Effect of modified Blalock-Taussig shunt anastomosis angle and pulmonary artery diameter on pulmonary flow

Prediction of hemoptysis in patients with anomalous systemic arterial supply to normal basal segments of the lower lobe using a combination of CT features and clinical materials

Background

Anomalous systemic arterial supply to the normal basal segments of the lower lobe (ASALL) is a rare anomaly with a common complication of hemoptysis. To estimate the risk of hemoptysis, this study aims to investigate the value of contrast-enhanced computed tomography (CT) and construct a risk-scoring model based on radiological features and clinical materials of patients with ASALL.

Methods

Forty-three eligible individuals (17 women and 26 males), who underwent multiphase contrast-enhanced CT, were included in this study. Hemoptysis was predicted by combined systemic arterial features (CD-A) and combined demographic and radiological features (CD-R). Potential hemoptysis predictors were identified using multivariate regression analysis. A receiver operating characteristic (ROC) curve analysis was used to assess the prediction efficiency. The coefficient of regression model was used to build a combined risk scoring (CRS) model for hemoptysis. The decision curve analysis (DCA) was performed to evaluate the clinical usefulness of the risk-scoring model.

Results

Hemoptysis was present in 17 (39.5%) ASALL patients. The areas under the curve (AUCs) for the predicted performance of CD-A and CD-R were 0.869 and 0.890, respectively. Independent predictors generated a scoring model using the formula CRS = 3 × age + 3 × sex + 4 × [ground glass opacity (GGO)] + 3 × (CD-A >0.522). The prediction performance of this model was displayed with an AUC of 0.939. This scoring model was demonstrated to be significantly preferable to CD-A (P=0.046) and CD-R (P=0.02) by the Hanley and McNeil test. The DCA showed that the CRS model was more beneficial when the threshold probability was between 5% and 92%.

Conclusions

The scoring model offers a viable method for evaluating the risk of hemoptysis in patients with ASALL by combining radiological and clinical data.

Commentary: A Complex Issue with a Straightforward Answer

See Article page 231.

Change in Pulmonary Arteries after Modified Blalock-Taussig Shunt Procedure: Analysis Based on Computed Tomography

Background

Although the modified Blalock-Taussig shunt remains the mainstay method of palliation for augmenting pulmonary blood flow in various congenital heart diseases, the shunt must be carefully designed to achieve the best outcomes. This study investigated the effect of shunt configuration on pulmonary artery growth and growth discrepancy.

Methods

Twenty patients with successful modified Blalock-Taussig shunt takedown were analyzed. Pulmonary artery and shunt characteristics were obtained using computed tomography scans. Differences in the baseline and follow-up diameter ratios and growth in the ipsilateral and contralateral arteries were calculated. The angle between the shunt and pulmonary artery, as well as the distance from the main pulmonary artery bifurcation, were measured. Correlations between pulmonary arteries and shunt configurations were analyzed.

Results

The median interval time between shunt placement and takedown was 154.5 days (interquartile range, 113.25-276.25 days). Follow-up values of the ipsilateral-to-contralateral pulmonary artery diameter ratio showed no significant correlation with the shunt angle (ρ=0.429, p=0.126) or distance (ρ=0.110, p=0.645). The shunt angle and distance from the main pulmonary bifurcation showed no significant correlation (ρ=-0.373, p=0.189). Pulmonary artery growth was negatively correlated with shunt angle (ipsilateral, ρ=-0.565 and p=0.035; contralateral, ρ=-0.578 and p=0.030), but not with distance (ipsilateral, ρ=-0.065 and p=0.786; contralateral, ρ=-0.130 and p=0.586).

Conclusion

Shunt configuration had no significant effect on growth imbalance. The angle and distance of the shunt showed no significant correlation with each other. A more vertical shunt was associated with significant pulmonary artery growth. We suggest a more vertical graft design for improved pulmonary artery growth.

