According to legend (and Wikipedia), a Norwegian doctor, Axel Cappelen, performed the first-ever surgery directly on the heart in 1895. Since then, Norwegian pride dictates scientists continue to finesse this surgery by experimenting with fresh methods and perfecting special techniques. A new study conducted at St. Olavs Hospital in Trondheim, Norway demonstrates how shutting off the blood supply to an arm or leg before surgery can protect the heart during an operation.

Specifically, a team of researchers from the Norwegian University of Science and Technology (NTNU) investigated how the muscle of the left chamber of the heart might be affected by remote ischemic preconditioning (RIPC) during cardiac surgery. This technique, which works by shutting off the blood supply to an arm or a leg before heart surgery, has been found to be protective of the heart, able to reduce risk to this most important organ.

“During heart surgery we have to stop the blood supply to the heart to be able to operate on it. After some time without fresh blood, the heart will reduce its ability to produce energy because it doesn't get oxygen,” explained Dr. Katrine Hordnes Slagsvold, the first author of the study. “When we shut off the blood flow to another large muscle, such as an arm or a leg, the body prepares for an upcoming challenge by mobilizing its defense system.”

Learning More about a Familiar Technique

While RIPC has been practiced by surgeons for some time now, its effects have never been tested on the left chamber of the heart. For the current study, then, Slagsvold and her co-researchers randomized 60 patients, all scheduled for coronary bypass surgery at St. Olavs Hospital, into two groups: an RIPC group and a control group. Coronary artery bypass grafting (CABG) is this most common of heart surgeries for adults and involves a surgeon grafting a healthy piece of artery or vein to a blocked heart artery as a way to improve blood flow.

Before surgery, the patients in the RIPC group underwent brief periods without blood supply to the arm; this was achieved by inflating a blood pressure cuff for five minutes three times. Meanwhile, control patients simply prepared for surgery as usual. After each of the 60 surgeries was complete, the researchers investigated cardiac tissue from the patient and then analyzed and compared the data.

“The heart muscle of the patients who had restricted blood flow to their arm before surgery was able to maintain the same level of energy production during the whole operation, while heart muscle from the other patients' hearts was not,” Slagsvold said. “This may be important because heart tissue is dependent on energy to survive, as well as to repair injuries the cells may have endured during surgery.”

During the study, the researchers also discovered how RIPC seemed to activate a protein called Akt. They believe this activation may be crucial to inducing the protective effect on the heart.

Source: Slagsvold KH, Moreira JBN, Rognmo O, et al. Remote ischemic preconditioning preserves mitochondrial function and activates pro-survival protein kinase Akt in the left ventricle during cardiac surgery: A randomized trial. International Journal of Cardiology. 2014.