Modeling and Optimization of Assisted Circulation

Many methods of mechanical assistance to aid the failing heart have been, and are being, extensively investigated. The hemodynamic goals of the different methods being studied vary depending upon the specific patient problems, however, they all fit into three general categories: decreasing the work of the failing myocardium by reducing the load on the left ventricle; increasing blood flow through the coronary circulation, and consequently increasing the oxygen supply to the hypoxic tissue; and increasing cardiac output, and thus increasing the blood supply to the peripheral organs. Mechanical assist devices have been designed for a variety of operating conditions. Anatomically they can operate either in series or in parallel with the failing left ventricle. From a performance point of view they can be permanent or temporary. Thus far, the controls for the devices have been readily available, but with the acceptance of permanent, implantable units it is likely that the controls will have to be automatic. In addition, even with temporary assist devices with available controls, it is advantageous if the timing controls are automatic and optimized to a physiological benefit. Recent model, experimental, and optimization studies have led to a much more complete understanding of assisted circulation which, when combined with the advances in microprocessor technology, can provide automatically controlled assist devices.