with left pulmonary artery acute angulation on computed tomography

Left pulmonary artery (LPA) stenosis with acute angulation commonly necessitates surgical revision in the treatment of tetralogy of Fallot (TOF). We investigated the clinical characteristics of acute angulation of the LPA in patients with TOF via computed tomography (CT). Between 2011 and 2022, 160 patients were diagnosed with TOF using CT. After excluding 28 patients due to insufficient records or age, 132 patients were included in the present analysis. The patients were divided into two groups according to the presence or absence of acute angulation of the LPA: group I (TOF with an acute angle of the LPA, n = 53) and group II (TOF without an acute angle of the LPA, n = 79). We retrospectively collected clinical data from electronic medical records. T-tests were used to analyze continuous variables (i.e., age, sex, weight, right ventricular outflow tract [RVOT] pressure on echocardiography, and distance to bifurcation), and Fisher's exact and chi-square tests were used to analyze categorical data (i.e., presence of the right aortic arch, pulmonary arterial atresia/hypoplasia, atrial septal defect [ASD], patent ductus arteriosus [PDA], and pulmonary valve). The groups did not differ significantly in terms of sex, weight, presence of the right aortic arch, pulmonary arterial atresia/hypoplasia, ASD, or distance to the bifurcation. Moreover, there was no significant difference between the presence and absence of PDA (P = 0.057); however, patients in group I were significantly older (143.2 ± 97.8 days) than those in group II (91.1 ± 76.0 days, P = 0.002). Furthermore, RVOT pressure was significantly higher among patients in group I (45.1 ± 22.5 mmHg) than in group II (25.0 ± 12.4 mmHg, P < 0.001). In the current study, acute angulation of the LPA in patients with TOF, as observed on CT, was associated with older age and higher RVOT pressure on echocardiography.

Surgical and transcatheter pulmonary valve replacement in patients with repaired tetralogy of Fallot: cardiac magnetic resonance imaging characteristics and morphology of right ventricular outflow tract

BACKGROUND

Pulmonary valve replacement is recommended in patients with repaired tetralogy of Fallot based on cardiac magnetic resonance imaging (MRI) criteria. This procedure is performed by surgical or transcatheter approaches.

OBJECTIVE

We aimed to investigate the differences in preprocedural MRI characteristics (volume, function, strain) and morphology of the right ventricular outflow tract and branch pulmonary arteries in patients for whom surgical or transcatheter pulmonary valve replacement was planned.

MATERIALS AND METHODS

Cardiac MRI of 166 patients with tetralogy of Fallot were analyzed. Of these, 36 patients for whom pulmonary valve replacement was planned were included. Magnetic resonance imaging characteristics, right ventricular outflow tract morphology, branch pulmonary artery flow distribution and diameter were compared between surgical and transcatheter groups. Spearman correlation and Kruskal-Wallis tests were performed.

RESULTS

Circumferential and radial MRI strain for the right ventricle were lower in the surgical group (P=0.045 and P=0.046, respectively). The diameter of the left pulmonary artery was significantly lower (P=0.021) and branch pulmonary artery flow and diameter ratio were higher (P=0.044 and P = 0.002, respectively) in the transcatheter group. There was a significant correlation between right ventricular outflow tract morphology and right ventricular end-diastolic volume index and global circumferential and radial MRI strain (P=0.046, P=0.046 and P= 0.049, respectively).

CONCLUSION

Preprocedural MRI strain, right-to-left pulmonary artery flow, diameter ratio and morphological features of the right ventricular outflow tract were significantly different between the two groups. A transcatheter approach may be recommended for patients with branch pulmonary artery stenosis, since both pulmonary valve replacement and branch pulmonary artery stenting can be performed in the same session.

The American Association for Thoracic Surgery (AATS) 2022 Expert Consensus Document: Management of infants and neonates with tetralogy of Fallot

OBJECTIVE

Despite decades of experience, aspects of the management of tetralogy of Fallot with pulmonary stenosis (TOF) remain controversial. Practitioners must consider newer, evolving treatment strategies with limited data to guide decision making. Therefore, the TOF Clinical Practice Standards Committee was commissioned by the American Association for Thoracic Surgery to provide a framework on this topic, focused on timing and types of interventions, management of high-risk patients, technical considerations during interventions, and best practices for assessment of outcomes of the interventions. In addition, the group was tasked with identifying pertinent research questions for future investigations. It is recognized that variability in institutional experience could influence the application of this framework to clinical practice.

