Harry C. Lowe

Frontiers in Cardiovascular Medicine

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PERSPECTIVES IN MEDICINE
published: 09 January 2015
doi: 10.3389/fcvm.2014.00016
Perspectives on imaging the left main coronary artery
using intravascular ultrasound and optical coherence
tomography
Harry C. Lowe*
Concord Repatriation General Hospital, Sydney, NSW, Australia
Edited by:
Rajesh Puranik, Royal Prince Alfred
Hospital, Australia
Reviewed by:
Sylvia S. M. Chen, The Epworth
Hospital, Australia
Christian Hamilton-Craig, University
of Queensland, Australia
*Correspondence:
Harry C. Lowe, Cardiology
Department, Concord Repatriation
General Hospital, Level 3West,
Concord 2139, NSW, Australia
e-mail: h.lowe@bigpond.net.au
Percutaneous coronary intervention (PCI) for significant left main coronary artery (LMCA)
stenosis is increasingly being viewed as a viable alternative to coronary artery bypass graft-
ing (CABG) (1).This is leading to an expectation of increasing numbers of such procedures
with a consequent focus on both the ability to image lesion severity and assess more accu-
rately the results of PCI.While there have been advances in physiological assessment of left
main severity using fractional flow reserve (FFR) and in non-invasive assessment of the left
main using coronary computerized tomography CT (2), imaging of the LMCA using intravas-
cular ultrasound (IVUS) and more recently optical coherence tomography (OCT) has the
specific advantage of being able to provide very detailed anatomical information both pre-
and post-PCI, such that it is timely to review briefly the current status of these two imaging
technologies in the context of LMCA intervention. This is presented specifically contrast-
ing the use of these technologies both in pre-PCI lesion severity assessment, and peri-PCI
procedural evaluation. Not discussed here is the separate issue of longer-term surveillance
of asymptomatic patients having undergone LMCA stenting, which may appropriately be
performed non-invasively using coronary CT, reviewed in detail elsewhere (2).
Keywords: coronary angiography, intravascular ultrasound, optical coherence tomography, left main coronary
artery, imaging
LEFT MAIN CORONARY ARTERY STENOSIS
The LMCA refers to the proximal coronary segment generally
arising from the left coronary sinus and extending to bifurcate
into the left anterior descending coronary artery and the circum-
flex coronary. It is generally considered to comprise three distinct
anatomical portions; the ostium, body, and distal portion (3). The
LMCA contains a higher elastic tissue component compared to
the rest of the coronary tree (4) and supplies large myocardial
territory, making significant disease of the LMCA often associ-
ated with severe ischemia, arrhythmias, and other life-threatening
sequelae.
PCI FOR LMCA STENOSIS
Percutaneous coronary intervention for LMCA stenosis has and
continues to be evaluated against conventional CABG in selected
patients, with favorable results, reviewed elsewhere (1). Event rates
are modest, but lower than for CABG in some groups (5 vs. 7.9% at
3 years for combined death and MI: PCI vs. CABG, p< 0.001) (1),
and mean that further improvements in outcomes may be expected
with improvements in imaging and techniques (Figure 1).
IVUS FOR LMCA STENOSIS
Intravascular ultrasound has been long considered the gold stan-
dard imaging modality for the assessment of LMCA stenosis
severity, prior to any intervention, and has been elegantly reviewed
elsewhere (5). Differences in outcomes have been reliably demon-
strated by a number of investigators using IVUS defined binary
cut-offs for lesion severity, with minimum lumen areas (MLA)
of between 6 and 7.5 mm2 as defining significant LMCA stenosis
severity (6, 7). Improved outcomes have been documented in those
patients with severe LMCA stenosis lesion undergoing revascu-
larization compared to those treated medically (5). Interestingly,
while IVUS is uniquely able to assess plaque volume in this context
(Figure 2), such estimates of plaque volume have not been used
clinically to add precision to assessments of MLA.
