Abstract: Objective To observe the efficacy of intravascular ultrasound (IVUS) and coronary angiography (CAG) in the treatment of non-culprit lesions (NCL) in patients with non-ST-segment elevation acute coronary syndrome (NSTE- ACS) with multi-vessel disease. Methods A total of 295 patients were included in NSTE-ACS with multivessel disease and successfully underwent percutaneous coronary intervention (PCI) for criminal lesions (CL). Patients were randomly divided into IVUS-guided treatment group (n=148) and CAG-guided treatment group (n=147). The IVUS group underwent gray-scale IVUS examination of NCL. Lesions with plaque burden (PB) ≥70% were detected by PCI. Patients in CAG group with the diameter of NCL greater than 90% were performed for PCI, and all patients were given strict secondary prevention drug treatment. The major adverse cardiovascular events (MACE) and disease-related quality of life assessment were followed up and compared between the two groups. Results (1) The stent implantation rate was significantly higher in the IVUS group than that of CAG group (P＜0.05), but the number of stent implantation was lower in IVUS group (P＜0.05). (2) There was no significant difference in the average hospital cost between the two groups (P＞0.05). (3) The follow-up showed that there was no significant difference in MACE incidence between the two groups (5.52% vs. 1.37%， χ2 =2.589， P＞0.05). The degree of physical activity limitation, angina pectoris frequency, and disease cognition score were significantly better in the IVUS group than those of the CAG group (P＜0.05). The Kaplan-Meier curve was used to compare the event-free survival time of the two groups, and there was no significant difference between the two groups (94.5% vs. 98.6％， Log-rank χ2 =3.276，P＞0.05). Conclusion IVUS-guided NCL therapy can reduce the average number of stent implantation, optimize stent implantation, not increase costs in treatment, and improve the quality of life.

Key words: acute coronary syndrome, coronary arteriography, intravascular ultrasound, non-culprit lesions, percutaneous coronary intervention, major adverse cardiovascular events