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  • In Vitro and In Vivo Characterization of Three Different Modes of Pump Operation When Using a Left Ventricular Assist Device as a Right Ventricular Assist Device

    Author(s)
    Stevens, Michael C
    Gregory, Shaun D
    Nestler, Frank
    Thomson, Bruce
    Choudhary, Jivesh
    Garlick, Bruce
    Pauls, Jo P
    Fraser, John F
    Timms, Daniel
    Griffith University Author(s)
    Pauls, Jo P.
    Gregory, Shaun D.
    Fraser, John F.
    Year published
    2014
    Metadata
    Show full item record
    Abstract
    Dual rotary left ventricular assist devices (LVADs) have been used clinically to support patients with biventricular failure. However, due to the lower vascular resistance in the pulmonary circulation compared with its systemic counterpart, excessively high pulmonary flow rates are expected if the right ventricular assist device (RVAD) is operated at its design LVAD speed. Three possible approaches are available to match the LVAD to the pulmonary circulation: operating the RVAD at a lower speed than the LVAD (mode 1), operating both pumps at their design speeds (mode 2) while relying on the cardiovascular system to adapt, ...
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    Dual rotary left ventricular assist devices (LVADs) have been used clinically to support patients with biventricular failure. However, due to the lower vascular resistance in the pulmonary circulation compared with its systemic counterpart, excessively high pulmonary flow rates are expected if the right ventricular assist device (RVAD) is operated at its design LVAD speed. Three possible approaches are available to match the LVAD to the pulmonary circulation: operating the RVAD at a lower speed than the LVAD (mode 1), operating both pumps at their design speeds (mode 2) while relying on the cardiovascular system to adapt, and operating both pumps at their design speeds while restricting the diameter of the RVAD outflow graft (mode 3). In this study, each mode was characterized using in vitro and in vivo models of biventricular heart failure supported with two VentrAssist LVADs. The effect of each mode on arterial and atrial pressures and flow rates for low, medium, and high vascular resistances and three different contractility levels were evaluated. The amount of speed/diameter adjustment required to accommodate elevated pulmonary vascular resistance (PVR) during support with mode 3 was then investigated. Mode 1 required relatively low systemic vascular resistance to achieve arterial pressures less than 100?mm?Hg in vitro, resulting in flow rates greater than 6?L/min. Mode 2 resulted in left atrial pressures above 25?mm?Hg, unless left heart contractility was near-normal. In vitro, mode 3 resulted in expected arterial pressures and flow rates with an RVAD outflow diameter of 6.5?mm. In contrast, all modes were achievable in vivo, primarily due to higher RVAD outflow graft resistance (more than 500?dyn糯cm5), caused by longer cannula. Flow rates could be maintained during instances of elevated PVR by increasing the RVAD speed or expanding the outflow graft diameter using an externally applied variable graft occlusion device. In conclusion, suitable hemodynamics could be produced by either restricting or not restricting the right outflow graft diameter; however, the latter required an operation of the RVAD at lower than design speed. Adjustments in outflow restriction and/or RVAD speed are recommended to accommodate varying PVR.
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    Journal Title
    Artificial Organs
    Volume
    38
    Issue
    11
    DOI
    https://doi.org/10.1111/aor.12289
    Subject
    Biomedical engineering
    Biomedical engineering not elsewhere classified
    Clinical sciences
    Publication URI
    http://hdl.handle.net/10072/69887
    Collection
    • Journal articles

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