Intravascular ultrasound has also been used to assess stent strut
apposition and peri-procedural complications post-PCI, although
IVUS image quality of stent strut apposition in particular does
have limitations (Figure 2). Non-randomized registry data from
975 patients undergoing PCI vs. CABG for LMCA stenosis sug-
gested improved outcomes with IVUS guided PCI compared to
angiography alone (mortality 4.7 vs. 16% at 3 years,p= 0.048) (8).
These and other data have supported the general clinical practice
of providing IVUS support for LMCA PCI when available.
OCT FOR LMCA STENOSIS
The novel intracoronary imaging modality of OCT provides
unique detail of superficial intravascular structures, reviewed in
detail elsewhere (9) and has seen important recent advances in
the assessment of the LMCA, particularly post-PCI. OCT pro-
vides precise information regarding superficial structures down to
depths of 2–3 mm within the vessel wall, with axial and lateral res-
olutions of 20–40µm, respectively (9). While this allows precise
identification of the endothelial surface, and hence, MLA, deeper
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Lowe Perspectives on imaging the left main coronary artery
FIGURE 1 | A bare metal stent (4.0mm×13mmVision) placed
suboptimally in proximal left main coronary artery, extending into
aorta taken at post-mortem (marked by arrow). There is proximal
extension of the stent to within the aorta of 2–3 mm.
FIGURE 2 | Left main coronary artery imaged with angiography
(A), optical coherence tomography (B,D), and intravascular ultrasound
(C,E), 1 year following stenting using a drug-eluting stent. (A) Coronary
angiography RAO view. Proximal mild left main lesion and dilated stent in
mid and distal portion of left main coronary artery. (B) OCT to mid left main.
Stent struts are seen well-apposed to the vessel wall, with precise detail
(arrows). Wire artifact shadow marked as asterisk. (C). IVUS to mid left
main at same site. Stent struts are seen, and appear well-apposed, but
without the precision of the OCT images (arrows). (D) OCT to ostium of left
main. The lumen is very clearly seen (area calculated at 7.1 mm2), but no
detail is provided as to the nature or extent of underlying atherosclerotic
plaque. Wire artifact shadow marked as asterisk. (E) IVUS to ostium of left
main at same site. The lumen is well visualized (lumenal area calculated at
6 mm2). The extent of underlying atherosclerotic plaque is evident, marked
with arrow (calculated at 40% area stenosis).
structures to calculate plaque burden may not be seen (Figure 2).
It might be expected that information regarding stenosis severity
acquired using OCT is similar to that gained by IVUS; however, a
recent comparison suggested that measurements are increased by
8–10% measured by IVUS compared to OCT (10). Long-term out-
come data of interventions based on OCT measurements of LMCA
stenosis severity are not available, though would seem intuitive,
with this caveat.
Optical coherence tomography for assessment of LMCA PCI
would appear superior to IVUS, both from the perspective of
acute assessment of stent strut apposition (11) and from the
longer-term follow-up. The improved axial and lateral resolu-
tion is of a magnitude greater with OCT, compared to IVUS,
meaning even minor degrees of stent strut mal-apposition are
apparent with OCT (11). While improving mal-apposition using
OCT would seem intuitively beneficial in improving outcomes
post-LMCA stenting, importantly this has not yet been tested in
a trial setting, and not yet shown to be associated with improved
outcomes.
CONCLUSION
Intravascular ultrasound, and more recently OCT, provide impor-
tant information guiding LMCA assessment both pre- and post-
PCI. Given the likely increasing frequency of LMCA intervention,
the use of both of these imaging modalities – particularly OCT – is
likely to increase. This is an important area of change in the field
of intracoronary imaging.
REFERENCES
1. Tierstein PS, Price MJ. Left main percutaneous coronary intervention. J Am Coll
Cardiol (2012) 60:1605–13. doi:10.1016/j.jacc.2012.01.085
2. Taylor AJ, Cerqueria M, Hodgson J, Mark D, Min J, O’Gara P, et al.
ACCF/SCCT/ACR/AHA/ASE/ASNC/ASNC/NASCI/SCAI/SCMR 2010 appro-
priate use criteria for cardiac computed tomography. J Cardiovasc Comput
Tomogr (2010) 4:407.e1–33. doi:10.1016/j.jcct.2010.11.001
3. Farinha JB, Kaplan MA, Harris CN, Dunne EF, Carlish RA, Kay JH, et al. Dis-
ease of the left main coronary artery. Surgical treatment and long-term follow
up in 267 patients. Am J Cardiol (1978) 42:124–8. doi:10.1016/0002-9149(78)
90996-7
4. Macaya C, Alfonso F, Iniguez A, Goicolea J, Hernandez R, Zarco P, et al. Stenting
for elastic recoil during coronary angioplasty of the left main coronary artery.
