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  • Title: Effect of exercise and pump speed modulation on invasive hemodynamics in patients with centrifugal continuous-flow left ventricular assist devices.
    Author: Muthiah K, Robson D, Prichard R, Walker R, Gupta S, Keogh AM, Macdonald PS, Woodard J, Kotlyar E, Dhital K, Granger E, Jansz P, Spratt P, Hayward CS.
    Journal: J Heart Lung Transplant; 2015 Apr; 34(4):522-9. PubMed ID: 25662859.
    Abstract:
    BACKGROUND: Continuous-flow left ventricular assist devices (CF-LVADs) improve functional capacity in patients with end-stage heart failure. Pump output can be increased by increased pump speed as well as changes in loading conditions. METHODS: The effect of exercise on invasive hemodynamics was studied in two study protocols. The first examined exercise at fixed pump speed (n = 8) and the second with progressive pump speed increase (n = 11). Patients underwent simultaneous right-heart catheterization, mixed venous saturation, echocardiography and mean arterial pressure monitoring. Before exercise, a ramp speed study was performed in all patients. Patients then undertook symptom-limited supine bicycle exercise. RESULTS: Upward titration of pump speed at rest (by 11.6 ± 8.6% from baseline) increased pump flow from 5.3 ± 1.0 to 6.3 ± 1.0 liters/min (18.9% increase, p < 0.001) and decreased pulmonary capillary wedge pressure (PCWP; 13.6 ± 5.4 to 8.9 ± 4.1 mm Hg, p < 0.001). Exercise increased pump flow to a similar extent as pump speed change alone (to 6.2 ± 1.0 liters/min, p < 0.001), but resulted in increased right- and left-heart filling pressures (right atrial pressure [RAP]: 16.6 ± 7.5 mm Hg, p < 0.001; PCWP 24.8 ± 6.7 mm Hg, p < 0.001). Concomitant pump speed increase with exercise enhanced the pump flow increase (to 7.0 ± 1.4 liters/min, p < 0.001) in Protocol 2, but did not alleviate the increase in pre-load (RAP: 20.5 ± 8.0 mm Hg, p = 0.07; PCWP: 26.8 ± 12.7 mm Hg; p = 0.47). Serum lactate and NT-proBNP levels increased significantly with exercise. CONCLUSIONS: Pump flow increases with up-titration of pump speed and with exercise. Although increased pump speed decreases filling pressures at rest, the benefit is not seen with exercise despite concurrent up-titration of pump speed.
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