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Ventricular Fibrillation

What is it?
Fibrillation is an abnormally fast and chaotic heartbeat, or heart rhythm. An abnormal heart rhythm is called an arrhythmia. Arrhythmias result from a problem in your heart's electrical system. When fibrillation occurs in the heart’s lower chambers (the ventricles), it is called ventricular fibrillation (VF).

VF causes the heart to beat more than 200-300 times per minute, rather than the normal rate of 60-100 beats per minute. VF is also a chaotic rhythm. That means the heart's ventricles try to contract so fast that they quiver rather than beat. This doesn't allow enough time for the ventricles to fill with blood before the blood is pumped out to the body. So less blood and oxygen are being sent to the body and—most important—to the brain.

VF is the most dangerous type of arrhythmia. Within seconds after VF begins, a person can lose consciousness. If the person doesn't receive immediate treatment from a defibrillator, sudden cardiac arrest (SCA) and sudden cardiac death (SCD) can occur within just a few minutes.

Other names for ventricular fibrillation: VF, VFib.

What is the cause?
Ventricular fibrillation (VF) is caused by a problem in your heart's electrical system. Electrical signals follow a certain path, which causes your heart to contract. During VF, however, far too many signals are present in the ventricles.

In addition, the signals are not traveling down the proper pathways. To learn more about your heart's electrical system, go to the Heart & Blood Vessel Basics section.

VF is very rare in people with normal, healthy hearts. It usually occurs in people who have certain types of heart or blood vessel disease.

What are the symptoms?
Ventricular fibrillation (VF) often strikes without warning. The first and often the only symptom of VF is loss of consciousness, since the heart is no longer pumping out enough blood.

What tests could I have?
If you have an episode of ventricular fibrillation (VF), it is an emergency situation. Tests are done in a hospital so that you can be monitored as testing is done. Your doctor may begin with the test listed below—to check the electrical system in your heart. Other tests may also be needed.

In some cases you may be sent to specialists for diagnosis and testing—and sometimes for treatment. To learn more, go to the Your Treatment Team section.

Electrocardiogram (ECG or EKG)

What is an ECG?
An electrocardiogram (ECG or EKG) reveals how your heart’s electrical system is working. The ECG senses and records your heartbeats, or heart rhythms. The results are printed on a strip of paper. An ECG can also help your doctor diagnose whether:
You have arrhythmias
Your heart medication is effective
Blocked coronary arteries (in the heart) are cutting off blood and oxygen to your heart muscle
Your blocked coronary arteries have caused a heart attack

In all, there are three kinds of tests that record your heart's electrical activity, each for a different period of time:
Electrocardiogram (ECG)—done in the doctor's office. It records your heart rhythms for a few minutes.
Holter monitoring—records and stores (in its memory) all of your heart rhythms for 24-48 hours.
Event recorder—constantly records your heart rhythms. But it stores the rhythms (in its memory) only when you push a button.

What are the parts of an ECG strip?
The peaks on an electrocardiogram (ECG) strip are called waves. Together, all the peaks and valleys give your doctor important information about how your heart is working:

• The P-wave shows your heart's upper chambers (atria) contracting
• The QRS complex shows your heart's lower chambers (ventricles) contracting
• The T-wave shows your heart's ventricles relaxing

What can I expect?
When you have an electrocardiogram (ECG) you undress from the waist up, put on a hospital gown, and lie on an exam table. As many as 12 small patches called electrodes are placed on your chest, neck, arms, and legs. The electrodes, which connect to wires on the ECG machine, sense the heart's electrical signals. The machine then traces your heart’s rhythm on a strip of graph paper.

What are the treatment options?
It's essential to get immediate treatment for ventricular fibrillation (VF), since it can easily progress to sudden cardiac arrest (SCA) and sudden cardiac death (SCD). Doctors have found than 95% of cardiac arrest victims die before reaching the hospital.

On-the-spot treatment includes:
Immediate CPR (cardiopulmonary resuscitation)—involves chest compressions and mouth-to-mouth breathing. CPR is critical in getting some oxygen to the brain until an electrical shock can be delivered.
Defibrillation—is the best treatment for VF. Defibrillators send a strong electrical shock to the heart to stop the arrhythmia and restore a normal heartbeat. Because brain damage begins within 4-6 minutes after VF begins, defibrillation should be done as soon as possible.

