FDA Approves Boston Scientific Defibrillators for Heart Failure


Thursday, September 16, 2010, the U.S. Food and Drug Administration approved Boston Scientific’s cardiac resynchronization therapy defibrillators (CRT-D) for a new indication – treating heart failure in patients with an abnormality known as left bundle branch block.

CRT-D discovers abnormal heart rhythm problem and shocks it back to normal

CRT-Ds are devices have two functions. As an implantable cardioverter defibrillator (ICD) the CRT-D will sense dangerous abnormal heart rhythms and then attempt to shock the heart back into a normal rhythm. The CRT-D is also used for cardiac resynchronization therapy. To do this, the device 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.

Left bundle branch block occurs when there is delayed activation and contraction of the left ventricle. LBBB is often asymptomatic and when it is no treatment is needed. Symptoms of LBBB may include fainting (syncope) and a slow heart rate (bradycardia).

The underlying cause of LBBB is most often some form of heart disease. It is this underlying cause that must be treated. Appropriate medications for associated heart arrhythmias or hypertension. Angioplasty (stents or coronary bypass surgery) for blocked coronaries arteries.


A pacemaker or CRT-D may be used to add in regulating the heart rate and rhythm. The CRT-Ds are to be used as an addition to, not a replacement for, heart failure drug therapy.

The FDA approval is based 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% of the study group, CRT-D showed a reduction in the risk of death and heart failure by 57%, as compared to ICD alone.

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.

The CRT-D devices cost about $25,000 to $35,000, or about $7,000 to $8,000 more than a standard ICD.