LVAD pump flow does not adequately increase with exercise.

Left ventricular assist devices (LVAD) restore cardiovascular circulatory demand at rest with a spontaneous increase in pump flow to exercise. The relevant contribution of cardiac output provided by the LVAD and ejected through the aortic valve for exercises of different intensities has been barely investigated in patients. The hypothesis of this study was that different responses in continuous recorded pump parameters occur for maximal and sub-maximal intensity exercises and that the pump flow change has an impact on the oxygen uptake at peak exercise (pVO2). Cardiac and pump parameters such as LVAD flow-rate (QLVAD ), heartrate (HR) and aortic valve (AV) opening were analyzed from continuously recorded LVAD data during physical exercises of maximal (bicycle ergometer test) and sub-maximal intensities (6-min walk test and regular trainings). During all exercise sessions the LVAD speed was kept constant. Cardiac and pump parameter responses of 16 patients for maximal and sub-maximal intensity exercises were similar for QLVAD : +0.89±0.52 vs +0.59±0.38 L/min (p=0.07) and different for HR: +20.4±15.4 vs +7.7±5.8 bpm (p<0.0001) and AV-opening with 71% vs 23% of pats (p<0.0001). Multi-regression analysis with pVO2 (R²=0.77) showed relation to workload normalized by bodyweight (p=0.0002), HR response (p=0.001), AV-opening (p=0.02) and age (p=0.06) whereas the change in QLVAD was irrelevant. Constant speed LVADs provide inadequate support for maximum intensity exercises. AV-opening and improvements in HR show an important role for higher exercise capacities and reflect exercise intensities. Changes in pump flow do not impact pVO2 and are independent of AV-opening and response in HR. An LVAD speed control may lead to adequate left ventricular support during strenuous physical activities. This article is protected by copyright. All rights reserved.