With this book, it was not our intention to provide a complete "textbook" on axial pumps and their use as temporary cardiac assist systems. It is more a sharing of experiences with a novel left-ventricular assist system, the Hemopump, as it was developed by R. K. Wampler. This device, marketed by Johnson & Johnson Interventional Systems, has not yet been widely used and accepted in clinical practice. It was offered to us some time ago to study its applicability in the experimental setting. At the moment, it is under investigation in many centers and it is commercially available. However, as with any other cardiac assist system, the axial pump has its own advantages and limitations. Needless to say, critical analysis of such a novel device is mandatory and, therefore, we are grateful to our colleagues who were willing to contribute to this book. They present, discuss, and analyze their experimental and clinical experience with the Hemopump and focus on side-effects, deficiency and efficiency of this device which, by virtue of its simplicity is revolutionary. Leuven, Belgium, 1991 Willem Flameng v Contributors H. Reul, Ph. D. Helmholtz Institute for Biomedical Engineering at the RWTH Aachen, Pauwelstrasse 30, D-5100 Aachen, FRG R. IC. Wample . D. Nimbus edical, Inc., 2890 ICilgore Road, Rancho Cordova, California 95670, USA IC. -H. Scholz, . D. ICliniken der Universitat Gottingen, Fachbereich edizin, Zentrum Innere edizin Abt. ICardiologie, Robert ICochstrasse 40, D-3400 Gottingen, FRG P. Wouters, . D.