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What is Heart Failure? A One-Minute Explainer

February 1, 2021

Watch this 1-minute video to see an illustrated explanation of how heart failure happens.
Poster for video

“People—not only physicians, but poets and writers—obsess about the heart in different ways,” says Tariq Ahmad, MD, MPH, an advanced heart failure and transplant cardiologist at Yale Medicine. “There are so many dimensions to the heart that are absolutely fascinating.”    

So, how does the heart actually work?

The heart has four chambers. The two on the top are called the atria—the right atrium and the left atrium. The bottom two chambers of the heart are called ventricles—the right ventricle and the left ventricle, says Dr. Ahmad.  

Basically, the heart is a muscle whose main job is to pump blood. “There is a right side of the heart, so the right atrium and right ventricle, which receives blood from the entire body. So, when blood from your legs and belly and brain come to the right side of the heart, it goes into the right atrium, then on to the right ventricle, which pumps that blood to the lungs,” says Dr. Ahmad.  

The lungs then infuse the blood with oxygen. The oxygenated blood is sent to the left side of the heart, entering through the left atrium. From there, it enters the left ventricle, which, says Dr. Ahmad, is the “most muscular chamber of the heart.” It then ejects the blood to the rest of the body.  

“That ejection has a lot of energy in it and that's what you feel when you put your finger on your pulse or on your hand to feel for your pulse,” he says. “When the heart is functioning normally, it can eject six or seven liters of blood in a minute.” But the strength and volume of the ejection can be weakened if certain condition cause the heart to fail.  

What causes heart failure?

The most common cause of heart failure is heart attack, or myocardial infarction. “The blood supply to the heart stops by most likely what is called atherosclerosis, or fatty plaque buildup, inside the blood vessel that supplies the heart with blood. And this can burst like a pimple, blocking off the blood vessels that supply the heart itself,” Dr. Ahmad says.  

The heart is one of the few organs in the body that cannot survive without a blood supply for even a few minutes. And unless the blocked blood vessel is opened up immediately, that muscle will die. And the rest of the remaining muscle then has to work extra hard to keep up with what's been lost. And over time, Dr. Ahmad says, it just can't keep up. And that's when heart failure develops.  

Other causes for heart failure include a virus (called myocarditis), genetics, and chemotherapy for cancer treatment. Other diseases, too, can lead to heart failure. “It’s the final common pathway when the body just gives out from illness,” says Dr. Ahmad. 

Watch this short video to see an illustrated explanation of how heart failure happens.

Yale Medicine's Advanced Heart Failure Program is a rapidly expanding service at the front lines of treating heart failure. Launched in 1988, the program builds upon decades of experience treating failing hearts.

Other resources on heart failure