IVUS for Left Main Coronary Artery Disease

Primary Indication: Assessment of Intermediate Left Main Stenosis

The American College of Cardiology recommends IVUS to assess angiographically indeterminate left main coronary artery stenosis, with deferral of revascularization safe when minimal lumen area is ≥6-7.5 mm² (or ≥4.5-4.8 mm² in Asian patients) 1, 2
The American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions guidelines provide a Class IIa recommendation for IVUS to help define lesion severity in patients with intermediate stenosis of the left main artery 1, 2, 3

A minimal lumen area (MLA) ≥7.5 mm² indicates that revascularization may be safely deferred 4, 5
An MLA <6 mm² indicates a physiologically significant lesion, and patients likely benefit from revascularization 4, 5
An MLA of 6-7.5 mm² requires further physiological assessment with FFR measurement 4, 5
For Asian patients, a lower cutoff of 4.5-4.8 mm² should be used due to smaller vessel size 1, 2

The American College of Cardiology recommends IVUS for guidance during left main coronary artery stenting, with a Class IIb recommendation 4, 6, 7, 8
IVUS should be performed after intracoronary nitroglycerin administration, beginning ≥20mm distal to the area of interest 9, 10
Key pre-intervention uses of IVUS include identifying reference segments and optimal landing zones for stent placement, selecting appropriate stent length and diameter, characterizing plaque composition, and resolving ostial ambiguity 9, 10

Target IVUS endpoints for optimal results include an MLA in the stented segment >5.0 mm² or ≥90% of distal reference MLA, a plaque burden <50% within 5mm of stent edges, and no edge dissection involving media with length >3mm 9, 10

IVUS identifies critical complications requiring immediate correction, including stent underexpansion, deformation, or malapposition, edge dissection, hematoma, or tissue protrusion, and geographic miss (inadequate lesion coverage) 9, 10

IVUS and FFR provide complementary information for assessing intermediate left main stenosis, with FFR may be similarly effective to IVUS for functional assessment 4, 5
FFR may reduce the need for revascularization compared to IVUS alone, and provides additional physiological confirmation when IVUS shows borderline MLA (6-7.5 mm²) 4, 5

IVUS offers substantially superior spatial resolution (100-150 μm) compared to angiography (300 μm), which is critical in left main disease where angiography has well-recognized limitations 1, 2, 3
IVUS can identify overlapping vessels, foreshortening, and ostial lesions that are difficult to evaluate angiographically 1, 2, 9

IVUS should not be used for routine lesion assessment when revascularization is not being contemplated (Class III: No Benefit) 4, 6, 7, 8