FRIDAY, Sept. 17 (HealthDay News) -- The U.S. Food and Drug Administration has approved a new use for three cardiac resychronization therapy defibrillators (CRT-D) to treat people with a heart abnormality called left bundle branch block who also have mild cases of heart failure or heart failure with no symptoms.

The devices are all made by Boston Scientific Corp. As CRT-D devices, they combine the ability to shock an abnormally beating heart back to its normal rhythm, and the ability to improve coordination of the heart's left and right ventricles as they pump blood through the body.

In people with left bundle branch block, activation of the left ventricle is delayed, causing it to beat out of step with the heart's right ventricle.

In a news release, the FDA said the new approval was based on results from an 1,820-person, three-year study that found among people with left bundle branch block, the CRT-D devices reduced the risk of death by 57 percent, compared to those fitted with a standard implanted defibrillator.

CRT-Ds are to be used in addition to heart failure drug therapy, not as a replacement for it, the agency warned.

As a condition of approval, the FDA said it is requiring Boston Scientific to conduct two long-term studies of the devices.

More information

The FDA has more about this approval.