METHODS

The TOF Clinical Practice Standards Committee is a multinational, multidisciplinary group of cardiologists and surgeons with expertise in TOF. With the assistance of a medical librarian, a citation search in PubMed, Embase, Scopus, and Web of Science was performed using key words related to TOF and its management; the search was restricted to the English language and the year 2000 or later. Articles pertaining to pulmonary atresia, absent pulmonary valve, atrioventricular septal defects, and adult patients with TOF were excluded, as well as nonprimary sources such as review articles. This yielded nearly 20,000 results, of which 163 were included. Greater consideration was given to more recent studies, larger studies, and those using comparison groups with randomization or propensity score matching. Expert consensus statements with class of recommendation and level of evidence were developed using a modified Delphi method, requiring 80% of the member votes with 75% agreement on each statement.

RESULTS

In asymptomatic infants, complete surgical correction between age 3 and 6 months is reasonable to reduce the length of stay, rate of adverse events, and need for a transannular patch. In the majority of symptomatic neonates, both palliation and primary complete surgical correction are useful treatment options. It is reasonable to consider those with low birth weight or prematurity, small or discontinuous pulmonary arteries, chromosomal anomalies, other congenital anomalies, or other comorbidities such as intracranial hemorrhage, sepsis, or other end-organ compromise as high-risk patients. In these high-risk patients, palliation may be preferred; and, in patients with amenable anatomy, catheter-based procedures may prove favorable over surgical palliation.

CONCLUSIONS

Ongoing research will provide further insight into the role of catheter-based interventions. For complete surgical correction, both transatrial and transventricular approaches are effective; however, the smallest possible ventriculotomy should be utilized. When possible, the pulmonary valve should be spared; and if unsalvageable, reconstruction can be considered. At the conclusion of the operation, adequate relief of the right ventricular outflow obstruction should be confirmed, and identification of a significant fixed anatomical obstruction should prompt further intervention. Given our current knowledge and the gaps identified, we propose several key questions to be answered by future research and potentially by a TOF registry: When to palliate or proceed with complete surgical correction, as well as the ideal type of palliation; the optimal surgical approach for complete repair for the best long-term preservation of right ventricular function; and the utility, efficacy, and durability of various pulmonary valve preservation and reconstruction techniques.

Patch Enlargement May Not Be a Good Strategy for Tetralogy of Fallot with Unbalanced Pulmonary Artery Branches

OBJECTIVES

To figure out the optimal strategy to manage Tetralogy of Fallot (TOF) with unbalanced pulmonary artery(PA) branches by investigating the different effects of PA plasty on the development of the hypoplastic PA (HPA).

METHODS

A single center, retrospective analysis was carried out to compare the outcome of different PA plasty methods on the development of HPA in patients of TOF with unbalanced PA branches. Size and balance of the PA branches were used to evaluate the outcome of PA plasty.

RESULTS

In the NATIVE group, 100% of the HPAs were well-developed and all the PA branches became balanced, while in the PATCH and EXTENSION groups, the percentage of well-developed HPAs was 40% and 33%, respectively, and none of the PA branches were balanced. In addition, HPAs became atretic in 28% of the patients in the patch enlargement group.

CONCLUSIONS

For TOF with unbalanced PA branches, patch enlargement may not be a good treatment strategy, as it reduces the growth potential of HPA and even causes iatrogenic atresia. Leaving the HPA in the native state without patch enlargement may be a good strategy.

