Some 70,000 Americans depend for their lives on pacemakers, tiny electrically powered devices implanted in the chest to correct a slow or irregular heartbeat. But from the first, the chief drawback of the conventional pacemaker has been that the chemical batteries which supply its energy must be changed at frequent intervals, sometimes requiring the patient to undergo the inconvenience and risk of an operation every year or two. Now this problem seems to have been eliminated. Patients are receiving a new type of pacemaker powered by nuclear energy and designed to last ten years or longer.

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