Dr. Clarence Walton Lillehei (1918–1999) was born in Minneapolis, received his medical degree from the University of Minnesota in 1942, and spent his entire career on the staff of the University of Minnesota Medical School. In the early 1950s he began to experiment with cross-circulation, a technique in which the blood vessels of a patient were connected to that of a donor (often a parent) with the purpose of oxygenating the blood during an operation. This led to open-heart surgery and other techniques that allowed surgeons to repair complex heart defects. In the 1960s, it further resulted in the development of improved cardiopulmonary bypass machines, meaning surgery could be done inside a still-beating heart without the need for cross-circulation.

In the past, few options had existed for treating congenital heart defects, and patients thus afflicted typically died very young. Using his new techniques, Lillehei performed the first successful open-heart operation using cross-circulation in 1954 on a five-year-old girl with a large atrial septal defect. Over the next several years, he refined and popularized his technique and developed procedures for correcting ventricular septal defects and for repairing the tetralogy of Fallot, allowing newborns with complex congenital heart defects to survive into adulthood.

A brilliant surgeon, Lillehei also treated adults, repairing or replacing heart valves such as mitral stenosis damaged by rheumatic fever. He was also responsible for the world’s first use of a small, external, portable, battery-powered pacemaker and for designing several models of implantable heart valves.

Lillehei received many honors in America and Europe, became professor and chairman of the surgery department at Cornell Medical Center in New York, and from 1966–67 served as president of the American College of Cardiology. As a dedicated educator, he trained more than 150 cardiac surgeons from forty nations, including Dr. Christiaan Barnard, at one time a fellow at the University of Minnesota. His work helped transform open-heart surgery from a risky last-resort procedure to one that saves thousands of lives every year.