Concept and first experimental results of a new ferromagnetic assist device for extra-aortic counterpulsation.
OBJECTIVE
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.
Clinic of Cardiac and Vascular Surgery, University Hospital Zurich, Zurich, Switzerland.
Christoph T
CT
Starck
Jakob
J
Becker
Roland
R
Fuhrer
Simon
S
Sündermann
Jan Wendelin
JW
Stark
Volkmar
V
Falk
D001011:Aorta / Q000503:physiopathology; D003035:Cobalt; D015908:Counterpulsation / Q000295:instrumentation* / Q000379:methods; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006353:Heart-Assist Devices; D006439:Hemodynamics; D006801:Humans; D006874:Hydrostatic Pressure; D058085:Iron Compounds; D008280:Magnetics / Q000295:instrumentation* / Q000379:methods; D059346:Magnets; D008422:Materials Testing; D053768:Metal Nanoparticles; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D012826:Silicone Elastomers
D058085:Iron Compounds; D012826:Silicone Elastomers; D003035:Cobalt; C515100:iron pentacarbonyl
Assist device; Extra-aortic counterpulsation; Heart failure