title: Design Concepts and Preclinical Results of a Miniaturized HeartWare Platform: The MVAD System.
abstract: OBJECTIVE
  Ventricular assist device (VAD) miniaturization is one design trend that may result in less-invasive implantation techniques and more versatility with patient selection. The MVAD System is a miniature, continuous-flow device implanted in the ventricle. The pump is capable of delivering between 0 and 7 L/min of flow at a mean arterial pressure of 75 mm Hg. The impeller was optimized from its original design to improve hydraulic performance, minimize shear regions, and enhance the impeller's radial stiffness. These studies evaluated the MVAD System with modified impeller in the preclinical setting.
  
  
  METHODS
  This modified pump design was tested through chronic studies (n = 6) in a healthy ovine model where 4 animals were implanted for a duration of 30 ± 5 days and 2 animals were implanted for a duration of 90 ± 5 days. The pump was placed in the left ventricular apex with the outflow graft anastomosed to the descending aorta. Postoperatively, no anticoagulant or antiplatelet therapies were administered throughout the study duration.
  
  
  RESULTS
  All 6 animals reached their elective date of kill, demonstrating no evidence of organ compromise or device-related complications. Average pump parameters did not deviate significantly, and average rotational speed, pump flow, and power consumption were 14095 ± 139 RPM, 4.1 ± 0.4 L/min, and 4.3 ± 0.1 W, respectively. Examination of pump components postexplant demonstrated no mechanical wear or thrombus formation.
  
  
  CONCLUSIONS
  Hemocompatibility and biocompatibility of the modified MVAD System were demonstrated through pump parameters, blood chemistry panels, and histopathology analysis.
authors.affiliation: From the *Division of Cardiothoracic Surgery, University of British Columbia, St. Paul's Hospital, Vancouver, BC Canada; and †HeartWare, Inc., Miami Lakes, FL USA.
authors.forename: Anson
authors.initials: A
authors.lastname: Cheung
authors.forename: Katherine
authors.initials: K
authors.lastname: Chorpenning
authors.forename: Daniel
authors.initials: D
authors.lastname: Tamez
authors.forename: Charles
authors.initials: C
authors.lastname: Shambaugh
authors.forename: Anne E
authors.initials: AE
authors.lastname: Dierlam
authors.forename: M Ertan
authors.initials: ME
authors.lastname: Taskin
authors.forename: Michael
authors.initials: M
authors.lastname: Ashenuga
authors.forename: Carlos
authors.initials: C
authors.lastname: Reyes
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: LaRose
mesh_terms: D000465:Algorithms; D000818:Animals; D004195:Disease Models, Animal; D005240:Feasibility Studies; D006333:Heart Failure / Q000628:therapy; D006352:Heart Ventricles; D006353:Heart-Assist Devices; D006452:Hemoglobinometry; D006801:Humans; D008422:Materials Testing / Q000295:instrumentation; D008904:Miniaturization / Q000295:instrumentation*; D011474:Prosthesis Design / Q000295:instrumentation / Q000379:methods; D012756:Sheep; D013927:Thrombosis / Q000209:etiology / Q000517:prevention & control