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Transcatheter stent implantation has been employed to treat re-coarctation of the aorta in adolescents and young adults. The aim of this work is to use computational fluid dynamics to characterise haemodynamics associated with re-coarctation involving an aneurysmal ductal ampulla and aortic isthmus narrowing, which created minimal pressure drop, and to incorporate computational fluid dynamics’s findings into decision-making concerning catheter-directed treatment.
Computational fluid dynamics permits numerically solving the Navier–Stokes equations governing pulsatile flow in the aorta, based on patient-specific data. We determined flow-velocity fields, wall shear stresses, oscillatory shear indices, and particle stream traces, which cannot be ascertained from catheterisation data or magnetic resonance imaging.
Computational fluid dynamics showed that, as flow entered the isthmus, it separated from the aortic wall, and created vortices leading to re-circulating low-velocity flow that induced low and multidirectional wall shear stress, which could sustain platelet-mediated thrombus formation in the ampulla. In contrast, as flow exited the isthmus, it created a jet leading to high-velocity flow that induced high and unidirectional wall shear stress, which could eventually undermine the wall of the descending aorta.
We used computational fluid dynamics to study re-coarctation involving an aneurysmal ductal ampulla and aortic isthmus narrowing. Despite minimal pressure drop, computational fluid dynamics identified flow patterns that would place the patient at risk for: thromboembolic events, rupture of the ampulla, and impaired descending aortic wall integrity. Thus, catheter-directed stenting was undertaken and proved successful. Computational fluid dynamics yielded important information, not only about the case presented, but about the complementary role it can serve in the management of patients with complex aortic arch obstruction.
Tetralogy of Fallot with pulmonary atresia is a heterogeneous group of defects, characterised by diverse sources of flow of blood to the lungs, which often include multiple systemic-to-pulmonary collateral arteries. Controversy surrounds the optimal method to achieve a biventricular repair with the fewest operations while basing flow to the lungs on the native intrapericardial pulmonary arterial circulation whenever possible. We describe an individualized approach to this group of patients that optimizes these variables.
Over a consecutive 10-year period, we treated 66 patients presenting with tetralogy of Fallot and pulmonary atresia according to the source of the pulmonary arterial flow. Patients were grouped according to whether the flow of blood to the lungs was derived exclusively from the intrapericardial pulmonary arteries, as seen in 29 patients, exclusively from systemic-to-pulmonary collateral arteries, as in 5 patients, or from both the intrapericardial pulmonary and collateral arteries, as in the remaining 32 patients. We divided the latter group into 9 patients deemed simple, and 23 considered complex, according to whether the pulmonary arterial index was greater than or less than 90 millimetres squared per metre squared, and whether the number of collateral arteries was less than or greater than 2, respectively.
We achieved complete biventricular repair in 58 patients (88%), with an overall mortality of 3%. Repair was accomplished in a single stage in all patients without systemic-to-pulmonary collateral arteries, but was staged, with unifocalization, in the patients lacking intrapericardial pulmonary arteries. Complete repair without unifocalization was achieved in all patients with the simple variant of the mixed morphology, and in 56% of patients with the complex variant. The average number of procedures per patient to achieve complete repair was 1, 2.2, 3.8, and 2.6 in patients with exclusively native intrapericardial, simple and mixed, complex and mixed and exclusively collateral pulmonary arterial flow, respectively.
An individualized approach based on the morphology of the pulmonary arterial supply permits achievement of a high rate of complete intracardiac repairs, basing pulmonary arterial flow on the intrapericardial pulmonary arteries in the great majority of cases, and has a low rate of reoperation and mortality.
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