Today advances in modern medicine have brought us many different technologies that can not only help extend the life expectancy of patients but also allow them to live a relatively normal life with a disease that a few decades prior would have been a death sentence. This ranges from new procedures to new medical devices. The pacemaker is a perfect example of one of these medical devices. They can be used to treat a variety of different heart conditions such as bradycardia, atrial fibrillation, or cardiac arrest that would have previously been either a death sentence or severely affected quality of life and life expectancy. There are a few different types of pacemakers used in the medical field: single-lead pacemakers, double-lead pacemakers, and leadless pacemakers. While these pacemakers do have some key differences they all function in a similar way. Pacemakers work by sending electrical pulses to the heart in order to correct the heartbeat if it is too slow or too fast, or to even restart the heart if it stops beating.

To understand how pacemakers work and why they use electrical signals to fix arrhythmias or restart the heart we need to understand how the heart is regulated and specifically how the heartbeat is regulated. The heart is regulated by two major systems the endocrine and nervous systems. The endocrine system releases hormones such as epinephrine and norepinephrine from the adrenal gland which speed up your heart rate. While the sympathetic cardiac nerves can force contractions and increase the heart rate. The parasympathetic nervous system can stimulate the release of acetylcholine which slows down your heart rate. Without stimulation from the nervous system, the heart would beat at a constant rate without adjusting to the changing conditions of the body. The heart is regulated by the conduction system of the heart which makes an electrical pulse that travels throughout the heart triggering a contraction. The electrical pulse starts at the sinoatrial or SA node which is located in the right atrium close to the opening for the superior vena cava. The SA node initiates the electrical impulse which spreads through the atria causing them to become depolarized and triggering them to contract. As the impulse from the SA node travels through and down the atria it reaches the atrioventricular or AV node as the septum makes it so that the impulse has to spread through the AV node in order to reach the ventricles. Upon reaching the AV node it takes 100 milliseconds for the impulse to travel through the node; this pause gives the atria time to contract and pump blood into the ventricles. After this, the impulse travels down the atrioventricular bundle which is connected to the AV node. The atrioventricular bundle travels down the septum and then splits into two branches the left and the right branch. The left branch is larger than the right since the left ventricle is larger than the right one. The right branch also extends to the moderator band. At the apex of the heart the atrioventricular bundle branches both connect to conductor fibers called Purkinje fibers. These help spread the impulse throughout the heart. After the ventricles relax this process starts all over again at the SA node. 

This is why pacemakers use electricity to reset the heart. They utilize the heart’s built-in electrical wiring to help correct a person’s heartbeat. While the pathway that regulates our heartbeat is complex, the components of a pacemaker are relatively simple since they have a pulse generator, wires or leads, and electrodes. The exception to this is a leadless pacemaker which as its name suggests doesn’t have leads. Leadless pacemakers are put inside the heart so they don’t need leads. The pulse generator as one would expect generates the electrical impulse that travels down the leads which connect the pulse generator to the heart. While the electrodes sense the heart’s natural heartbeat and deliver the impulse to your heart when they detect that your heartbeat is off.

My artwork is called “Battery Operated”. It’s a drawing of a heart that shows the general placement of a double-lead pacemaker. I am thankful that we have made so many advances in medicine, especially since my grandpa has a pacemaker, and without it, he would have died shortly after I was born. Advancements like the pacemaker are truly amazing, helping to improve the quality of life of people with lifelong diseases and conditions, in addition to increasing their life expectancy. 

References

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Tang, N., Chen, X., Zhang, D., & Li, H. (2024). Implantable cardiac monitor and leadless pacemaker in the management of syncope due to intermittent high-degree atrioventricular block: a case report. Journal of Cardiothoracic Surgery, 19(1). https://doi.org/10.1186/s13019-024-02962-x