ICDs Artificial Hearts
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Heart failure
Heart Transplant
 Updated January 20, 2007

ICDICD means Implanted Cardioverter Defibrillator. Another name is AICD, for Automatic ICD. ICDs are miniature, internal versions of those shock paddles paramedics use to zap people back to life after a cardiac arrest.
     The device is really a small electric generator hooked up to wires called leads. The generator is made of electronic circuits plus a battery sealed into one unit. A typical ICD weighs about 4 ounces, and measures about 1/2 inch thick by 2 inches wide.
     The lead (or leads) are the wires that connect the ICD to your heart. They are flexible insulated wires with an electrode tip. The tip is placed against the heart wall and carries electrical impulses from the ICD to the heart. It also sends information from your heart back to the ICD for storage as data, like files on the hard drive in your computer.
     An ICD lead has a shocking coil (some leads have 2 coils) on its tip to deliver large amounts of energy to the heart. Wire coils make up the inside of the lead.

ICD diagramThe Implant - This procedure generally takes about 2 hours. During this procedure, you'll be sedated with an IV drug, but you'll be breathing on your own, unlike open heart surgery - which this is not. You will be pretty much out of it, but not asleep. A local anesthetic will also be given so your skin being cut doesn't hurt you.
     A cut is made under your collarbone, and the ICD is implanted under your skin in the upper chest (sometimes in the abdomen). A vein near your collarbone is cut during the procedure so the lead (or leads) can be guided through the cut vein into your heart's chambers, beginning with the right ventricle. The tip of the lead touches your heart's inner wall.
     You may need another lead positioned in the upper right chamber of your heart. Where the leads go depends on your individual needs. You might need a lead placed just under the skin next to your rib cage. This would be placed through a small cut in your left side. Sometimes a lead is placed on the outside of your heart.
     After the leads are in place, they're tested to make sure they read your heart beat properly. Then the leads are stitched to nearby tissue so they stay put. Finally, the leads' ends are hooked up to the generator. Your doctor will deliberately make your heart go into a funky rhythm. That's so he can test your ICD and make sure it will shock your heart back into normal rhythm on its own.
     For a short time after the implant, the electrode at the end of the lead will actually "grow into" the wall of the ventricle - this won't interfere with heart function. You won't sense any of this because the inside wall of the heart is not sensitive to pain.

Batteries - Most ICDs now have a battery life of 5 to 7 years. The battery will be checked now and then at your doctor's office. The ICD has an internal beeper that will alert you if the battery gets too low. When the battery wears down, the whole ICD generator unit has to be replaced. This is done like the original procedure but since leads usually do not have to be replaced, it's quicker and easier.

How It Works - An ICD monitors your heart all the time but only shocks you if it's software spots a rhythm problem. When it detects an incorrect heart rhythm, it can do one of 3 things:

  1. implanted ICDPace your heart like a pacemaker for a short period of time. You may not even feel this. The ICD's software calculates the speed of a tachycardia by averaging 4 or 5 heart beats from just before the arrhythmia - your ICD is always on the job. Then it uses a percentage of that average heart rate to pace your heart. It paces your heart at a faster than usual rate. This is called "overdrive" pacing.
         Why pace your heart at a fast rate instead of just knocking it all the way back to normal? Well, the ICD is trying to control your heart rhythm to prevent your fast heart rate from turning into fibrillation, which is very dangerous. Trying to slow your heart down all the way quickly probably wouldn't work.
         If your ICD can temporarily pace your heart at a fast rate - but at a constant speed and in a steady rhythm - it may be able to avoid zapping you, by letting your heart get control of its own rhythm again. Letting your heart rate just keep getting faster and faster could result in fibrillation - and a zap!
  2. Cardiovert your heart. This is a relatively low energy shock to persuade your heart to get back into proper rhythm. How will this feel to you? Unfortunately, it might as well be an out and out zap. Studies show that all shocks using more than 1.5 joules of "juice" feel the same to you - the person getting the shock. So, what makes a "cardioversion" different from a "defibrillation?"
         Let's say your ICD detected tachycardia and tried to pace your heart like I described above, but it didn't work. Your ICD now tries to "cardiovert" your heart to normal rhythm and rate. What's the difference? The ICD gets ready to shock you but it waits for a certain point in your heart rhythm.
         If the ICD can time its shock just right, it will successfully put you back into normal rhythm. Cardioversion success depends on the timing of when the ICD delivers a shock. If it shocked you at the wrong spot (time) in your heart rhythm, it could actually send you into fibrillation. Its programming prevents that.
  3. Defibrillate your heart. This is the zap, a high energy shock to stop your heart. The "cardioversion" jolts your heart back into normal rhythm when it is beating too fast. A "defib" out and out stops your heart when your heart rhythm is erratic (irregular) enough to be dangerous. This gives your heart's natural pacemaker time to get control of your heart's rhythm again. You can read more about your heart's natural pacemaker on my pacemaker page.
         When your ICD delivers a defib (zap) it is meant to stop your heart for a programmed amount of time, not at a certain time. Often it tries to stop your heart for a full 1/2 second. Your ICD may use as much as 4 times more energy to zap you than it uses to cardiovert you.
         The zap is a nasty thing and may even knock you down or knock you out, but this is a life-saver!

