Mechanical bridge to cardiac transplant: where do we stand in 1990?

Various mechanical devices have been used to support the circulation in patients requiring cardiac transplantation who are in cardiogenic shock. The devices produce either a pulsatile or nonpulsatile blood-flow pattern. Of the former, the intra-aortic balloon pump is the most frequently used. However, it augments but does not replace the function of the left ventricle. At the Ottawa Heart Institute, orthotopic replacement of both ventricles with a total artificial heart has proven a reliable and effective bridge to transplantation in selected patients. Heterotopic ventricles, known as ventricular assist devices, may also be used to replace the function of one or both ventricles and are increasingly being used to maintain the circulation. The future of nonpulsatile devices for mechanical support remains unclear because the long-term effects of this unphysiologic flow pattern are unknown. As refinements in circulatory support devices continue and as patient selection and timing of device insertion become more clearly defined, the results in these patients will likely approach those of elective cardiac transplantation.