FDA Approves Devices for Left Bundle Branch Block

FDA approves three cardiac resynchronization therapy defibrillators

/ Author:  / Reviewed by: Joseph V. Madia, MD

The FDA has approved three new cardiac resynchronization therapy defibrillators (CRT-D) to treat certain heart failure patients.  The devices are intended to treat patients with left bundle branch block who have either mild heart failure or heart failure with no apparent symptoms.

Boston Scientific Corp. manufactures the three devices.

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, MD, 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 which 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. 

For more information:

Media Inquiries:   Dick Thompson, 301-796 7566; [email protected]
Consumer Inquiries:  888-INFO-FDA

Reviewed by: 
Review Date: 
September 17, 2010
Last Updated:
August 22, 2012