Unexpected release of microparticles during endovascular treatment of arterial obstructions may cause serious damage to target tissues and organs. There is currently little information about net type embolic protection devices (nEPD). The aim of this study was to analyse the differences between nEPD in terms of efficacy, in addition to hemodynamic changes, before and after the injection of particles in an in vitro model designed for this purpose.

An in vitro experimental study of repeated measurements (10 for each nEPD) in a hemodynamic model was conducted. Devices were tested with 140 μm diameter spherical polystyrene particles. Four types of nEPD were evaluated (nEPD 1-4). A laser particle counter was used to know the number of injected particles and assess the loss in each phase of the experiment (particle loss ratio). We also introduced the beta ratio (βR) value as a new parameter for filtration quality (βR140 was calculated by dividing the number of upstream 140 μm particles by downstream 140 μm particles). Flow resistance was calculated in peripheral resistance units (PRU). Data were expressed by mean (plus standard deviation [SD]), percentages and ratios. Multiple linear regression and Tukey contrast test were used for the efficacy analysis. Morphometric analyses were also studied using digital micro images. Hemodynamic changes included pressure gradient (ΔP) and flow volume and resistance.

Before particle injection, the greatest decrease in flow was found for nEPD1 (nEPD1: 28.77% [2.37%], nEPD4: 21.75% [1.48%], nEPD3: 12.46% [1.93%], and nEPD2: 3.51% [0.00%]; p <0.001). This finding was correlated with increased ΔP and higher flow resistance. After the injection of particles (mean 1760 [292]), the greatest percentage of flow drop was for nEPD4 (nEPD4: 80.89% [4.04%], nEPD1: 49.11% [4.63%], nEPD3: 30.71% [3.01%] and nEPD2: 2.14% [0.71%]; p <0.001), and consequently an increased ΔP, with enhanced resistance. The nEPD that demonstrated the best capture efficacy (percentage of particles retained with the deployed device) was nEPD4 (nEPD4: 97.84% [1.31%], nEPD1: 63.69% [5.18%], nEPD3: 78.67% [6.50%], and nEPD2: 33.24% [4.43%]; p <0.001); the devices with the lowest ratio of particle loss were nEPD3 and nEPD4 (nEPD3: 0.21 [0.11] and nEPD4: 0.21 [0.7] vs nEPD1: 0.45 [0.13] and nEPD2: 0.58 [0.19]; p <0.005). The final efficacy (percentage of particles retained at the end of the experiment) decreased in all of them and was persistently higher for nEPD4 (nEPD4: 77.28% [6.71%], nEPD3: 62.75% [13.82%], nEPD1: 35.27% [9.65%] and nEPD2: 14.17% [6.41%]; p ≤0.01). The best βR140 was found for nEPD4 (nEPD4: 61.74 [22.19]; p < 0.001). Structural differences observed in morphometric analysis (porosity: nEPD2 68.01%, nEPD3 21.74%, nEPD4 21.72% and nEPD1 12.59%) could at least partially justify these results.

Differences between the nEPD models were demonstrated in terms of their hemodynamic behaviour. These changes were significantly modified after particle injection due to filter saturation, observing a different behaviour for each model. The efficacy study showed that there are differences in the ability of capturing, withdrawal, final efficacy and βR. Based on these results, we believe that it may be necessary to introduce some improvements in these devices, as well as to include in their technical sheet, specific features such as its resistance, porosity, and beta ratio to facilitate decision-making.

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