X-ray of patient with pacer and ICDYour ICD also records your heart's activity just before, during, and after each episode. Your doctor can see that information in his office or in the hospital to see why you are getting zapped. This info also helps him fine-tune your ICD to prevent unnecessary zaps. He uses a device called a "programmer" to communicate with the software in your ICD. The programmer is actually a small, powerful computer, designed for one purpose only - to maintenance ICDs. There is usually no need to get to the ICD physically to reprogram it. There is an antennna built into your ICD that can receive signals from the programmer to make most software changes.

Why Do You Need An ICD? - Your heart has a natural pacemaker called the SA node (sinoatrial node), that produces electrical signals inside your heart. It's in the upper right chamber (atrium) of your heart. The SA node's signals travel through certain pathways in the heart muscle, causing the heart's chambers to beat as a team. That electrical system can get out of whack for various reasons and make your heart rhythm go very fast, very irregular, or very slow - all bad. This is called arrhythmia.
     Certain types of arrhythmia can be dangerous. For people with a dangerous arrhythmia that comes and goes, either anti-arrhythmic drugs or an ICD - or both - may be needed.

Living With An ICD - If your ICD shocks you, it may just be annoying or it may knock you unconscious. If you get a shock, call your doctor. He may just say to wait for your next appointment or he may want to add a med, or reprogram your ICD.
     If you have more than 2 shocks close together, or feel really sick like you get dizzy, clammy, or if you get palpitations, you should call an ambulance to bring you to the emergency room. Always tell doctors, surgeons, and dentists treating you that you have an ICD.
     If your arrhythmia made you pass out or nearly so, you won't be allowed to drive for awhile after getting your ICD - for obvious reasons. You can still use most appliances safely, including TV sets, microwave ovens, VCRs, radios and stereo components, kitchen appliances, power tools (unless they are magnetized), and your personal computer.
     You should avoid strong electrical or magnetic fields, including electrical power plants, ignition systems, stereo speakers, and magnetic wands like airport security people use. You can walk through metal detector gates but your ICD may set off the alarm; It won't hurt you or your ICD, though. Avoid arc welding equipment, power generators, MRI scanners, and some medical procedures like electrocautery to stop bleeding or the heat therapy that physical therapists use on muscles. Obviously contact sports are out! Never put a magnet on or near your ICD and keep cell phones 6 inches or more away from the device. That means use your other ear!

ICD Studies

A-fib Cardioverters

WWW Links

 Guidant Recalls ICDs

June 17, 2005 - Guidant has recalled a whole boatload of defective ICDs. See the FDA site, specifically www.fda.gov/bbs/topics/NEWS/2005/NEW01185.html for more information. That page lists the following Guidant devices as being part of this recall, along with more information:

The Guidant web site also lists the ICDs in this recall. See www.guidant.com/news/500/web_release/nr_000548.shtml. Here are the ICDs listed there:

Patients and doctors with questions can call the company at 1-866-GUIDANT.