Surgical Modulation of Pulmonary Artery Shear Stress: A Patient-Specific CFD Analysis of the Norwood Procedure

PURPOSR

This study created 3D CFD models of the Norwood procedure for hypoplastic left heart syndrome (HLHS) using standard angiography and echocardiogram data to investigate the impact of shunt characteristics on pulmonary artery (PA) hemodynamics. Leveraging routine clinical data offers advantages such as availability and cost-effectiveness without subjecting patients to additional invasive procedures.

METHODS

Patient-specific geometries of the intrathoracic arteries of two Norwood patients were generated from biplane cineangiograms. "Virtual surgery" was then performed to simulate the hemodynamics of alternative PA shunt configurations, including shunt type (modified Blalock-Thomas-Taussig shunt (mBTTS) vs. right ventricle-to-pulmonary artery shunt (RVPAS)), shunt diameter, and pulmonary artery anastomosis angle. Left-right pulmonary flow differential, Qp/Qs, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) were evaluated.

RESULTS

There was strong agreement between clinically measured data and CFD model output throughout the patient-specific models. Geometries with a RVPAS tended toward more balanced left-right pulmonary flow, lower Qp/Qs, and greater TAWSS and OSI than models with a mBTTS. For both shunt types, larger shunts resulted in a higher Qp/Qs and higher TAWSS, with minimal effect on OSI. Low TAWSS areas correlated with regions of low flow and changing the PA-shunt anastomosis angle to face toward low TAWSS regions increased TAWSS.

CONCLUSION

Excellent correlation between clinically measured and CFD model data shows that 3D CFD models of HLHS Norwood can be developed using standard angiography and echocardiographic data. The CFD analysis also revealed consistent changes in PA TAWSS, flow differential, and OSI as a function of shunt characteristics.

Evaluating the efficacy of the punch-out technique in systemic-to-pulmonary shunts: A computational fluid dynamics approach

BACKGROUND

Systemic-to-pulmonary shunt is a palliative procedure used to decrease pulmonary blood flow in congenital heart diseases. Shunt stenosis or occlusion has been reported to be associated with mortality; therefore, the management of thrombotic complications remains a challenge for most congenital cardiovascular surgeons. Despite its importance, the optimal method for shunt anastomosis remains unclear.

OBJECTIVE

The study investigates the clinical benefits of the punch-out technique over conventional methods in the anastomosis process of Systemic-to-pulmonary shunt, focusing on its potential to reduce shunt-related complications.

METHODS

Anastomotic models were created by two different surgeons employing both traditional slit and innovative punch-out techniques. Computational tomography was performed to construct three-dimensional models for computational fluid dynamics (CFD) analysis. We assessed the flow pattern, helicity, magnitude of wall shear stress, and its gradient.

RESULTS

The anastomotic flow area was larger in the model using the punch-out technique than in the slit model. In CFD simulation, we found that using the punch-out technique decreases the likelihood of establishing a high wall shear stress distribution around the anastomosis line in the model.

CONCLUSION

The punch-out technique emerges as a promising method in SPS anastomosis, offering a reproducible and less skill-dependent alternative that potentially diminishes the risk of shunt occlusion, thereby enhancing patient outcomes.

The Hemodynamic Effect of Modified Blalock–Taussig Shunt Morphologies: A Computational Analysis Based on Reduced Order Modeling

The Modified Blalock Taussig Shunt (MBTS) is one of the most common palliative operations in case of cyanotic heart diseases. Thus far, the decision on the position, size, and geometry of the implant relies on clinicians’ experience. In this paper, a Medical Digital Twin pipeline based on reduced order modeling is presented for fast and interactive evaluation of the hemodynamic parameters of MBTS. An infant case affected by complete pulmonary atresia was selected for this study. A three-dimensional digital model of the infant’s MBTS morphology was generated. A wide spectrum of MBTS geometries was explored by introducing twelve Radial Basis Function mesh modifiers. The combination of these modifiers allowed for analysis of various MBTS shapes. The final results proved the potential of the proposed approach for the investigation of significant hemodynamic features such as velocity, pressure, and wall shear stress as a function of the shunt’s morphology in real-time. In particular, it was demonstrated that the modifications of the MBTS morphology had a profound effect on the hemodynamic indices. The adoption of reduced models turned out to be a promising path to follow for MBTS numerical evaluation, with the potential to support patient-specific preoperative planning.

