Abstract Background/Introduction The challenges that physicians face in implementing evidence-based lipid-lowering therapy in patients at high risk of atherosclerotic cardiovascular disease (ASCVD) are relatively undocumented. Purpose This study aimed to provide insights into the challenges that Korean physicians face in assisting their high-risk ASCVD patients in achieving guideline-recommended low-density lipoprotein cholesterol (LDL-C) levels. Methods We enrolled 704 patients from 10 tertiary hospitals in South Korea, between November 2020 and November 2022. These patients were at very high risk of ASCVD, with baseline LDL-C levels ≥70mg/dL (1.8 mmol/L) while receiving maximally tolerated statins and/or ezetimibe. We measured the proportion of participants achieving LDL-C levels <70mg/dL at visit 1(0)/ visit 2(6-16)/ visit 3 (18-30 weeks), and recorded physician feedback on lipid-lowering treatment strategies. Results Out of the 704 enrolled patients (mean [IQR] age, 66.0 [59–72] years; 580 men [82.4%]), the median (IQR) baseline LDL-C level was 82.0 (74.0–94.5) mg/dL. Lipid-lowering therapy at baseline included statins in 99.0% (with 1.0% statin intolerant) or statins and ezetimibe in 56.4%. The proportion of participants achieving LDL-C levels <70mg/dL at each visit were 0%, 56.3%, and 58.7%, respectively. Among 307 patients on maximally tolerated statins at baseline, physicians did not have an intention to intensify the lipid-lowering treatment regimen in 171 (55.7%) of those patients. (Figure 1) Physician disagreement with the guidelines was the major reason for not using the recommended therapy (70.8%), followed by the patient’s refusal for reasons other than the cost (8.2%), medical limitations such as comorbidities (7.0%), and drug costs (6.4%). Among 397 patients on maximally tolerated statins and ezetimibe at baseline, physicians did not have an intention to intensify the lipid-lowering treatment regimen in 299 (75.3%) of those patients. (Figure 2) Physician disagreement with the guidelines was the major reason for not using the recommended therapy (46.2%), followed by the patient’s refusal for reasons other than the cost (15.7%), medical limitations such as comorbidities (14.4%), and drug costs (12.7%). Conclusion In this implementation science study, the proportion of patients at very high risk of ASCVD who achieved LDL-C levels <70mg/dL via lipid-lowering therapy was less than 60%. Physician disagreement with the guidelines was the main reason for not adopting the recommended intensified LDL-C lowering therapy.Figure 1Figure 2