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New models of assistant ventricles have been produced steadily, in improved shapes and for both ventricles (see diagram, left). It is only seven weeks ago that the DeBakey team ran what it thought was a highly successful experiment with a unit that replaced both of a dog's ventricles. Yet progress in the field is so fast that within four days the researchers were dismissing their test as old hat. They were getting as good or better results with a single ballooning sac inserted in the left ventricle alone. It seems, says Dr. Hall, that this may be enough in many cases to stimulate, if not precisely duplicate, the work of nature's complex four-chambered heart.
What really counts is a strong and steady beat in the left ventricle to send blood coursing through the trunk to the head and limbs. Once that is achieved, nature is likely to take over and get the rest of the circulatory system, including the three other chambers, to work effectively in unison. However, if both left and right ventricles have been severely damaged, they might be replaced by a two-in-one prosthesis with a single pump (see diagram, right).
Muscles or Batteries. All artificial hearts or half-hearts so far have relied on an external power source almost as bulky as a washing machine and infinitely more complex and delicate. The patient has to stay in bed, hooked up to this pulsating pump by an air hose passing through a hole in his chest. For a man with an artificial heart to get up from his bed and walk, let alone work, the power supply must be inside him. It may be electrical, depending on the long-lived, high-performance mercury batteries now being perfected for cardiac pacemakers (TIME, Jan. 11, 1960). Another possibility would be to install an electric coil inside the body and have it operated through induction by a power pack worn outside the heart. Either system would supply adequate electrical stimuli but only a smidgen of mechanical power.
Better yet, DeBakey and his co-workers believe, it may eventually be possible to harness one of the body's powerful muscles, perhaps in the shoulder girdle, to such a pacemaker. Then, when the little device gives its electrical command, the muscle will contract, and in the process it will squeeze an implanted bellows, which in its turn will squeeze the left ventricle or both (see diagram, center). Like all gadgeteers, the heart researchers also dream of using atomic power.
Just two weeks ago, the DeBakey team was well pleased with the results of a 40-hour test in a 150-lb. calf with a complete artificial heart. But the problems to be solved before routine use in man are still forbidding. The external heart-lung machine, which Dr. DeBakey has done so much to advance, can tide a patient over for only a few hours, during and after surgery. Dr. DeBakey wants an artificial heart element that can be installed while a patient is still on the operating table and left in place to tide him over the first few dangerous days of recovery. Then it might be removed.