Computational fluid dynamics analysis of endoluminal aortic perfusion

Abstract

Introduction: In peripheral percutaneous (VA) extracorporeal membrane oxygenation (ECMO) procedures the femoral arteries perfusion route has inherent disadvantages regarding poor upper body perfusion due to watershed. With the advent of new long flexible cannulas an advancement of the tip up to the ascending aorta has become feasible. To investigate the impact of such long endoluminal cannulas on upper body perfusion, a Computational Fluid Dynamics (CFD) study was performed considering different support levels and three cannula positions.

Methods: An idealized literature-based- and a real patient proximal aortic geometry including an endoluminal cannula were constructed. The blood flow was considered continuous. Oxygen saturation was set to 80% for the blood coming from the heart and to 100% for the blood leaving the cannula. 50% and 90% venoarterial support levels from the total blood flow rate of 6 l/min were investigated for three different positions of the cannula in the aortic arch.

Results: For both geometries, the placement of the cannula in the ascending aorta led to a superior oxygenation of all aortic blood vessels except for the left coronary artery. Cannula placements at the aortic arch and descending aorta could support supra-aortic arteries, but not the coronary arteries. All positions were able to support all branches with saturated blood at 90% flow volume.

Conclusions: In accordance with clinical observations CFD analysis reveals, that retrograde advancement of a long endoluminal cannula can considerably improve the oxygenation of the upper body and lead to oxygen saturation distributions similar to those of a central cannulation.

Keywords: aortic perfusion; computational fluid dynamics analysis; endoluminal; extracorporeal membrane oxygenation; simulation; watershed.

Figure 1.

Cannula Positions for ideal and patient aorta.

Figure 2.

Ideal aorta (left) and human aorta (right). Tetrahedral meshes with triangular prism extrusions.

Figure 3.

Results of velocity patterns presented by streamlines in different cannula positions and for different support levels. For better visualisation, the legend values were scaled to highlight low flow velocities inside the aorta.

Figure 4.

Results of oxygen saturation in different cannula positions and for different support levels. Saturation values were projected onto the geometry’s surfaces representing exactly the saturation distributions found inside the aorta.