Smart Angioplasty Research Team-Optimal Strategy for Side Branch Stenting in Coronary Bifurcation Lesion With Drug-Coated Balloon

Inclusion Criteria * Subject must be at least 19 years of age * Patients with acute or chronic coronary syndrome intended for percutaneous coronary intervention (PCI) * Patients with de novo complex coronary bifurcation with clinically relevant side branch. Definition of complex coronary bifurcation with clinically relevant side branch is true bifurcation lesion (Medina 1,1,1 / 1,0,1 / 0,1,1) with side branch lesion length ≥10mm and should meet at least one of the below criteria. i. Left main bifurcation with side branch stenosis severity ≥70% by visual estimation ii. Non-left main bifurcation with side branch reference vessel diameter ≥2.75mm and stenosis severity ≥90% by visual estimation * Subject who can verbally confirm understandings of risks, benefits and treatment alternatives of receiving invasive approach and he/she or his/her legally authorized representative provides written informed consent prior to any study related procedure. Exclusion Criteria * Hemodynamically unstable condition (SBP \<90 mmHg even after administration of vasopressor, ventricular arrhythmias, or cardiogenic shock) * Known true anaphylaxis to contrast medium (not allergic reaction but anaphylactic shock) * Known significant congenital, severe valvular or cardiomyopathic (hypertrophic or dilated cardiomyopathy, or any other forms) process which could explain cardiac symptoms. * Severe left ventricular systolic dysfunction (ejection fraction \<30%) * Intolerance to aspirin, clopidogrel, ticagrelor, prasugrel, or heparin. * Non-cardiac co-morbid conditions are present with life expectancy \<1 year or that may result in protocol non-compliance (per site investigator's medical judgment) * Unwillingness or inability to comply with the procedures described in this protocol.