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What are arrhythmias?

If you’ve ever watched a medical drama like Grey’s Anatomy or ER, you’ve probably heard of cardia arrhythmias, but just don’t know what they are. You’ve probably heard the doctors and nurses in the show use terms like tachycardia, fibrillation, a-fib, v-fib, and more. But, have you ever wondered what these terms actually mean?

A cardiac arrhythmia is an irregular heartbeat, which is caused when the electric signals that tell the heart how to beat don’t work properly. While arrhythmias can be harmless, the can also be life-threatening, because it can cause your heart to beat too fast, too slow, or in a pattern that is irregular. Arrhythmias are usually classified into two (or sometimes three) categories: Tachycardia, which is when the heart beats too fast; fibrillation, which is when the heart beats irregularly (this can sometimes be classified under tachycardia); and bradycardia, which is when the heart beats too slow.

Different types of cardiac arrhythmias

Bradycardia

Bradycardia is a type of cardiac arrhythmia during which the heart beats too slow, which is considered below 60 beats per minute (bpm). A lot of the time, bradycardia is harmless. The more a person exercises, the slower their heart rate is, so when a person is very fit their heart rate naturally drops. However, when someone’s heart rate is below 60 bpm and their body is unable to pump enough blood to reach all parts of the body fast enough, they may have bradycardia, which can be dangerous.

Sick Sinus Syndrome

Sick Sinus Syndrome is a type of bradycardia that is cause when the sinus node is damaged. The sinus node is responsible for controlling the pace of the heart, and when it is damaged, the heart rate can be irregular and slow. Sick Sinus Syndrome is most common in older adults.

Conduction Block

A conduction block is something else that can trigger bradycardia. A conduction block is a block of the heart’s electrical pathways, which can slow or skip heartbeats, causing bradycardia. The heart is told to beat through electrical pathways, so when these pathways are damaged, the heart may not get those signals.

Tachycardia and Fibrillation

Tachycardia and fibrillation are similar types of arrhythmias, and fibrillation can also fall under the category of tachycardia. Tachycardia is when the heart beats excessively fast, or over 100 bpm and fibrillation is when the heart twitches or quivers irregularly and ineffectively. Similar to how all squares are rectangles but not all rectangles are squares, fibrillation is a form of tachycardia, but tachycardia is not always fibrillation. If the heart rhythm isn’t reset soon, tachycardia can lead to heart failure or stroke.

Types of Fibrillation

Fibrillation is a quivering or twitching of the heart that ineffectively pumps blood to the body. There are two main types of fibrillation: ventricular fibrillation (V-Fib) and atrial fibrillation (A-Fib), which take place in either the ventricles or atria of the heart, respectively.

Atrial Fibrillation vs. Ventricular Fibrillation

Atrial fibrillation is the more common of the two, and also the one that isn’t as dangerous. Atrial fibrillation is characterized by shortness of breath, chest pain, and fatigue, and though not immediately life-threatening, if not treated can lead to a stroke. A-fib affects the atria (upper chambers) of the heart, and cause them to beat irregularly. To help grasp just how fibrillation can affect the body, here’s a brief overview of how blood flows through the heart:

1. Oxygen-low blood flows into the right atrium through the superior vena cava and inferior vena cava, which are two large veins¹ in your body.
2. The blood travels through the tricuspid valve² from the right atrium down to the right ventricle
3. From there, blood travels through the pulmonary valve through the pulmonary artery³ to the lungs
4. In the lungs, blood releases carbon dioxide and gains oxygen
5. Oxygen-rich blood flows back to the heart through the pulmonary veins to the left atrium
6. Blood gets pumped through the mitral valve to the left ventricle
7. The left ventricle pumps the blood through the aortic valve to the aorta, the main artery
8. The aorta then distributes blood to the rest of the body

Now that we know how the blood flows through the heart, we can grasp a better understanding of how a-fib and v-fib affects the body. Ventricular fibrillation affects the ventricles (lower chambers) of the heart, and is extremely dangerous and life-threatening. While a-fib is usually treated with drugs, v-fib requires a defibrillator⁴ to shock the heart and reset it. The right ventricle is the chamber of the heart responsible for pumping blood to the lungs to get oxygenated, and the left ventricle is responsible for pumping blood to the body. The atria, however, are responsible for pumping blood to the ventricles. Because of this, during atrial fibrillation the heart may pump blood irregularly, but it still pumps blood. This is why a-fib is usually considered to be less dangerous than v-fib, because when ventricular fibrillation occurs the heart stops pumping blood completely.

Other types of Tachycardia

1. Atrial Flutter: More organized, rapid atrial beats
2. Sinus Tachycardia: The heart’s natural pacemaker (the sinus node) fires rapidly, often due to caffeine, stress, fever, or dehydration
3. Atrioventricular Reentrant Tachycardia (AVRT): A rapid heart rhythm that is caused by an electrical short circuit between the atria and ventricles

In conclusion, a cardiac arrhythmia is an irregular heartbeat. While some arrhythmias, like bradycardia, are usually harmless, many, like ventricular tachycardia, can be life-threatening. Understanding different types of arrhythmias allows one to realize when a symptom they are experiencing isn’t right, and having a better understanding of what to do and what it is can make the difference between dying and surviving.

Footnotes:

1. Blood vessels that carry blood to your heart. They lie closer to the surface of your skin, and carry de-oxegenated blood that is usually duller in color. When people get minor injuries, blood that comes out of the body is from the veins. ↩︎
2. Flaps of tissue that act as passageways between the chambers of the heart. The four heart valves are the tricuspid valve (connects the right atrium and right ventricle), the pulmonary valve (connects the right ventricle and the pulmonary artery), and the mitral valve (connects the left atrium and left ventricle), and the aortic valve (connects the left ventricle and the aorta). ↩︎
3. Blood vessels that carry blood away from your heart. They lie farther below the skin, and carry oxygen rich blood which is bright red in color. If these veins burst or get cut, it can be life-threatening. ↩︎
4. A machine used to reset a dangerously erratic and irregular heart rhythm by delivering an electric shock, which essentially “jump starts” the heart. ↩︎