Basic Cardiology: How the Heart Works

95% – perhaps more – of Heart Moms and Dads have no medical training. You probably have a normal, non medical job, and never really thought about the heart until that fateful day when a doctor sat you down and said “We think there could be a problem with your child’s heart…”

If you want to try to stay one step ahead of a Congenital Heart Defect, you’d better learn all you can about a complex organ in a very short time. It can difficult, especially when you are under pressure – how many times have Heart Parents asked their doctor to hold on just a moment and explain what he’s saying? You’d be surprised at how much heart parents without medical backgrounds know about the human heart, but when you are trying to learn so much as rapidly as possible, you get swamped. It can feel as if you are trying to trying to drink from a fire hose.

So let’s slow down, and take a walk through a healthy human heart. First, here’s a nice diagram we can follow. If you have an engineering background, or a chart just makes more sense, you might want to look at this schematic. (You can click this chart and make it bigger!)

The heart is not a pump. It’s actually two pumps fused together – The right side pumps blood to the lungs and back; the left side of the heart pumps blood through the body. Blood that has already made the trip through the body flows through the Superior Vena Cava and the Inferior Vena Cava into the Right Atrium. This blood has little oxygen. The Atrium contracts, squeezing the blood through the Tricuspid Valve into the Right Ventricle. When the Right Ventricle contracts, the blood is squeezed through the Pulmonary Valve into the Pulmonary Artery, and then to the lungs.

There are two large blood vessels on top of the heart. The Aorta rises out of the Left Ventricle, loops downward and carries blood to the lower half of the body, which makes it look like an upside down U. The Pulmonary Artery splits just after it leaves the heart, taking blood to the right and left lung. This makes it look like a T, and it is tucked neatly into the arch created by the Aorta.

The Pulmonary Artery is also misnamed. Every artery in the body carries blood with a high oxygen content… except the Pulmonary Artery. Yes, it sounds strange, but it matches an older definition of arteries and veins: Arteries move blood away from the heart, veins move blood towards the heart.

In the lungs carbon dioxide is exchanged for oxygen and the blood returns to the heart, arriving in the Left Atrium. The left Atrium contracts, and blood flows through the Mitral Valve into the Left Ventricle. When the Left Ventricle contracts, blood flows through the Aortic Valve into the Aorta, and out into the body.

You’ll notice that while the Right Ventricle is larger, its heart wall is not as thick. The Right Ventricle is not a very strong pump, but that’s ok… all it has to do is move the blood to the lungs and back. The Left Ventricle is just a little smaller but the heart wall is thicker. It’s the heart’s main muscle, delivering a powerful squeeze to send blood throughout the entire body. This is one of the main reasons why right-side heart defects (like Tricuspid Atresia) have been survivable for some time while left-side defects are much more difficult. As I’ve mentioned before, Hypoplastic Left Heart Syndrome (HLHS) was almost 100% fatal until the mid 1980’s, and the oldest HLHS survivors are just reaching adulthood.

I hope this basic look at a heart has been helpful to you. Some of Funky Heart‘s readers learned all this long ago, and they may find it a little boring. But in the United States, someone  is born with a Congenital Heart Defect every fouteen minutes. There is always a need to review the basics!


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3 Responses to “Basic Cardiology: How the Heart Works”

  1. Ronnie Says:

    Hi, Thanks for this interesting article. I wthought you might be interested to include a link to the European Society of Cardiology patient website on heart failure. We have some fabulous animations showing how the heart works:
    Kind regards,

  2. jim gardner Says:

    I have a leaking atrial valve and Af.Ihave had gabbage 5 arteries,and the vavle was repaired by a ring insertion,unfortunately after some time it started leaking again.I have ben informed that further surgery is not possible due to scar tisue. The question i ask is why you cannot fit 2 or possibly only 1valves in the pulmonary veins returning t o the left atrrum. Fluid is non compressable,so that any moving through the atriaum valve will be stopped by the next valve. It is essentialy like having 2 atriaum valves It would seem to be a less invasive operation to that performed know

    • Steve Says:

      I don’t know, Jim. I’m not a doctor; I’m just a guy with a heart defect. These questions are best answered by your own local doctor.

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