From the Guidelines
The significant minimal lumen area for major coronary arteries is 6 mm², below which patients may benefit from revascularization, while an area of 7.5 mm² or greater suggests that revascularization may be safely deferred. This threshold is based on the 2011 ACCF/AHA/SCAI guideline for percutaneous coronary intervention, which suggests that a minimal lumen area of 6 mm² indicates a physiologically significant lesion 1. For non-left main stenoses, a minimal lumen diameter of 2.0 mm and minimal lumen area of 4.0 mm² correlate with low event rates, but in smaller-diameter arteries, measurement of FFR may more accurately reflect a significant stenosis 1. The use of intravascular ultrasound (IVUS) is recommended for the assessment of angiographically indeterminant left main CAD, and may be reasonable for the assessment of non-left main coronary arteries with angiographically intermediate coronary stenoses 1.
Some key points to consider when evaluating the minimal lumen area include:
- The size of the coronary artery, with smaller vessels having lower thresholds for significance
- The location of the stenosis, with left main coronary artery stenosis considered significant at a higher threshold
- The use of IVUS or other imaging modalities to accurately assess the minimal lumen area
- The clinical context, including the presence of symptoms or evidence of myocardial ischemia
Overall, the assessment of minimal lumen area is a critical component of coronary artery disease management, and a threshold of 6 mm² is a reasonable cutoff for determining the significance of a coronary stenosis 1.
From the Research
Minimal Lumen Area for Coronary Arteries
The minimal lumen area (MLA) is a significant parameter in assessing the severity of coronary artery stenosis. Several studies have investigated the MLA criteria for functionally significant coronary artery stenosis.
- The study by 2 found that the lower range of normal minimum lumen area for the left main coronary artery (LMCA) was 7.5 mm^2.
- Another study by 3 determined that an IVUS-derived MLA of ≤4.5 mm^2 is a useful index of a fractional flow reserve (FFR) of ≤0.80 in patients with isolated ostial and shaft intermediate LMCA stenosis.
- The study by 4 provided computed tomography angiography-derived reference values of lumen dimensions in proximal and middle coronary segments in a healthy population, with the lower limit of normal for the LMCA being 7.0 mm^2 for women and 10.8 mm^2 for men.
- The study by 5 analyzed the histologic sections of the LM and other major coronary arteries in 152 patients with fatal coronary heart disease and found that narrowing of the LM indicates severe narrowing of usually all major coronary arteries.
- The study by 6 assessed IVUS measurement accuracy in defining functional ischemia by FFR and found that an MLA <3.09 mm^2 is the best threshold value for FFR <0.8, with the correlation between FFR and IVUS being better for large vessels compared to small vessels.
MLA Criteria for Significant Coronary Artery Stenosis
The MLA criteria for significant coronary artery stenosis vary depending on the study and the specific coronary artery segment. However, the following MLA values have been suggested as indicators of significant stenosis: