Open-heart surgery is a lifesaving procedure commonly performed in the U.S. to replace failing hearts, bypass clogged arteries, and repair leaky valves. While most patients recover fully, some suffer long-term effects — or even fatal heart failure — from the stress caused by the operation.

Surgeons use a cardiopulmonary bypass machine to perform the heart’s functions while it is not beating during a procedure. Because the blood supply to the heart is interrupted, cardiac cells can be injured.

Scientists at the Cedars-Sinai Heart Institute examined damaged cells in tissue samples taken from patients before and after surgery. Their work demonstrates for the first time in human hearts that cardiac muscle cells react to this type of injury by both destroying and creating new mitochondria, the tiny energy factories inside each cell.

“By accelerating beneficial aspects of this process, doctors one day may be able to speed up recovery of heart function after open-heart surgery,” says Roberta Gottlieb, MD, director of Molecular Cardiobiology at the Cedars-Sinai Heart Institute, the Dorothy and E. Phillip Lyon Chair in Molecular Cardiology in honor of Clarence M. Agress, MD, and the study’s principal investigator.