1954
a. After a blackout in the Twin Cities, Dr. Earl E. Bakken designed the first wearable, battery-powered, transistorized cardiac pacemaker at the request of Dr. C. Walton Lillihei at the University of Minnesota.

Photo of Dr. C. Walton Lillihei in front of a display about cross-circulation
Dr. C. Walton Lillihei in front of a display about cross-circulation
b. The first cross-circulation operation was performed by Dr. C. Walton Lillihei. The one-year-old patient had the 0+ blood type, and so did his father. In the cross-circulation technique, the father was connected to the child and provided oxygenated blood to the child's body during surgery. This landmark surgery helped to generate hope in the medical community regarding open-heart surgery for complicated congenital heart defects, such as ventricular septal defect (VSD).

[Photo courtesy of Lillehei Heart Institute, Department of Medicine, Medical School, Academic Health Center, University of Minnesota]