Effect of increasing pump speed during exercise on peak oxygen uptake in heart failure patients supported with a continuous‐flow left ventricular assist device. A double‐blind randomized study

Abstract

Aims Continuous‐flow left ventricular assist device (CF‐LVAD) implantation is associated with improved quality of life, but the effect on exercise capacity is less well documented. It is uncertain whether a fixed CF‐LVAD pump speed, which allows for sufficient circulatory support at rest, remains adequate during exercise. The aim of this study was to evaluate the effects of fixed versus incremental pump speed on peak oxygen uptake (peak VO2) during a maximal exercise test. Methods and results In CF‐LVAD (HeartMate II) patients exercise testing measuring peak oxygen uptake (VO2) was performed on an ergometer bike twice in one day: once with fixed pump speed (testfix) and once with incremental pump speed (testinc). The order of testfix and testinc in each patient was determined by randomization. During testinc pump speed was increased from the baseline value by 400 rpm/2 min. Fourteen patients (aged 23–69 years) were included with a mean support duration of 465 ± 483 days. Baseline CF‐LVAD speed was 9357 ± 238 rpm and during testinc speed was increased by a mean of 1486 ± 775 rpm. Mean peak VO2 was significantly higher in testinc compared with testfix (15.4 ± 5.9 mL/kg/min vs. 14.1 ± 6.3 mL/kg/min; P = 0.012), corresponding to a 9.2% increase. All exercise tests (n = 28) were adequately performed with RER > 1. Conclusion Increasing pump speed during exercise augments peak VO2 in patients supported with CF‐LVADs. An automatic speed‐change function in future generations of CF‐LVADs might improve functional capacity.

Comprehensive review and suggested strategies for the detection and management of aortic insufficiency in patients with a continuous-flow left ventricular assist device

“…This loop extends the time-history of shear stress exposure of the blood, increasing hemolysis and thromboembolism risks; (ii) the development of AV dysfunction, including acquired AS and AI, may reduce the likelihood of "bridge to myocardial recovery" in those patients for whom CF-LVAD support is projected to be temporary; and (iii) exercise-induced augmentation of cardiac output, correlated with fewer adverse events and a higher quality of life, may be limited by an incompetent valve. 13,18,19 Although not clinically proven, there is concern that even mild to moderate, continuous AI may lead to increased morbidity and mortality in patients on prolonged LVAD support. Theoretically, continuous AI could lead to elevated wedge pressures with resultant exercise intolerance and gradual end-organ dysfunction.…”

“…Pulsatility with AV opening may benefit patient exercise tolerance and enhance LV myocardial recovery attempts. 13,18,19 A patent AV also provides a "bail-out" mechanism should acute CF-LVAD malfunction occur. As such, a bioprosthetic AVR may be considered for management of native AS in selected CF-LVAD recipients.…”

Relation Between Pressure and Volume Unloading During Ramp Testing in Patients Supported with a Continuous-Flow Left Ventricular Assist Device

“…Thus pressure-volume relations during exercise with increased pump speed are of general interest, and the chosen increase of +800 RPM in this study has previously been shown clinically safe. 5,6 Central pressures, CO, and mixed venous blood oxygen saturation (SvO 2 ) were measured by right heart catheterization (RHC), via the right internal jugular vein, using a Swan-Ganz catheter (Edwards Lifesciences, Irvine, California). Cardiac output was measured three times at each ramp step by standard thermodilution with cold water injection, and the average result was recorded.…”

Functional Status in Left Ventricular Assist Device–Supported Patients: A Literature Review

“…(34,35) Brassard et al showed cardiac output increased at submaximal exercise with increased pump speed (at rest cardiac output was 6 ± 2.1 L/min; submaximal exercise 60W cardiac output was 8.7 ± 1.1 L/min). (34) But, this study did not demonstrate significant differences at maximal exercise between the increased pump speed and constant pump speed groups.…”