How Does a Normal Heart Beat?

The heart is a hollow muscular organ – approximately the size of your clenched fist – that beats 40 million times per year (between 60 and 100 beats per minute).  The heart’s pumping action is controlled by its electrical system, which gives rise to the heart rhythm.

Normal cardiac rhythm results from electrical impulses that begin in a special group of cells that form the sinoatrial (SA) node, also called the sinus node. Located in the right upper chamber of the heart, sinus node cells act as the heart's natural pacemaker.  Impulses spread from the sinus node to the right and left atria (the upper chambers of the heart), causing them to contract at the same time. The impulses then travel to the AV (atrioventricular) node, the region that manages impulse traffic from the atria to the ventricles (the lower chambers of the heart). Here, impulses are slowed slightly to give the atria time to contract before the signal reaches the ventricles.

From the AV node, the impulses travel through a system of specialized heart tissue.  Located in the wall that separates the two ventricles, this conducting system splits to form the right and left bundle branches that travel to the respective ventricles.  Via this conducting pathway, powerful electrical "jump-start" signals are delivered to the ventricular muscle of the heart. In the healthy heart, these impulses travel at the same speed so that the two ventricles contract at the same time, and oxygen-rich blood from the lungs is pumped throughout the body.

What are arrhythmias?

An abnormal heart rhythm occurs when there is a change in the speed or pattern of electrical impulses within the heart. Arrhythmias can cause the heart to beat too slowly or too rapidly, thereby interfering with the heart’s ability to pump blood effectively. Some symptoms of arrhythmias include, but are not limited to:

• weakness
• fatigue
• palpitations
• low blood pressure
• dizziness
• fainting

The symptoms of arrhythmias may resemble other medical conditions. Consult your physician for a diagnosis.

What is a pacemaker?

A permanent pacemaker is a small device that prevents the heart from beating too slowly. A pacemaker is implanted under the skin (most often in the shoulder area just under the collarbone) and sends electrical signals to start or regulate a slow heartbeat. A permanent pacemaker may be used to regulate the heartbeat if the heart's natural pacemaker (the SA node) is not functioning properly or if the electrical pathways are blocked.

A permanent pacemaker has two components:

• a pulse generator which has a sealed battery and an electronic circuitry package. The pulse generator produces the electrical signals that make the heart beat. Modern pulse generators also have the capability to receive and respond to signals that are sent by the heart itself.
• one or more wires (also called leads). Leads are insulated flexible wires that conduct electrical signals to the heart from the pulse generator. At one end of the lead is a tiny electrode that delivers electrical impulses to the heart. The leads may also relay signals from the heart to the pulse generator. One end of the lead is attached to the pulse generator and the electrode end of the lead is positioned in the atrium (the upper chamber of the heart) or in the ventricle (the lower chamber of the heart).

Pacemaker leads may be positioned in the atrium or ventricle or both, depending on the condition requiring the pacemaker to be inserted.

How is a pacemaker implanted?

Pacemakers are usually inserted in a special procedure room. The patient is awake during the procedure, although sedation may be given to help the patient relax during the procedure. A small incision is made just below the collarbone. The pacemaker lead(s) is inserted into the heart through a blood vessel that runs under the collarbone. Once the lead is in place, it is tested to make sure it is in the right place and is functional. The lead is then attached to the generator, which is placed just under the skin through the incision made earlier. Once the procedure has been completed, the patient goes through a recovery period of several hours and often is observed in the hospital overnight.

What should I know about living with a pacemaker?

