Caterina Cara

Veno-arterial extra-corporeal membrane oxygenation (VA-ECMO) is a life-support treatment for patients with cardiogenic shock (CS). The VA-ECMO is a bridge therapy that guarantees blood oxygenation and supports the heart pumping function in patients who should undergo a heart transplant. Besides, this therapy has positive benefits for heart recovery in patients with temporary heart failure. The ECMO consists essentially of a pump, an oxygenator, and drainage and return cannulas inserted in the femoral artery/vein. In the last 10 years, the use of the VA-ECMO has significantly increased, but its use remains controversial owing to several side effects associated with its application. Among those, we mention bleeding, kidney failure, and limb ischemia. Being the latter due to the obstruction of the femoral artery by the cannula, innovative designs of this component have been recently presented to ensure sufficient limb perfusion.

A complete hemodynamic analysis of the system cannula/VA-ECMO is lacking in the literature, in particular for what the new generation cannulas is concerned. Therefore, the aim of this research is to shed light on the hemodynamic effects of this life-support treatment at the systemic/pulmonary level and to assess the efficacy of different cannula designs in preventing limb ischemia. The study hence focuses on two different scales, which will be treated with different approaches: 0D and 3D modelling, for the global and local evaluation, respectively.

A simple lumped parameters model has been developed so far as a preliminary predictive tool of hemodynamics in subjects supported on ECMO. The model couples the complete circulation and a VA-ECMO pump parallel circuit, that drains/delivers blood at the level of the right atrium/aortic valve, respectively (Figure 1a). The above preliminary model is going to be updated by both increasing the number of included cardiovascular functional elements and including the oxygenation module. Blood flow in the vascular district close to the access of the ECMO cannula will be described by 3D modelling aimed at analysing the effects of different cannula designs on the local distribution of the velocity, shear rate, pressure, and flow rate. The issue will be first investigated by CFD. FSI simulations can be developed in a second phase to extend the analysis to the deformation of the access site.

The results obtained so far confirm the appropriateness of 0D modelling as strategy to effectively investigate both the positive (e.g., left ventricle recovery) and negative (e.g., worsening of spontaneous oxygenation) effects of treating CS by VA-ECMO. Moreover, the automation of the VA-ECMO management and control at the bedside seems also a possible outcome.