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IMAGING VIGNETTE

High-Risk Plaque Features onCoronary CT Angiography

Harvey S. Hecht, MD,* Stephan Achenbach, MD,y Takeshi Kondo, MD, PHD,z Jagat Narula, MD, PHD*

CORONARY COMPUTED TOMOGRAPHIC ANGIOGRAPHY (CTA) HAS BECOME AN ACCEPTED TOOL FOR THE

evaluation of obstructive coronary artery disease, with high accuracy and proven prognostic implications.Although detailed information regarding plaque characteristics is available in coronary CTA datasets of suf-ficient quality, clinical decision making utilizing the information offered by computed tomography–basedplaque analysis is not widely utilized. Nonetheless, the Society of Cardiovascular Computed TomographyGuidelines for the Interpretation and Reporting of Coronary Computed Tomographic Angiography go beyondmere stenosis measurement: “If coronary disease is present, stenosis severity, plaque morphology, and extentshould be described.. Plaque type should be described as calcified, predominant calcified, noncalcified,predominant noncalcified, or partially noncalcified.. Other morphologic descriptors of a stenotic lesion, suchas . apparent dissection or ulceration, and positive remodeling may also be appropriate.. Reporting ofHounsfield units in the plaque is discretional; it must be recognized that significant overlap exists betweenlipid and fibrous material, making interpretation of plaque HU problematic” (1).

Here, we present selected images featuring high-risk plaques in coronary CTA, with accompanying clinicalscenarios that indicate potential applications not currently covered by guidelines (Figures 1 to 4). A surveyquerying clinical decisions based on the images was e-mailed to 2,250 Society of Cardiovascular ComputedTomography members; 10% responded, and the answers are indicated in the case descriptions. It must beemphasized that considerably more data are required before formal recommendations can be made. Withfurther research and technical developments, computed tomography–based plaque analysis may, in the future,provide noninvasive insight into the “vulnerability” of specific lesions and may possibly contribute to theprevention of acute coronary events.

From the *Cardiology Department, Icahn School of Medicine at Mount Sinai, New York, New York; yCardiology Department,

University of Erlangen, Erlangen, Germany; and the zCardiology Department, Fujita University of Health Sciences, Toyoake,

Aichi, Japan. Dr. Hecht has served as a consultant to Philips Medical Systems. Dr. Narula has received research support in the

form of equipment grants to institution from GE and Philips Healthcare. All other authors have reported that they have no

relationships relevant to the contents of this paper to disclose.

Manuscript received October 22, 2014; accepted November 14, 2014.

FIGURE 1 HRPs by CTA

(A and B) Two examples of high-risk plaques (HRPs),

which typically demonstrate large plaque burden, carry

large necrotic cores (NC), and are covered by intensely

inflamed thin fibrous caps. In A, the lumen (L) is criti-

cally compromised, whereas modest occlusion is seen in

B. These plaques usually demonstrate outward

remodeling. (C and D) The necrotic cores are conve-

niently identified as low attenuation plaques on

computed tomographic angiography (CTA); intravas-

cular ultrasound–verified necrotic cores usually mea-

sure 30 Hounsfield units or lower. HRPs on CTA almost

always demonstrate positive remodeling of 110% or

more. These plaques have been referred to as 2-feature

positive plaques (low attenuation plaques and positive

remodeling) on CTA. Stable plaques lack these charac-

teristics and are called 2-feature negative plaques (1).

These figures are unrelated, and an attempt was made

to match clinical and pathological data.

FIGURE 2 HRP Associated With #50% Diameter Stenosis

Clinical scenario: A 66-year-old man presented with atypical

exertional chest pain; he had low-density lipoprotein of 75

mg/dl and was on statin therapy. The 2013 American College

of Cardiology/American Heart Association 10-year risk esti-

mate was 9.0%, deserving of moderate- to high-intensity

statin therapy. After an equivocal nuclear stress test, he un-

derwent CTA followed by invasive angiography because of

persistent symptoms. Images: Multiplanar reconstruction of

the right coronary artery (RCA) (A) reveals a 50% distal ste-

nosis (white arrow). Cross-sectional analysis (B to D) reveals

HRP features: a low attenuation lipid core adjacent to the

lumen (2 to 25 Hounsfield unit [HU]), spotty calcification (223

HU), and positive remodeling. Stenosis <50% was noted on

invasive angiography (E, white arrow). Survey response: 89%

of the respondents favored maximally intensifying medical

therapy because of HRP. Comment: Several studies have

demonstrated the beneficial effects of statins on CTA plaque

progression. A significant reduction in low attenuation plaque

on statin treatment has been reported compared with no

change in patients without statin treatment in serial CTA

studies, but formal studies are required before it can be

concluded that these elements also predict lower future

event rates. RI ¼ remodeling index; other abbreviations as in

Figure 1.

