Heart Failure Therapy Confirmed:

"Cardiac Resynchronization in Chronic Heart Failure."
William T. Abraham, M.D., et. al. for the MIRACLE study group
New England Journal of Medicine, June 13, 2002
Read the article on the NEJM Web site

Treatment options for heart failure

Q & A:

What was MIRACLE?
What were the goals of MIRACLE?
How was MIRACLE performed?
What were the results of MIRACLE?
Why is the information important to me or anyone who has heart failure?
Who should receive cardiac resynchronization therapy?

Q: What was MIRACLE?
A: MIRACLE (Multicenter InSync® Randomized Clinical Evaluation) was a study of cardiac resynchronization therapy in individuals with moderate to severe heart failure (New York Heart Association Functional Class III or IV) with ventricular dysynchrony, lack of coordination of the bottom heart chambers [ventricles] to contract together, and who were receiving optimal drug therapy for their condition.

Q: What were the goals of MIRACLE?
A: MIRACLE was designed to evaluate whether cardiac resynchronization therapy would improve these individuals’ quality of life, functional capacity and exercise tolerance. Heart failure symptoms, such as fatigue or shortness of breath, were also assessed before and after receiving cardiac resynchronization therapy.

Q: How was MIRACLE performed?
A: Individuals with moderate to severe heart failure with documented ventricular dysynchrony, limited exercise tolerance, and currently receiving optimal drug therapy were eligible to participate in this study. Individuals meeting these criteria then had a baseline assessment of their heart function, exercise capacity (how much exercise was tolerated) and quality of life.

Following this initial evaluation, all the patients had surgical implantation of the Medtronic InSync cardiac resynchronization therapy system. The InSync cardiac resynchronization therapy system is a device that paces the ventricles to contract in a more coordinated manner or "resynchronize" the heart.

Patients were then randomly assigned to one of two groups. One group received cardiac resynchronization therapy – their InSync device was programmed "ON" to help the heart beat in a more coordinated fashion. Patients in the other group had their InSync device turned "OFF." Both groups continued to receive appropriate drug therapy for heart failure. Neither the patients nor the heart failure physicians performing the study evaluations were aware of whether the device was turned ON or OFF. Only the doctor who implanted the device had this information.

Individuals in both groups were then followed for 6 months, and the baseline measurements were repeated and compared to the initial results to determine the effects of cardiac resynchronization therapy.

Q: What were the results of MIRACLE?
A: When the two groups were compared, many of those who received cardiac resynchronization therapy showed improvement in their heart function, exercise capacity, heart failure symptoms, and quality of life score. Differences in favor of cardiac resynchronization therapy were apparent as early as one month into treatment, and the magnitude of the improvement was maintained for the entire study period.

Q: Why is the information important to me or to anyone who has heart failure?
A: The MIRACLE results suggest that cardiac resynchronization therapy may offer improvements in heart function, exercise capacity, and quality of life beyond that seen with medications alone.

Q: Who should receive cardiac resynchronization therapy?
A: MIRACLE studied those individuals with moderate to severe heart failure with ventricular dysynchrony who remained symptomatic despite optimal drug therapy; therefore, conclusions about cardiac resynchronization therapy benefits can only be made for this group of individuals. Additional studies are ongoing, however, to determine if others, such as those with less severe heart failure, might also benefit from cardiac resynchronization therapy.

It is also important to note that cardiac resynchronization therapy is not without possible risk – it does require a surgical procedure to implant the cardiac resynchronization therapy system as well as a possible overnight stay in the hospital. There are risks associated with any surgical procedure. Only your doctor who is familiar with your condition can adequately assess whether you might be a candidate for cardiac resynchronization therapy.

The Medtronic InSync System was studied in the United States in patients with moderate to severe heart failure (NYHA Functional Class III and IV), limited functional capacity, systolic ventricular dysfunction, and ventricular dysynchrony. Please consult with your physician to determine if you are a candidate. As with any active implantable device, there are potential risks associated with the InSync System.

In the U.S. clinical study investigating the InSync System, not all patients receiving cardiac resynchronization therapy reported an improvement in their heart failure status. Some patients experienced loss of cardiac resynchronization because of lead dislodgement or other lead related events, and required an additional surgical procedure to replace the lead. Your physician should discuss these and other potential risks with you.

Read the article on the New England Journal of Medicine Web site.