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ICD - Implantable Cardioverter Defibrillator
For individuals who experience irregular heart rhythms that can be life threatening, the insertion of an implantable cardioverter defibrillator (ICD) may be required. This procedure involves the implantation of a small battery-operated device under the left or right collarbone. Once positioned, leads are inserted into the heart. Should a life threatening incident occur in the heart’s rhythm, the device is capable of automatically shocking the heart to return to a normal rhythm.




i – THE ICD:

The implantable cardioverter defibrillator (ICD) is a device that monitors your heart rhythms. If the ICD detects any abnormalities in your heartbeat, it will decide if the detected rhythm should be treated. The type of treatment delivered by the device will depend on the settings programmed into your ICD. The ICD also has a pacemaker in it to ensure your heart does not beat too slowly.

Remember that the ICD treats the rhythm problem when it occurs, it does not prevent it.



Your ICD system consists of a pulse generator, leads and a programmer.


The ICD system consists of a pulse generator connected to wires (leads) that sense and pace your heart rhythm. The pulse generator and the leads are surgically implanted. There is also a programmer that is used to communicate with your ICD.


  1. The Pulse Generator:

    The pulse generator is about the size of a pager, is powered by a battery, and monitors the electrical signals in your heart. When an arrhythmia (irregular heartbeat) is detected in your heart, the pulse generator will determine whether the abnormal rhythm is to be treated. If so, the generator will pace the heart and/or deliver electrical shock(s) to your heart via the leads (implanted wires). Depending on the programming of your ICD, different types of treatments are delivered and different amounts of information can be stored.

  2. The Lead System:

    The leads are wires threaded into veins under your collarbone and implanted into your heart that actually detect your heart rhythm. The tip of the lead(s) has a sensor that “sees” your heart rhythm all the time and this information is then sent to the computer in the generator. As well, any electrical energy that the pulse generator sends to the heart travels along the leads. Depending on the make and model of your ICD system, you might have separate leads that monitor and deliver shocks, or you may have leads that perform both functions.

  3. The Programmer:

    The programmer is a laptop computer-like device that communicates with your ICD in the same fashion that a remote control communicates with a television set. Using the programmer, the functions and settings of your ICD are programmed and tested after implant. Also when you visit the ICD clinic, the programmer is used to retrieve information about your heart rhythms, stored in the pulse generator. Every time you have what your ICD considers to be a fast, abnormal rhythm, the ICD stores the:

  1. date and time it occurred

  2. an ECG (electrocardiogram) taken before, during and after the rhythm

  3. measurements taken during the episode

    This information helps the Clinic staff to determine if all of your settings (and medications) are correct.

  1. ICD Therapies:

    Anti-tachycardia Pacing (ATP): When a rapid, regular rhythm such as VT (ventricular tachycardia) is recognized, the device can deliver a series of rapid pacing pulses at a rate slightly faster than your VT rhythm. This alone is often enough to correct the rhythm. You may not even be aware this has happened, or you may feel a slight fluttering feeling.

    Shock: If the ATP does not correct the rhythm (VT) or if the rhythm is VF(ventricular fibrillation), the ICD will deliver a high energy shock to restore the rhythm to normal.

  2. What a Shock Feels Like:

    When your ICD sends a shock, you will feel a distinct “kick” in the chest. This is usually unpleasant but not dangerous and usually not extremely painful. There may be times that you do not feel a treated arrhythmia, but your ICD will treat any irregular rhythms it detects.


    When your ICD device delivers a shock, you will feel a distinct “kick” in the chest. Anyone touching you when you get a shock may feel a slight tingling sensation, but will not get a shock and will not be harmed in any way.

    When you receive a shock:

  1. Stop what you are doing and ask yourself how you feel.

  2. If you feel well before and after the shock, call the Defibrillator Clinic, we can discuss your follow-up. We need to determine whether we feel your device is functioning appropriately. We also need to determine how urgently you need to see us in the office or the clinic.


    If you feel unwell and are concerned, go to your local emergency department. Inform your local hospital that you have a defibrillator. Also inform them that you are followed at Southlake Regional Health Centre and that they should feel free to contact us at any time. Bring your list of medications and dosages with you.

  3. Remember to write down the date, time, symptoms and activities surrounding the shock in your diary.

    If you receive 2 or more shocks together, please go to your local emergency department.

    If your condition changes in any way and you are worried, please do not hesitate to call to discuss your concerns. If you feel symptoms of your rapid heart rhythm that do not go away, you should contact our office or your physician.


    a) Usually the pulse generator is implanted in the upper chest area on the left side, but it may also be implanted in the right upper chest or in the abdomen. How and where the pulse generator is implanted will depend on your size, anatomy, and medical history. An ICD implantation is generally considered relatively minor surgery and the operation itself usually takes about an hour.