There are two types of defibrillators:

• External defibrillators use paddles to deliver the shock to the outside of the chest. You've often seen this on TV medical dramas. Some public buildings like sports arenas and airports now have external defibrillators available for such emergencies.
• Implantable cardioverter defibrillators (ICDs) are implanted devices that can sense arrhythmias and deliver lifesaving shocks.

People who are at high risk of VF—or who are VF survivors—might also be treated with procedures or medications. However, the American Heart Association says that VF is thought to be the arrhythmia that most often leads to SCA and SCD. And medications alone have not proven to be very effective in reducing SCA.

Procedures

Defibrillator Implant

Defibrillator Implant (ICD Device Implant)
What is a defibrillator (ICD device)?
An implantable cardioverter defibrillator (ICD) is a small device that treats abnormal heart rhythms called arrhythmias. Specifically, an ICD treats fast arrhythmias in the heart's lower chambers (ventricles). Two such arrhythmias are ventricular tachycardia (VT) and ventricular fibrillation (VF).

Arrhythmias result from a problem in your heart's electrical system. Electrical signals follow a certain path through the heart. It is the movement of these signals that causes your heart to contract. To learn more about your heart's electrical system, go to the Heart & Blood Vessel Basics section.

During VT or VF, however, far too many signals are present in the ventricles. In addition, the signals often do not travel down the proper pathways. The heart tries to beat in response to the signals, but it cannot pump enough blood out to your body. If you have either VT or VF, you are at high risk of sudden cardiac arrest (SCA). If not treated immediately with defibrillation, SCA can result in sudden cardiac death (SCD).

An ICD can treat VT and VF and restore your heart to a normal rhythm. So it reduces your risk of SCD. The device can deliver several types of treatment:

• Anti-tachycardia pacing (ATP) delivers very small amounts of energy to your heart—so small that you can't feel the treatment.
• Cardioversion is a low-energy shock that treats fast but regular arrhythmias.
• Defibrillation is a high-energy shock that treats fast and chaotic (irregular) rhythms. Defibrillation is painful for an instant, but it can also save your life.

A device implant is a procedure that uses local numbing. General anesthesia is usually not needed.

How is the implant procedure done?
An Implantable cardioverter defibrillator (ICD) system has two parts.
Device—the device is quite small and easily fits in the palm of your hand. It contains small computerized parts that run on a battery.
Leads—the leads are thin, insulated wires that connect the device to your heart. The leads carry electrical signals back and forth between your heart and your device.

Your doctor inserts the leads through a small incision, usually near your collarbone. Your doctor gently steers the leads through your blood vessels and into your heart. Your doctor can see where the leads are going by watching a video screen with real-time, moving x-rays called fluoroscopy.

The doctor connects the leads to the device and tests to make sure both work together to deliver treatment. Your doctor then places the device just under your skin near your collarbone and stitches the incision closed.

What can I expect?
Usually you are told not to eat or drink anything for a number of hours before the procedure. You undress and put on a hospital gown or sheet. Your procedure will be performed in a ”cath lab." You lie on an exam table and an intravenous (IV) line is put into your arm. The IV delivers fluids and medications during the procedure. The medication makes you groggy, but not unconscious.

The doctor makes a small incision near your collarbone to insert the leads. The area will be numbed so you shouldn't feel pain, but you may feel some pressure as the leads are inserted. You may be sedated when the device is tested, since it delivers a shock to your heart.

You may be in the hospital overnight, and there may be tenderness at the incision site. Afterwards most people have a fairly quick recovery.

Important Safety Information
Medications, procedures and tests can have some risks and possible side effects. Results may vary
from patient to patient. This information is not meant to replace advice from your doctor. Be sure to talk
to your doctor about these risks and possible side effects.

An implantable cardioverter defibrillator can protect you from the effects of sudden cardiac arrest by
reviving your heart rhythm. But it is not for everyone, including people with certain steroid allergies.
Procedure risks include infection and tissue damage. In some cases, the device may not respond to
irregular heartbeats or may deliver inappropriate shocks. In rare cases severe complications or device
failures can occur. Electrical or magnetic fields can affect the device. Only your cardiologist knows what
is right for you.

GUIDANT is a trademark and HEARTISTRY is a service mark of Guidant Corporation. All other brand names mentioned are used for identification purposes only and are trademarks of their respective owners.

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www.guidant.com

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