Two new studies on implantable defibrillators show that these cardiac devices failed to improve the study groups’ life.

The studies results were presented this Tuesday at the annual conference of the American Heart Association, in Orlando, Fla. They are expected to be published in the Dec. 13 issue of the New England Journal of Medicine.

Both studies centered on the efficiency of a technique called Cardiac Resynchronization Therapy that uses surgically implanted heart defibrillators to deliver electrical impulses to both ventricles at the same time in order to improve pumping efficiency. The implants work like peacemakers and shock the heart back when it stops beating and also control the rhythm of the chambers of the heart.

The first study was conducted by researchers from University of Chicago on two groups of 85 patients each, one using defibrillator device and the other one without it. The results showed no significant improvement.

The second one year study was conducted on 197 heart failure patients by researchers from the Institute of Internal Medicine and Cardiology in Florence, Italy. The study showed that the resynchronization implants failed to prevent permanent atrial fibrillation, an abnormal heart rhythm.

Researchers said they will continue the study for another year, because there were few people that got atrial fibrillation, and this way, they will obtain more concluding results.

Dr. John Beshai, director of pacemaker services at the University of Chicago stated that “further research will be necessary to determine which additional groups might benefit from CRT.”