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

BACKGROUNDS

Peak exercise cardiac output (CO) increase is associated with an increase of peak oxygen uptake (VO), provided that arteriovenous O difference [Δ(Ca-Cv)O] does not decrease. At anaerobic threshold, VO, 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 VO 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 2days at LVAD pump speed set randomly at 2 and 4.

RESULTS

Increasing LVAD pump speed from 2 to 4 increased CO from 3.4±0.9 to 3.8±1.0L/min (ΔCO 0.4±0.6L/min, p=0.04) and from 5.3±1.3 to 5.9±1.4L/min (ΔCO 0.6±0.7L/min, p<0.01) at rest and peak exercise, respectively. Similarly, VO increased from 788±169 to 841±152mL/min (ΔVO 52±76mL/min, p=0.01) and from 568±116 to 619±124mL/min (ΔVO 69±96mL/min, p=0.02) at peak exercise and at anaerobic threshold, respectively. Δ(Ca-Cv)O did not change significantly, while ventilatory efficiency improved (VE/VCO slope from 39.9±5.4 to 34.9±8.3, ΔVE/VCO -5.0±6.4, p<0.01).

CONCLUSIONS

In HF, an increase in CO with a higher LVAD pump speed is associated with increased peak VO, postponed anaerobic threshold, and improved ventilatory efficiency.