1-month vs 12-month DAPT for ACS Patients Who Underwent PCI Stratified by IVUS: IVUS-ACS and ULTIMATE-DAPT Trials

A total of 3486 subjects with ACS who met inclusion criteria and do not have any exclusion criterion will be randomized to IVUS- or Angiography-guidance group (first randomization). In the IVUS-guidance group, IVUS will be used to evaluate the lesion's specificity and to measure lesion length, landing zone, and reference vessel diameter prior-to stenting; and to assess stent expansion, extension, apposition, and possible complications after stent implantation. The IVUS- defined criteria for the optimal stent deployment included: 1) the minimal stent area (MSA) in the stented segment is \>5.0 mm\^2, or 90% of the MLA at the distal reference segments; 2) plaque burden 5-mm proximal or distal to the stent edge is \<55%; and 3) absence of \>Type B edge dissection. Further treatment will be required if stenting procedure is defined as suboptimal according to IVUS definition. IVUS will be not allowed to be used in the Angiography-guidance group. Those patients who have had no death, STEMI, stroke, ST, TVR or major bleeding (BARC 3 or 5) within 30 days and have continued on aspirin and ticagrelor for 30 days without interruption for \>48 hours will be randomized 1:1 to: 1. Ticagrelor plus+ matching placebo for an additional 11 months (SAPT group) 2. Ticagrelor plus aspirin (study drug) for an additional 11 months (DAPT group) Follow-up of all subjects will continue for 1 year with an option for additional follow-up to 3 years.