Biomedical subjects

Tain-Yen Hsia

Publications and source records attributed to Tain-Yen Hsia.

4 recordsLinked to original sources

PubMed2006

Factors influencing neurologic outcome after neonatal cardiopulmonary bypass: what we can and cannot control.

Advances in cardiopulmonary bypass and surgical techniques have led to progress in the early repair of congenital heart defects in children. However, as increasing numbers survive their initial cardiac operation, an awareness is emerging that significant early and late neurologic morbidities continue to complicate otherwise successful operative repairs. Adverse neurologic outcomes after neonatal cardiac surgery are multifactorial and relate to both fixed and modifiable mechanisms. The purpose of this review is to (1) review mechanisms of brain injury after neonatal cardiopulmonary bypass, (2) examine risk factors, and (3) speculate on how investigations may improve our understanding of neurologic injury.

Alkalosis↗

PubMed2005

Multiscale modelling in biofluidynamics: application to reconstructive paediatric cardiac surgery.

Multiscale computing is a challenging area even in biomechanics. Application of such a methodology to quantitatively compare postoperative hemodynamics in congenital heart diseases is very promising. In the treatment of hypoplastic left heart syndrome, which is a congenital heart disease where the left ventricle is missing or very small, the necessity to feed the pulmonary and systemic circulations is obtained with an interposition shunt. Two main options are available and differ from the sites of anastomoses: (i) the systemic-to-pulmonary conduit (Blalock-Taussig shunt known as the Norwood Operation (NO)) connecting the innominate artery (NO-BT) or the aorta (NO-CS) to the right pulmonary artery and (ii) the right ventricle to pulmonary artery shunt (known as Sano operation (SO)). The proposition that the SO is superior to the NO remains controversial. 3-D computer models of the NO (NO-BT and NO-CS) and SO were developed and investigated using the finite volume method. Conduits of 3, 3.5 and 4 mm were used in the NO models, whereas conduits of 4, 5 and 6 mm were used in the SO model. The hydraulic nets (lumped resistances, compliances, inertances and elastances) which represent the systemic, coronary and pulmonary circulations and the heart were identical in the two models. A multiscale approach was adopted to couple the 3-D models with the circulation net. Computer simulation results were compared with post-operative catheterization data. Results showed that (i) there is a good correlation between predicted and observed data: higher aortic diastolic pressure, decreased pulmonary arterial pressure, lower pulmonary-to-systemic flow ratio and higher coronary perfusion pressure in SO; (ii) there is a minimal regurgitant flow in the SO conduit. The close correlation between predicted and observed clinical data supports the use of mathematical modelling, with a mandatory multiscale approach, in the design and assessment of surgical procedures.

Algorithms↗

PubMed2004

Computational fluid dynamic study of flow optimization in realistic models of the total cavopulmonary connections.

OBJECTIVES AND BACKGROUND: In the Fontan circulation, pulmonary and systemic vascular resistances are in series. The influence of various inferior vena cava to pulmonary artery connections in this unique circulatory arrangement was evaluated using computation fluid dynamics methods. METHODS: Realistic three-dimensional models of total cavopulmonary connections were created from angiographic measurements to include the hepatic vein, superior vena cava, and branches of the pulmonary arteries. Steady-state finite volume analyses were performed using identical in vivo boundary conditions. Computational solutions calculated the percent hydraulic power dissipation and left-to-right pulmonary arterial flow distribution. RESULTS: Simulations of the lateral tunnel, intra-atrial tube, extracardiac conduit with left and right pulmonary artery anastomosis demonstrated extracardiac conduit with left pulmonary artery anastomosis having the lowest energy loss. Varying the extracardiac conduit from 10 to 30 mm resulted in the least energy dissipation at 20 mm. Serial dilation of the lateral tunnel pathway showed a small incremental worsening of energy loss. CONCLUSIONS: Maximizing energy conservation in a low-energy flow domain, such as the Fontan circulation, can be significant to its fluid dynamic performance. Although computational modeling cannot predict postoperative failure or functional outcome, this study confirms the importance of local geometry of the surgically created pathway in the total cavopulmonary connection.

Blood Vessel Prosthesis↗

PubMed2002

Surgical repair of supposedly multiple defects within the apical part of the muscular ventricular septum.

BACKGROUND: A distinct defect has been described within the apical part of the muscular ventricular septum, which has multiple orifices when seen from its right ventricular aspect. Closure has been suggested using umbrella devices introduced on a catheter. Such an intervention, however, can be technically difficult in small infants. METHODS: We have recently seen two examples of this type of complex communication between the apexes of both left and right ventricles. Neither could be closed by catheterization. A surgical approach was used through a modified apical right ventriculotomy. We have also studied two autopsied specimens, which clarify the morphologic arrangement. RESULTS: Both patients were closed successfully, with trivial residual shunt and good biventricular functions. The patients were clinically well at 2-year follow-up. CONCLUSIONS: Surgical division of right ventricular trabeculations makes it feasible to identify and repair the septal deficiency, which is a solitary hole. On the basis of our morphologic study, we offer an explanation for the anatomic arrangement that differs from the one proposed by recent previous investigators. If the ventricular incision is appropriately placed, our anatomic studies suggest that it is possible to visualize the solitary opening from its right ventricular aspect, and achieve surgical closure with a single patch.

Cardiac Surgical Procedures↗