CABG to improve survival is recommended for patients with significant (>50% diameter stenosis) left main coronary artery stenosis.73,381,412,959 962 (Level of Evidence: B) Class IIa 1. PCI to improve survival is reasonable as an alterna- tive to CABG in selected stable patients with signif- icant (>50% diameter stenosis) unprotected left main CAD with: 1) anatomic conditions associated with a low risk of PCI procedural complications and a high likelihood of good long-term outcome (eg, a low SYNTAX score [<22], ostial or trunk left main CAD); and 2) clinical characteristics that predict a significantly increased risk of adverse surgical out- comes (eg, STS-predicted risk of operative mortality >5%).949,953,955,958,963 979 (Level of Evidence: B) 2. PCI to improve survival is reasonable in patients with UA/NSTEMI when an unprotected left main coronary artery is the culprit lesion and the patient is not a candidate for CABG.949,968 971,976 979,981 (Level of Evidence: B) 3. PCI to improve survival is reasonable in patients with acute STEMI when an unprotected left main coronary artery is the culprit lesion, distal coronary flow is less than TIMI (Thrombolysis In Myocardial Infarction) grade 3, and PCI can be performed more rapidly and safely than CABG.965,982,983 (Level of Evidence: C) Class IIb 1. 