Friday, June 16, 2006

Why Heart Patients Should Know Their 'EF'

I continue to be amazed at the number of people who come into my clinic and know their cholesterol "numbers" like their "total" cholesterol, LDL (or "bad") cholesterol, and HDL ("good" cholesterol), or even their blood pressure, but when I ask a patient with heart disease what their "EF" number is, they look at me with a blank stare.

What is my "EF"?
"EF," or ejection fraction, is the percentage (or fraction) of blood that is ejected (squirted out) from the main pumping chamber of the heart, the left ventricle, with each heart beat. If half the blood is pumped out of the left ventricle with each heart beat, then your "EF" (or "ejection fraction") is 50%. If only one quarter of the blood is ejected from the left ventricle with each heart beat, your EF is 25%.

Why is The EF Important?
The ejection fraction is the single most powerful measurable index in cardiology that can determine one's mortality from heart disease and heart rhythm abnormalities. In study after study, patients with low EFs are more likely to die of cardiac causes than those with normal EFs - plain and simple. Its a really important number for your cardiologist to know as well.

Who Should Know Their EF?
Anyone with a history of heart problems or family history of heart problems, be it hardening of the arteries (atherosclerosis), heart failure (weak heart muscle), valvular heart disease, or heart rhythm disturbances, should know their EF. People seeing their doctor for other non-heart related matters probably should not concern themselves about this number.

How is the EF Determined?
The ejection fraction is usually determined using either an echocardiogram (an ultrasound of the heart) or a nuclear medicine scan (sometimes called a "thallium scan" or "MUGA" scan). These tests are generally ordered by cardiologists or internists if there is a suspicion of possible heart disease. So if you get one of these tests, you should ask what your EF value was.

What is a NORMAL EF value?
Normal ejection fractions are typically 50% or greater.

What Does a Low EF Number Mean?
Patients with mildly reduced EF's (36-49%) often need to be on medications to preserve heart muscle function. Medications found to be particularly helpful in this regard include:

  • Beta blockers (like Metoprolol (Toprol), Atenolol (Tenormin), or carvedilol (Coreg)),
  • ACE inhinbitors (like enalapril (Vasotec), lisonopril (Zestril), captopril (Capoten), and others) , or
  • ARB inhibitors (like Altace, Cozaar, and others)
Patients with markedly reduced EF's (35% and less) might be at increased risk of sudden, unexpected, and potentially fatal cardiac heart rhythm disorders. You should discuss this with your doctor. While patients with low EF's typically demonstrate symptoms of shortness of breath with exertion, leg swelling, persistent cough made worse with lying flat, and the like, many people feel perfectly normal. Maggie Dixon, Army's womens' basketball coach who died recently, was a good example of someone with a very weak heart, but very few symptoms.

My EF is under 35%. What should I do?
First an foremost, you should be on good medical therapy with at least some of the classes of drug outlined earlier for the moderately reduced ejection fraction people. In addition, you should discuss surgical implantation of a permanent implantable cardiac defibrillator with your doctor. An automatic cardiac defibrillator is a device that is surgically implanted beneath the skin (usually beneath the collar bone) and is connected to wires placed into the heart that has the ability to pace or shock the heart to restore abnormal heart rhythms back to normal. (Questions I often answer regarding defibrillators can be found here).

Since 2004, very important information about the life-saving benefits of defibrillators was conclusively studied in a broad group of patients with markedly reduced ejection fractions. These include:

  • MADIT II - The Multicenter Automatic Defibrillator Implantation Trial - II - Studied 1232 patients with prior heart attack and EFs less than or equal to 30% and found a 31% reduction in mortality in the group with defibrillators over the group treated just with the best medical therapy available.
  • SCD-HeFT - Sudden Cardiac Death in Heart Failure Trial - Demonstrated that patients with a history of significant heart failure from any cause with EFs less than 35% treated with a defibrillator had a 23% reduction in mortality than patients treated with medications alone.
  • COMPANION - A large device trial that compared conventional medical therapy with a novel pacing therapy for heart failure called cardiac resynchronization therapy (CRT), and a third arm which included CRT pacing with a defibrillator all in one device (CRT-D) in patients with severe heart failure and ejectrion fractions less than 35%. The trial was stopped early because of the superiority of defibrillators to prevent sudden unexpected death in these patients.
Therefore, knowing your EF might just save your life. And if your EF is under 35%, then talk to your doctor to see if a defibrillator might be right for you.


1 comment:

Gary Spring said...

I am a recent receipt of a Medtronic Maximo ICD. the device has functioned perfectly by providing both appropriate pacing and shocking therapy