Provisional Angioplasty in Left Main: What MSA Values Should We Target?

Percutaneous coronary intervention (PCI) of the unprotected left main coronary artery (LMCA) represents one of the most challenging scenarios. Clinical practice guidelines recommend the use of IVUS as an essential tool to optimize outcomes, with clear advantages over conventional angiography in selecting device size, detecting malapposition, and particularly in identifying underexpansion.

Nevertheless, uncertainty remains regarding the optimal threshold or “target value” of minimal stent area (MSA) in the LMCA, especially in the provisional crossover strategy with a single stent toward the left anterior descending artery (LAD). 

The Asan Medical Center group (Seoul), led by Kim et al., had previously evaluated these “cut-off points” using the 5-6-7-8 criteria and other MSA values in two-stent PCI for LMCA. In this new investigation, presented in EuroIntervention, they propose quantitative MSA thresholds to predict five-year events in single-stent procedures.

The study included 829 patients with unprotected LMCA treated with DES through a LMCA-LAD crossover strategy optimized with IVUS. Cases requiring a second stent in the circumflex (Cx) ostium, crossover to Cx, prior CABG, or in-stent restenosis of the LMCA were excluded. The mean post-PCI MSA was 11.9±2.5 mm² in the proximal LMCA, 10.1±2.2 mm² in the distal LMCA, and 8.7±1.9 mm² in the LAD ostium.

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When assessing optimal thresholds by ROC curves to predict MACE, adequate values were determined as proximal LMCA ≥11.4 mm² (AUC 0.62), distal LMCA ≥8.4 mm² (AUC 0.58), and LAD ostium ≥8.1 mm² (AUC 0.57). Using these cut-offs, underexpansion rates were 46.2%, 19.2%, and 41.1%, respectively. 

Subexpansion <11.4 mm² in the proximal LMCA doubled the risk of five-year MACE (adjusted HR 2.34; p<0.001) and was associated with increased all-cause mortality (adjusted HR 2.12; p=0.003). In adjusted models including all three MSA values, only proximal LMCA MSA retained independent association with MACE.

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Additionally, double distal underexpansion (distal LMCA and LAD ostium) proved hazardous, showing higher MACE risk (24.2%) and an independent association with increased TLR (adjusted HR 4.30).

Conclusions

This study, focused on the provisional single-stent technique, highlights the importance of IVUS and the relationship between underexpansion and adverse outcomes across LMCA segments. A proximal LMCA MSA ≥11.4 mm² was the only parameter with independent prognostic value after multivariable adjustment, underscoring the need for vigorous post-dilatation with larger diameter balloons at high pressure until the proposed threshold is achieved. Moreover, the presence of double distal underexpansion significantly increases the risk of MACE and TLR.

Original Title: Optimal minimal stent area after crossover stenting in patients with unprotected left main coronary artery disease.

Reference: Kim JH, Kang DY, Ahn JM, Kweon J, Chae J, Wee SB, An SY, Park H, Kang SJ, Park DW, Park SJ. Optimal minimal stent area after crossover stenting in patients with unprotected left main coronary artery disease. EuroIntervention. 2025 Sep 15;00(0):000-000. doi: 10.4244/EIJ-D-25-00122.