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. PCI to improve survival may be reasonable as an alter- native to CABG in selected stable patients with significant (>50% diameter stenosis) unprotected left main CAD with: 1) anatomic conditions associated with a low to intermediate risk of PCI procedural complications and an intermediate to high likelihood of good long-term out- come (eg, low intermediate SYNTAX score of <33, bi- furcation left main CAD); and 2) clinical characteristics that predict an increased risk of adverse surgical out- comes (eg, moderate severe chronic obstructive pulmo- nary disease, disability from previous stroke, or previous cardiac surgery; STS-predicted risk of operative mortal- ity >2%).301,305,307,311,319 336,340 (Level of Evidence: B) Class III: HARM 1. PCI to improve survival should not be performed in stable patients with significant (>50% diameter steno- sis) unprotected left main CAD who have unfavorable Table 2. 