Dr. MJ Bazos MD,
Patient Handout
Implantable
Cardioverter-Defibrillator
What is an
implantable cardioverter-defibrillator?
An implantable cardioverter-defibrillator (often
called an ICD) is a device that briefly passes an electric current through the
heart. It is "implanted", or put in your body surgically. It includes a pulse
generator and one or more leads. The pulse generator constantly watches your
heartbeat. It is like a small computer that runs on a battery. The lead (say:
"leed") is a wire from the pulse generator to the inside of your heart. The lead
takes signals from your heart to the ICD and then takes an electric current from
the pulse generator to your heart.
Why might I need
an ICD?
Normally, your heart has a natural pacemaker
that helps your heart beat steadily. An electrical current starts in one of the
upper chambers (called the atria) of the heart and goes through the heart to the
bottom chambers (called the ventricles). You may need an ICD if you have had, or
are at high risk of having, certain heart rhythm problems (ventricular
tachycardia or ventricular fibrillation).
What is
ventricular tachycardia?
When the heart beats too fast, it's called
tachycardia. When the problem begins in the bottom chambers of the heart, it's
called ventricular tachycardia. When your heart goes into ventricular
tachycardia, it doesn't pump blood as well. As a result, less blood is pumped to
your body and your brain. You may feel your heart pounding, or you may feel
dizzy or faint. If ventricular tachycardia isn't treated properly, it can be
life-threatening.
What is
ventricular fibrillation?
When a ventricular arrhythmia (irregular
heartbeat) becomes very fast and irregular, it's called ventricular
fibrillation. The heart just quivers, and no blood is pumped to the body or the
brain. A person with ventricular fibrillation usually passes out very quickly.
Unless treatment is given in 5 to 10 minutes, ventricular fibrillation causes
death.
In people who don't have an ICD, ventricular
fibrillation is treated with an external defibrillator. Paddles are put on the
outside of the chest, and an electrical shock is given through the paddles. This
shock goes through the heart and stops the irregular beat. The heart then goes
back to a more regular rhythm.
Unfortunately, ventricular fibrillation can
occur without warning - often, treatment can't be given in time. An ICD may be
recommended for you because your doctor thinks you're at high risk for having
ventricular fibrillation. The ICD can quickly recognize and stop ventricular
fibrillation.
How does the ICD
work?
The ICD constantly watches your heart rhythm. If
it sees that your heart is beating fast, it delivers the treatment programmed by
your doctor. The ICD can do several things:
- Pacing. If you have ventricular
tachycardia that isn't too fast, the ICD can deliver several pacing signals in a
row. When those signals stop, the heart may go back to a normal rhythm.
- Cardioversion. If the pacing doesn't work,
cardioversion can be used. In cardioversion, a mild shock is sent to the heart
to stop the fast heartbeat.
- Defibrillation. If ventricular
fibrillation is detected, a stronger shock is sent. This stronger shock can stop
the fast rhythm and help the heartbeat go back to normal.
- Pacemaker. The ICD can also see when your
heart beats too slowly. It can act like a pacemaker and bring your heart rate up
to normal.
What does
treatment with an ICD feel like?
When the ICD delivers pacing therapy, you may
not feel anything. Some people feel a fluttering in their chest. They usually
say that it doesn't feel uncomfortable or painful.
Cardioversion is stronger than a pacing pulse.
It feels like being thumped in the chest.
The defibrillator shock is the strongest
treatment. Many people say it feels like being kicked in the chest. It usually
comes suddenly and lasts only a second. Although you may feel upset for a short
time after a defibrillator shock, it is good to know that the ICD is treating
the heart rhythm problem.
Pacing a slow heart rate uses very little
energy. You may not feel it at all.
How is an ICD
implanted?
The pulse generator may be implanted either
under your collarbone on the left or right side of your chest, or in your
abdomen (stomach area). In either place, the generator can be put in a "pocket"
the doctor makes under your skin or, sometimes, in a muscle. One end of the lead
wire is put into a vein that goes to your heart. The wire is moved through the
vein until it reaches the heart. The other end of the wire is attached to the
pulse generator. Once it is implanted, the doctor will program the ICD to treat
your specific heart rhythm problem.
How will an ICD
affect my lifestyle?
So that you can heal well, your doctor will want
you to limit your activities for the first few weeks after you get the ICD. Then
you can slowly go back to your normal lifestyle. Depending on your condition and
your local laws, your doctor will tell you when it's safe for you to drive a
car. In general, you can expect to be back to normal after a
month.
You'll need to stay away from machines that
could interfere with your ICD. You shouldn't work near strong magnetic fields or
strong electric fields. The ICD is built to be protected from most home shop
tools and electric appliances, including microwave ovens. However, you need to
be certain that all electric items are properly grounded and in good repair.
Your doctor will help you understand what to avoid when you have an
ICD.