 Implant Infection Rate Higher

August 27, 2001 - Patients with ICDs who get staphylococcus aureus bacteremia may have infected devices also. This risk is much higher than anyone guessed before. Researchers now estimate that about 70% of S aureus bacteremia patients who have an implanted device may also have a device infection.
     Dr. Anna Chamis studied 33 patients with ICDs or pacemakers who had S aureus bacteremia over a 6 year period. Device infection was found in 15 of these patients (45%). "The majority of device infections showed no obvious signs," Dr. Chamis said.
     In the 12 patients who had their device implanted within one year of infection, 9 had confirmed device infections; So did 6 patients whose device had been implanted for more than a year. Device infection was suspected in another 9 patients, but these patients died of blood poisoning before tests were completed.
     Heart device infection is not always obvious, especially when the infection involves the "pocket" where the device generator is implanted. Sixty percent of the patients with confirmed device infection showed no "detectable signs of generator pocket infection," the researchers said. Neither physical exam nor an echo can definitely spot this type of infection.
     In patients who get S aureus bacteremia, the device is usually involved, and 40% of these patients do show signs of infection. However, in patients who get S aureus bacteremia more than a year after device implant, the device is not usually the source of bacteremia, and there are no signs of device infection - even if the device is infected. The implanted device is involved in about 28% of these patients.
     Doctors with patients who get S. aureus bacteremia should worry about device infection, Dr. Chamis said. Device infection results in increased illness and death. If the infected device is not replaced, there is increased risk of death.
     If the device becomes infected, it should be replaced, Dr. Chamis said. "If the device is not infected, then the patient should get extended treatment with antibiotics. If test results are uncertain, patients should be closely followed with repeated blood testing."
Title: Staphylococcus aureus Bacteremia in Patients With Permanent Pacemakers or Implantable Cardioverter-Defibrillators
Authors: Anna Chamis, Gail Peterson, Christopher Cabell, G. Corey, Robert Sorrentino, Ruth Greenfield, Thomas Ryan, L. Reller, Vance Fowler Jr
Source: Circulation 2001;104:1029-1033
Correspondence to Vance G. Fowler, Jr, Box 3281, Division of Infectious Diseases, Duke University Medical Center, Durham, NC 27710. E-mail fowle003@mc.duke.edu

 Device Implant Infections Way Up

May 26, 2006 - Risk of infection from device implants has risen much faster than the number of implants in the past 8 years. The risk grew faster for both ICDs and pacemakers. Researchers studied a database of device-related infections. Their study shows that getting an infection from device implant - whether in the device location or myocarditis - increased risk of death 300%.
     Most device implant infections happen in the "pocket" where the device actually goes while almost one in five occur as myocarditis. This study used numbers from 1996 to 2003 in the National Hospital Discharge Survey. In 1996 roughly 160,000 devices were implanted and there were about 4000 infections. By 2003, there were roughly 238,000 implants with nearly 13,000 infections. Hospitalizations for device-related infections rose about twice as fast as number of devices implanted. For unknown reasons, being older or female, or both, lowered risk of infection from implant.
     Infections are usually "staph" of one sort or another. Many possible reasons for the higher risk of infection were given but none are certain. What is certain is that device implant, and generator/lead replacements carry a risk of infection and this kind of infection raises risk of death. Something to keep in mind.
Source: Heart Rhythm Society 2006 Scientific Sessions
Presenter: Dr Andrew Voigt

 MADIT - ICD Versus Drug Treatment

December 1, 1995 - We studied the effect of different treatments on ventricular arrhythmias. Fifty-nine people had an ICD, 53 took anti-arrhythmic drugs and 179 got no arrhythmia treatment. We studied mortality and type of death in these 291 consecutive patients evaluated for heart transplant.
     There were 109 deaths (37%) during a 15 month follow-up; 21% were sudden death, 14% non-sudden death, and 2% were not heart-related. Sudden death rate was lowest in the ICD group, intermediate in the no-treatment group, and highest in the drug-treatment group. Anti-arrhythmic drug use was linked to sudden death. ICDs were linked to non-sudden death (pump failure).
     Sudden death rates were lowest in ICD patients. Although ICDs reduced sudden death in high-risk CHF patients, the effect on long-term survival was limited, because these patients had high non-sudden death rates.
Title: Influence of the implantable cardioverter/defibrillator on sudden death and total mortality in patients evaluated for cardiac transplantation
Authors: Sweeney MO, Ruskin JN, Garan H, McGovern BA, Guy ML, Torchiana DF, Vlahakes GJ, Newell JB, Semigran MJ, Dec GW
Source: Circulation 1995 Dec 1;92(11):3273-81
Comments in: Circulation 1996 Nov 1;94(9):2308-10 and Circulation 1997 Mar 18;95(6):1666 and Circulation 1997 Mar 18;95(6):1666-7
PMID: 7586314, UI: 96080082

