Pacemaker

The patch of cells in the heart which stimulated the heartbeat was well known for decades, and bulky pacemakers worn outside the body had been built before, but this invention marked the first compact pacemaker which could be implanted subcutaneously.
 Clarence Walton Lillehei United States 1957 Pacemaker

The patch of cells in the heart which stimulated the heartbeat was well known for decades, and bulky pacemakers worn outside the body had been built before, but this invention marked the first compact pacemaker which could be implanted subcutaneously.