Development of Terumo implantable left ventricular assist system (T-ILVAS) with a magnetically suspended centrifugal pump

The research group of Terumo, NTN, and the Setsunan University have been developing an implantable left ventricular assist system (T-ILVAS) featuring a centrifugal blood pump with a magnetically suspended impeller (MSCP). The present study describes recent progress in the development of the T-ILVAS, focusing on ex vivo and in vivo evaluations of the prototype MSCP. The MSCP is composed of four parts: a magnetic bearing, an impeller, a housing, and a DC burshless motor. The impeller is suspended by a magnetic bearing, thus providing contact-free rotation of the impeller inside the pump. The prototype MSCP was placed paracorporeally in three sheep and implanted intrathoracically in two sheep to evaluate its long-term durability and nonthrombogenicity. One sheep implanted ex vivo with the paracorporeal MSCP (Model I) survived for 864 days without any mechanical failure or thromboembolic complications, and with negligible hemolysis. The implantable Model II pump was evaluated ex vivo in two sheep and intrathoracically implanted in one sheep. These experiments were terminated 70, 79, and 17 days after implantation due to mechanical failure caused by blood leakage through the intrahousing connector of the Model II pump. However, there was no intradevice thrombus formation in any of the retrieved pumps. The dual connector system was then introduced to the Model II pump (the modified Model II), and the pump was intrathoracically implanted in a sheep. The sheep survived for more than 14 months without major complications, and the study is being continued. The preliminary chronic animal experiments demonstrated improved durability and nonthrombogenicity of the MSCP, with a low hemolysis rate for up to 864 days. Thus, the MSCP has significant potential for longterm application as an implantable circulatory assist system. Further developments toward a totally implantable system, including an implantable controller and a transcutaneous energy/information transfer system, are under way.