Pacemakers may seem like futuristic bionic devices, but they've actually been around for decades. While millions of people have pacemakers, they aren't commonly discussed like other ailments. In fact, there are lots of misunderstandings about what pacemakers really do, how they work, and who might need them.

People get pacemakers to correct a problem with the heart known as a cardiac arrhythmia. In layman's terms, it means the heart's natural rhythm is getting out-of-whack.

To some extent, everyone suffers from a bit of arrhythmic behavior at one time or another, but for a person to get a pacemaker, the arrhythmia is something that is persistent and severe enough to impact lifestyle. Symptoms that may mean you need a pacemaker include fatigue, dizziness, lightheadedness, even fainting, as well as inability to exercise without getting overly out of breath.

These are pretty vague symptoms and a person could easily have all of those conditions and not need a pacemaker. But let's talk about what's really going on.

The healthy heart beats in a specific rhythm that coordinates the heart's upper chambers (atria) and lower chambers (ventricles) in such a way that the heart beat is quite efficient at moving a very large quantity of blood throughout the body. This blood is called cardiac output. If cardiac output drops to zero, the person dies in a matter of minutes.

But in many cases, the electrical system of the heart (not the pumping ability) starts to falter. This is an electrical problem of the heart—not the heart's inability to pump out blood efficiently. Yet many people do not even realize the heart as an electrical system.

Electrical impulses produced by the heart guide the heart's rhythm. If the heart stops producing electricity in a regular manner or the electricity no longer travels properly through the heart muscle, the result can be an arrhythmia.

There are two main types of arrhythmia that can lead to a person's getting a pacemaker. The first is called "sinus node dysfunction," which sounds very complicated. It really means that the heart no longer produces electrical energy at the right rate.

The heart has the amazing ability to produce electricity. This is accomplished by a small area of tissue called the sinoatrial node (nicknamed "sinus node" or just "sinus") in the upper right hand side of the heart. If the sinus node gets sluggish or produces electricity erratically or produces electricity fine at low rates but can't keep up when you exercise and need a faster heart rate ... that is sinus node dysfunction.

About half of all people with pacemakers have this condition. The resulting arrhythmia for a person with sinus node dysfunction is a heart rate that is too slow to support normal activity. The medical term for this is "sinus bradycardia." Because you don't get enough cardiac output to do normal things, you can find yourself getting winded, tired, dizzy, or even passing out doing things you used to do.

The other type of arrhythmia has a simpler name but it's a bit misleading. It's called "heart block." Heart block isn't really a blockage at all. Instead, it means that the electrical impulses produced by the heart no longer travel efficiently through the heart muscle. The electrical energy gets delayed or even blocked in some areas.

In the healthy heart, the electrical energy that causes the heart to beat starts in the sinoatrial node (top, right side of the heart). It then travels out over the atria and then downward. As it makes its ways to the ventricles, it passes through a junction called the "atrioventricular node" or AV node.

Once the electrical energy goes through the AV node, it travels to the ventricle and causes the ventricles to contract and pump blood. Heart block occurs when there is a problem at the AV node. Sometimes the electrical energy gets delayed in such a way that the atria and ventricles are no longer working together.

In extreme forms of heart block, the energy from the top half of the heart cannot make its way down to the bottom half at all (this is called "complete heart block"). Because the atria and ventricles do not work in harmony, cardiac output is impaired. The result is the same slew of symptoms: lightheadedness, dizziness, shortness of breath, feeling tired all of the time, and even fainting.

About half of all people who need pacemakers have some form of heart block (it can be mild to severe).

Arrhythmias can get fairly complicated. For example, one person might have both types of these arrhythmias that require a pacemaker, that is, one person can have sinus node dysfunction and heart block at the same time. Even people who only have one type of problem today are at risk of developing the other.

Pacemakers accomplish this by "filling in the missing beats."

Pacemakers are small electrical devices implanted in the chest. They deliver electrical energy to the heart at precisely the right moment to keep it beating in a way that is as "normal" as possible. In many patients, pacemakers restore normal heart rhythm. In some patients, the arrhythmia may be too severe for a normal heart rhythm to be restored, but the pacemaker can at least come close.

Pacemakers "know" when to deliver electrical energy to the heart because they monitor every beat of the heart and respond according to how the physician programs them. This is a useful feature since many pacemaker patients do not require constant pacing. In fact, for many people, arrhythmias are not permanent at all, but come and go, sometimes for brief periods. The pacemaker monitors the heart's activity and jumps in with stimulating (pacing) energy when an arrhythmia occurs.

There is, at the moment, no cure for arrhythmias in the sense that an erratic heart rhythm cannot be restored with an operation or a pill. True, operations, pills, and other remedies can help manage symptoms or even correct part of the problem.

Pacemakers are actually very safe ways of dealing with specific arrhythmias. Although they're implanted in the body, they do not deliver drugs or other chemicals into the body. They use electricity, which is the very substance the body would generate itself, if it could.

Doctors have a lot of flexibility in terms of how the pacemaker is programmed, so they are suitable for a wide range of people, from athletes to newborns to bedridden seniors.

And pacemakers have a memory so that they can report back to the doctor what's been going on in the patient's heart. Not all arrhythmias can be treated with a pacemaker. But for rhythm disorders like heart block or sinus bradycardias, pacemakers are a safe, effective, and well proven technology that can make a big difference in the lives of those that need them.