Bundle branch block after a
heart attack
When combined with a low ejection fraction, BBB indicates a high risk of sudden death
By DrRich
Dateline: 05/20/02
In a previous article, we discussed findings from the MADIT II trial, indicating that the implantable defibrillator significantly prolonged the life span of heart attack survivors who had reduced left ventricular ejection fractions (a measure of the pumping efficiency of the heart.) Last week, at the North American Society of Pacing and Electrophysiology meetings in San Diego, investigators reported on a substudy from the MADIT II trial showing that if bundle branch block was also present, the effect of the implantable defibrillator in prolonging survival was even more dramatic. (Click here for a quick and easy review of bundle branch block.)
The MADIT II trial enrolled more than a thousand patients who had prior heart attacks and whose left ventricular ejection fractions were less than 30% were randomized to receive either standard medical therapy, or the same standard medical therapy plus the implantable defibrillator. The results were striking: patients who received the defibrillator experienced a 31% reduction in mortality compared to patients without the defibrillator. As a result of MADIT II, the Food and Drug Administration is being petitioned to grant a new indication for using the implantable defibrillator - the indication would be for heart attack survivors with reduced ejection fractions. The FDA is expected to grant this new indication relatively soon.
In the new substudy, investigators evaluated other features of the patients enrolled in the MADIT II trial to see if anything else besides ejection fraction would predict a benefit from the implantable defibrillator. What they found was dramatic: In people with prior heart attacks whose ejection fractions were less than 30%, and who also had evidence of bundle branch block (specifically, patients whose QRS complexes were greater than 120 milliseconds in duration,) had a 63% reduction in mortality if they received the implantable defibrillator.
What this means to you
We have already pointed out that if you have had a heart attack in the past, and your ejection fraction is below 30%, you need to talk to your doctor about receiving an implantable defibrillator. Since many doctors remain inappropriately reluctant to discuss implantable defibrillators with their patients, it is often up to the patient to initiate such discussions.
The new data from the MADIT II substudy points out a group of readily indentifiable patients who have an especially high risk of sudden death, and in whom the implantable defibrillator has an extraordinarily high chance of prolonging life. So if you have had a heart attack, have a reduced ejection fraction, and have bundle branch block, you need to talk to your doctor right away about an implantable defibrillator. If the doctor says you don't need one, remind him that he might be hearing from your widow/widower if he proves to be wrong.
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