Am J Cardiol (1992) 70:105–7. doi:10.1016/0002-9149(92)91400-X
5. Puri R, Kapadia SR, Nicholls SJ, Harvey JE, Kataoka Y, Tuzcu EM. Optimizing
outcomes during left main percutaneous coronary intervention with intravas-
cular ultrasound and fractional flow reserve. The current state of evidence. J Am
Coll Cardiol Interv (2012) 5:697–707. doi:10.1016/j.jcin.2012.02.018
6. Fassa AA, Wagatsuma K, Higano ST, Mathew V, Barsness GW, Lennon RJ, et al.
Intravascular ultrasound-guided treatment for angiographically indeterminate
left main coronary artery disease: a long-term follow-up study. J AmColl Cardiol
(2005) 45:204–11. doi:10.1016/j.jacc.2004.09.066
7. de la Torre Hernandez JM, Hernández Hernandez F, Alfonso F, Rumoroso JR,
Lopez-Palop R, Sadaba M, et al. Prospective application of pre-defined intravas-
cular ultrasound criteria for assessment of intermediate left main coronary
artery lesions results from the multicenter LITRO study. JAmColl Cardiol (2011)
58:351–8. doi:10.1016/j.jacc.2011.02.064
8. Park SJ, Kim YH, Park DW, Lee SW, Kim WJ, Suh J, et al. Impact of intravas-
cular ultrasound guidance on long-term mortality in stenting for unprotected
left main coronary artery stenosis. Circ Cardiovasc Interv (2009) 2:167–77.
doi:10.1161/CIRCINTERVENTIONS.108.799494
9. Lowe HC, Narula J, Fujimoto J, Jang IK. Intracoronary optical diagnostics: cur-
rent status, limitations and potential. J AmColl Cardiol Interv (2011) 4:1257–70.
doi:10.1016/j.jcin.2011.08.015
10. Kubo T, Akasaka T, Shite J, Suzuki T, Uemura S, Yu B, et al. OCT
compared with IVUS in a coronary lesion assessment: the OPU-CLASS
Frontiers in Cardiovascular Medicine | Cardiovascular Imaging January 2015 | Volume 1 | Article 16 | 2
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lowe Perspectives on imaging the left main coronary artery
study. JACC Cardiovasc Imaging (2013) 6:1095–104. doi:10.1016/j.jcmg.2013.
04.014
11. Alcock R, Yong ASC, Yiannikas J, Lowe HC. Optical coherence tomography-
guided left main stem stenting: a new approach? Tex Heart Inst J (2012) 4:1–2.
Conflict of Interest Statement: The author declares that the research was conducted
in the absence of any commercial or financial relationships that could be construed
as a potential conflict of interest.
Received: 28 October 2014; paper pending published: 07 November 2014; accepted: 15
December 2014; published online: 09 January 2015.
Citation: Lowe HC (2015) Perspectives on imaging the left main coronary artery using
intravascular ultrasound and optical coherence tomography. Front. Cardiovasc. Med.
1:16. doi: 10.3389/fcvm.2014.00016
This article was submitted to Cardiovascular Imaging, a section of the journal Frontiers
in Cardiovascular Medicine.
Copyright © 2015 Lowe. This is an open-access article distributed under the terms of the
Creative Commons Attribution License (CC BY). The use, distribution or reproduction
in other forums is permitted, provided the original author(s) or licensor are credited
and that the original publication in this journal is cited, in accordance with accepted
academic practice. No use, distribution or reproduction is permitted which does not
comply with these terms.
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Perspectives on Imaging the Left Main Coronary Artery Using Intravascular Ultrasound and Optical Coherence Tomography

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