Left ventricular assist device (LVADs) have been used with increasing frequency since the late 1980s. Technology has improved these devices to make them less thrombogenic and has decreased their size to allow greater application. By definition, the LVAD only assists or supports the pumping function of the left ventricle, unlike cardiopulmonary bypass which provides total circulatory and pulmonary function. LVADs support the circulation for hours to days and occasionally for weeks when the left and/or right ventricle has failed and is therefore unable to sustain the circulation. The hope is that by temporarily supporting the circulation, ventricular function will return. In other instances, LVAD type devices (also known as prosthetic ventricles) are used to 'bridge' the time until a suitable heart donor can be located for transplantation.