June 4, 2014
News Review From Harvard Medical School -- Implant May Help Moderate Heart Failure
Implantable cardioverter-defibrillators (ICDs) are used to help people with advanced heart failure. But new research suggests that they may also help those with moderate heart failure live longer. Moderate heart failure is defined as having ejection fractions of between 30% and 35%. An ejection fraction is the percent of blood the heart can pump out of its main chamber with each heartbeat. Ejection fractions below 30% indicate advanced heart failure. Researchers looked at 2 groups over the course of 3 years. The first group, of 3,120 people, had moderate heart failure. The second group, of 4,578 people, had advanced heart failure. In each group, researchers compared survival rates between those who had an ICD and those who did not. For those with an ICD, survival rates improved in both groups. The Journal of the American Medical Association published the study. HealthDay News reported on it June 3.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Heart failure is a scary term. It sounds like the heart is ready to stop beating soon. But that is hardly the case. People are living longer and longer with heart failure. And an implantable device called a cardioverter-defibrillator is one of the reasons why.
Heart failure means that the heart is either too weak or too stiff to pump blood normally. This causes symptoms such as fatigue, shortness of breath and swollen feet.
Heart failure caused by weak heart muscles is called systolic dysfunction heart failure. It is diagnosed when the ejection fraction falls below 40%. The ejection fraction is the percent of blood pumped out of the main chamber of the heart (the left ventricle) with each heartbeat. A normal ejection fraction is about 65%. The heart never pumps out all of the blood with each beat.
Drug treatment has greatly improved the quality of life and prognosis for people with this type of heart failure. However, despite advances in therapy, heart failure carries a substantial risk of sudden death.
The weak, enlarged heart is "electrically irritable." That can produce a life-threatening, very fast and/or irregular heart beat (arrhythmia). The lower chambers of the heart (ventricles) beat too fast (ventricular tachycardia) or just quiver (ventricular fibrillation).
Both arrhythmias can be stopped by an implantable cardioverter-defibrillator, or ICD. It shocks the heart back into a normal rhythm. It's like having the paramedics inside your chest.
Doctors consider placing an ICD in people with heart failure if their ejection fraction is 35% or less. Until this study, it has not been clear that survival improves in people with ejection fractions between 30% and 35%. These researchers provide data that supports the use of an ICD for heart failure with ejection fractions of 35%. But there is a more impressive survival benefit when the ejection fraction is 30% or less.
What Changes Can I Make Now?
ICDs save the lives of some heart failure patients. But that doesn't mean it is the right thing for everyone with heart failure and a low ejection fraction.
- Not all sudden death in people with heart failure is caused by an arrhythmia related to heart failure.
- Most people with heart failure do not die from life-threatening arrhythmias. The most common way for heart failure patients to die is that their hearts gradually give out. Blood flow slackens, so organs fail.
- The older you are, the less likely it is that you will die from an arrhythmia. You are more likely to die from something totally unrelated to heart failure.
- ICDs are very expensive. The device and cost to implant one is about $40,000.
- Some people experience multiple "false alarms." The device can send very uncomfortable shocks even though the heart was actually not at risk of a ventricular arrhythmia.
Whether or not you are a candidate for an ICD, these are the best ways to improve quality of life and survival:
- Restrict salt intake
- Get regular exercise as prescribed by your doctor
- Take a beta blocker drug
- Take an angiotensin converting enzyme inhibitor (ACEI) drug or angiotensin receptor blocker (ARB) drug
- Take a potassium sparing water pill (diuretic), such as spironolactone
What Can I Expect Looking to the Future?
The results of this study did not change the current guidelines regarding use of ICDs in heart failure. But this was still an important study because of the high cost of ICDs.
We need more studies like this that provide proof of how effective therapies are. That includes therapies currently being reimbursed by Medicare and other insurance, especially the most costly ones.