Surgical approach to hyploplastic left heart syndrome - Norwood Stage I

3D Simulation Analysis of Central Shunt in Patient-Specific Hemodynamics: Effects of Varying Degree of Pulmonary Artery Stenosis and Shunt Diameters

The objective of this study was to compare the effects of different shunt diameters and pulmonary artery (PA) stenosis grades on the hemodynamics of central shunts to determine an optimal surgical plan and improve the long-term outcomes of the operation. A 3D anatomical model was reconstructed based on the patient's clinical CT data. 3D computational fluid dynamics models were built with varying degrees of stenosis (the stenosis ratio α was represented by the ratio of blood flow through the main pulmonary artery to cardiac output, ranging from 0 to 30%; the smaller the value of α, the more severe the pulmonary artery stenosis) and varying shunt diameters (3, 3.5, 4, 4.5, and 5 mm). Our results show that the asymmetry of pulmonary artery flow increased with increasing shunt diameter and α, which will be more conducive to the development of the left pulmonary artery. Additionally, the pulmonary-to-systemic flow ratio (Q_P/Q_S) increases with the shunt diameter and α, and all the values exceed 1. When the shunt diameter is 3 mm and α = 0%, Q_P/Q_S reaches the minimum value of 1.01, and the oxygen delivery reaches the maximum value of 205.19 ml/min. However, increasing shunt diameter and α is beneficial to reduced power loss and smoother PA flow. In short, for patients with severe PA stenosis (α is small), a larger-diameter shunt may be preferred. Conversely, when the degree of PA stenosis is moderate, a smaller shunt diameter can be considered.

Ring-reinforced Sano right ventricular to pulmonary artery conduit at Norwood stage I

Reinterventions for proximal conduit obstruction or on the pulmonary arteries are frequent after Sano-modified stage I Norwood palliation of hypoplastic left heart syndrome. We report our experience with a modified Sano stage I, in which the right ventricle-to-pulmonary artery (PA) conduit used is reinforced by external rings to avoid collapse, and the conduit is inserted into the right ventricle through a limited ventriculotomy and 'dunked' into the ventricular cavity. In our experience, this modification was associated with fewer reinterventions or complications with the proximal anastomosis (P = 0.046 and 0.004), improved PA pulse pressure (9.1 ± 4.1 vs 4.8 ± 3.8 mmHg in controls, P < 0.001) and Nakata index (213 ± 76 vs 134 ± 68 mm(2)/m(2) in controls, P < 0.0001), although overall survival to a median of 20 months was not significantly different from controls. Right ventricular function at stage II-bidirectional Glen was marginally better in patients with the modified Sano conduit, however not to a significant level. Further evaluation of late ventricular function is currently ongoing.

A systematic review of the impact of volume of surgery and specialization in Norwood procedure

Background

The volume-outcome relationship is supposed to be stronger in high risk, low volume procedures. The aim of this systematic review is to examine the available literature on the effects of hospital and surgeon volume, specialization and regionalization on the outcomes of the Norwood procedure.

Methods

A systematic literature search was performed in Medline, Embase, and the Cochrane Library. On the basis of titles and abstracts, articles of comparative studies were obtained in full-text in case of potential relevance and assessed for eligibility according to predefined inclusion criteria. All relevant data on study design, patient characteristics, hospital volume, surgeon volume and other institutional characteristics, as well as results were extracted in standardized tables. Study selection, data extraction and critical appraisal were carried out independently by two reviewers.

Results

We included 10 studies. All but one study had an observational design. The number of analyzed patients varied from 75 to 2555. Overall, the study quality was moderate with a huge number of items with an unclear risk of bias. All studies investigating hospital volume indicated a hospital volume-outcome relationship, most of them even having significant results. The results were very heterogeneous for surgeon volume.

Conclusions

The volume-outcome relationship in the Norwood procedure can be supported. However, the magnitude of the volume effect is difficult to assess.

Computational hemodynamic analysis in congenital heart disease: simulation of the Norwood procedure

Hypoplastic left heart syndrome (HLHS) is a congenital heart disease which should be treated at neonate. Even now, its operation is one of the greatest challenges. However, currently there are no quantitative standards to evaluate and predict the outcome of the therapy. In this study, computational fluid dynamics (CFD) was used to estimate the performance of first stage HLHS surgery, the Norwood operation. An image data transfer system was developed to convert clinical images into three-dimensional geometry. To confirm software applicability, a validation process was carried out to eliminate any influence of numerical procedures. The velocities derived from echocardiography measurements were used as boundary conditions, and pressure waves measured by a cardiac catheter simultaneous with an electrocardiogram (ECG) were employed to validate the results of CFD simulation. Calculated results were congruent with the in vivo measurement results. The blood flow circulations were successfully simulated and the distribution of blood flow in each vessel was estimated. Time-varying energy losses (EL), local pressure and wall shear stress (WSS) were analyzed to estimate clinical treatment. The results indicated that pulsatile simulation is essential in quantitative evaluation. Computational hemodynamics may be applied in the surgical optimization for the treatment of HLHS.