CABG to improve survival is recommended for patients with significant (>50% diameter stenosis) left main cor- onary artery stenosis.312 318 (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%).301,305,307,311,319 336 (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.301,324 327,332,333,335 337 (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 Thrombolysis In Myocardial Infarction grade 3, and PCI can be performed more rapidly and safely than CABG.321,338,339 (Level of Evidence: C) Class IIb 1. 