Vivid Valves: The Role of 3D Echo

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Source: 3d-echo.jpg - Ruptured P2 Chords
Ruptured chords involving P2 by 3D imaging.
Surgical findings confirm ruptured P2 chords but also an elongated chord and prolapse at A1.
Source: Circulation. 2013;128:653-658

3D echocardiography has swept the cardiology world off its feet, but can these new images transform any surgeon into a mitral valve repair expert?

The rapid adoption of 3D transesophageal echocardiography is a testament to the quality of images it creates. It provides beautiful views that are easy for surgeons to read and understand, and accurately displays the mitral valve during preoperative assessment. Despite all the positivity, 3D echo does have limits.

For Patrick M. McCarthy, MD, of Northwestern University Feinberg School of Medicine in Chicago, the first sign that the love affair with 3D echo might be going too far was when he listened to a cardiologist lecture an audience on the topic. The speaker asserted that since cardiac surgeons can now see everything with 3D echo, anybody could do a mitral valve repair, including less experienced surgeons.

“That’s really overstating the case for 3D echo,” says McCarthy.

This set the stage for a pair of published point-counterpoint articles on the merits of 3D echo (Circulation 2013;128:653-658). While McCarthy argued for some perspective on the benefits, Roberto M. Lang, MD, of the University of Chicago Medical Center, along with Wendy Tsang, MD, from Toronto General Hospital, wrote about how essential the advanced echocardiography technique has become.

What's in a Name? Rethinking Nomenclature
Physicians in the paravalvular leak program at the Mayo Clinic in Rochester, Minn., noticed an issue with communication in the cardiac catheterization laboratory ahead of surgery. There can be discrepancies between the interventionist, who is used to looking at fluoroscopy images, and the echocardiographer, who is helping to guide the procedure with transesophageal echo. Descriptions of orientation such as anterior or posterior can become confused because interventionists and echocardiographers are using different modalities from different perspectives. Additionally, patient characteristics also can have an effect. An elderly woman with chronic obstructive pulmonary disease may have a heart oriented more vertically, while obese patients may have more horizontal orientation of the heart, for example. "What we tried to do was come up with anatomic-based nomenclature that allowed us to have more facile communication in the lab," says Daniel B. Spoon, MD, of the Mayo Clinic. Spoon and colleagues developed a simple fix based on 2D and 3D echo nomenclature that would improve correlation with fluoroscopic localization of leaks. Anatomic structures were used to triangulate lesions, with the aortic valve labeled anterior, the atrial septum labeled medial and the left atrial appendage labeled anterolateral. An assessment of the new nomenclature found that 95 percent of lesions were localized accurately when the anatomical method was used in a cohort featuring 119 lesions. Spoon adds that the improved communication also shortened procedure times, improving workflow.

Pros & cons

The advantages of 3D echo in the assessment of the mitral valve are numerous, according to Lang and Tsang. It improves lesion localization, identification of the mechanisms causing mitral regurgitation and quantification of the severity of mitral regurgitation. Views offered by 3D echo can be displayed similarly to what the surgeon actually will encounter during a procedure. Measurements obtained from 3D parametric maps have shown that prolapsing height and anterior leaflet surface area are the strongest predictors of surgical repair complexity in degenerative mitral valve disease.

“This is a growing imaging modality that is gaining acceptance and people more and more understand … how it can help in the operating room and how this technique can help guide different types of percutaneous procedures for structural heart disease,” says Lang. “People are accepting this all over the world.”

While having great respect for 3D echo’s abilities—he uses it in 100 percent of his mitral valve procedures—McCarthy notes some shortcomings. “They see things quite well, but they don’t really see everything, not as well as when we do a good evaluation of the valve,” he says.

For McCarthy, the most important component in mitral valve repair is the operating surgeon, and 3D echo can potentially lull a cardiologist into a false sense of comfort about how simple a repair will be. Because the shape of the mitral valve changes during a repair, experienced surgeons are required. McCarthy also points out that while findings on 3D echo match surgical findings for predominant pathology in the vast majority of cases, there are situations where subtle, secondary findings may be missed, particularly in the subvalvular apparatus.

McCarthy shared a story about a 50-year-old man who was diagnosed with a new murmur and fatigue, and was eventually identified by 3D echocardiography as having severe mitral regurgitation. The man had ruptured chords involving the middle scallop of the posterior leaflet along with normal left ventricular function and trivial tricuspid regurgitation, so it was anticipated to be a straightforward valve repair. However, an isolated area of prolapse was hidden and not appreciated on echocardiography and further treatment was required.

Daniel B. Spoon, MD, of the Mayo Clinic in Rochester, Minn., adds that a good 3D image can’t be generated without good 2D windows. He says that while he and his colleagues often hear in their work that the focus should be on 3D and that 2D isn’t as essential, they understand there can be some artifacts and that 3D images have trouble with localization unless adequate 2D is used to generate 3D images.

“2D images for decades have been the tried and true nomenclature of cardiology, so while … I think 3D will continue to advance, I don’t know anybody here who’s comfortable with just a 3D image,” says Spoon.

Directing patients

Ultimately, the role of 3D echo in mitral valve regurgitation will be in determining the best strategy for repair and helping to funnel patients to surgeons with the proper level of experience. “There’s some world-class surgeons who could probably do this operation without echo because they have so much experience,” says Lang. “I think commonly it will be very useful to have 3D echo to preprogram or preplan surgical strategy.”

McCarthy says the world has evolved to where there’s two groups of surgeons: those who do a lot of mitral valve repairs and those who don’t. According to Bridgewater et al, a surgeon needs to handle about 25 cases a year to gain the experience necessary to handle the most complex cases, but the average surgeon performs just five mitral valve repairs annually (Heart 2006;92:939–944).

Technology doesn’t stand still. Lang says the future of 3D echo will rely on improving image quality, increasing frame rate and, eventually, more automated functions. The field is moving toward automatic quantification of lesions, and with it, an ever expanding role for 3D echo.