August 20, 2018
A Look At Arrhythmia
By Michael D. Shaw
An arrhythmia is a variation from the normal rate or regularity of the heartbeat, usually resulting from problems within the electrical conduction system of the heart. For a better understanding, I offer some background.
The heart has four chambers: Two atria (the upper chambers) and two ventricles (the lower chambers). The heartbeat is controlled by electrical impulses, which travel across the heart, making it contract. The atria contract first, sending blood into the ventricles. Then, the ventricles contract, sending blood to the lungs and around the body.
The atria and ventricles are described as being “left” or “right” from the point of view of the patient. Thus, all diagrams of the heart depict these right and left chambers on the opposite sides, from the point of view of the observer.
Functionally, the right side of the heart collects blood from the body and pumps it to the lungs while the left side of the heart receives blood from the lungs and pumps it to the body.
1. Oxygen-rich blood from the lungs enters the left atrium through the pulmonary veins.
2. Blood then flows into the left ventricle where it is pumped into the aorta and is distributed to the rest of the body.
3. Returning blood enters the right atrium, via the vena cava. It is depleted of oxygen and carries waste product carbon dioxide. This blood is pumped to the right ventricle.
4. From the right ventricle, the blood travels through the pulmonary artery to the lungs. Carbon dioxide is removed, oxygen is replaced, and the cycle continues, back to the left atrium.
Normal heart rate for adults ranges between 60 and 100 beats per minute, with variations for exercise and rest. In children, this range can vary, but “normal” also means that the heart is beating in a predictable and constant normal sinus rhythm. “Sinus” refers to the sinus node aka sinoatrial node aka S-A node—a small mass of tissue embedded into the right atrium that originates the impulses stimulating the heartbeat. Thus, the S-A node is the heart’s natural pacemaker. Tachycardia refers to a heart rate greater than 100 beats per minute. Bradycardia refers to a heart rate less than 60 beats per minute.
While occasional rhythm irregularities are normal, and some might be asymptomatic, others can cause worrying and even life-threatening symptoms. In asymptomatic cases, your doctor may discover that something’s up by listening to your heartbeat. Then, an electrocardiogram is taken to determine the specifics of your condition.
Mayo Clinic lists some noticeable symptoms of arrhythmia…
- A fluttering in your chest
- A racing or slow heartbeat
- Chest pain
- Shortness of breath
- Lightheadedness or dizziness
- Fainting or near fainting
The Texas Heart Institute describes several types of arrhythmias, going well the beyond the scope of this article. But, some common ones are worthy of inclusion here.
Atrial fibrillation is the most common type of serious arrhythmia, and is termed a “growing epidemic.” It involves a very fast and irregular contraction of the atria. A-fib usually isn’t life-threatening, but it can be dangerous if it causes the ventricles to beat too rapidly. 15-20% of strokes happen in people with atrial fibrillation.
Ventricular fibrillation occurs if disorganized electrical signals make the ventricles quiver instead of pumping normally. Without the ventricles pumping blood to the body, sudden cardiac arrest and death can occur within a few minutes. This arrhythmia is what those Automated External Defibrillators are primarily intended for.
Premature ventricular contractions may be discerned as a “skipped heartbeat,” or not even be felt at all. Generally, they are harmless and reflect the ventricle contracting a bit too soon. These are among the most common arrhythmias. They can be related to stress or too much caffeine or nicotine. But sometimes, PVCs can be caused by heart disease or electrolyte imbalance.
The good news about arrhythmias is that nearly all of them can be treated. As with any health condition, if you notice something wrong, get it looked at promptly. Be Heart Smart.