Assessment of cardiac function during axial-flow left ventricular assist device support using a left ventricular pressure-derived relationship: comparison with pre-load recruitable stroke work.

BACKGROUND: 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.
METHODS: 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.
RESULTS: 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).
CONCLUSIONS: 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.