The Effects of the Mechanical Properties of Vascular Grafts and an Anisotropic Hyperelastic Aortic Model on Local Hemodynamics during Modified Blalock-Taussig Shunt Operation, Assessed Using FSI Simulation

Cardiovascular surgery requires the use of state-of-the-art artificial materials. For example, microporous polytetrafluoroethylene grafts manufactured by Gore-Tex^® are used for the treatment of cyanotic heart defects (i.e., modified Blalock–Taussig shunt). Significant mortality during this palliative operation has led surgeons to adopt mathematical models to eliminate complications by performing fluid–solid interaction (FSI) simulations. To proceed with FSI modeling, it is necessary to know either the mechanical properties of the aorta and graft or the rheological properties of blood. The properties of the aorta and blood can be found in the literature, but there are no data about the mechanical properties of Gore-Tex^® grafts. Experimental studies were carried out on the mechanical properties vascular grafts adopted for modified pediatric Blalock–Taussig shunts. Parameters of two models (the five-parameter Mooney–Rivlin model and the three-parameter Yeoh model) were determined by uniaxial experimental curve fitting. The obtained data were used for patient-specific FSI modeling of local blood flow in the “aorta-modified Blalock–Taussig shunt–pulmonary artery” system in three different shunt locations: central, right, and left. The anisotropic model of the aortic material showed higher stress values at the peak moment of systole, which may be a key factor determining the strength characteristics of the aorta and pulmonary artery. Additionally, this mechanical parameter is important when installing a central shunt, since it is in the area of the central anastomosis that an increase in stress on the aortic wall is observed. According to computations, the anisotropic model shows smaller values for the displacements of both the aorta and the shunt, which in turn may affect the success of preoperative predictions. Thus, it can be concluded that the anisotropic properties of the aorta play an important role in preoperative modeling.

Case Report: "Smart Palliation" and "Clepsydra Shape": A new approach in complex congenital heart disease

A limiting factor in using vascular conduits in the pediatric/newborn population is their inability to grow. Many complex congenital heart diseases require palliative surgery, but using rigid and nonexpandable conduits does not allow the structures to grow and anticipates the need for redo surgery. In newborns, a way to increase the palliation time according to the patient's growth is desirable. In recent years, expandable shunts (exGraft™ PECA) have been developed. According to recent material studies, a shunt could increase diameter after endovascular balloon dilatation. In this case report, we describe the first case of endovascular Blalock-Thomas-Taussig shunt (mBT) shunt expansion in a Tetralogy of Fallot / atrial-ventricular Septal Defect complete (TOFAVSDc) patient with trisomy 21 who went to palliative treatment for tracheomalacia (noncardiac lesion association), severe pulmonary arteries hypoplasia, and low weight. This case introduces the "Smart Palliation concept" in the clinical scenario of selected growing patients where the lifetime of the Blalock-Thomas-Taussig (BT) shunt, anatomic substrates, and complexity of clinical status may require an additional palliation time. The limitation of endovascular conduit expansion is the fragility of the anastomosis site. The anastomosis site is a lesser strength structure of the conduit, and dilatation could develop procedure complications. For this reason, in this paper, we introduced our project design: a new technique (Clepsydra Shape) that consists, before surgical implantation, of pre-expansion of the proximal and distal anastomotic parts of the shunt to obtain an increase of 30% in size of both anastomotic sides, preventing stress- and stretch-related lesion of future balloon dilatation.