单选题
Just seven years ago, the Jarvik-7 artificial heart was being cheered as the model of human creativeness. The sight of Barney Clark alive and conscious after trading his diseased heart for a metal and plastic pump the press, the public and many doctors convinced that the future had arrived. It hadn"t. After monitoring production of the Jarvik-7, and reviewing its effects on the 150 or so patients (most of whom got the device as a temporary measure) in the U.S. Food and Drug Administration concluded that the machine was doing more to endanger lives than to save them. Last week the agency cancelled its earlier approval, effectively banning the device.
The recall may hurt Symbion Inc. , maker of the Jarvik-7, but it won"t end the request for an artificial heart. One problem with the banned model is that the tubes connecting it to an external power source created a passage for infection. Inventors are now working on new devices that would be fully placed, along with a tiny power pack, in the patient"s chest. The first sample products aren"t expected for another 10 or 20 years. But some people are already worrying that they"ll work and that America"s overextended health care programs will lose a precious $2.5 billion to $5 billion a year providing them for a relatively few dying patients. If such expenditures cut into funding for more basic care, the net effect could actually be a decline in the nation"s health.
单选题
According to the passage, the Jarvik-7 artificial heart proved to be ______.