JACC: CARDIOVASCULAR IMAGING

VOL. 8, NO. 7, 2015

ª 2015 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION

ISSN 1936-878X/$36.00

PUBLISHED BY ELSEVIER INC.

http://dx.doi.org/10.1016/j.jcmg.2015.04.009

EDITORIAL COMMENT

Utility of CT Angiography to Guide Coronary Intervention of CTO* Gerald S. Werner, MD,y Harvey Hecht, MD,z Gregg W. Stone, MDx

T

he procedural success rates of percutaneous

that the success rate of percutaneous coronary in-

intervention for chronic total coronary occlu-

tervention (PCI) is highly operator-dependent (7).

sions (CTOs) over the past decade have been

Comparing features of successful versus failed cases

increasing, driven by the development of specialized

is confounded by the capability of the expert operator

guidewires and microcatheters and the introduction

to overcome the most hostile coronary anatomies. For

of new technical strategies, including antegrade sub-

complex CTO anatomies, advanced techniques, such

intimal re-entry and the retrograde transcollateral

as antegrade dissection and re-entry (with or without

approach. An ongoing challenge is to select the most

ultrasound guidance) and the retrograde transcol-

promising strategy early to reduce total procedure

lateral approach, are available, which allow $90%

time, to reduce radiation and contrast exposure, and

primary success rates. Nonetheless, selecting the

to further improve complication-free procedural suc-

optimal approach on the basis of angiographic char-

cess rates. In this regard, procedural planning is typi-

acteristics is often more art than science, and high

cally based on the angiographic assessment of the

success rates are only achieved by readily switching

occluded lesion, including features of the proximal

when necessary (e.g., from a failed antegrade to a

cap, the extent of calcification, and the apparent

retrograde approach). Selecting the procedural strat-

length of the lesion (1). Pre-procedural coronary com-

egy on the basis of coronary CTA-derived imaging

puted tomographic angiography (CTA) with modern

might streamline the approach to CTOs, reduce

high-resolution scanners may provide incremental in-

contrast use and radiation exposure, and enhance

formation about the features of the coronary occlu-

procedural success.

sion, which might enhance procedural planning and outcomes.

SEE PAGE 804

In early studies in which coronary CTA was used

The report by Luo et al. (8) in this issue of iJACC

to visualize CTOs, the prominent features observed

addresses the extent to which contemporary 256-slice

were the extent of calcification, occlusion length,

high-resolution coronary CTA can provide incremen-

and identification of the vessel course within a long

tal information to angiography in identifying baseline

occluded segment (2,3). In more recent studies with

predictors of CTO procedural success versus failure

improved resolution computed tomography (CT)

with an initial antegrade approach (8). The new

scanners, the degree and distribution of calcification

aspect of this study was to identify factors, derived

has remained the most relevant predictor of CTO

both from coronary CTA and from diagnostic angi-

procedural success (4–6). However, it is well known

ography, that would predict a successful antegrade procedure and, thus, to categorize cases beforehand that might alternatively benefit from an initial retro-

*Editorials published in JACC: Cardiovascular Imaging reflect the views of

grade procedural approach. The size of the study is

the authors and do not necessarily represent the views of JACC:

limited, but it is comparable to the numbers analy-

Cardiovascular Imaging or the American College of Cardiology. From the yMedizinische Klinik (Cardiology & Intensive Care), Klinikum Darmstadt GmbH, Darmstadt, Germany; zIcahn School of Medicine at Mount Sinai, New York, New York; and the xColumbia University

zed in previous reports. The major difference in this study compared with others is the relationship of outcomes to the procedural approach. An impor-

Medical Center, New York-Presbyterian Hospital, and the Cardiovascular

tant finding was that pre-procedural coronary CTA

Research Foundation, New York, New York. Dr. Hecht has served as a

contributed prognostic information beyond angiog-

consultant for Philips Medical Systems; and is on the advisory board of Arineta and Orient Scientific. All other authors have reported that

raphy alone. The independent coronary CTA features

they have no relationships relevant to the contents of this paper to

determining procedural failure of the antegrade

disclose.

approach were negative remodeling and lesion length

Werner et al.

JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 7, 2015 JULY 2015:814–6

Editorial Comment

>32 mm, whereas calcification did not seem to be

lesions were not excluded (or otherwise not referred

different in failed and successful cases. Angiographic

for CTO intervention). In addition, the information

location of the occlusion at the ostium or at a bifur-

afforded by coronary CTA may be even more valuable

cation site was also an independent predictor of

when coregistered with angiography in the catheter-

failure. An additive relationship was present between

ization laboratory during the procedure, as was done

the number of these variables present and the likeli-

in the study by Luo et al. (8). Similarly, Rolf et al. (10)

hood of antegrade failure, such that if 2 or more risk

used printouts from coronary CTA adapted to var-

factors were present the success rate was only 20%,

ious angiographic gantry positions to help illustrate

whereas the absence of any of these adverse factors

the vessel course within the CT body. Using this

predicted nearly 100% success by the antegrade

approach, the success rate was significantly higher

approach.

