Help and Support For Heart ICD Pacemaker Cardioverter Defibrillator Implant Recipients

The process of implantation of an ICD is similar to implantation of a pacemaker.

Implantable Cardioverter Defibrillator

Answers to your questions about implanted defibrillators and more!

An implantable cardioverter-defibrillator (ICD), also known as an automated implantable cardioverter-defibrillator (AICD), is a small battery powered electrical impulse generator which is implanted in patients who are at risk of sudden cardiac death due to ventricular fibrillation. The principles of cardiac arrhythmia detection and treatment are incorporated into the implantable device. In current variants the ability to revert ventricular fibrillation has been extended to include atrial and ventricular arrhythmias as well as the ability to perform biventricular pacing in patients with congestive heart failure and to pace should there be any marked bradycardia.

The process of implantation of an ICD is similar to implantation of a pacemaker. Similar to pacemakers, these devices typically include electrode wire/s which pass through a vein to the right chambers of the heart, usually being lodged in the apex of the right ventricle.

ICDs constantly monitor the rate and rhythm of the heart and can deliver therapies, by way of an electrical shock, when the electrical manifestions of the heart activity exceeds the preset number. More modern devices can distinguish between ventricular fibrillation and ventricular tachycardia (VT), and may try to pace the heart faster than its intrinsic rate in the case of VT, to try to break the tachycardia before it progresses to ventricular fibrillation. This is known as fast-pacing, overdrive pacing, or anti-tachycardia pacing (ATP). ATP is only effective if the underlying rhythm is ventricular tachycardia, and is never effective if the rhythm is ventricular fibrillation.

Many modern ICDs use a combination of various methods to determine if a fast rhythm is normal, ventricular tachycardia, or ventricular fibrillation.

Rate discrimination evaluates the rate of the lower chambers of the heart (the ventricles) and compares it to the rate in the upper chambers of the heart (the atria). If the rate in the atria is faster than or equal to the rate in the ventricles, then the rhythm is most likely not ventricular in origin, and is usually more benign. If this is the case, the ICD does not provide any therapy.

Rhythm discrimination will see how regular a ventricular tachycardia is. Generally, ventricular tachycardia is regular. If the rhythm is irregular, it is usually due to conduction of an irregular rhythm that originates in the atria, such as atrial fibrillation.

Morphology discrimination checks the morphology of every ventricular beat and compares it to what the ICD believes is a normally conducted ventricular impulse for the patient. This normal ventricular impulse is often an average of a multiple of beats of the patient taken in the recent past.

The development of the ICD was pioneered at Sinai Hospital in Baltimore by a team including Stephen Heilman, Alois Langer, Morton Mower, Michel Mirowski, and Mir Imran, with the help of industrial collaborator Intec Systems of Pittsburgh. Mirowski teamed up with Mower and Staewen, and together they commenced their research in 1969 but it was 11 years before they treated their first patient. Imran was the young engineer who was able to turn the benchtop idea into a working device. Using analogue tape recordings of patients heartbeats, Imran developed algorithms and hardware that are the foundation of todays ICD's and Cardiac Rhythm Management industry. Similar developmental work was carried out by Schuder and colleagues at the University of Missouri.

More than a decade of research went into the development of an implantable defibrillator that would automatically sense the onset of ventricular fibrillation and deliver an electric countershock within 15-20 seconds, converting the rhythm to sinus rhythm. Improved versions were programmed to be able to detect ventricular tachycardia, often a forerunner of ventricular fibrillation. These were then called implantable cardioverters.

The work was commenced against much skepticism even by leading experts in the field of arrhythmias and sudden death. There was doubt that their ideas would ever become a clinical reality. In 1972 Bernard Lown, the inventor of the external defibrillator, stated in the journal Circulation - "The very rare patient who has frequent bouts of ventricular fibrillation is best treated in a coronary care unit and is better served by an effective antiarrhythmic program or surgical correction of inadequate coronary blood flow or ventricular malfunction. In fact, the implanted defibrillator system represents an imperfect solution in search of a plausible and practical application".

The problems to be overcome were the design of a system which would allow detection of ventricular fibrillation or ventricular tachycardia. Despite the lack of financial backing and grants, they persisted and the first device was implanted in February 1980 at Johns Hopkins Hospital by Dr. Levi Watkins, Jr. Modern ICDs do not require a thoracotomy and possess pacing, cardioversion, and defibrillation capabilities.

