This article has been retracted. Please see:
Author + information
- Jun Pu, MD,
- Akiko Maehara, MD∗ ( and )
- Gary S. Mintz, MD
- ↵∗Columbia University Medical Center, New York-Presbyterian Hospital, Cardiovascular Research Foundation, 111 East 59th Street, 12th Floor, New York, New York 10022
We appreciate the interest by Dr. Falk in our paper (1) and his insightful comments, which especially focus on our findings regarding echo-attenuated plaque. In comparison to the gold standard of histopathology in 2,294 human coronary autopsy specimens, we found that echo-attenuated signature, in particular that with superficial location, indicated a high-risk plaque containing a large necrotic core (NC).
We agree with Dr. Falk’s comment that the definition of “echo-attenuated plaque” should be standardized for clinical practice implementation. On the basis of our study, we recommend that the grayscale intravascular ultrasound (IVUS) echo-attenuated signature be defined as the absence of ultrasound signal behind plaque that was either hypoechoic or isoechoic to reference adventitia, but without bright calcium. By definition, echo-attenuated plaque excludes “attenuation (or, more correctly, shadowing) behind hyperechoic calcium.” Our proposal would certainly be the most specific, although a definition that includes mixed plaque might be more sensitive.
Furthermore, we propose to define the location of attenuation as superficial (leading edge of attenuation closer to the lumen than to the adventitia) or deep (leading edge of attenuation closer to the adventitia than to the lumen). As demonstrated in our paper (1), the location of attenuation was an important characteristic related to plaque biologic instability. Dr. Falk expresses concern about the “different” findings on the echo-attenuated plaques in this in vitro study using histopathology in patients at necropsy (1) versus findings in our recent in vivo study using virtual histology-IVUS in patients with acute coronary syndromes (2). In particular, he is concerned with the location of lipid/NC in relation to echo attenuation. First, because the thickness of the “echogenic cap” of the echo-attenuated plaque was different from that of the histologic fibrous cap covering the lipid/NC and because trailing-edge measurements by ultrasound might be unreliable, we did not present data regarding the “cap” thickness in the setting of echo attenuation in the present study. Second, it should be noted that in our IVUS histological validation study, the leading edge of the histologic lipid/NC that produced attenuation was always in front of the leading edge of attenuation on IVUS. In other words, the lipid/NC produces both the “echogenic cap” that is superficial to the area of attenuation as well as the attenuation itself; in fact, as shown in Figure 1, the 2 are interrelated. This is analogous to calcium that produces both a hyperechoic acoustic signature as well as deeper shadowing. Third, current grayscale IVUS technology does not have the ability to resolve a fibrous cap thickness <65 μm, the commonly accepted criterion for a thin-cap fibroatheroma. Finally, the more advanced the atherosclerotic plaque, the more complex and heterogeneous the plaque components that contributed to attenuation of ultrasound signal (i.e., the closer to the leading edge of the lipid/NC).
We do concur with Dr. Falk that the current qualitative plaque classification scheme by IVUS grayscale image characteristics, which do not correlate well with histological plaque composition, should be updated. The cited papers are both more than 10 years old, and as pointed out by Dr. Falk, echo-attenuated signature is a novel IVUS signature that is not described in the existing IVUS guidelines or consensus documents. It would be especially valuable if such an update were done using outcomes data as the end point.
Please note: Dr. Pu has received research grant support from the National Natural Science Foundation of China (81470389/81270282) and Boston Scientific, China. Dr. Maehara is a consultant to and has received research and grant support from Boston Scientific. Dr. Mintz has received consulting fees from Boston Scientific and Volcano; and research and grant support from Boston Scientific, InfraReDx, and Volcano.
- American College of Cardiology Foundation
- Pu J.,
- Mintz G.S.,
- Biro S.,
- et al.
- Pu J.,
- Mintz G.S.,
- Brilakis E.S.,
- et al.