J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . 8 , N O . 1 1 , 2 0 1 5 Hecht et al.N O V E M B E R 2 0 1 5 : 1 3 3 6 – 9 Clinical Implications of Plaque Features

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FIGURE 3 HRP Associated With Intermediate Stenosis

Clinical scenario: A 65-year-old man with typical angina on dual antianginal therapy underwent CTA that revealed an intermediate (50% to 70%) left anterior descending

(LAD) stenosis. The plaque revealed positive remodeling (PR), low attenuation plaques (LAP), and spotty calcification. Invasive angiography confirmed an intermediate

stenosis, and the fractional flow reserve (FFR) was 0.81. Images: Multiplanar reconstruction of the LAD (A) demonstrates an intermediate (50% to 70%) proximal

stenosis (arrow). Cross-sectional analysis (C) and schematic (D) of the straightened vessel (B) reveals LAP adjacent to the lumen (�8 to 38 HU) and spotty calcification

(745 HU); PR compared with the normal segment (RI 1.18) was also noted. Survey response: 49% of the responses favored over-riding the normal FFR and performing

percutaneous coronary intervention because of the HRP. Comment: A normal FFR does not guarantee a benign outcome. In the FAME (Fractional Flow Reserve Versus

Angiography for Multivessel Evaluation) study (2), 3.2% of patients who were deferred for intervention on the basis of a normal FFR had death, myocardial infarction, or

revascularization within 2 years. This presents a difficult problem, and FFR may not incorporate the plaque prognostic information. A high likelihood of developing acute

coronary syndrome (22% over a mean of 27 � 10 months) in patients with CTA-verified LAP and/or in whom PR has been reported (3). Abbreviations as in Figures 1 and 2.

Hecht et al. J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . 8 , N O . 1 1 , 2 0 1 5

Clinical Implications of Plaque Features N O V E M B E R 2 0 1 5 : 1 3 3 6 – 9

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FIGURE 4 HRP Associated With Severe Stenosis Prone to Distal Embolization During PCI

Clinical scenario: CTA in a 62-year-old woman with continued exertional angina on multiple medications revealed a critical right coronary artery (RCA) stenosis with

circumferentially calcified plaque, PR, and LAP. Percutaneous coronary intervention (PCI) was planned. In this scenario, it has been presumed that a downstream “basket”

may decrease the likelihood of slow flow post-PCI. Images: The curved multiplanar reconstruction (A) demonstrates a >70% mid-RCA stenosis (arrow). Cross-sectional

analyses (B) at multiple levels of the straightened multiplanar reconstruction (top) revealed severe luminal reduction, LAP adjacent to the lumen (�1, 3, 12 HU), and PR

(RI 1.32) compared with the normal segment. No reflow phenomenon developed in this patient during stent placement (C), and intracoronary nicorandil restored flow

(D). Survey response: 79% of the responses favored urgent, rather than elective, percutaneous intervention because of the HRP, and 73% favored deployment of a

downstream protection device for PCI. Comment: There are no studies specifically addressing the ideal timing of intervention following the identification of HRP in an

otherwise stable clinical state. However, the wealth of data documenting the accompanying higher incidence of acute coronary syndromes, as well as the higher rupture

rate associated with >75% plaque area, may support the wisdom of intervening sooner, rather than later, after discovery of a higher-likelihood culprit lesion. CTA-

defined circumferential plaque calcification, defined as calcium occupying >180� of the perimeter for at least one-third of the plaque length, was associated with a high

odds ratio for developing slow flow during PCI. In addition, no reflow following stenting has been identified in the setting of an extensive lipid core demonstrated by near

infrared spectroscopy. The identification of these features by CTA might be a harbinger of periprocedural complications. Abbreviations as in Figures 1 to 3.

J A C C : C A R D I O V A S C U L A R I M A G I N G , V O L . 8 , N O . 1 1 , 2 0 1 5 Hecht et al.N O V E M B E R 2 0 1 5 : 1 3 3 6 – 9 Clinical Implications of Plaque Features

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REPRINT REQUESTS AND CORRESPONDENCE: Dr. Harvey S. Hecht, Mount Sinai Medical Center, One GustaveL. Levy Place, Box 1030, New York, New York 10029-6574. E-mail: harvey.hecht@mountsinai.org.

R EF E RENCE S

1. Leipsic J, Abbara S, Achenbach S, et al. SCCTguidelines for the interpretation and reporting ofcoronary computed tomographic angiography.J Cardiovasc Comput Tomogr 2014;8:342–58.

2. Tonino PAL, De Bruyne B, Pijls NHJ, et al.Fractional flow reserve versus angiography for

guiding percutaneous coronary intervention. NEngl J Med 2009;360:213–24.

3. Motoyama S, Sarai M, Harigaya H, et al. Computedtomographic angiography characteristics of athero-sclerotic plaques subsequently resulting in acute cor-onary syndrome. J Am Coll Cardiol 2009;54:49–57.

KEY WORDS clinical implications, coronarycomputed tomography angiography, high riskplaque