 ICDs Versus Amiodarone

November 27, 1997 - Patients who survive life-threatening ventricular arrhythmias are at risk of it happening again. We compared 2 treatments: ICD and anti-arrhythmic drugs. Patients had been resuscitated from near-fatal ventricular fibrillation or had been cardioverted from sustained ventricular tachycardia. Patients also had either fainting spells or other serious cardiac symptoms, and an EF of 40% or less.
     One group of patients had an ICD implanted and the other group got class 3 anti-arrhythmic drugs, usually amiodarone (Cordarone). Over the 4 year period, 507 patients got an ICD and 509 took an anti-arrhythmic drug. Forty-five percent had ventricular fibrillation and 55% had ventricular tachycardia. The primary endpoint was overall mortality. Overall survival was higher with ICD than with drug therapy.

ICDs versus Anti-arrhythmic drugs
Follow-up  ICD survival  Drug survival 
one year 89% 82%
two years 82% 75%
three years 75% 64%

Authors; The Antiarrhythmics versus Implantable Defibrillators (AVID) Investigators
Source: N Engl J Med 1997 Nov 27;337(22):1576-83
Comments in: N Engl J Med 1997 Nov 27;337(22):1621-3 and ACP J Club 1998 May-Jun;128(3):60-1
PMID: 9411221, UI: 98026791

 ICDs Versus Amiodarone - AMIOVERT

November 25, 2000 - NSVT (non-sustained ventricular tachycardia) is a risk factor for sudden death in patients with DCM not caused by clogged arteries. Figuring out which patients are at risk for SCD is tough. EP studies usually don't help much in this situation.
     Trials such as CHF-STAT and GESICA suggest that amiodarone (Cordarone) may reduce mortality in DCM patients. However, no study has compared amiodarone to an ICD in these patients. The AMIOVERT study tested whether an ICD was more effective than amiodarone for reducing mortality in DCM patients with NSVT.
     Patients were randomly assigned to either an ICD implant or 400mg amiodarone twice a day for one week, followed by 400mg amiodarone once a day for 51 weeks, then 300mg once a day. Liver function tests, thyroid function tests, and chest x-rays were closely watched.
     The study was stopped early because the endpoint was not going to be reached. Patients not treated were enrolled in a registry.
     Outcomes in both groups were similar. There were 72 patients in the amiodarone group and 102 patients in the ICD group. Primary endpoint was mortality at 2 years. Secondary endpoints included cause of death, arrhythmia-free survival, cost, and quality of life. All patients had an EF less than 36%, NSVT without symptoms, and class one to class 3 CHF.
     There were 8 deaths in the amiodarone group and 13 in the ICD group. Arrhythmia-free survival was better in amiodarone patients than in ICD patients (arrhythmias are stopped with an ICD, not prevented). This study did show that in DCM patients with a low EF and NSVT, overall mortality at 4 years is the same whether the patient is treated with amiodarone or an ICD.
Source: American Heart Association Scientific Sessions 2000
Title: Amiodarone vs Implantable Defibrillator in Patients With Nonischemic Cardiomyopathy and Asymptomatic Nonsustained Ventricular Tachycardia
Author: Dr. S. Strickberger

 Do ICDs Benefit CHFers?

October, 1998 - Do heart failure patients get benefit from an ICD? We studied whether heart class was related to benefit from ICDs. We studied data stored in the memory of ICD software.
     Between 1989 and 1996, 603 patients used an ICD that "remembers" EKGs taken by the ICD during an episode. Seventy-seven percent of these patients were men, 59% had coronary artery disease and 16% had DCM. Their average age was 57 years and their average EF was 44%.
     We studied the link between heart class at ICD implant to overall mortality and recurrence of arrhythmias. The benefit was defined as the difference between mortality and the hypothetical death rate if the device had not been implanted.
     A significant difference between hypothetical death rate and overall mortality was seen (14% at 1 year, 24% at 3 years, and 27% at 5 years). This suggests a benefit from ICDs in people with heart failure.

