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Pacemaker/Implantable Cardiac Defibrillator

Your Heart's Electrical System


The healthy heart beats approximately 100,000 times a day. Its steady rhythm sends oxygen-rich blood and nutrients to all of your body's cells with every heartbeat.


Your heart's rhythm is created and controlled by its own conduction system. Special tissues generate electrical signals that travel along pathways through the heart, keeping the heart beating at an appropriate pace. For more information about your heart's electrical system, see the section entitled "The Heart".


Problems with the Electrical System


There are many reasons why a heart's conduction system may become impaired. These include hereditary defects, certain drugs and scarring from a previous heart attack. Sometimes the conductive tissue itself may lose its ability to transmit electrical impulses. The symptoms below can be signs that your conduction system is having problems:

  • shortness of breath
  • dizziness
  • fatigue
  • fainting

When your heart beats at a more normal rate, your symptoms should be relieved.



A pacemaker is a small electronic device implanted into the body to regulate the heart rate. The pacemaker monitors the contraction of the heart's atrial and ventricular activity to see if pacing is needed. If so, it provides electrical pacing, closely mimicking the heart's natural way of working.


A bi-ventricular pacemaker is especially designed for people with congestive heart failure. It keeps the right and left ventricles pumping together, decreasing side effects of congestive heart failure. These pacemakers utilize three separate pacing leads, which can be placed via the venous system, but sometimes requires an incision and direct placement on the heart surface. There can also be a combination of BI-V and ICD components.

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Implantable Cardiac Defibrillator (ICD)


Ventricular tachycardia and ventricular fibrillation are two abnormally fast rhythms that can be very dangerous, even life threatening, if not properly treated. If untreated, the heart cannot pump blood effectively and cardiac arrest occurs.


To treat this condition, your doctor will suggest an Implantable Cardioverter Defibrillator (ICD). The ICD is programmed to deliver rapid pacing signals

to restore a normal rhythm. If pacing does not stop the abnormal rhythm, a low energy to high energy cardioversion shock is delivered as needed until the heart resumes a safe, normal rhythm.


Pacing and cardioversion are often times not felt or associated with only mild discomfort. Defibrillation is often times described by patients as "temporary and fleeting, but also distressing". It startles them, but passes very quickly.


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