Establishment of a Rabbit Model for MRI-Based Blood Flow Analysis under Extracorporeal Circulation

Background: The choice of the optimal extracorporeal circulation (ECC) cannulation strategy is still under debate. To allow for visualization and exact measurements of the impact of different ECC scenarios on the arterial blood flow, magnetic resonance imaging (MRI) is required. Therefore, we established a miniaturized MRI-compatible rabbit ECC model, and conducted MR-based measurements of real-time blood flow, wall shear stress and turbulences in dependency on different ECC scenarios.

Method: Eight New Zealand white rabbits underwent ECC by antegrade (n = 4; via ascending aorta) or retrograde (n = 4; via abdominal aorta) perfusion. MRI measurements were conducted in a 9.4-Tesla MR scanner with an inner gradient diameter of 30 cm. 3D flow data were acquired by phase contrast velocity mapping using Bruker FLOWMAP sequences (spatial resolution = 500 × 500 × 500 µm³, VENC = 200 cm/s). All data were analyzed in MATLAB. The blood pressure and ECC flow rates were continuously measured. Every 30 minutes, blood gas analyses were conducted.

Results: The exact blood flow profiles were measured in the MRI during ante- and retrograde perfusion with a special focus on the cannulation sites. During the whole experiments (276.25 ± 76.6 minutes), in both perfusion scenarios, ECC was established with adequate blood flow rates (242.9 ± 21.83 mL/min), arterial pressure (49.18 ± 6.58 mm Hg before the onset of ECC vs. 41.9 ± 3.77 mm Hg during ECC), partial pressure of oxygen (229.15 ± 49.96 mm Hg vs. 561.68 ± 61.05 mm Hg), and oxygen saturation (99.79 ± 0.17% vs. 99.96 ± 0.1%). All rabbits showed adequate and constant hemoglobin levels after the onset of ECC (11.5 ± 1.3 g/dL before the onset of ECC vs. 7.66 ± 0.8 g/dL during ECC).

Conclusion: To the best of our knowledge, this is the first in vivo study on real-time blood flow measurements during ECC. In our miniaturized rabbit ECC model, adequate perfusion and oxygenation was established during the whole experiments. This model can be further used for validating and optimizing existing numerical blood flow simulation algorithms, and to compare the impact of different ECC scenarios on arterial blood flow and organ perfusion.

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Artikel online veröffentlicht:
28. Januar 2023