Link between heart class and ICD benefit in CHFers
Follow-up  Heart class at implant  Benefit from ICD - Risk of death lowered by:
class oneone year15%
class one3 years29%
class one5 years36%
class 2 to class 33 years22%
class 2 to class 35 years23%

Even class 3 patients with a history of decompensated heart failure benefited from an ICD. Stored EKG data shows that in patients with a history of ventricular tachycardia or ventricular fibrillation, an ICD may prolong life in class 1, class 2, and class 3 patients. The benefit is greatest in class 2 and class 3 patients at first but benefit may last longest in class one patients.
Title: Potential benefit from implantable cardioverter-defibrillator therapy in patients with and without heart failure
Authors: Bocker D; Bansch D; Heinecke A; Weber M; Brunn J; Hammel D; Borggrefe M; Breithardt G;
Source: Circulation 1998 Oct 20;98(16):1636-43
PMID: 9778329 UI: 98451630

 ICDs Are Safe Going Through Detectors

July 26, 1999 - People with ICDs can safely walk through electronic anti-theft systems. The anti-theft machines use an electronic beam to spot security-tagged merchandise being carried out of a store. Some people worried that an ICD might interpret the electronic beam as a rapid heartbeat, triggering a zap from the ICD.
     Dr. Douglas Zipes, the study's author says, "There is absolutely no danger from a slow stroll through the gates, even if it takes 10 seconds." In the study, one person even went through in a walker without any problems. "A person should not lean on, or linger in between, theft detection devices; but in normal use there is nothing to worry about," says Zipes.
     "We tried to duplicate a normal situation of someone shopping and just passing through the machines," he says. In tests on 169 ICD wearers, they found no problems from a normal 10 to 15 second walk through the security gates. The researchers used a magnetic programmer tool to prevent shocks during the tests. Although the devices continued to record data so it was known whether a shock would have been delivered, the shocking mechanism was turned off. "When an ICD fires, it is like a mule kick in the chest. It's not pleasant," Zipes explains.
     When the patients received a lot of exposure by standing within 6 inches of the transmitter pole for 2 full minutes, 19 of the 169 people had ICD interference. Seven of those episodes would have delivered shocks, Zipes says.
     This is in line with an FDA letter of 1998, which said that although the anti-theft machines seemed safe, patients should not lean on or linger in the machines. That same letter advised patients being scanned with hand-held metal detectors like those used in airports, to warn security personnel that they have an ICD and to ask them not to hold the metal detector near the device any longer than necessary. (Jon's note: Always carry your ICD wallet card with you!)
Source: Circulation 1999;100:387-392

 ICDs Best For Low EF Patients

October 4, 1999 - Survivors of life-threatening arrhythmia face a high risk of another fatal episode, according to Dr. Michael Domanski, from the AVID study. The report says that an ICD works better than anti-arrhythmic drugs to improve survival of patients whose EF is less than 35%.
     Patients with an EF higher than 35% did no better with an ICD than with drug treatment, but those with an EF below 35% had significantly better survival with an ICD than with drug therapy. Patients with an EF below 20% however, had only a 2 to 3% survival advantage with an ICD versus drug therapy.
Source: Journal of the American College of Cardiology 1999;34:1090-1095

 Who Really Benefits From An ICD?

March 21, 2002 - ICDs prolong survival in patients with ischemic cardiomyopathy and a positive EPS. The MADIT II trial tested whether ICDs prolong survival in another patient group: those with prior heart attack and ejection fractions under 30%, but who have not had an EPS.
     1,232 such patients were randomized in a 3 to 2 ratio to either ICD or standard drug therapy. Follow-up was 20 months. The mortality rate was much lower in the ICD group (14.2%) than in the drug group (19.8%). No ICD patients died. ICD patients did have more worsening heart failure (19.9%) than drug-only patients (14.9%).
     Notably, EPS was not used to identify high-risk patients. The results suggest that ICDs should be considered for all patients with ischemic cardiomyopathy. The precise reason for increased heart failure hospitalizations in the ICD group and cost-effectiveness need further study.
Title: Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction
Authors: Moss AJ, et al
Source: N Engl J Med 2002 Mar 21; 346:877-83 and
Title: Expanding indications for implantable cardiac defibrillators
Authors Bigger, JT
Source: N Engl J Med 2002 Mar 21; 346:931-3

