Pulsatile vs. continuous flow

Earlier left ventricular assist devices (LVADs) were volume displacement pumps (VDPs) that delivered pulsatile flow. However, due to improved survival rates of rotary blood pumps (RBPs), they are now the preferred device. Originally, RBPs operated at a constant speed and therefore delivered flow continuously with an absent or diminished pulse. Although RBPs were an improvement to the previous VDPs, the delivery of continuous flow has led to secondary complications, such as vascular and aortic valve dysfunction and gastrointestinal bleeding. Therefore, research has been made toward pulsatile RBPs by rapidly modulating pump speed. However, deriving pulsatile flow with RBPs has not been without controversy. Issues of debate have included the quantification of an adequate pulse and the influence of blood trauma and power consumption when generating a pulse with a RBP. Meanwhile, the pulsatility controversy has also expanded to total artificial heart and extracorporeal membrane oxygenator (ECMO) support. Nevertheless, commercial developments have been made toward combining the benefits of improved durability and survival rates of RBPs with a pulsing mechanism for mechanical circulatory support.