than in a matched control group. Several com-

Negative vessel remodeling is a common feature of

panies are working on online coregistration systems

CTOs (especially older occlusions [9]) and cannot be

that allow the actual simultaneous presentation of a

appreciated by angiography. Negative remodeling by

volume-rendered coronary CTA image of the course

coronary CTA as a predictor of procedural failure has

of the occluded artery next to, or overlaid with, the

been previously noted (3). However, it is surprising

angiographic image, thus providing a roadmap of

that the extent of calcification was not related to

the presumed wire course through the occlusion.

procedural outcome in the present study. This finding

The limitation of this approach will remain the syn-

is in direct contrast to previous studies, in which

chronization with both the heart beat and respiration.

calcification was the most prominent predictor of

Which, if any, patients should currently undergo

procedural failure (4–6). The location of and extent of

pre-procedural coronary CTA? In countries like Japan,

calcium within the plaque is likely to be extremely

the rate of patients undergoing such diagnostic im-

important: circumferential diffuse calcification versus

aging is extremely high, in some centers approaching

localized deep calcification pose different obstacles to

100%, despite a lack of objective evidence for benefit.

the progress of a guidewire during attempted ante-

In other countries like the United States and much of

grade recanalization. In the present study, few lesions

Europe, the number of these procedures is much

were heavily calcified and none had 360  calcification.

lower due to a lack of reimbursement in the face of

Indeed, the presence of circumferential calcium at the

clinical equipoise. Is such an approach needed at all?

proximal or distal cap may render determination of

In expert hands, the procedural success of PCI in

lesion length by coronary CTA inaccurate due to

CTOs with angiographic guidance alone has sur-

blooming artifact. The lack of influence of calcification

passed 90%, but it still involves considerable proce-

in the present study is thus likely due to selection bias

dural investment in terms of time and equipment

excluding extremely calcified lesions, which the

(and cost). The risk of procedural complications

operator believed were likely to have a low rate of

should also not be dismissed, and may be affected by

procedural success. Whether this is true with new

strategic approach. It thus may be worthwhile to

techniques of proximal dissection and re-entry de-

identify the features discriminating a CTO that might

serves further study.

be treated with less complex approaches from those

There is no doubt that the detailed images pro-

that might require more complex procedures or that

vided by modern CT equipment provide a greater

should be referred to specialized centers to avoid

understanding of occlusion morphology than simple

unnecessary failed procedures with potential clinical

angiographic “lumenography,” but will this knowl-

hazards to the patient. The angiographically-based

edge really improve the outcome or facility of the

J-CTO score, which is a simple 5 point score based

procedure? The current study, like most previous

on the stump morphology, lesion length, calcifica-

studies, did not randomize patients to PCI with

tion, lesion tortuosity and history of a previous

versus without coronary CTA procedural planning,

attempt, may be used for this purpose (1), and the

and the issue of selection bias cannot be ignored.

list of risk factors identified by Luo et al. (8) adds

Although the present study suggested a slightly

coronary CTA variables to further consider (although

overall higher success rate in the group undergoing

the lesion length cutoff of 32 mm requires prospective

CT scanning as compared with those without pre-

validation). A study of angiographic and coronary

procedural coronary CTA, we cannot know with cer-

CTA

tainty that the lesions were of equal complexity.

(and at additional centers) is warranted to establish an

features

in

a

broader

patient

population

Moreover, in the “real world,” more complex CTOs

improved discriminatory scoring system. In addi-

might benefit from coronary CTA, but in the present

tion, the incremental cost, radiation, and contrast use

study, we cannot be sure that the most complex

of coronary CTA must be taken into consideration.

815

816

Werner et al.

JACC: CARDIOVASCULAR IMAGING, VOL. 8, NO. 7, 2015 JULY 2015:814–6

Editorial Comment

With early-generation multislice CT equipment the

the risk-benefit profile of pre-procedural coronary

additional radiation exposure was considerable (11),

CTA for CTO interventional planning, and building

but contemporary scanners and imaging protocols

on the present study by Luo et al. (8), we now

have markedly reduced the radiation dose (although

have the essential information required to plan such

no information in this regard is provided by the

a trial.

present study). Given the additional cost of preprocedural coronary CTA, a selective strategy may

REPRINT REQUESTS AND CORRESPONDENCE: Dr.

be warranted. For example, patients with a J-CTO

Gerald S. Werner, Medizinische Klinik I, Klinikum

score >1 might be selected to undergo pre-procedural

Darmstadt,

coronary CTA. Randomization is necessary to address

Germany. E-mail: [email protected].

Grafenstrasse

9,

D-64283

Darmstadt,

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3. Ehara M, Terashima M, Kawai M, et al. Impact of

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9. Sakakura K, Nakano M, Otsuka F, et al. Comparison of pathology of chronic total occlusion with and without coronary artery bypass graft. Eur Heart J 2014;35:1683–93. 10. Rolf A, Werner GS, Schuhback A, et al. Preprocedural coronary CT angiography significantly improves success rates of PCI for chronic total occlusion. Int J Cardiovasc Imaging 2013;29: 1819–27. 11. Garcia-Garcia HM, van Mieghem CA, Gonzalo N, et al. Computed tomography in total coronary occlusions (CTTO registry): radiation exposure and predictors of successful percutaneous intervention. EuroIntervention 2009;4:607–16.

KEY WORDS conventional coronary angiography, coronary computed tomography angiography, negative remodeling, percutaneous coronary intervention