Background: Left ventricular assist devices (LVAD) are increasingly used for heart failure (CHF); however, the level of optimal support has not been elucidated. We hypothesize that partial LVAD support in an ovine model of microinfarction-induced CHF significantly reduces left ventricular myocardial oxygen consumption (LVVO2).
Methods and results: Microembolization of the circumflex coronary artery was used to induce CHF in 5 sheep (ejection fraction 28 +/- 2%). Four months later, animals underwent implantation of a centrifugal LVAD. LVAD flow was incrementally increased from 0% (baseline) to 25%, 50%, and 75% support of the LV. LVVO2 and stroke work (SW) were calculated at each increment. At baseline, LVVO2 (microL/100 g LV/beat) measured 43.2 +/- 3.4. LVVO2 decreased to 26.5 +/- 8.2,* 20.3 +/- 8.9,* and 12.6 +/- 6.3* at 25%, 50%, and 75% support (*P < .05). SW (mm Hg/mL) measured 1933.0 +/- 275.7 at baseline and decreased to 1588.0 +/- 204.1, 1181.0 +/- 157.2,* and 764.5 +/- 171.7* at 25%, 50%, and 75% support. Cardiac output, heart rate, and left main coronary artery blood flow were unaffected with partial support.
Conclusion: Complete support with a centrifugal LVAD is not necessary for achieving significant reductions in LVVO2 . Partial support of as little as 25% significantly reduces LVVO2 in CHF through comparatively minor reductions in cardiac work. This is the first study to examine partial LVAD support in a CHF model.