title: Selective reduction of afterload in right heart assist therapy: a mock loop study†.
abstract: OBJECTIVE
  The treatment of right ventricular failure is closely linked to effects on pulmonary vascular resistance and thus the right ventricular (RV) afterload. Medical therapy includes afterload-decreasing drugs such as nitric oxide and prostacycline. However, current devices for mechanical unloading of the right ventricle aim at a decrease in preload increasing the pulmonary volume loading. In our concept study, we tested a minimally invasive right ventricular assist device (MIRVAD) that specifically reduces the afterload.
  
  
  METHODS
  The MIRVAD is supposed to be a foldable device for temporary transvascular placement in the pulmonary artery. We incorporated a MIRVAD prototype into a mock circulatory loop that can reproduce haemodynamic interaction between the pump and the physiological system. Pulmonary hypertension (PH), right heart failure (RHF) and MIRVAD-assisted cases were simulated. The key haemodynamic parameters for RV unloading were recorded.
  
  
  RESULTS
  Mock loop simulation attested to a sufficient right ventricular unloading by serial application of a miniaturized impeller pump in the pulmonary artery. The afterload, represented by the pulmonary arterial root pressure, was recovered to the healthy range (32.62-10.93 mmHg) for the simulated PH case. In the simulated RHF case, the impaired pulmonary perfusion increased from 43.4 to 88.8% of the healthy level and the total ventricular work reduced from 0.381 to 0.197 J at a pump speed of 3500 rpm. At pump speeds higher than 3500 rpm, the pulmonary valve remains constantly open and the right ventricular configuration changes into a simple perfused hollow body.
  
  
  CONCLUSIONS
  The feasibility of RV unloading by a selective decrease in RV afterload was proved in principle. By alternation of the pump speed, gradual reloading in sense of a myocardial training may be achieved. The results will be validated by future animal trials where the relationship between the level of support and pulmonary vascular pressure can be investigated in vivo. Further device design concerning foldable impeller leaflets will be carried out. At a final stage, the crimped version is supposed to reach a size below 1 cm to facilitate minimally invasive insertion.
authors.affiliation: Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany.
authors.forename: Po-Lin
authors.initials: PL
authors.lastname: Hsu
authors.affiliation: Department of Thoracic and Cardio-Vascular Surgery, University Hospital RWTH Aachen, Aachen, Germany nhatam@ukaachen.de.
authors.forename: Nima
authors.initials: N
authors.lastname: Hatam
authors.affiliation: Department of Thoracic and Cardio-Vascular Surgery, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Unterkofler
authors.affiliation: Department of Thoracic and Cardio-Vascular Surgery, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Goetzenich
authors.affiliation: Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany.
authors.forename: Madeleine
authors.initials: M
authors.lastname: McIntyre
authors.affiliation: Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany.
authors.forename: Kai Chun
authors.initials: KC
authors.lastname: Wong
authors.affiliation: Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Egger
authors.affiliation: Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmitz-Rode
authors.affiliation: Department of Thoracic and Cardio-Vascular Surgery, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Autschbach
authors.affiliation: Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, Helmholtz Institute, RWTH Aachen University, Aachen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Steinseifer
mesh_terms: D003198:Computer Simulation; D005240:Feasibility Studies; D006333:Heart Failure / Q000503:physiopathology / Q000628:therapy*; D006353:Heart-Assist Devices; D006439:Hemodynamics; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology / Q000628:therapy*; D008422:Materials Testing; D008904:Miniaturization; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D011651:Pulmonary Artery / Q000503:physiopathology; D018497:Ventricular Dysfunction, Right / Q000503:physiopathology / Q000628:therapy*; D016278:Ventricular Function, Right
keywords: In vitro; Mechanical circulatory support; Minimally invasive device; Mock circulatory system; Right heart failure; Right ventricular assist device; Simulation; Ventricular assist device