Heart transplantation is being considered when a patient suffers from advanced cardiac failure and the condition cannot be improved by any other therapeutic intervention. Cardiac damage can result from coronary heart diseases (narrowing or blockage of the blood vessels in the heart, infarcts), advanced cardiac insufficiency following an infection, or heart defects in children and newborns which cannot be 'fixed' by surgery. Many heart diseases also induce damage to the lungs, making combined heart-lung transplantation necessary. Even today, heart surgeons only consider transplantation at the end-stage of a disease process, because the intervention bears considerable risks for the organ recipient; besides, comparatively few donor hearts are available. The waiting time for a donor heart may sometimes be bridged with the aid of an artificial heart pump, which means that the patient must stay in hospital and will be hardly able to withstand stress during that period. Due to the seriousness of the underlying disease, many patients die while they are waiting for a suitable donor organ. On the other hand, the outcome of heart transplantations is very good by now. According to results from the Collaborative Transplant Study conducted by the University of Heidelberg, on average more than 80% of the hearts transplanted worldwide continue to function one year after the operation, and 70% still work well after five years.