Quantitative M-mode and Two-dimensional Echocardiography

Quantitative M-mode and Two-dimensional Echocardiography

Varun Dixit, John C. Sciarra and Christopher J. Gallagher

M-mode provides a one-dimensional, “ice pick” view through the heart and updates the B-mode images at a very high rate.¹ Doppler recordings reflect blood velocity, whereas M-mode motion of cardiac structures reflects volumetric blood flow. The two examinations are hemodynamically complementary. In certain situations, M-mode recordings of the valves and inter-ventricular septum can be particularly helpful.² M-mode is a superior method of examining the timing of the cardiac events especially when displayed with the electrocardiogram.

Edge Recognition

Seeing the edges is easiest when the signal hits the objects at 90 degrees. (Don’t get fooled here, Doppler does best at 0 degrees or 180 degrees, but the best 2-D images are picked up when the beam is 90 degrees to the object.) The clearest edges are right down the middle of the image. Picking out edges along the side is trickier, less clear.

Knowing where the edge ends is important when you are looking at ventricular function. Good function shows good wall thickening and good chamber emptying. Without seeing the edges clearly, it’s hard to read either wall thickening or chamber emptying.

M-mode gives you a good edge, but to make sense of those squiggles I think you need the $250 Italian leather designer shoes and snappy silk ties of the cardiologist.

Edge Components

When measuring “where is the real live edge” in the ventricle, the back of the mid-papillary muscle view is the most appropriate. Then, the whole deal centers on where does the blood stop and where does the ventricle start. For this, you are best off using contrast, as noted above. Other than that anemic explanation, I don’t know beans about how they’d ask you a test question on “Edge Components”.

Temporal Resolution

Anything that takes more scan lines will slow down your temporal resolution. In other words, anything that makes the transducer process more data will slow it down. That makes sense, if you think about it. Even your PC at home, when processing a lot of stuff at once, slows down.

Deeper field?—That would take more information in, so temporal resolution would be worse.

Shallower field?—That would take less information in, so temporal resolution would be better.

Wider field?—More information coming in, therefore worse temporal resolution.

Narrower field?—You’re getting it. Less info, therefore better temporal resolution.

Aortic Valve in M-Mode

The aortic valve can be evaluated in different views but one of the best for M-mode is the mid-esophageal long-axis view. On the right-hand corner is the view through the ME AV LAX view and the cursor is through the aortic valve. If you press the M-mode button on your ECHO machine, you will get this image. Let’s try to make sense of this picture.

First you will see the chest wall. The next hypoechoic shadow is the right ventricular outflow tract. The next ‘ice pick’ line you get is the aortic anterior wall.

The ‘box car’ represents the cusp separation of the aortic valve.

The second ice pick line is the posterior wall of the aorta. Behind the posterior wall is the left atrium, depending your view.

The picture explains the same landmarks in greater details. Try to correlate the diagram shown below with the real life ECHO picture above.

The diagram shown on the left is of an aortic valve in case of aortic stenosis. Try to appreciate the small cusp separation, and the thickened cusps of the aortic valve (small box cars). Cusp separation below 8 mm represents severe aortic stenosis. Always correlate the M-mode with the EKG.

This diagram shows the aortic regurgitation in M-mode. Note continuous flow during the two consecutive ‘box cars’ representing the leak in the aortic valve.

Mitral Valve in M-Mode

Again, the mitral valve can reviewed in various views, in fact it should be evaluated in different views. One of the easiest is to get the mid-esophageal four-chamber view and then get the curser through the mitral valve and hit the M-mode button.

In the image shown above, the first hypoechoic image will be of the left atrium. Then there will be the mitral valve leaflets.

Note, the two leaflets of the mitral valve move in M-shaped mirror image pattern in diastole. At the onset of systole the two leaflets come together and generate the first heart sound.

Ventricular Wall Assessment with M-Mode

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Tags: Board Stiff Tee Transesophageal Echocardiography

Jun 4, 2016 | Posted by admin in CARDIOLOGY | Comments Off

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