The heart is a four-chambered muscle that pumps blood through your body. Normally the contraction of heart muscle is well regulated. Muscle fibers surrounding a chamber contract in unison (all at the same time) and the different chambers work together to move the blood. The electrical impulses that bring about this coordination sometimes, however, fail. It is possible to keep a person alive and even restore him to normal activity by providing correct impulses from some artificial source. This is what a cardiac pacemaker does.
The first pacemakers were large devices that stimulated the heart through large electrodes (metal pieces for electrical contact) placed on the chest. In 1952 Paul M. Zoll, working with engineers of the Electrodyne Company, developed the first successful external pacemaker. Because large impulses were required, use of the device caused pain and burns. In 1957 a somewhat better device was created, which was implanted in the chest and used smaller impulses. The obvious drawback was that the chest needed to be opened and wires run to an external pulse generator.
Earl Bakken’s prototype pacemaker was first used on patients in 1958. It ran on batteries and was used on patients whose hearts failed to begin beating after surgery. Courtesy: Bakken Library and Museum.
In the last month of 1957 and the first months of 1958 the engineer Earl Bakken designed and built a transistorized pacemaker. The transistor revolutionized electronics in all industries including the medical industry, by allowing things to be made smaller. In 1958 and 1959 the engineer Wilson Greatbatch and the cardiologist W.M. Chardack developed a fully implantable pacemaker (that is, it could be placed on top of the heart). Six years later Greatbatch improved on the design by making a so-called inhibited demand pacemaker. It provided impulses to the heart only when they were needed. Since then, many further improvements have been made, and today cardiac pacemakers enable millions of people to lead normal lives.
A modern pacemaker. Courtesy: Medtronic, Inc