MEDICAL MONDAYS NEWS NOTES
Drew Pickett, MD, electrophysiologist cardiologist
Rebecca Hung, MD, cardiologist
SAINT THOMAS HEART
TOPIC: Re-Energize Your Heart
Monday, October 6, 2008
Implantable Cardioverter-Defibrillator (ICD)
An implantable cardioverter-defibrillator (ICD), also known as an automatic implantable cardioverter-defibrillator (AICD), is a small device that doctors use to watch for and fix life-threatening abnormal heart rhythms. The doctor surgically implants the defibrillator under the skin, usually below the left collarbone. A wire threaded through a large vein connects the device to the heart.
If you have had a serious episode of an abnormally fast heart rhythm or are at high risk for having one, you may need an ICD. If you have coronary artery disease, heart failure, or a problem with the structure or electrical system of the heart, you may be at risk for an abnormal heart rhythm.
How does an ICD work?
An ICD continuously monitors your heart. If it detects a life-threatening rapid heart rhythm, it sends an electric shock to your heart to restore a normal rhythm. The device then goes back to its monitoring mode.
After the shock, your heart may beat very slowly for several minutes. So ICDs also act as pacemakers, sending weaker shocks that pace the heart if the rate falls below a certain preset level.
Your doctor sets both the rate at which a shock will occur and the level of shock needed to convert to a normal rate and rhythm. If the first shock does not reset your heart rhythm, the device will send progressively stronger shocks until the heart converts to a normal rate.
Although an ICD effectively treats life-threatening episodes of abnormal heart rhythms, it does not prevent them. You will also need to take a medicine to prevent or at least decrease how often you have abnormal heart rhythms so that you are not getting too many shocks.
Living with an ICD
You may feel worried by the possibility of being shocked. The shock itself can be uncomfortable- it may feel like you are being kicked in the chest. You may pass out before the device fires, and you likely won't remember the shock. Be reassured though, that the shock is life-saving.
Strong electric or magnetic fields can interfere with the ICD. Most electrical equipment and household appliances create very weak magnetic fields and do not interfere with ICDs. So you can safely use most household and office equipment. And you can usually avoid electrical interference from magnetic or electrical sources by keeping certain things a few inches away from your pacemaker or ICD. You should completely avoid things like heavy electrical or industrial equipment.
The table below lists electrical and magnetic sources that are safe and sources that you should avoid. This table does not list all magnetic or electrical sources that you might use. Ask your doctor about the safety of sources not listed here.
Safe and unsafe electrical or magnetic sources
Sources that are SAFE to use
Sources to AVOID
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Keep at least 6in. away from your pacemaker or ICD:
Keep at least 12in. away from your pacemaker or ICD:
Driving is something else you need to think about if you have an ICD. Talk to your doctor about whether you should restrict your driving. Your doctor will check your medical history as well as your risk of having another arrhythmia that could make driving unsafe. To help doctors with this decision, the American Heart Association and Heart Rhythm Society recommend the following driving restrictions:1, 2
It is important to keep your regular follow-up appointments with your doctor. He or she will check the device to see whether it has delivered any shocks since your last visit. This will help determine whether your medicines need to be adjusted. During your follow-up visits, your doctor will also check the battery and replace it at regular intervals.
Heart Device May Not Hurt Life Quality
Study of Heart Failure Patients Shows No Drop in Quality of Life After Getting Implantable Defibrillator
By Miranda Hitti
WebMD Health News
Sept. 3, 2008 -- Getting an implantable cardioverter defibrillator (ICD) doesn't hamper quality of life for patients with stable heart failure, a new study shows.
Heart failure doesn't mean the heart totally fails; it means it doesn't pump blood as well as it should. Patients with heart failure are at higher risk of developing dangerous heart rhythms. ICDs are surgically implanted devices that don't actually cure heart failure, but shock the heart back to a normal rhythm when needed.
The new study builds on previous research showing lower death rates among heart failure patients who get ICDs. But receiving a defibrillator shock can be unsettling and uncomfortable, and even though patients live longer, their quality of life may be affected.
According to a new study, getting an ICD "does buy some time and that this time is worthwhile to patients," states an editorial published with the study in tomorrow's edition of The New England Journal of Medicine.
New Defibrillator Study
The study included 2,479 adults (average age: 59-60) with stable congestive heart failure.
The patients were divided into three groups. One group got ICDs. The other two groups got standard medical care plus either the drug amiodarone or a placebo.
Previous research had shown better survival rates in the ICD group. The new analysis focuses on quality of life.
"Basically, we wanted to find out if ICD therapy improves longevity but only at the cost of worse quality of life," says Daniel Mark, MD, MPH, a Duke University cardiologist who worked on the study.
The patients rated their quality of life -- including psychological well-being -- at the study's start and again after three months, one year, and 30 months.
Quality-of-life ratings were higher for the ICD group than the other groups at three months and one year. At 30 months, quality of life was comparable for all groups.
The one exception: Patients who had gotten an ICD shock up to two months before a quality-of-life rating tended not to rate their quality of life as highly. But that appeared to be a short-term effect.
The results show that quality of life was "sufficiently good" with ICDs, write the editorialists, who included cardiologist Jeff Healey, MD, of Canada's McMaster University. Healey's team notes that the study lasted less than four years and might not capture the quality-of-life impact of all potential ICD complications.
In the journal, Mark and several colleagues disclose financial ties to Medtronic, the company that made the ICDs used in the study and helped fund the portion of the study that focused on mortality rates; the National Heart, Lung, and Blood Institute funded the quality-of-life study. Healey and his fellow editorialist both note financial ties to Boston Scientific, another ICD maker.