What are the components of an ICD?

Implantable Cardioverter Defibrillators (ICDs) are like miniaturized computers capable of monitoring the heart’s spontaneous activity. They are made up of a pulse generator and a lead system.

Pulse Generator

The pulse generator is a sealed titanium metal container that contains:

• a battery, to power the system

• the capacitors, which store the electric charge needed to shock the heart

• a microprocessor (small computer)

• electronic circuits

The pulse generator's computer memory stores:

• treatment settings your doctor has programmed

• the number and kinds of treatments your heart

  has received between each office visit

• how successful each treatment was

• the status of the pulse generator's battery

• the status of the pulse generator's battery (how much current it has consumed)

The pulse generator constantly monitors the electrical signals from your heart. If it detects an abnormal rhythm, it delivers a treatment, which can be either an electrical shock (which patients can feel) or a sequence of painless pacing pulses (which patients may or may not feel) to bring your back to a normal rhythm.

Leads

The pulse generator is connected to the heart by 2 insulated wires called leads. These leads allow the ICD to:

• monitor your heart rhythm

• pace the heart, if necessary

• deliver a shock, if necessary

The leads are threaded into the heart through veins, making their implantation a simple procedure.

Programmer

The programmer is a computer-like device which communicates with the pulse generator by means of a wand held over the area of your pulse generator.

It is used to:

• test your ICD after it is implanted

• program the ICD treatments

• retrieve the information stored between office visits in the pulse generator's memory.

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