Preoperative Morphological Prediction of Early Reoperation Risk After Primary Repair in Tetralogy of Fallot: A Contemporary Analysis of 83 Cases

This study was conducted to investigate the pulmonary artery (PA) variations in tetralogy of Fallot (TOF) and preoperative morphological predictors for early reoperation. Eighty-three TOF patients and 20 children with normal PA were included. The TOF group was divided into two subsets according to whether or not reoperation was performed within 3 years postoperatively. Clinical information was obtained, along with computed tomography (CT)-based three-dimensional geometry of the PA. Morphological measurements of the length of the main PA branches, the angles between them, and the cross-sectional area of each segment of the PAs were acquired using computer software. Logistic regression and receiver operating characteristic curves were applied to analysis. The TOF group showed a significantly smaller PA size and irregular PA shape, with lower Nakata and McGoon indices, than the control group. The median bifurcation angle (angle-γ) was greater than 100° in the TOF group, as compared to 66.70° in the control group (P < 0.000). Residual obstruction of the infundibulum or PAs was the main reason for early reoperation in this series. The development of the main PA and left PA was poorer in the reoperation subset than in the non-reoperation subset (P ≤ 0.01). The preoperative angle-γ in the reoperation subset was larger than that in the non-reoperation subset (median, 117.8° vs. 112.0°, P = 0.026). Higher weight (OR = 0.372) and McGoon index (OR = 0.122) were protective factors, while larger angle-γ (> 114.8°, OR = 5.040) and angle-γ normalized by body surface area (BSA) (γ/BSA > 297.9, OR = 18.860) were risk factors. This study provides an intuitive perspective of PA anatomical variations in TOF. Larger preoperative PA bifurcation angle and γ/BSA were morphological risk predictors of postoperative reoperation in patients with TOF.

Characterization of Flow Dynamics in the Pulmonary Bifurcation of Patients With Repaired Tetralogy of Fallot: A Computational Approach

The hemodynamic environment of the pulmonary bifurcation is of great importance for adult patients with repaired tetralogy of Fallot (rTOF) due to possible complications in the pulmonary valve and narrowing of the left pulmonary artery (LPA). The aim of this study was to computationally investigate the effect of geometrical variability and flow split on blood flow characteristics in the pulmonary trunk of patient-specific models. Data from a cohort of seven patients was used retrospectively and the pulmonary hemodynamics was investigated using averaged and MRI-derived patient-specific boundary conditions on the individualized models, as well as a statistical mean geometry. Geometrical analysis showed that curvature and tortuosity are higher in the LPA branch, compared to the right pulmonary artery (RPA), resulting in complex flow patterns in the LPA. The computational analysis also demonstrated high time-averaged wall shear stress (TAWSS) at the outer wall of the LPA and the wall of the RPA proximal to the junction. Similar TAWSS patterns were observed for averaged boundary conditions, except for a significantly modified flow split assigned at the outlets. Overall, this study enhances our understanding about the flow development in the pulmonary bifurcation of rTOF patients and associates some morphological characteristics with hemodynamic parameters, highlighting the importance of patient-specificity in the models. To confirm these findings, further studies are required with a bigger cohort of patients.

Blood flow simulations in the pulmonary bifurcation in relation to adult patients with repaired tetralogy of Fallot

Understanding the haemodynamic environment of the pulmonary bifurcation is important in adults with repaired conotruncal congenital heart disease. In these patients, dysfunction of the pulmonary valve and narrowing of the branch pulmonary arteries are common and can have serious clinical consequences. The aim of this study was to numerically investigate the underlying blood flow characteristics in the pulmonary trunk under a range of simplified conditions. For that, an in-depth analysis was conducted in idealised two-dimensional geometries that facilitate parametric investigation of healthy and abnormal conditions. Subtle variations in morphology influenced the haemodynamic environment and wall shear stress distribution. The pressure in the left pulmonary artery was generally higher than that in the right and main arteries, but was markedly reduced in the presence of a local stenosis. Different downstream pressure conditions altered the branch flow ratio, from 50:50% to more realistic 60:40% ratios in the right and left pulmonary artery, respectively. Despite some simplifications, this study highlights some previously undocumented aspects of the flow in bifurcating geometries, by clarifying the role of the stagnation point location on wall shear stress and differential branch pressures. In addition, measurements of the mean pressure ratios in the pulmonary bifurcation are discussed in the context of a new haemodynamic index which could potentially contribute to the assessment of left pulmonary artery stenosis in tetralogy of Fallot patients. Further studies are required to confirm the results in patient-specific models with personalised physiological flow conditions.

