Concept and first experimental results of a new ferromagnetic assist device for extra-aortic counterpulsation.

OBJECTIVES

Based on a ferromagnetic silicone cuff for extra-aortic counterpulsation, a new assist device concept was developed. The driving force is generated by an external magnetic field, which leads to contraction of a soft magnetic cuff. The force generation capacity of the device was tested in a silicone aorta model.

METHODS

Magnetic elastomers can be constructed through dispersion of micro- or nanoparticles in polymer matrices and were designed to act as soft actuators. Two magnetically active silicone cuffs were produced with a nanomagnet loading of 250 wt% (Cuff 1) and a micromagnet loading of 67 wt% (Cuff 2). The magnetic cuffs were applied on a silicone aorta model and contracted against hydrostatic pressure.

RESULTS

A full contraction of Cuff 1 was possible against a maximal hydrostatic pressure of 30 cmH₂O (22 mmHg) at a magnetic flux density of 0.4 T (Tesla) and 65 cmH₂O (48 mmHg) at a magnetic flux density of 1.2 T. A 50% contraction of Cuff 2 was possible against a maximal hydrostatic pressure of 80 cmH₂O (59 mmHg) at a magnet-cuff-distance (MCD) of 0 cm. At MCDs of 1 and 2 cm a 50% contraction was possible against 33 cmH₂O (24 mmHg) and 10 cmH₂O (7 mmHg), respectively.

CONCLUSIONS

Combining the advantages of magnetic elastomers with the principle of extra-aortic counterpulsation in a new assist device concept avoids the need for anticoagulation (no contact with bloodstream). With regard to the magnetic principle of action, no intra- to extracorporeal connection is needed. More experimental work is needed to further increase the force generated by the silicone cuff and to transfer the device concept into an in vivo setting.