Objectives: The impact of different extracorporeal circulation (ECC) scenarios on arterial blood
flow profiles and resulting wall shear stress values remains yet unclear. To allow
for exact blood flow profile measurements, magnetic resonance imaging during ECC is
required. Therefore, the present feasibility study aimed at developing an animal model
of ECC that can be examined by means of magnetic resonance imaging.
Methods: New Zealand White rabbits (n = 2; 4 kg body weight) were used to realize this model, since in rabbits, atherosclerosis
can be additionally induced for future investigations. To enable high resolution magnetic
resonance imaging, we developed an extracorporeal circuit of a total length of 20
m so that the blood pump and control unit of the heart lung machine can be placed
outside of the strong magnetic field. The miniaturized ECC system via thoracic access
comprised an infant oxygenator (Medtronic Affinity Pixie), a pulsatile centrifugal
pump (Medos Deltastream DP3), 1/8” tubes, a 10 Fr aortic cannula and a 12 Fr venous
two-stage cannula for vacuum-assisted drainage.
Results: We generated a miniaturized ECC system with a very low priming volume (240ml) to
reduce the system-inherent hemodilution to ~1:1. Consequently, hemoglobin rates were
higher than 6 g/dl and adequate oxygenation could be obtained. Optimized venous drainage
by an additionally inserted pulmonary vein vent catheter (6 Fr) resulted in sufficient
blood flow (300 ml/min) that was maintained for more than 60 minutes as either pulsatile
or non-pulsatile flow.
Conclusions: The developed miniaturized extracorporeal circuit guarantees adequate perfusion in
rabbits while allowing for simultaneous magnetic resonance imaging. Thus, for the
first time, real time blood flow profile measurements during ECC would be possible.
Furthermore, this model could be used for validating and optimizing blood flow simulation
algorithms to compare the impact of different ECC scenarios without further animal
experiments.