Outflow tract geometries are associated with adverse outcome indicators in repaired tetralogy of Fallot

OBJECTIVES

A wide variety of right ventricular outflow tract (RVOT) and pulmonary artery (PA) geometries has been reported in patients with repaired tetralogy of Fallot (rTOF). We aimed to investigate the associations between RVOT/PA geometries and outcome indicators in a large rTOF cohort receiving non-conduit repair.

METHODS

Three-dimensional magnetic resonance angiographic images of 206 patients with rTOF who had a pulmonary regurgitation (PR) fraction ≥20% were reviewed. Patients' RVOT geometry was quantitatively classified into 4 distinct shapes (tubular, hourglass, pyramid, and inverted trapezoid). Bilateral PA size discrepancy was defined as the diameter of the smaller side being less than 70% of that of the bigger side.

RESULTS

Based on lateral projection of the 3-dimensional images, patients with an inverted trapezoid-shaped RVOT had the smallest RV end-diastolic volume index (EDVi) (108.7 ± 24.3 mL/m²) and pulmonary valve annulus diameter, and shortest QRS duration, whereas those with a pyramid-shaped RVOT had the largest RV EDVi (161.0 ± 44.6 mL/m²) and pulmonary valve annulus diameter. Similar trends of differences were also observed if such classifications were based on the frontal projections. Multivariable analysis revealed that RVOT shapes, subvalvular diameter, PR fraction, QRS duration, and the presence of bilateral PA size discrepancy were independent determinants of RV EDVi. Furthermore, having bilateral PA size discrepancy (25.2%) was independently associated with lower peak oxygen consumption (P = .041).

CONCLUSIONS

Distinct RVOT morphologies and branch PA size discrepancy are associated with variations in RV remodeling and exercise capacity in patients with rTOF. These findings may aid decision-making regarding reintervention for PR and branch PA size discrepancy.

Computational Pre-surgical Planning of Arterial Patch Reconstruction: Parametric Limits and In Vitro Validation

Surgical treatment of congenital heart disease (CHD) involves complex vascular reconstructions utilizing artificial and native surgical materials. A successful surgical reconstruction achieves an optimal hemodynamic profile through the graft in spite of the complex post-operative vessel growth pattern and the altered pressure loading. This paper proposes a new in silico patient-specific pre-surgical planning framework for patch reconstruction and investigates its computational feasibility. The proposed protocol is applied to the patch repair of main pulmonary artery (MPA) stenosis in the Tetralogy of Fallot CHD template. The effects of stenosis grade, the three-dimensional (3D) shape of the surgical incision and material properties of the artificial patch are investigated. The release of residual stresses due to the surgical incision and the extra opening of the incision gap for patch implantation are simulated through a quasi-static finite-element vascular model with shell elements. Implantation of different unloaded patch shapes is simulated. The patched PA configuration is pressurized to the physiological post-operative blood pressure levels of 25 and 45 mmHg and the consequent post-operative stress distributions and patched artery shapes are computed. Stress–strain data obtained in-house, through the biaxial tensile tests for the mechanical properties of common surgical patch materials, Dacron, Polytetrafluoroethylene, human pericardium and porcine xenopericardium, are employed to represent the mechanical behavior of the patch material. Finite-element model is experimentally validated through the actual patch surgery reconstructions performed on the 3D printed anatomical stenosis replicas. The post-operative recovery of the initially narrowed lumen area and post-op tortuosity are quantified for all modeled cases. A computational fluid dynamics solver is used to evaluate post-operative pressure drop through the patch-reconstructed outflow tract. According to our findings, the shorter incisions made at the throat result in relatively low local peak stress values compared to other patch design alternatives. Longer cut and double patch cases are the most effective in repairing the initial stenosis level. After the patch insertion, the pressure drop in the artery due to blood flow decreases from 9.8 to 1.35 mmHg in the conventional surgical configuration. These results are in line with the clinical experience where a pressure gradient at or above 50 mmHg through the MPA can be an indication to intervene. The main strength of the proposed pre-surgical planning framework is its capability to predict the intra-operative and post-operative 3D vascular shape changes due to intramural pressure, cut length and configuration, for both artificial and native patch materials.

