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Relationship between pump speed and exercise capacity during HeartMate II left ventricular assist device support: influence of residual left ventricular function
Author(s) -
Noor Mumin R.,
Bowles Christopher,
Banner Nicholas R.
Publication year - 2012
Publication title -
european journal of heart failure
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.149
H-Index - 133
eISSN - 1879-0844
pISSN - 1388-9842
DOI - 10.1093/eurjhf/hfs042
Subject(s) - ejection fraction , medicine , cardiology , heart failure , ventricular function , ventricular assist device
Aims Patients treated with a Thoratec HeartMate II left ventricular assist device (LVAD) are supported at a fixed pump speed. It is uncertain whether pump speed has a significant effect on exercise capacity. We investigated the relationship between pump speed and exercise capacity and the influence of residual LV function Methods and results We exercised 30 patients 6 months after HeartMate II implantation at clinical pump speed (typically 9000 r.p.m.) and again at the lowest speed available (6000 r.p.m.). Overall, peak oxygen uptake (pkVO 2 ) positively correlated with LV ejection fraction (LVEF) both at the clinical pump speed ( r = 0.41, P = 0.03) and after pump speed reduction ( r = 0.50, P = 0.01). We divided the patients into two groups; those with higher LVEF (LVEF ≥40%) and those with lower LVEF (LVEF <40%) at the time of exercise testing. The response to speed change was different between the two groups. In the higher LVEF group, the impact of LVAD pump speed reduction was minimal (pkVO 2 21.4 ± 4.8 mL/kg/min vs. 20.8 ± 5.5 mL/kg/min, P = 0.38). In the lower LVEF group, the pkVO 2 was lower at both speeds; 17.2 ± 5.3 and 14.7 ± 5.9 mL/kg/min, respectively. In the lower LVEF group, the pkVO 2 decreased by 2.5 mL/kg/min ( P = 0.02) with speed reduction. Conclusions HeartMate II patients with lower residual LV function had a lower pkVO 2 and were more sensitive to pump speed reduction. This suggests that modulation of LVAD speed during exercise could be of benefit to this group of patients.