The majority of patients currently implanted with left ventricular assist devices have the expectation of support for more than 2 years. As a result, survival alone is no longer a sufficient distinctive for this technology, and there have been many studies within the last few years examining functional capacity and exercise outcomes.
Despite strong evidence for functional class improvements and increases in simple measures of walking distance, there remains incomplete normalization of exercise capacity, even in the presence of markedly improved resting hemodynamics. Reasons for this remain unclear. Despite current pumps being run at a fixed speed, it is widely recognized that pump outputs significantly increase with exercise. The mechanism of this increase involves the interaction between preload, afterload, and the intrinsic pump function curves. The role of the residual heart function is also important in determining total cardiac output, as well as whether the aortic valve opens with exercise. Interactions with the vasculature, with skeletal muscle blood flow and the state of the autonomic nervous system are also likely to be important contributors to exercise performance.
Further studies examining optimization of pump function with active pump speed modulation and options for optimization of the overall patient condition are likely to be needed to allow left ventricular assist devices to be used with the hope of full functional physiological recovery.
aHeart Failure and Transplant Unit, Victor Chang Cardiac Research Institute, St Vincent's Hospital, University of New South Wales, Sydney, New South Wales, Australia
bDepartment of Cardiovascular Sciences, Clinical Cardiac Surgery, Katholieke Universiteit Leuven, Leuven, Belgium
Correspondence to Professor Christopher S. Hayward, MD, Department of Cardiology, St Vincent's Hospital, Victoria St, Darlinghurst, NSW 2010 Australia. Tel: +61 2 8382 6880; fax: +61 2 8382 6881; e-mail: email@example.com