Study: Implantable Defibrillator Can Save Your Life

Analysis finds benefit even for healthier heart patients
heart with heartbeat

An implantable cardioverter defibrillator (ICD) can save your life, even if you only have mild heart damage.

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Multiple studies show that ICDs improve survival in people with badly damaged hearts. Recent analysis of data shows that people with less severe cardiac damage have improved survival rates with cardioverter defibrillator devices implanted.

ICDs help keep the beat

Implantable cardioverter defibrillators keep your heart beating steadily.

They monitor your heart rhythm and when necessary, send a strong shock to fix dangerous, potentially fatal abnormal rhythms.

The risks of a damaged heart

When you have a heart attack, the area of the heart muscle that doesn’t get blood and oxygen dies. Afterward, your heart forms scars in the place where the normal tissue was.

This scar tissue causes different problems. The scar tissue doesn’t function like healthy muscle tissue. It doesn’t contract and relax seamlessly with the rest of the heart.

Scar tissue can also generate faulty electrical signals that interfere with or block normal signals that regulate heart rate and heart function.

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All of these problems increase your risk for sudden death due to a dangerous arrhythmia (abnormal heart rhythm).

ICD study takes another look

Many ICD studies done in the past mostly included people with heart failure and severely impaired hearts that had an average ejection fraction of about 23 percent. Ejection fraction is a measure of the heart’s pumping ability. A retrospective cohort study conducted by Duke Clinical Research Institute analyzed data from the National Cardiovascular Data Registry’s ICD Registry. It found that ICDs improved survival times in patients who had less severe heart impairment, measured as an ejection fraction of 30 to 35 percent.

Researchers analyzed the large database for similar patients, some of whom had received ICDs and some who had not. Those who received ICDs had a 3.6 percent boost in survival rate as measured over a 3-year time period.

Until the Duke study, research focused on ICDs in patients who had more advanced heart failure and more significantly reduced pumping ability, or ejection fraction.

Study validates early ICD treatment

Bruce Wilkoff, MD, Director of Cardiac Pacing and Tachyarrhythmia Devices and Medical Information Officer of the Heart and Vascular Institute at Cleveland Clinic, did not participate in the study but reviewed it and says that it validates early ICD treatment for heart attack and heart damage.

“This study examines patients with less severe heart muscle problems and shows that significant benefit is obtained. There are additional trials that are in process now with even more preserved ejection fractions looking for benefits of ICDs.”

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Expanded role for ICDs

Dr. Wilkoff explains that the greater the cardiac damage, the greater a patient’s risk for fatal arrhythmia, but that even relatively healthy patients are at risk.

“The risk of fatal ventricular arrhythmias and heart failure increases with the amount of heart muscle that is replaced with scar … but, even patients with smaller amounts of scar on the heart can develop these same arrhythmias that are just as lethal,” he says.

He stresses the study is important in shedding light on a subgroup of cardiac patients that had been understudied until recently.

“This study examines only the patients with less severe heart muscle problems and shows that significant benefit is obtained. This is critical because a large majority of the people who die suddenly with these arrhythmias have normal or only mildly abnormal ejection fractions.”

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