The 17 Segment Model

Published on 06/02/2015 by admin

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Last modified 22/04/2025

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The 17 Segment Model

John C. Sciarra

(Update note: In the ancient history of the first edition, there were 16 segments. Apparently we have evolved a 17th segment!)

This chapter requires some artist skill. When I say some, I mean very little. If you can draw a line and a circle you are, for the purposes of this chapter, an artist.

The 17 segment model is the way we as doctors communicate which sections of the heart we are talking about. It is also a great tool for designing test questions. For example, the patient is a gunshot wound victim, and he has a hole in segment 8. What coronary artery is spurting blood? What leads on the ECG do you expect to see abnormalities? See what I mean? Well, I am not going to tell you the answer; you just have to read on—and draw. And draw you will. You will draw what I call:

First off, draw a line. Just a straight line. As seen below this is a straight line.

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Wow, that was not so bad. Now comes the tricky part. You have to add two more lines in a cross pattern as seen below. It kind of reminds me of an asterisk, or star. That’s you–an echo star!

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Grip your pencil tightly because I am going to ask you to do something completely different. Draw a circle on top of your star.

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Good job Picasso, you have drawn the basic foundation for the 17 segment model. Next we have to number the segments. Start in the lower left, inside the circle, and do 1 thru 6, as seen below.

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Now start again outside the circle at the same lower left and do 7 thru 12. It should look like this. If you are not drawing at this point and just reading you are missing the point. Get out your pen and do it.

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13 thru 17 start close to your original starting point, which is the bottom. Circle around and finish at the bottom with 17. 17 is the apex or bottom of the heart, so that is where the number should be. It should look like this:

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That’s it. Now you have to practice this without looking. Go ahead. Find a piece of paper and start with the line, and finish with 17. You should be able to do this in 5 seconds. I am waiting…. Do it.

Now that you are an artist, you may feel like painting your living room. Hold on, since we now need to go over how your master work relates to the heart. Your 17 segment model is a segmental version of the cross section of the heart as seen below, which you may recognize from other sections in this book. Or a dozen other inferior books on TEE.

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We start at the top of the heart and work our way to the bottom, numbering as we go. “Wait” you say. The number one is in the wrong place. This is due to the fact that in TEE things are backwards from trans-thoracic scanning. I just put these images here to show you how the numbers relate to the levels: basal, mid, apical, and apex.

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This is the image you might see in most cardiology textbooks—if you ever dared to crack one open.

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Alright, let’s get back to the world of anesthesia. This next image is the one that has the positional planes lined up as the heart sits in the chest and as the probe is at the back of the heart. Our orientation is the top of the page is the back of the heart—the inferior portion—and the front of the heart is at the bottom of the page or TEE image—anterior. This should all be crystal clear in the cool exploded 3-D image I made below, which I drew from an actual exploded heart.

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To review the coronary anatomy. Which really shouldn’t be necessary—but what the heck:

(I hope those little memory hints help.)

This appears in another portion of the book. Learning thru repetition is a time-honored teaching tool they say. And they say it over and over for some reason.

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So let’s answer our question from the beginning. Remember gunshot to segment 8? Look at your drawing. Segment 8 is right in the middle of the anterior portion of the heart. Kind of a bulls-eye if you will. The anterior wall is the distribution of the LAD. See how easy that was. So he as a hole in his LAD! Quick, get a doctor!

At this point I should be able to shout out a segment, and you shout out a coronary artery—and vice versa. If not, go back to the beginning and start reading again. And this time draw it out. Lastly, I want to explain how some of the TEE planes relate to my 17 segment star. If you draw some dashed lines in between the lines of the star, these represent the planes of the TEE probe in certain views. The four-chamber view slices thru segments 3 and 6, for example. Next is the two-chamber view with the plane going anterior to inferior. Last is the ME long-axis cutting segments 7 and 4 among others.

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So there you have it. The star makes it all come together. I recommend trying to draw the 17 segment star in a few days to see if you remembered it. Then in the future, during say, some exam, you see a question involving the coronary arteries, wall segments, or ECG changes, just draw the star and figure it out. Nothing will stop your star power!

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