With advances in technology, artificial pacemakers today generally last seven to ten years (depending upon the type of heart condition) and, in most cases, allow a person to lead a normal life. In addition, advances in pacemaker circuitry have reduced the interference risk from certain machinery, such as microwaves, which in the past may have altered or otherwise affected the pacemaker. Even so, certain precautions must be taken into consideration when a person has an artificial pacemaker. The following precautions should always be considered and discussed in detail with your physician:

• Keep cell phones away from direct contact with the pacemaker. Use and wear cell phones on the side of the body opposite to where the pacemaker is implanted.
• Use caution when going through airport security detectors. Check with your physician about the safety of going through such detectors with your particular pacemaker.
• Avoid magnetic resonance imaging (MRI) machines or other large magnetic fields.
• Abstain from diathermy (the use of heat in physical therapy to treat muscles).
• Turn off large motors, such as cars or boats, when working on them (they may temporarily "confuse" your pacemaker's rate).
• Avoid certain high-voltage or radar machinery, such as electric arc welders, high-tension wires, radar installations, or smelting furnaces. Avoid direct contact with radio or television transmitters.
• If you are having a surgical procedure performed by a surgeon or dentist, tell your surgeon or dentist that you have a pacemaker, so that electrocautery will not be used to control bleeding (the electrocautery device can change the pacemaker settings).

• Always carry an ID card that states you are wearing a pacemaker.
• Always consult your physician if you have any questions concerning the use of certain equipment near your pacemaker.

Once the pacemaker has been implanted, people with pacemakers should be able to participate in the same activities as everyone else in their age group. When you have a pacemaker, after consulting with your physician, you may still be able do the following:

• exercise moderately, upon advice from your physician
• drive your car or travel
• return to work
• work in the yard or house
• participate in sports and other recreational activities
• take showers and baths
• continue sexual relationships

When involved in a physical, recreational, or sporting activity, a person with a pacemaker should avoid receiving a blow to the skin over the pacemaker. A blow to the chest near the pacemaker can affect its functioning. If you do receive a blow to that area, see your physician.

How can I ensure that my pacemaker is working properly?

Although your pacemaker is built to last many years, always check your pacemaker regularly to ensure that it is working properly. The proper method for checking the accuracy of your pacemaker includes the following:

• Have your pacemaker checked in your doctor's office according to the schedule recommended by your physician. In addition, you may participate in a telephonic check up for your pacemaker on a periodic basis. Your physician will provide special instructions.
• See your physician regularly for check-ups.
• Report any unusual symptoms or symptoms similar to those you had prior to the pacemaker insertion to your physician.

Frequently Asked Questions About Pacemakers

May I use a cell phone?
Yes. It is recommended that you do not leave the cell phone turned on while in a breast pocket over the pacemaker. As long as you follow these instructions, and use the phone on the ear opposite the pacemaker, there should be no interference.

Do pacemakers need to be adjusted periodically?
Some pacemakers may need to be adjusted if a person's medical condition or lifestyle changes. Your physician will instruct you about the schedule of follow-up visits you should keep based on your condition and type of device. In addition, you may participate in telephonic assessment of your device on a periodic basis.

When do I have to replace my pacemaker?
Most pacemakers will last between 7 and 10 years, after which the entire pacemaker needs to be replaced. Replacing a pacemaker is usually done on an outpatient basis. An incision is made over the existing pacemaker, the unit is removed, and a new pacemaker is attached to the wires ("leads").

When replacing a pacemaker, are the leads also replaced?
Leads are the wires that carry the electrical charges to areas of the heart. If the original leads are functioning properly, in most cases, they can be left in place and reattached to the new pacemaker.

Can I travel with my pacemaker?
Yes, you can travel with your pacemaker and drive a car unless otherwise directed by your physician. You should be sure to always have your pacemaker identification card with you wherever you go.

Can I exercise with a pacemaker?
Upon consulting your physician, you may be able to enjoy moderate exercise with your pacemaker, including housework and yard work.

Will I feel the pacemaker?
At first, you may feel the weight of the pacemaker in your chest. However, over time, most people become accustomed to the pacemaker. The generator is very small, about the size of two silver dollars.

May I have an MRI scan if I have an implanted pacemaker?
In the past, patients with pacemakers were advised not to have an MRI scan. If your physician recommends an MRI, you should discuss it with the implanting physician since new protocols are being developed to allow pacemaker patients to have MRIs.