A number of clinical trials have demonstrated the superiority of the ICD over AAD (antiarrhythmic drugs) in the prevention of death from malignant arrhythmias. The SCD-HeFT trial (published in 2005) showed a significant all-cause mortality benefit for patients with ICD. Congestive heart failure patients that were implanted with an ICD had an all-cause death risk 23% lower than placebo and an absolute decrease in mortality of 7.2 percentage points after five years in the overall population.1 Reporting in 1999, the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial consisted of 1,016 patients, and deaths in those treated with AAD where more frequent (n=122) compared with deaths in the ICD groups (n=80, p < 0.001)[1]

Initially ICDs were implanted via thoracotomy with defibrillator patches applied to the epicardium or pericardium. The device was attached via subcutaneous and transvenous leads to the device contained in a subcutaneous abdominal wall pocket. The device itself acts as an electrode. Most ICDs nowadays are implanted transvenously with the devices placed in the left pectoral region similar to pacemakers. Intravascular spring or coil electrodes are used to defibrillate. The devices have become smaller and less invasive as the technology advances. Current ICDs weigh only 70 grams and are about 12.9 mm thick.

What to Expect During

ICD Implantation

Implantable cardioverter defibrillator (ICD) implantation surgery generally takes place in an operating room, cardiac catheterization, or electrophysiolgy (EP) laboratory. The room will be full of equipment and medical personnel. You will be asked to lie on a bed with safety straps placed over your legs. Your arms are secured at your sides, as it is important that the arms remain still during the procedure.

Your chest is then washed again and drapes are placed over the implant area. You will receive one or more shots of numbing medicine in your chest area. Because of the drapes, you won't see the shot. The doctor may touch the area and ask if you are losing sensation in your upper chest.

There are several methods of ICD implantation. The type of surgery you will undergo depends upon many factors, including prior surgeries and type of device. There are four main steps to any ICD implantation procedure.

- Lead Placement

- Testing

- ICD Placement

- Additional Testing

Lead Placement
The implantation procedure begins with the placement of one or more leads (depending upon which will provide the best therapy for you).

Transvenous Approach
Transvenous means through the vein. With this method, the physician makes a small incision near your collarbone and maneuvers one or more leads through a vein into your heart. The tip of each lead (called the electrode) is positioned next to the inside heart wall (endocardium). The ICD is then implanted under the skin in a specially prepared pocket, usually in the right or left upper chest. This is the most common technique used today.

Thoracotomy
The term thoracotomy is general and refers to several types of open-chest procedures. A thoracotomy is used to sew patch leads on the outside of the heart (epicardium). The leads are insulated wires connected to thin oval patches made of rubber and wire mesh.

Sternotomy
This approach is similar to a thoracotomy; however, the incision is made over the breastbone, or sternum, and the leads are advanced into the heart. This is the type of operation that is commonly used in coronary bypass and heart valve surgery.

Subxiphoid Approach
This approach is also similar to a thoracotomy; however, the incision is made slightly to the left of the sternum.

Testing
Once implanted, the leads are tested to ensure they will perform. The medical team provokes, or induces, a rhythm disorder and allows the device to deliver therapy. If the therapy is inadequate, the lead is moved to a different position in the heart. It is not uncommon to have to reposition a lead to get most effective therapy.

ICD Placement
Once testing is completed and your physician is assured that the leads are in good position, the ICD is connected to the leads. The device is then usually placed under the skin either near the collarbone or somewhere above or at the waistline.

Additional Testing
Once the ICD is implanted, additional testing is performed to ensure the system will effectively correct your arrhythmia. If the test results are unsatisfactory, the problem may be with the device. Only after the leads and ICD are tested successfully is the procedure concluded.

Heart and Vessel Procedures
ICD (Defibrillator) Implantation
What Can I Do to Prepare for My Defibrillator Implantation?

Your doctor or nurse will give you specific instructions about preparing for your ICD implant. Common guidelines involve whether you should continue or stop certain medications, if you should avoid eating or drinking in the hours before surgery and what the hospital check-in procedures are.
What Happens During the Procedure?

The procedure to implant an ICD has been greatly simplified over the years. During the surgery, you will be attached to several monitors. Usually, the medication you will be given makes you very relaxed and drowsy.
Determining Where to Implant

The ICD system may be implanted in either your chest or your abdomen. Your doctor will determine the best way to implant your pulse generator. Your age and the size of your heart will be considered. Your doctor will also consider whether you have ever had chest surgery. Your activities and lifestyle may suggest where the ICD is implanted. Overall, the method selected will offer the greatest safety for you.