 Do Not Resuscitate & ICDs

April 17, 2000 - ICDs are becoming more common, and so are patients' who don't want to be resuscitated when they die. Should doctors assume that a patient with a DNR (Do Not Resuscitate order) wants his ICD deactivated? Consider the case of a 66 year old man with DCM and serious arrhythmia.
     He was brought to the hospital with a massive stroke and congested lungs. He was sent to the intensive care unit. One year before this, he had suffered sudden cardiac death, and had an ICD implanted. The patient did not improve. Permission to write a DNR order was obtained from the patient's family. Only after the family left the hospital did the doctors realize that the patient was not to be resuscitated, but would be automatically revived by the ICD if a lethal arrhythmia occurred. Did the family's consent to the DNR order mean the ICD should be deactivated?
     A patient's DNR order is a refusal of CPR. In general, it is wrong to assume that it includes anything else. In the case of an ICD however, the treatment in question is electrical defibrillation, which is in the same category as CPR.
     The ICD was already in use when the DNR order was written. To understand why this matters, let's consider the ventilator. The patient was placed on a ventilator for lung congestion. The family might reasonably expect that since the patient was already on a ventilator when the DNR was written, he would stay on the ventilator. Therefore the family might reasonably expect that since the ICD was functioning when the DNR was written, it would stay turned on.
     Also, the ICD is an internal device and may be said to be part of the patient. In this way, it is different from an external defibrillator, or even the hands of a doctor performing CPR. The question is, "Has the ICD become a part of the patient or is it just another form of CPR?" If the ICD is just another form of CPR, it should be turned off and there is no reason to tell the family. On the other hand, if the ICD is now part of the patient, then the DNR order does not allow us to turn off the ICD.
     Although the ICD is firmly imbedded inside the patient and its removal would damage the patient (surgery would be required), the ICD does not have to be removed to be deactivated. We believe the ICD falls into that gray area between being a part of the patient - like a transplanted organ - and being just another medical treatment. Thus, the patient should decide. So consenting to a DNR does not authorize a doctor to deactivate an ICD without a specific order to do so.
     As implanted devices become more common, doctors will run into these issues more often. Doctors must discuss these issues with their patients who have implanted devices. Doctors must encourage those patients to express their views in advance directives.
Title: Deactivating the Implantable Cardioverter-Defibrillator: A Biofixture Analysis
Author: Frederick Paola and Robert Walker
Source: South Med J 93(1): 20-23, 2000

 Inducible Tachycardia A Danger Sign

June 30, 2000 - During an EPS, a doctor uses a catheter tool to make your heart go into an irregular rhythm. If he succeeds, it means you are at higher risk for having it happen at any time. If he cannot cause (induce) an irregular rhythm, you may not be at high risk for an arrhythmia episode.
     Most sudden deaths result from ventricular tachycardia (VT) or ventricular fibrillation (VF). Researchers in the USA and Canada studied more than 1,700 patients. Of those patients, 353 had inducible VT and 1,397 did not. The patients were followed for over 3 years.

Inducible versus Non-inducible VT
Patient group  Follow-up  Risk of cardiac arrest/death  All-cause mortality 
with inducible VT2 years18%28%
without inducible VT 2 years12%21%
with inducible VT5 years32%48%
without inducible VT5 years24%44%

Patients had coronary artery disease, an EF of 40% or less and spontaneous, unsustained ventricular tachycardia. Results show that "inducible" sustained VT identifies patients at much higher risk for sudden death, the authors conclude. These patients may be candidates for ICDs.
Source: N Engl J Med 2000;342:1937-1945

 Online Network For ICD Wearers

January 2, 2002 - Medtronic has received FDA approval for their CareLink Network. This system allows an ICD wearer to transmit his ICD data straight from his device to a doctor over a regular phone line.
     The ICD wearer has a wand that looks like a computer mouse connected by a wire to a small console - this is called the monitor. You push a button on the console, then wave the wand over your ICD. The wand collects data from your implanted device and transfers it to the console automatically through the wire. The console then automatically dials a toll-free phone number and sends the data to the Network over a regular phone line.
     Doctors get their patients' data by logging onto a doctors' web site. Patients can view their information on a personalized web site. At first, only patients with GEM II DR/VR ICDs will be involved. However, the network is designed to support many other devices, including pacemakers. Existing implanted devices work with this system - no changes or adjustments are needed.
     Medtronic will sell patient monitors and software packages to doctors, and will charge a fee for each use of the network. Patients may have to pay a fee. Doctors may be able to bill patients' insurance companies the cost of a follow-up visit each time they access patient data. Ten pilot sites will start the network.
     The monitor is portable so it can be used when traveling as long as a standard USA phone line is available. The network will also provide data management for other health information. Medtronic is trying to protect confidentiality and security by requiring registration and passwords to access the web sites.
     Jon's notes - Will they really keep this info secure? I have no idea. Big-name sites that depend on e-commerce to survive have not mastered online security so I wonder how secure this venture can really be. I would definitely not want my health care information online, especially if I improve enough to go back to work. Once your medical history is out in the open, there is no way to regain its confidentiality, ever, period.
     Billing insurers for online accesses to patient information opens up a delightful source of fraud. Can Medtronic keep this under control? I doubt it, but will wait and see. This is a truly wonderful idea that is going to be very, very tough to keep legitimate and secure.
Sources: Reuters, AP, Medtronic's press releases

