Previous clinical practice guidelines recommended against PCI of nonculprit artery stenoses at the time of primary PCI in hemodynamically stable patients with STEMI (9,10). Planning for routine, staged PCI of non- infarct artery stenoses on the basis of the initial angio- graphic ndings was not addressed in these previous guidelines, and noninfarct artery PCI was considered only in the limited context of spontaneous ischemia or high- risk ndings on predischarge noninvasive testing. The earlier recommendations were based in part on safety concerns, which included increased risks for procedural complications, longer procedural time, contrast nephrop- athy, and stent thrombosis in a prothrombotic and proin- ammatory state (9,10), and in part on the ndings from many observational studies and meta-analyses of trends toward or statistically signi cant worse outcomes in those who underwent multivessel primary PCI (12 16,21 23). Four RCTs have since suggested that a strategy of multivessel PCI, either at the time of primary PCI or as a planned, staged procedure, may be bene cial and safe in selected patients with STEMI (17,18,24,27) (Data Supple- ment). In the PRAMI (Preventive Angioplasty in Acute Myocardial Infarction) trial (n 465) (24), the composite primary outcome of cardiac death, nonfatal myocardial infarction (MI), or refractory angina occurred in 21 pa- tients (9%) treated with multivessel primary PCI, compared with 53 patients (22%) treated with culprit artery only PCI (HR: 0.35; 95% CI: 0.21 to 0.58; p<0.001). In the CvLPRIT (Complete Versus Culprit-Lesion Only Primary PCI) trial (18), 296 patients were randomized to culprit artery only or multivessel PCI during the index hospitalization (72% underwent multivessel primary PCI). 