title: The Use of Fluid Mechanics to Predict Regions of Microscopic Thrombus Formation in Pulsatile VADs.
abstract: We compare the velocity and shear obtained from particle image velocimetry (PIV) and computational fluid dynamics (CFD) in a pulsatile ventricular assist device (VAD) to further test our thrombus predictive methodology using microscopy data from an explanted VAD. To mimic physiological conditionsin vitro, a mock circulatory loop is used with a blood analog that matched blood's viscoelastic behavior at 40% hematocrit. Under normal physiologic pressures and for a heart rate of 75 bpm, PIV data is acquired and wall shear maps are produced. The resolution of the PIV shear rate calculations are tested using the CFD and found to be in the same range. A bovine study, using a model of the 50 cc Penn State V-2 VAD, for 30 days at a constant beat rate of 75 beats per minute (bpm) provides the microscopic data whereby after the 30 days, the device is explanted and the sac surface analyzed using scanning electron microscopy (SEM) and, after immunofluorescent labeling for platelets and fibrin, confocal microscopy. Areas are examined based on PIV measurements and CFD, with special attention to low shear regions where platelet and fibrin deposition are most likely to occur. Data collected within the outlet port in a direction normal to the front wall of the VAD shows that some regions experience wall shear rates less than 500 s-1, which increases the likelihood of platelet and fibrin deposition. Despite only one animal study, correlations between PIV, CFD, andin vivodata show promise. Deposition probability is quantified by the thrombus susceptibility potential, a calculation to correlate low shear and time of shear with deposition.
authors.affiliation: Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Topper
authors.affiliation: Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Navitsky
authors.affiliation: Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Medvitz
authors.affiliation: Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Eric G
authors.initials: EG
authors.lastname: Paterson
authors.affiliation: Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA ; Department of Surgery, Penn State Hershey Medical Center, The Pennsylvania State University, Hershey, PA 17033, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Siedlecki
authors.affiliation: Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA.
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Slattery
authors.affiliation: Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Deutsch
authors.affiliation: Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA ; Department of Surgery, Penn State Hershey Medical Center, The Pennsylvania State University, Hershey, PA 17033, USA.
authors.forename: Gerson
authors.initials: G
authors.lastname: Rosenberg
authors.affiliation: Department of Bioengineering, The Pennsylvania State University, 205 Hallowell Building, University Park, PA 16802, USA ; Department of Surgery, Penn State Hershey Medical Center, The Pennsylvania State University, Hershey, PA 17033, USA.
authors.forename: Keefe B
authors.initials: KB
authors.lastname: Manning
keywords: computational fluid dynamics; fibrin; fluid mechanics; particle image velocimetry; platelets; surface analysis; thrombosis; ventricular assist device