 Risk After MI Reduced By ICD

March 19, 2002 - Heart attack survivors with low EF can reduce their risk of death by 31% with an ICD implant. The MADIT-II trial results were presented at the American College of Cardiology 51st Scientific Session. The study enrolled 1,232 patients who had suffered at least one MI and had an EF of 30% or less.
     742 patients had an ICD implanted plus got drug therapy, while the rest were managed with drug therapy alone. During an average follow-up of 20 months, mortality in ICD patients was 14.2% compared to 19.8% for non-ICD patients. That is a relative risk reduction of 31%. Mortality from arrhythmia was 3.6% in ICD patients and 9.4% in the drug group.
Source: Reuters Health

 ICD + Pacemaker Approved For CHF

July 5, 2002 - The FDA has approved Medtronic's InSync ICD system. It combines an ICD with a heart failure pacemaker (CRT therapy). The implanted device synchronizes the heart beat and can slow a fast heart rate, as well as deliver a shock to stop dangerous irregular beats.
     A similar device by Guidant was approved in May. Medtronic's device supposedly uses fewer shocks to slow a rapidly beating heart.
Source: AP

 Magnetic ICDs To Stop A-Fib

January 15, 1998 - In Control, Inc., announced today that Dr. Steven Kutalek implanted a Metrix atrial defibrillator in a 42-year old man. James Gamble suffered from a-fib, which is an irregular heart rhythm that can lead to strokes. A-fib causes fatigue, shortness of breath, and dizziness in many people. Drugs did not relieve his symptoms. Now when Mr. Gamble feels a-fib, he can pass a magnet over his chest to trigger the new device, which will return his heart to normal rhythm.
     "A-fib episodes are not life threatening, but they can drive you nuts, keeping patients from doing day-to-day activities," explained Dr. Kutalek, "The larger concern is that chronic a-fib can lead to stroke," he said. People with a-fib are about 5 times more likely to have a stroke than healthy people.
     Until now, treatment for a-fib was drugs, often used with external cardioversion - an electric shock given with paddles like you see on tv shows. The Metrix device can spot a-fib and deliver an electric shock to restore normal rhythm, or the patient can trigger the unit himself by passing a special magnet over his chest when he begins to feel symptoms.
Author: Sue Morgan
Source: Allegheny News

 Atrioverter In Trials

1998 - This article is about an implanted device that converts a-fib to normal rhythm with low-energy shocks. The trial included 51 patients. The device was the InControl Metrix Atrioverter system. This is an implanted device with 3 leads - right atrial and sinus leads, and a ventricular pacing lead. After being implanted, the devices were set in monitoring mode. A doctor delivered the shocks while the patient was hospitalized during the trial.
     Average follow-up was 259 days. A total of 3,719 shocks were delivered: 3,049 during testing and 670 for spontaneous a-fib episodes. The detection software was 100% correct in recognizing normal rhythm and 92% correct recognizing a-fib.
     The device converted 96% of the episodes. Ten episodes could not be converted. Early recurrence of a-fib was defined as the return of a-fib within one minute after a shock that successfully converted rhythm to normal. This happened in 51% of patients. The device was safe.
     By the end of follow-up, all but 3 patients were on drug therapy, mostly sotalol or amiodarone. Complications included vein blockage in 2 patients. Four patients required repositioning of a lead. Two patients developed infection, requiring removal of the device and leads.
Conclusion: The atrioverter recognizes arrhythmias. It was effective in converting a-fib, restoring 74% of episodes to normal rhythm by itself. Overall effectiveness of the device was 86%. Early recurrence occurred in 27% of shock episodes. This may be a problem outside the hospital setting. The success of the device will ultimately lie in the ability of patients to handle the shocks without sedation, especially if more than one shock is required for success.
Title: Atrioverter: An Implantable Device for the Treatment of Atrial Fibrillation
Authors: Wellens J, Lau CP, Luderitz B, Akhtar M, Waldo AL, Camm AJ, Timmermans C, Tse HF, Jung W, Jordaens L, Ayers G
Source: Circulation 98:1651-1656, 1998