Just as the best position of the pulse generator is determined for each individual, lead placement is customized for each patient as well. Some patients may require an additional lead for treating fast rhythms. This lead can be placed just under the skin next to your rib cage through a small cut in your left side. Or, sometimes an additional lead is placed on the outside of the heart. These steps are taken to insure that the ICD system can adequately sense the life-threatening rhythms and deliver the appropriate energy to treat them.
Placing the Pulse Generator and Leads

After numbing the area of the implant, the doctor will make a small pocket under the skin for the pulse generator and will place the lead or leads. For most patients, the leads are placed inside the heart. The doctor opens a vein, usually through a small cut near your collarbone. The doctor can then thread the lead through the vein and position it inside your heart chamber. The tip of the lead rests against the inner heart wall.

If your heart condition requires two-chamber pacing, another lead is positioned in the upper right chamber (atrium) of your heart. This dual-chamber lead system allows the pulse generator to watch and treat the areas of heart that your doctor has determined need monitoring.
Testing the System

After the leads are in position, they are tested to make sure they sense your heart signals clearly. The leads are then stitched to nearby tissue so that they won't move. The leads are connected to the pulse generator.

During the operation, the whole ICD system will be tested to make sure it is working properly. For this test, your doctor will start an arrhythmia in your heart. The ICD system will sense the rhythm and give the programmed treatment.
What Happens Right After the Procedure?

After the operation, you may be in the hospital for the first day or two. This allows the doctors and nurses to watch and record your heart rhythm with an ECG machine. When you are ready, you will be allowed to return home.
Testing Your ICD

Before you leave the hospital, your doctor may test the ICD again.

Your experience of ICD therapy will be as unique as you are. People with abnormal heart rhythms may experience unusual sensations during their arrhythmias, but not everyone feels their arrhythmias. Your ICD system will deliver treatment based on what it senses even if you don't feel any symptoms. You may, however, feel sensations during therapy delivery. These feelings have been described in a variety of ways.

* Antitachycardia pacing – You may not feel pacing therapy when it is delivered to your heart. You may have a feeling of fluttering in your chest. Most patients who receive ATP therapy say it is painless.
* Cardioversion – These low-energy shocks are stronger than pacing pulses. Many patients say cardioversion is mildly uncomfortable. It feels like a thump on the chest.
* Defibrillation – Many patients faint or become unconscious shortly after a very fast VT or VF rhythm starts. As a result, they do not feel these high-energy shocks. Of those patients who are conscious, some describe the shock like a "kick in the chest." Usually, the shock comes suddenly. The sensation lasts for only a second. While many find the shock reassuring, other patients may feel anxious for a short time after shock therapy is delivered.
* Bradycardia pacing – These pacing pulses are very low energy and typically are not felt by patients.

Before leaving the hospital, some patients also perform an exercise treadmill test. This test helps your doctor watch your heart rhythm with the ECG machine and know that your ICD is working.

Paul Stanley, a singer and guitarist with rock band Kiss, was forced to pull out of a show in California on Friday after his heart started beating at more than twice the normal level, he said on his Web site.

The apparent tachycardia happened while the band was rehearsing for a performance at a casino in San Jacinto, California, about 90 miles east of Los Angeles.

"My heart spontaneously jumped to 190 plus beats per minute, where it stayed for over an hour necessitating paramedics to start an IV and give me a shot to momentarily stop my heart and get it into a normal pattern," Stanley, 55, wrote on his site (http://www.paulstanley.com)

A normal heart rate at rest is about 60 to 80 beats a minute, according to the American Heart Association.

Tachycardia, or rapid heart rate, can cause palpitations, shortness of breath, chest pain, dizziness, lightheadedness, fainting or near fainting, the group said on its Web site (http://www.americanheart.org).

Stanley said he was advised performing would be risky, and the show went on without him. Fellow principal Gene Simmons told fans the group would play as a trio, and turned the show into a tribute to his ailing bandmate.

A call to Kiss manager Doc McGhee for an update on Stanley's condition was not immediately returned late on Saturday.

Stanley, born Stanley Eisen, and Simmons co-founded Kiss in New York City in 1973. Adored by fans, despised by critics, the group made a name for itself performing in white face make-up and ghoulish costumes.

Hits during its heyday included such anthems of teen rebellion as "Rock and Roll All Nite" and "Shout It Out Loud." Stanley released a solo album last year.

the Zapper, zaplife.org