Abstract
In this study we evaluate load-independent ventricular function during left ventricular assist device (LVAD) support based solely on telemetered measurements of left ventricular (LV) pressure, which has not been reported previously. Adult sheep underwent placement of an axial-flow LVAD, a telemetered LV pressure manometer and instruments for pressure-volume analysis. In unsedated sheep, the simultaneous determination of both stroke work/end-diastolic volume (SW/EDP [PRSW]; slope: M(W)) and LV triple-product (TP = LVSP . dP/dt . HR) vs LV end-diastolic pressure (TP/EDP; slope: M(TP)) were performed before and then after beta(1)-blockade using the LVAD to acutely unload the ventricle. LVAD support (4.5 +/- 0.31 liters/min) was maintained for 1 week. During LV unloading "runs," the LVAD flow (Q(V)) increased (up to 5.8 +/- 0.71 liters/min), although there were decreases in SW (3,061 +/- 747 to 1,556 +/- 410 mm Hg ml(-1)), LV TP (3,127 +/- 397 to 1,019 +/- 335 x 10(5)) and LV EDP (18.2 +/- 1.2 to 9.7 +/- 1.8 mm Hg). The TP/EDP and SW/EDV relationships established during the unloading runs were highly linear (R(2) up to 0.95) and their slopes were reduced by beta-adrenergic blockade (p < 0.001). The TP/EDP relationship established during LVAD unloading of the LV was load-independent and sensitive to changes in cardiac inotropy, and correlated with PRSW.
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