 Sleep, Breathing, and ICDs

August 28, 2002 - Sleep-related breathing disorders may raise the risk of arrhythmias in some people with ICDs. Dr. Joachim Fichter did a sleep study of 38 patients. All had weak hearts with reduced ejection fractions, averaging 36%. All also had life-threatening too-fast ventricular arrhythmias and ICDS.
     Sleep-related breathing disorders were diagnosed in 14 patients. Of these, 8 showed Cheyne-Stokes respiration and the remaining 6 had obstructive sleep apnea.
     Monitoring showed that 4 of the Cheyne-Stokes patients and 4 of the sleep apnea patients had ventricular arrhythmias during sleep. It was also showed that arrhythmias during episodes of disordered breathing were worse than during normal breathing.
Source: Chest 2002;122:558-561


March 31, 2003 - Implanting a combination ICD/CRT pacemaker in heart failure patients on best drug therapy reduced all-cause mortality 43%, according to the 1,634 patient COMPANION study. "We saw that 43% reduction on top of best drug therapy. We are also getting fewer hospitalizations," said Dr. Michael Bristow, trial co-author.
     Best drug therapy was defined as a beta-blocker, ACE inhibitor, and Aldactone (spironolactone). Dr. Bristow thinks that when a cost analysis is done, this will be cost-effective because it reduces hospitalizations. Patients who got either a CRT pacemaker or a CRT pacemaker with ICD "had 35% fewer hospitalizations for any cause and 39% fewer hospitalizations for heart failure." Of the patients enrolled in the study, 55% "had ischemic heart disease and the effect was the same in those patients," Dr. Bristow said.
     Dr. Jon Kobasigawa said, "This may be a quality of life issue. If the device can reduce hospitalizations, it may significantly improve quality of life for these patients." Dr. Kobasigawa added that devices are expensive, adding $20,000 or more to the cost of treatment.
     Dr. Bert Pitt said he "didn't think you can make the case for cost-effectiveness when we can significantly reduce symptoms and risk of death with drug therapy." Dr. Pitt added that eplerenone treatment "costs pennies compared to an ICD. I could throw pills at patients all day and it still wouldn't add up to the money spent on these devices."
     Dr. Bristow countered that Dr. Pitt's trial studied "a different population. Those were post-heart attack patients rather than chronic advanced heart failure patients." Dr. Bristow added that he isn't presenting a case for devices instead of drug therapy but added to heart failure drugs.
Source: ACC 52nd Annual Scientific Sessions; Medscape

 ICD Zap Survivors Need Monitoring

December 21, 2004 - Researchers analyzed data from the MADIT-II trial to study long-term prognosis of patients who got life-saving zaps from their ICDs. Of 720 patients with an ICD (average follow-up 21 months), 169 patients received 701 needed ICD zaps. Probability of surviving at least one year after first ICD zap for either ventricular tachycardia (VT) or ventricular fibrillation (VF) was 80%.
     Compared to those who did not get any zaps from their ICD, people who were zapped were 3 times more likely to have heart failure episodes or die from pump failure - worsening CHF. This study shows that successful appropriate ICD shocks for VT or VF are associated with 80% survival one year later. These patients are at increased risk for heart failure and non-sudden cardiac death (pump failure) after successful ICD zaps.
     Patients who get ICD shocks should receive special attention to prevent and manage worsening left heart failure during long-term follow-up.
Title: Long-term clinical course of patients after termination of ventricular tachyarrhythmia by an implanted defibrillator.
Authors: Moss AJ, Greenberg H, Case RB, Zareba W, Hall WJ, Brown MW, Daubert JP, McNitt S, Andrews ML, Elkin AD. E-mail: heartajm@heart.rochester.edu
Source: Circulation. 2004 Dec 21;110(25):3760-5. E-published 2004 Dec 6.
PMID: 15583079.

All information on this site is opinion only. All concepts, explanations, trials, and studies have been re-written in plain English and may contain errors. I am not a doctor. Use the reference information at the end of each article to search MedLine for more complete and accurate information. All original copyrights apply. No information on this page should be used by any person to affect their medical, legal, educational, social, or psychological treatment in any way. I am not a doctor. This web site and all its pages, graphics, and content copyright © 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Jon C.

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