SciTech

How Things Work: Pacemakers

“Lub-dub, lub-dub” is the sound of the heart pumping five liters of blood throughout the body every minute. Many people take it for granted that their hearts beat well and properly, allowing them to live their daily lives without fatigue. There are many people, however, whose hearts do not beat on track. Luckily, today’s technology can correct for this and allow any person with an irregular heartbeat to live a healthy life.

A person’s irregular heartbeat can be corrected by a pacemaker, an electrical device surgically inserted in the heart. How can a man-made device possibly work with a human heart to correct for irregularities?

The heartbeat is caused by electrical impulses generated by the heart. The impulse triggers the heart muscle to contract in a coordinated manner. If the electrical signal is not signaled properly, cardiac arrhythmias occur. These are irregularities in the force or rhythm of the heartbeat. A normal heart beats 60 times per minute on average. Irregular heart beats, however, can either be too fast or too slow. Bradycardia is the condition of a slower heart rate and tachycardia is the condition of a faster heart rate.

In order to correct for these irregularities, an electrical device known as a pacemaker can be inserted in the heart. The electrical signals that are sent down the cardiac muscle cause the heart to contract and beat. A pacemaker is a tool that analyzes the heart’s own electrical system and, when necessary, sends electrical signals to the heart to correct for abnormalities. It can be thought of as a supplemental checking system for the heart. If the heart is not being electrically stimulated in the right way, the pacemaker steps in and corrects it. Most pacemakers are designed to correct bradycardias.

How exactly does an electrical device fix an irregular heartbeat? Pacemakers are made up of two major parts: the generator and the lead. The generator is a tiny computer, a battery, and a lithium container. The battery’s lifetime is six or seven years, and the generator is the size of a half-dollar coin. The lead is a flexible electrical wire. One end is attached to the generator and the other end travels inside a vein into the heart. A lead attaches to the heart to detect its electrical activity. The lead then sends that information to the generator, which determines, by analyzing the input information, whether an electrical impulse must be produced to correct for an irregular heartbeat.

If the heart rate is too slow, a tiny electrical signal is transmitted that stimulates the heart muscle to contract. Pacemakers also maintain coordination between the atria and the ventricles, the upper and lower compartments of the heart.

Without a pacemaker, a person whose heart beats irregularly will experience weakness, fatigue, dizziness, loss of consciousness, and even death in some cases.

The implantation of a pacemaker into a patient is considered a minor surgery. Complications may occur, as with all surgeries. These include bleeding and infection. In the case of severe bleeding, a blood transfusion can take place, while infection can be treated quickly and effectively with antibiotics.

After being surgically inserted into the body, pacemakers must be checked once or twice each year in order to ensure it is normally functioning. Long after implantation, a person can experience generator failure or lead failure. Both conditions are rare, but can occur because of manufacturer error.

Equipment and instruments that generate powerful magnetic fields, such as medical devices and industrial motors, can interfere with the performance of pacemakers. MRI scans and radiation therapy are extremely unfavorable for people with pacemakers; therefore, it is important to have the pacemaker shielded from the radiation.

Pacemakers are but one example of recent technological advancements that have allowed many people an improved quality of life.