In 1958, engineer Earl Bakken of Minneapolis, Minnesota, produced the first wearable external pacemaker. This transistorized pacemaker, housed in a small plastic box, had controls to permit adjustment of pacing heart rate and output voltage and was connected to electrode leads which passed through the skin of the patient to terminate in electrodes attached to the surface of the myocardium of the heart.

1958 – First wearable external pacemaker