Elsevier

International Journal of Cardiology

Volume 325, 15 February 2021, Pages 168-175
International Journal of Cardiology

Intravascular ultrasound guidance in the evaluation and treatment of left main coronary artery disease

https://doi.org/10.1016/j.ijcard.2020.10.008Get rights and content

Highlights

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    PCI of left main coronary is an acceptable revascularization strategy.

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    Angiography is challenging and limited in its accuracy.

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    IVUS provides accurate imaging and measurements.

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    IVUS for LMCA PCI should be performed before, during, and after intervention.

Abstract

Percutaneous coronary intervention (PCI) of left main coronary artery (LMCA) disease has become an acceptable revascularization strategy. Evaluating the extent and characteristics of obstructive disease of the LMCA by angiography is challenging and limited in its accuracy. In contrast, intravascular ultrasound (IVUS) provides accurate imaging of the coronary lumen as well as quantitative measurements and quantitative assessment of the vessel wall components. IVUS for LMCA PCI should be performed before, during, and after intervention; IVUS enhances every step in the procedure and is associated with a mortality advantage in comparison with angiographic guidance alone. In this review, we provide an update on LMCA PCI and the role of IVUS for lesion assessment and stent optimization. In addition, the latest clinical evidence of the benefits of IVUS-guided LMCA PCI as compared to angiography is reviewed.

Introduction

Atherosclerotic obstruction of the left main coronary artery (LMCA) is present in approximately 4% of all coronary angiograms [1]. Patients with obstructive LMCA disease left untreated have a particularly poor prognosis [2]. Recent trials have demonstrated the role of LMCA stenting, especially in patients with less complex disease or those unsuitable for surgery [3,4]. Revascularization of obstructive LMCA with percutaneous coronary intervention (PCI) requires careful consideration, as the artery provides blood supply to >75% of the left ventricle [5], and complications may lead to rapidly progressive hemodynamic instability [6].

Angiographic assessment of the LMCA can be difficult [7,8]. Because of its two-dimensional shadowgraphic nature, coronary angiography cannot provide an accurate evaluation of the extent of disease or insight into the vessel-wall characteristics [9]. Limitations include lack of a well-defined reference, diffuse atherosclerosis in the LMCA with involvement of the bifurcation [10], and angiographically silent calcific disease, which makes lesions more difficult to dilate and can lead to stent underexpansion [11,12]. In addition, coronary angiography has limitations in assessing ostial LMCA involvement, in which the operator is required to rely on indirect signs of lesion severity, such as pressure damping during catheter engagement or lack of contrast dye backflow during selective injection. Even using more “modern” equipment or incorporating fractional flow reserve (FFR), LMCA assessment remains challenging [13,14].

As compared to coronary angiography, intravascular ultrasound (IVUS) is an accurate technique for assessment of both the lumen and wall characteristics and dimensions [15], making it particularly useful for imaging the LMCA, and this is reflected in the guidelines [16,17]. In this review, we discuss indications for obstructive LMCA PCI, the role of IVUS guidance, and the impact of IVUS on clinical outcomes.

Section snippets

Coronary Artery Bypass Grafting versus PCI in LMCA Disease

Coronary artery bypass grafting (CABG) has been the mainstay of treatment for obstructive LMCA disease [5], with a well-documented prognostic benefit related to the very high rate of long-term patency of the left internal mammary artery [18,19]. However, advancements in stent devices, technique refinements, and adjunctive medical therapy have led to improved PCI outcomes [20]. Recent data have demonstrated that LMCA PCI can be as safe as CABG in certain patients [[21], [22], [23]]. The Synergy

The Normal LMCA and Plaque Distribution

The sizing of a normal LMCA and its bifurcation into the left anterior descending artery (LAD) and left circumflex artery (LCX) can be predicted using Murray’s Law (the cube of the radius of the parent vessel is equal to the sum of the cubes of the radii of the daughter blood vessels) [30], is consistent among studies [7,31,32], and has been confirmed in cross-sectional data from the PROSPECT study [33]. The PROSPECT study also demonstrated that the LMCA undergoes positive remodeling in

IVUS Assessment of LMCA Stenosis Severity

The minimal lumen area (MLA) is the IVUS parameter used to determine whether an intervention should be performed and, more importantly, when it can be safely deferred. The currently accepted value is ≤6.0 mm2 (Fig. 2) for the LMCA. This cutoff was initially validated by Jasti et al. [39] using FFR as a marker of significant physiological ischemia. After this validation, the cutoff of ≤6.0 mm2 was assessed clinically by the Spanish Working Group on Interventional Cardiology (LITRO) study [40].

IVUS Step by Step

IVUS-guided PCI of the LMCA should start before stent implantation and finish as the final step in the PCI procedure.

Pre-PCI imaging from both the LAD and LCX should be performed to assess plaque composition (calcific vs. non-calcific plaque) and need for lesion modification (rotational or orbital atherectomy or intravascular lithotripsy), plaque distribution (single vessel vs. two stents based on extent of involvement of both the LAD and LCX), disease at the aorto-ostial junction, and choice

IVUS vs. Optical Coherence Tomography in LMCA PCI

Optical coherence tomography (OCT) is another available invasive imaging modality that uses infrared light and provides information concerning plaque distribution and vessel characteristics [62]. However, the higher tissue penetration of ultrasound compared to infrared light makes IVUS superior to OCT in the LMCA, allowing for quantitative and qualitative assessment. In addition, IVUS imaging provides better visualization of the LMCA ostium because it does not require contrast injection to

Clinical Outcomes Using IVUS for LMCA PCI

Multiple analyses have demonstrated that IVUS-guided LMCA PCI is associated with improved long-term clinical outcomes in comparison with angiography-guided PCI. An outline of the major studies involving IVUS-guided LMCA PCI is listed in Supplemental Table 1. However, these studies rarely included a prespecified protocol for IVUS guidance and stent optimization. However, a recent study demonstrates that when following a protocol with predefined optimization criteria, IVUS guidance of LM stenting

Conclusions

Every step in performing LMCA PCI, from lesion assessment to procedure optimization, is enhanced with IVUS guidance, and IVUS guidance is associated with fewer events and even a lower mortality rate compared to no IVUS guidance. Given the current controversy regarding PCI vs. CABG for LMCA disease, perhaps the next step would be a randomized trial of IVUS-guided LMCA stenting with a carefully drafted optimization protocol vs. CABG.

Authors’ declaration

All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author Contribution Statement

Brian C. Case, MD: Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Project administration; Resources;  Validation; Visualization; Writing - original draft; Writing - review & editing.

Charan Yerasi, MD: Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Project administration; Resources;  Validation; Visualization; Writing - original draft; Writing - review & editing.

Brian J. Forrestal, MD: Conceptualization; Data curation; Formal

Declaration of Competing Interest

Ron Waksman – Advisory Board: Amgen, Boston Scientific, Cardioset, Cardiovascular Systems Inc., Medtronic, Philips, Pi-Cardia Ltd.; Consultant: Amgen, Biotronik, Boston Scientific, Cardioset, Cardiovascular Systems Inc., Medtronic, Philips, Pi-Cardia Ltd.; Grant Support: AstraZeneca, Biotronik, Boston Scientific, Chiesi; Speakers Bureau: AstraZeneca, Chiesi; Investor: MedAlliance.

Evan Shlofmitz – Consultant: Abbott Vascular, Opsens Medical.

Gary S. Mintz- Honoraria from Boston Scientific,

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