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Technical Data

Implantable defibrillators are used to treat heart rhythms that are abnormally fast and life threatening. AICDs (automatic implantable cardioverter defibrillators) often are used to treat sudden cardiac death (SCD), and have been found to reduce the SCD mortality rate for these patients from as high as 55 percent to less than 2 percent as verified in more than 65,000 implants .

An implantable cardioverter defibrillator (ICD) is a device that is implanted in the chest to monitor for and, if necessary, correct episodes of rapid heartbeat. If the heartbeat gets too fast (ventricular tachycardia), the ICD will stimulate the heart to restore a normal rhythm (antitachycardia pacing). In cases where the heartbeat is so rapid that the person may die (ventricular fibrillation), the ICD will also give an electric shock (defibrillation) to “reset” the heartbeat.

An ICD is similar in many respects to an artificial pacemaker, which is another type of device that corrects an abnormal heart,  (bradycardia),
whereas ICDs are uImplantable Defibrillatorsed to correct a heart rhythm that is too fast (tachycardia).
The ICD is implanted into the chest of the patient during a minor surgical procedure (not open-heart surgery). A short stay in the hospital is usually required and some  patients may need to take medications that help the heart maintain a normal rhythm (antiarrhythmics). Once the ICD is in place, it runs on batteries for about four to seven years, depending on how often an electric shock is discharged. ICD batteries will not run out unexpectedly. Physicians can detect when the battery is running low during a routine hospital visit.

People with ICDs need to be careful in certain situations. More information on the lifestyle considerations of living with an ICD can be found in the HeartCenterOnline patient guide: Living with an Implantable Defibrillator.

 

How an Implantable Defibrillator Works

To help you understand these concepts, we may use a few technical terms but we want you to know we’ll do our best to define them in a way that makes sense. Below are a few basic elements of the defibrillator system that is implanted in patients with heart rhythm problems:

The Body of the Defibrillator

The body of the defibrillator is called a pulse generator and it acts like a small computer that runs on a battery. It houses the brains of the defibrillator and checks the heart’s electrical signals and delivers electrical energy to the heart when it senses an abnormal rhythm. Smaller than a pager, the pulse generator is programmed by a doctor to deliver the specific kind of therapy the patient’s heart needs.

There is built-in “memory” in the device that stores information and enables a doctor to see a picture (or electrocardiogram/ECG) of the particular heart rhythm pattern. This one-dimensional picture allows the doctor to do a better job of programming exactly the treatment the patient needs.

The Lead System

Leads are insulated wires that are connected to the pulse generator and are threaded through the patient’s veins into the heart. They work as a two-way street… carrying information from the heart back to the pulse generator, while also carrying electrical energy from the pulse generator to the heart. Depending on the patient’s condition, one or more leads may be placed in different chambers of the heart.

The Electronic Programmer

While all defibrillators are built similarly, each individual device needs to be programmed specifically for the patient’s particular arrhythmia(s). During the implantation procedure, an electronic programmer is used to exchange information with the defibrillator via radio frequency signals. This enables the doctor to program the defibrillator to respond to the exact needs of the heart’s rhythm problem.

The programmer is also used to test the defibrillator soon after it is implanted and again before the patient leaves the hospital. When the patient returns for a follow-up, the programmer is again used to read the information stored inside the pulse generator’s memory. This procedure is simple and painless and can be performed while the patient is fully clothed. A wand is placed over the implant site and communicates via radio waves to the programmer. Also at this time, the doctor may change the programmed functions of the defibrillator based on the patient’s needs.

How an ICD feels

How The Electrical Signal Therapy Feels When it is Delivered – Different Conditions Result in Different Degrees of Impact and Sensation
Antitachycardia Pacing
(Treats regular but fast heartbeats)		 You may not even feel it, or you may feel a slight fluttering in your chest
Cardioversion
(Treats regular but very fast heartbeats)		 Many say cardioversion is mildly uncomfortable, like a thump in the chest
Defibrillation
(Treats irregular and very fast heartbeats – those with Ventricular Fibrillation are at risk from Sudden Cardiac Death) 		For Ventricular Tachycardia (VT) or Ventricular Fibrillation (VF), you may need a high-energy shock. Some patients faint or become unconscious shortly after a fast VT or VF rhythm starts. Those who are conscious describe it as a “kick in the chest” and lasts usually for only a second.
Bradycardia Pacing
(Treats very slow heartbeats) 		Usually uses very low energy and signals are typically not felt.

What is the Defibrillator
Implant Procedure Like?

The method of implanting an ICD has been greatly simplified over the years. Today, patients are given medication to relax or sleep during the procedure. The procedure typically lasts about an hour.

The ICD system’s pulse generator is usually implanted just beneath the skin in the chest… just beneath the collarbone, although some are implanted in the abdomen. Doctors make this placement decision based on age, the size of the heart, the patient’s history of chest surgery, patient’s activities and lifestyle.

To position the leads, a small incision is made near the collarbone and the lead wires are passed through a vein and positioned inside the heart. Throughout the procedure, the doctor is carefully testing the defibrillator to be sure it is working properly and seeing that it is responding to the patient’s specific heart requirements. The entire system is customized for the patient’s specific heart condition and optimal therapy.

A Review of Basic Facts
About Defibrillators

  • Heart attack survivors who have developed arrhythmias can benefit from an implantable defibrillator.

     
  • The device can be programmed to meet your heart’s specific needs.

     
  • The doctor can easily and painlessly get information on how well your heart is working while using a programmer with your defibrillator – this enables the physician to better manage your condition.

     
  • The device is implanted just beneath the skin

     
  • With defibrillators, people with more serious types of heart rhythm problems have the peace of mind that they are protected against unconsciousness or even death no matter where they are, day or night, asleep or awake, at home or away.

     
  • Defibrillators have been around for many years and are clinically proven to be safe and effective in treating certain arrhythmias.

     
  • Thousands of people in the United States and abroad have defibrillators implanted inside of them.