Consequences of an early catheter-based intervention on pulmonary artery growth and right ventricular myocardial function in a pig model of pulmonary artery stenosis

OBJECTIVE

To determine the consequences of an early catheter-based intervention on pulmonary artery (PA) growth and right ventricular (RV) myocardial function in an animal model of branch PA stenosis.

BACKGROUND

Acute results and safety profiles of deliberate stent fracture within the pulmonary vasculature have been demonstrated. The long-term impact of early stent intervention and deliberate stent fracture on PA growth and myocardial function is not understood.

METHODS

Implantation of small diameter stents was performed in a pig model of left PA stenosis at 6 weeks (10 kg) followed by dilations at 10 (35 kg) and 18 weeks (65 kg) with intent to fracture and implant large diameter stents. Hemodynamics, RV contractility, and 2D/3D angiography were performed with each intervention. The heart and pulmonary vasculature were histologically assessed.

RESULTS

Stent fracture occurred in 9/12 and implantation of large diameter stents was successful in 10/12 animals with no PA aneurysms or dissections. The final stented PA segment and distal left PA branch origins equaled the corresponding PA diameters of sham controls. Growth of left PA immediately beyond the stent was limited and there was diffuse fibro-intimal proliferation within the distal left and right PA. RV contractility was diminished in the intervention group and the response to dobutamine occurred uniquely via increases in heart rate.

CONCLUSIONS

Early stent intervention in this surgically created PA stenosis model was associated with improved growth of the distal PA vasculature but additional investigation of PA vessel physiology and impact on the developing heart are needed.

Design and Fabrication of a Three-Dimensional In Vitro System for Modeling Vascular Stenosis

Vascular stenosis, the abnormal narrowing of blood vessels, arises from defective developmental processes or atherosclerosis-related adult pathologies. Stenosis triggers a series of adaptive cellular responses that induces adverse remodeling, which can progress to partial or complete vessel occlusion with numerous fatal outcomes. Despite its severity, the cellular interactions and biophysical cues that regulate this pathological progression are poorly understood. Here, we report the design and fabrication of a three-dimensional (3D) in vitro system to model vascular stenosis so that specific cellular interactions and responses to hemodynamic stimuli can be investigated. Tubular cellularized constructs (cytotubes) were produced, using a collagen casting system, to generate a stenotic arterial model. Fabrication methods were developed to create cytotubes containing co-cultured vascular cells, where cell viability, distribution, morphology, and contraction were examined. Fibroblasts, bone marrow primary cells, smooth muscle cells (SMCs), and endothelial cells (ECs) remained viable during culture and developed location- and time-dependent morphologies. We found cytotube contraction to depend on cellular composition, where SMC-EC co-cultures adopted intermediate contractile phenotypes between SMC- and EC-only cytotubes. Our fabrication approach and the resulting artery model can serve as an in vitro 3D culture system to investigate vascular pathogenesis and promote the tissue engineering field.

Aggressive Patch Augmentation May Reduce Growth Potential of Hypoplastic Branch Pulmonary Arteries After Tetralogy of Fallot Repair

BACKGROUND

Potential surgical strategies for hypoplastic branch pulmonary arteries (BPAs) during tetralogy of Fallot repair include (1) extensive patch augmentation to the hilum (PATCH), (2) limited extension arterioplasty to the proximal pulmonary artery (EXTENSION), or (3) leaving the native vessels unaugmented (NATIVE). We explored the effect of these strategies on reintervention and BPA growth.

METHODS

From 2000 to 2012, 434 children underwent complete tetralogy of Fallot repair. Risk-adjusted parametric models were used to analyze the risk of BPA reintervention for (1) all children, (2) children with BPAs of 4 mm or smaller, and (3) children with BPAs of 3 mm or smaller. Repeated-measures analysis of more than 2,000 echocardiograms was used to characterize postoperative BPA growth and right ventricular pressure by using nonlinear mixed models.

