The U.S. Food and Drug Administration today approved a new indication for three cardiac resynchronization therapy defibrillators (CRT-D) used to treat certain heart failure patients. The new use is for patients with an abnormality known as left bundle branch block, which occurs when there is delayed activation and contraction of the left ventricle. The three devices, all manufactured by Boston Scientific Corp., are intended to treat patients with left bundle branch block who have either mild heart failure or heart failure with no apparent symptoms.
The CRT-D device combines two functions. As an implantable cardioverter defibrillator (ICD) it senses dangerous abnormal heart rhythms and then attempts to shock the heart back into a normal rhythm. As cardiac resynchronization therapy, it generates small electrical impulses to coordinate the beating of the left and right ventricles so that they work together more effectively to pump blood throughout the body.
CRT-Ds are to be used as an addition to, not a replacement for, heart failure drug therapy.
"This approval allows heart failure patients with left bundle branch block to benefit from this therapy," said Jeffrey Shuren, M.D., director of the FDA's Center for Devices and Radiological Health. "The FDA is pleased to safely make this new technology available for a greater number of heart failure patients."
The FDA based its approval on the results of the 1,820-patient Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) clinical study. The study followed 1,820 patients for an average of nearly three years at 110 centers in the United States, Europe, Canada, and Israel. It compared CRT-D therapy to ICD-only therapy in specific heart failure patients to determine whether it reduced the risk of death and heart failure. In patients with left bundle branch block, who represented 70 percent of the study group, CRT-D showed a reduction in the risk of death and heart failure by 57 percent, as compared to ICD alone.
The rate of complications was considered to be acceptable by the FDA for this device; however, physicians should adequately inform patients about potential complications.
As a condition of FDA approval, Boston Scientific must conduct two post-approval studies. One study will evaluate complications and long-term mortality benefits of CRT-D in patients with left bundle branch block identified through the National Cardiovascular Data Registry. The other will follow patients from the original MADIT-CRT clinical study every six months for five years to assess long-term mortality benefits of CRT-D vs. ICD.
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