Original title: Intravascular Ultrasound-Derived Minimal Lumen Area Criteria for Functionally Significant Left Main Coronary Artery Stenosis. Reference: Seung-Jung Park et al. J Am Coll Cardiol Intv. 2014;7(8):868-874.

Deciding on a course of action when facing intermediate main left stenosis is usually challenging. We tend to overestimate the lesion or to use additional methods, other than angiography, to tip the scales. The intravascular ultrasound (IVUS) can be of use but the minimal lumen area criteria for predicting functional significance remains uncertain, especially when considering 0.80 fractional flow reserve (FFR) as the gold standard.

This study included 112 patients with ostial and shaft left main coronary artery stenosis (LMCA) of 30% and 80% angiographic diameter who underwent IVUS and FFR measurement.

Overall, 66 patients had an FFR ≤ 0.80, with smaller reference vessel, higher diameter stenosis, longer lesion length, smaller minimal lumen area, larger plaque burden and more frequent plaque rupture.

Independent predictors of ≤ 0.80 FFR were plaque rupture (OR 4.47; p=0.014), BM index (OR 1.19; p=0.05), age (OR 0.95; p=0.031) and minimal lumen area by IVUS (OR 0.37; CI 95% 0.25 to 0.56; p < 0.001), the latter being the most significant.

The minimal lumen area value that best predicted ≤ 0.80 FFR was 4.5 mm2 (77% sensitivity, 82% specificity, 84% positive predictive value, negative predictive value 75%, area under the curve 0.83, CI 95% 0.76 to 0.96; p < 0.001). Adjustment by body surface area, BM index and left ventricular mass did not improve diagnostic accuracy over IVUS minimal lumen area alone.

Conclusion

In patients with ostial or shaft intermediate LMCA stenosis, an IVUS derived MLA ≤ 4.5 mm2 correlates well with ≤ 0.80 FFR.

Editorial Comment

The FIRST study (Fractional Flow Reserve and Intravascular Ultrasound Relationship Study) had already found a correlation between MLA by IVUS and FFR ≤ 0.80 (gold standard) but this correlation was modest (64% sensitivity and specificity) and did not specifically study LMCA. 

This study has found a better correlation and the minimal lumen area that best predicts FFR ≤ 0.80 lowers the historical MLA cut off values from 6 mm2 to 4.5 mm2.

It is important to note that this study did not include patients with bifurcation lesions or more distal lesions of the anterior descending or de circumflex arteries that could complicate the interpretation of FFR.

SOLACI