What is a Pacemaker?

When people refer to a pacemaker, they are actually discussing a pacing system: a pacemaker, a pacing lead, and programmer. Two parts are placed inside the body:

The pacemaker is a small metal case that contains electronic circuitry and a battery. The pacemaker sends a tiny electrical pulse at a specific time.

A pacing lead is an insulated wire that carries the tiny electrical pulse to the heart so a heartbeat can begin.

The third part, the Programmer, is kept in a hospital or clinic. A nurse or doctor uses this specialized computer to see how the pacemaker is working and if necessary, to adjust the settings of a pacemaker.

The three parts of a pacing system work together to relieve symptoms of bradycardia (a heart rate that is too slow). A pacing system increases the heart rate to meet the oxygen needs of the body.

By increasing the heart rate, the symptoms of bradycardia are often eliminated. This often means patients have more energy and less shortness of breath. However, a pacing system is not a cure, but rather a treatment for a slow heart rhythm. A pacing system will not prevent or stop heart disease (coronary artery disease), nor will it prevent heart attacks.

As of today, the only treatment for bradycardia is a pacemaker. This remarkable invention has been benefiting more than 2 million people for over 50 years. Because of a pacemaker, people with bradycardia can expect to lead normal lives.

Part 2: Pacing Lead

A pacing lead is an insulated wire that is connected to a pacemaker. Leads are extremely flexible in order to withstand the twisting and bending caused by body movement and movement by the heart itself.

A pacing lead performs two functions:

  1. It carries a tiny electrical pulse from the pacemaker to the heart.
  2. It relays information about the heart's electrical activity back to the device.

The four parts of a pacing lead are:

  1. Connector Pin. The portion of the lead that is inserted into the connector block on the pacemaker.
  2. Lead Body. An insulated metal wire that carries electrical energy from the pacemaker to the heart.
  3. Fixation Mechanism. The small mechanism near the tip of the lead that holds the lead to the heart muscle.
  4. Electrode. At least one electrode is located at the tip of the lead. The electrode delivers the electrical energy from the pacemaker to the heart tissue. The electrode may also relay information about the heart's electrical activity back to the pacemaker.

Where a lead is placed: inside or outside of the heart.  For most adults, a lead is usually inserted through a vein and guided into the right ventricle or the right atrium of the heart. This is called an endocardial lead ("endo" means "inside", "cardia" means "heart") or a transvenous lead (because it is inserted through a vein).

Sometimes the lead is attached to the outside of the heart. This is called an epicardial lead ("epi" means outside). An epicardial lead is often used for children because their bodies will grow. An epicardial lead is also used when another surgery is being done and the outside of the heart is easy to reach.

Medication where lead touches the heart tissue. Regardless of whether a lead is placed on the inside or outside of the heart, the location where the lead touches the heart naturally produces an inflammatory response. This response is similar to what is observed when you've scraped your skin: the area around the scrape is red and may result in a scar as your body repairs itself. When a lead is placed in your heart, a similar response occurs. By placing a medication at the tip of the lead reduce this inflammation.

The special medication placed at the tip is called a steroid. This very tiny amount of steroid (less than 1 mg) is located just at the tip of the electrode. When the lead is placed in (or on) the heart, the medication is released and the build-up of scar tissue between the electrode and the heart tissue is minimized. Reducing the amount of scar tissue helps the pacing system work more efficiently.

Part 3: Programmer

A programmer is a specialized computer used to monitor and adjust pacemakers.

During a follow-up visit, or during a hospital stay, a doctor or nurse may place the magnetic wand (or programming head) of the programmer over the pacemaker. This allows the programmer to:

  • receive information from your pacemaker. The information received from the pacemaker shows how your pacemaker and your heart have been working. Based on this information, the doctor or nurse may want to change the therapy.

  • send instructions to your pacemaker. When the therapy needs to change, the nurse or doctor can send the new instructions to the pacemaker – without any surgery.

A programmer is one part of a pacing system which helps your heart condition. The system is a combination of a programmer, a pacemaker, and one or more leads working together.

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