Lvad pump speed increase is associated with increased peak exercise cardiac output and vo2, postponed anaerobic threshold and improved ventilatory efficiency

Backgrounds Peak exercise cardiac output (CO) increase is associated with an increase of peak oxygen uptake (VO2), provided that arteriovenous O2 difference [\u394(Ca 12 Cv)O2] does not decrease. At anaerobic threshold, VO2, is related to CO. We tested the hypothesis that, in heart failure (HF) patients with left ventricular assistance device (LVAD), an acute increase of CO obtained through changes in LVAD pump speed is associated with peak exercise and anaerobic threshold VO2 increase. Methods Fifteen of 20 patients bearing LVAD (Jarvik 2000) enrolled in the study successfully performed peak exercise evaluation. All patients had severe HF as shown by clinical evaluation, laboratory tests, echocardiography, spirometry with alveolar-capillary diffusion, and maximal cardiopulmonary exercise testing (CPET). CPETs with non-invasive CO measurements at rest and peak exercise were done on 2 days at LVAD pump speed set randomly at 2 and 4. Results Increasing LVAD pump speed from 2 to 4 increased CO from 3.4 \ub1 0.9 to 3.8 \ub1 1.0 L/min (\u394CO 0.4 \ub1 0.6 L/min, p = 0.04) and from 5.3 \ub1 1.3 to 5.9 \ub1 1.4 L/min (\u394CO 0.6 \ub1 0.7 L/min, p < 0.01) at rest and peak exercise, respectively. Similarly, VO2 increased from 788 \ub1 169 to 841 \ub1 152 mL/min (\u394VO2 52 \ub1 76 mL/min, p = 0.01) and from 568 \ub1 116 to 619 \ub1 124 mL/min (\u394VO2 69 \ub1 96 mL/min, p = 0.02) at peak exercise and at anaerobic threshold, respectively. \u394(Ca 12 Cv)O2 did not change significantly, while ventilatory efficiency improved (VE/VCO2 slope from 39.9 \ub1 5.4 to 34.9 \ub1 8.3, \u394VE/VCO2 12 5.0 \ub1 6.4, p < 0.01). Conclusions In HF, an increase in CO with a higher LVAD pump speed is associated with increased peak VO2, postponed anaerobic threshold, and improved ventilatory efficiency