Hemodynamic Performance of Stage-2 Univentricular Reconstruction: Glenn vs. Hemi-Fontan Templates

Abstract

Flow structures, hemodynamics and the hydrodynamic surgical pathway resistances of the final stage functional single ventricle reconstruction, namely the total cavopulmonary connection (TCPC) anatomy, have been investigated extensively. However, the second stage surgical anatomy (i.e., bi-directional Glenn or hemi-Fontan template) has received little attention. We thus initiated a multi-faceted study, involving magnetic resonance imaging (MRI), phase contrast MRI, computational and experimental fluid dynamics methodologies, focused on the second stage of the procedure. Twenty three-dimensional computer and rapid prototype models of 2nd stage TCPC anatomies were created, including idealized parametric geometries (n = 6), patient-specific anatomies (n = 7), and their virtual surgery variant (n = 7). Results in patient-specific and idealized models showed that the Glenn connection template is hemodynamically more efficient with (83% p = 0.08 in patient-specific models and 66% in idealized models) lower power losses compared to hemi-Fontan template, respectively, due to its direct end-to-side anastomosis. Among the several secondary surgical geometrical features, stenosis at the SVC anastomosis or in pulmonary branches was found to be the most critical parameter in increasing the power loss. The pouch size and flare shape were found to be less significant. Compared to the third stage surgery the hydrodynamic resistance of the 2nd stage is considerably lower (both in idealized models and in anatomical models at MRI resting conditions) for both hemi- and Glenn templates. These results can impact the surgical design and planning of the staged TCPC reconstruction.

Patient-specific surgical planning and hemodynamic computational fluid dynamics optimization through free-form haptic anatomy editing tool (SURGEM)

“…On the right, the patient specific configurations with different IVC locations and crosssectional diameters are presented. Final merging is completed using commercial modeling tools (six out of nine candidate models are shown) the skelitalization tool are reported elsewhere [49]. From these results it is observed that anatomical modification of the confluence region, model A, and inclusion of a proximal flare located upstream of the stenosis at the RPA, model D, produced minor effects in hydrodynamic power loss values.…”

3D printing based on imaging data: review of medical applications

“…Compliant models can be manufactured using materials such as silicon or polyurethane to mimic the elastic properties of vessels [26,46]. Physiological and pathophysiological processes as well as post-operative hemodynamics can be assessed with patient-based phantoms simulating in vivo conditions and compared to computational fluid dynamics [42,47]. This may give new insights into hemodynamic or aerodynamic aspects of cardiovascular or airway diseases [48].…”

Boundary conditions of patient-specific fluid dynamics modelling of cavopulmonary connections: possible adaptation of pulmonary resistances results in a critical issue for a virtual surgical planning

“…Such models were constructed using MR angiography with intravenous administration of a gadolinium-based contrast agent, which allows one to identify even small pulmonary branches. In the present work, as well as in other similar studies [26,27], MR angiographic methods were not used and, therefore, simpler anatomical models were reconstructed, owing to the fact that gadolinium contrast is not systematically administered to younger patients in the clinical centre providing the imaging data. Although multi-branched threedimensional models account for a larger number of pulmonary arterial branches, the compliance properties of such vascular portions are not considered, while they might be important for the hemodynamics in the surgical region.…”