Intraoperative 3-D Echocardiography

Published on 06/02/2015 by admin

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Last modified 06/02/2015

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Intraoperative 3-D Echocardiography

Gian Paparcuri

Transesophageal echocardiography is probably the most frequently used imaging technique in cardiac surgery. This powerful technology provides timely information, about cardiac structures (anatomy) and function (hemodynamics) without disrupting the surgical workflow.

Developed decades ago, far from being a dead technology, echocardiography is a constantly evolving technique, requiring new skills and expertise. Over the years echocardiography has evolved from 2-D into 3-D. Just like the movies. Some authors say that “3-D represents the natural evolution of 2-D echocardiography”. But why do we need 3-D echocardiography?

The answer is simple:

3-D Echo:

With 3-D echocardiography, people who aren’t echocardiographers can appreciate valve anatomy and physiology in three dimensions. Surgeons tend to very much appreciate 3-D images because the echo image looks exactly like what they see when the heart is open. Finally, for those of you taking the well-known echocardiography course in San Diego, expect to see a lot of 3-D. It seems like the speakers are not allowed to talk about echocardiography if they don’t complement their presentation by adding some 3-D images.

Believe it or not, there are 3-D detractors out there. People are afraid of change. But it is human to feel anxious when a new technology is trying to be introduced. It is easier to welcome this new technology when limitations of existing technology are appreciated.

2-D echocardiography is the representation of a 3-D structure (the heart) in 2 planes. The echocardiographer has to mentally visualize (cognitive 3-D reconstruction) a complex 3-D structure based on a series of 2-D views in order to obtain a 3-D object (the heart). Another limitation is that 2-D echocardiography is based on a lot of assumptions. We assume specific geometric shapes of cardiac structures for ejection fraction quantification every day. Even worse, we assume the whole ventricle behaves like the one displayed on the screen. Many times, these assumptions fail because of the presence of RWMA.

To be honest, 3-D echocardiography is nothing new under the sun—it’s been here for more than 15 years. But because of early limitations it was not universally applied. In its beginnings 3-D echocardiography was a tedious process: slow acquisition process, images acquired in 2-D had to be reconstructed in 3-D using a program. It used to take a long time, simply because it was not really 3-D. Displaying 3-D images requires a huge amount of data to process. More than 60 heart beats—images, acquired over several hundred consecutive beats had to be gathered with the ECG or respiratory rate for subsequent volume rendering and cropping. And after this time-consuming process the computer was able to reconstruct (offline) a 3-D image which very often was of poor quality with frequent artifacts. In its early years 3-D echocardiography was very impractical in the operative theater. New technology overcomes some of these limitations.

With real time 3-D gone is the need to sum information for 61 beats. What is new about it these days is that instead of images that are acquired in 2-D and then reconstructed into a 3-D image using software, the images can be acquired in 3-D volumes and displayed in real time. The new technology uses a special scanner (probe). The scanner used a unique matrix array to scan a volume without physically moving the transducer. The transducer gathers information from a single beat, resulting in a very low-latency display.

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