Exercise physiology in patients with left ventricular assist devices.

LVAD use in the heart failure population is increasing and allows severely impaired patients an opportunity for exercise rehabilitation before cardiac transplantation. Although the LVAD provides nearly all of the cardiac output at rest, the native left ventricle contributes a modest amount during exercise, with the LVAD capable of providing a mechanical cardiac output of 10 L/min or greater. Given the parameters of the LVAD, exercise training responses should yield greater changes in submaximal exercise tolerance rather than changes in peak oxygen consumption. Heart rate and LVAD rate are driven by separate mechanisms but increase similarly during exercise. Blood pressure responses are somewhat variable early post LVAD implantation but normalize. Ratings of perceived exertion appear to be reliable and useful in this population. Evidence to date suggests that early mobilization and progressive exercise training in this population is safe and improves the transplantation experience. Although central contributions to oxygen consumption are limited by the inherent mechanical parameters of the LVAD, adequate cardiac output is provided for routine physical activities and moderate exercise training while the patient awaits transplantation.