Cross-circulation

History

Before the invention of reliable heart-lung machines, open-heart surgery in the early 1950s faced a major obstacle: there was no safe way to keep blood flowing and oxygenated while the heart was stopped. In 1954, surgeon C. Walton Lillehei at the University of Minnesota tackled this problem with a technique called cross-circulation. He temporarily linked the patient’s bloodstream to that of a healthy donor, usually a parent. The donor’s own heart and lungs did the work of pumping and oxygenating blood for both people during the operation. This method made it possible to successfully repair congenital heart defects years before mechanical bypass machines became standard. Despite its success, the original version of cross-circulation carried serious ethical and safety risks for the donor. By the early 1960s, it had been largely replaced by mechanical heart-lung machines. Still, it stands as a pivotal achievement in cardiac surgery and helped pave the way for later extracorporeal support systems.

Starting around the 2010s, researchers gave cross-circulation a new purpose: keeping donor organs alive and healthy outside the body. Inspired by the original surgical technique, teams at Columbia University and Vanderbilt University adapted the concept to support ex-vivo organs using a living pig as a biological life-support system. In this modern setup, an external circuit connects the donor organ—such as a lung or liver—to the pig. The pig’s body provides dynamic hormonal, immune, and metabolic regulation that standard mechanical perfusion machines cannot offer. Cardiothoracic surgeon Matthew Bacchetta and biomedical engineer Gordana Vunjak-Novakovic led early experiments showing that this approach could keep ex-vivo lungs functioning at body temperature for four days. It also repaired lungs damaged by ischemia, aspiration, or infection—injuries that would normally rule them out for transplant. The team developed new cannulation strategies and circuit designs to improve safety and make the platform more practical. By combining durable physiological support with targeted treatments, this revived cross-circulation technique actively helps organs recover, modulates their immune response, and promotes functional regeneration.