RESULTS

Overall survival (99% [3 deaths]) was excellent. The 10-year freedom from BPA reintervention was 84%. In risk-adjusted models (including baseline BPA z-score), PATCH had a decreased freedom from reintervention (73%; p < 0.01) vs EXTENSION (87%) or NATIVE (91%). For children with BPAs of 4 mm or smaller (28 PATCH, 60 EXTENSION, 75 NATIVE), baseline characteristics were similar. The risk-adjusted 5-year freedom from reintervention was 68% for PATCH, 76% for EXTENSION, and 85% for NATIVE. PATCH trended toward an increased risk of reintervention (p = 0.07). For children with BPAs of 4 mm or smaller left in their NATIVE state, only ∼15% required reintervention. After adjustment for baseline BPA z-score, the time-related BPA growth was decreased (p < 0.014) and right ventricular pressure was increased (p = 0.03) for the PATCH group.

CONCLUSIONS

Aggressive PATCH augmentation of hypoplastic BPAs improves the short-term geometry but may lead to late stenosis and higher rates of reintervention. Hypoplastic BPAs in tetralogy of Fallot tend (∼85%) to grow well without instrumentation.

Numerical investigation of regurgitation phenomena in pulmonary arteries of Tetralogy of Fallot patients after repair

Pulmonary regurgitation is a very common phenomenon in pulmonary arteries after repair of patients of Tetralogy of Fallot (TOF) which is the most common complex congenital heart diseases. The aim of this study is to use numerical approaches to simulate flow variations in pulmonary artery after repair of patients of TOF. We analyze the flow patterns in an in-vitro bifurcation pulmonary artery and consider effects of various regurgitation fractions (RF or b/f) in left pulmonary artery (LPA) and right pulmonary artery (RPA). We not only observe the variation of flow patterns, but also analyze the results of b/f and net volumetric flow rates in LPA and RPA. In general, the b/f of LPA is higher than RPA in the measured data provided by phase-contrast magnetic resonance imaging (PC-MRI). We validate the result using numerical approaches to analyze the flow patterns in pulmonary artery in this study. The results will be useful for medical doctors when they perform operations for TOF patients.

Morphometry-based impedance boundary conditions for patient-specific modeling of blood flow in pulmonary arteries

Patient-specific computational models could aid in planning interventions to relieve pulmonary arterial stenoses common in many forms of congenital heart disease. We describe a new approach to simulate blood flow in subject-specific models of the pulmonary arteries that consists of a numerical model of the proximal pulmonary arteries created from three-dimensional medical imaging data with terminal impedance boundary conditions derived from linear wave propagation theory applied to morphometric models of distal vessels. A tuning method, employing numerical solution methods for nonlinear systems of equations, was developed to modify the distal vasculature to match measured pressure and flow distribution data. One-dimensional blood flow equations were solved with a finite element method in image-based pulmonary arterial models using prescribed inlet flow and morphometry-based impedance at the outlets. Application of these methods in a pilot study of the effect of removal of unilateral pulmonary arterial stenosis induced in a pig showed good agreement with experimental measurements for flow redistribution and main pulmonary arterial pressure. Next, these methods were applied to a patient with repaired tetralogy of Fallot and predicted insignificant hemodynamic improvement with relief of the stenosis. This method of coupling image-based and morphometry-based models could enable increased fidelity in pulmonary hemodynamic simulation.

Usefulness of branch pulmonary artery regurgitant fraction to estimate the relative right and left pulmonary vascular resistances in congenital heart disease

In postoperative congenital heart patients with pulmonary regurgitation, individual branch pulmonary artery regurgitant fractions estimate relative pulmonary vascular resistance independent of pulmonary blood flow distribution.

Alternative approach for angioplasty of stenosed left pulmonary artery following intracardiac repair of tetralogy of Fallot

A 5-year-old boy with stenosed left pulmonary artery following total correction of tetralogy of Fallot underwent surgical pulmonary arterioplasty through a left anterolateral thoracotomy on a normothermic perfused heart under cardiopulmonary bypass. We found this to be a convenient approach, and recommend it for correction of this lesion in the absence of gross pulmonary regurgitation and right ventricular outflow tract dilatation.