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How the heart works: a detailed overview

How the Heart Works Diagram Diagram showing the heart and how it works.

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The human heart—about the size of one’s fist—provides oxygen and nutrient-rich blood throughout the body to sustain life. This powerhouse organ beats 100,000 times a day, pumping five or six quarts of blood each minute, or about 2,000 gallons per day. 

“In simplistic terms, the heart is a mechanical pump,” said Army Lt. Col. (Dr.) Eugene Soh, an  interventional cardiologist and assistant chief of cardiology at the Walter Reed National Military Medical Center in Bethesda, Maryland. “I equate it’s structure to be similar to that of a house; there are four ‘rooms’, and each chamber is separated from the other by a ‘door’—the doors are the four main valves of the heart. It has an electrical system and a ‘plumbing system’. The electrical system tells the heart when and how fast or slow to beat. It reacts to external stimuli, such as exercise or stress—which can cause one’s heartbeat to increase-- and will slow down when one is resting. The ‘plumbing system’ of the heart are the coronary arteries. They provide the blood supply to the heart.” 

The four chambers mentioned by Soh, are the two atria and two ventricles. The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle. The right ventricle pumps the oxygen-poor blood to the lungs. The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle. 

When it comes to heart disease, Soh talked about how the cause can be due to a number of factors. “You can have valvular disease, which can make the valves of the heart leak too much, or become too narrow, you can have electrical problems which can be due to a heart rate that’s too slow—and requires the use of a pacemaker—or having fast arrhythmias develop, which can be fatal in some cases. And then you have coronary disease, which is the most common form or heart disease. Heart disease is the number one killer of all Americans, more than all cancers combined.” 

With coronary heart disease, a waxy substance called plaque builds up inside the coronary arteries. When this plaque builds up in the arteries, the condition is called atherosclerosis. Over time, plaque can harden or break open. Hardened plaque narrows the coronary arteries and reduces the flow of oxygen-rich blood to the heart, which can cause a heart attack. 

“The most common symptom of a heart attack is when someone is experiencing chest pain or discomfort,” said Soh. “In many cases, someone who is experiencing a heart attack may not be feeling a crushing pain. In fact, I’ve treated many patients in emergency rooms who have delayed coming in because they didn’t feel an ‘elephant on their chest’. So sometimes the symptoms can be subtle, like having shortness of breath or  nausea.”  Other associated symptoms may include breaking out into a sweat or having the pain radiate to the jaw, neck, or arm. 

Soh also went on to say that when it comes to providing first aid to someone who is experiencing a heart attack, the first thing you should do is call 9-1-1. “That is absolutely the first measure we should all take,” he said. “Not all heart attacks are immediately life-threatening, but they need to get to a monitored setting as quickly as possible. And certainly, don’t drive yourself [to the hospital] unless there are no other options.  An ambulance is definitely the best option.” 

To help prevent heart disease or heart attacks, Soh urges everyone to become engaged in some form of daily exercise. “The power of exercise is truly amazing,” said Soh. “Exercise has been shown to reduce the risk of heart disease and heart attacks. Eating healthy is also important.  I cannot stress enough how beneficial staying fit can be to one’s long-term health.”

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