Murray-law based single-view quantitative flow ratio (µQFR) has been recommended for guiding percutaneous coronary intervention (PCI) in selective patients. However, it's reliability has not been validated in bifurcation lesions which present complex anatomy and flluid conditions before and after PCI. The goal of this study is to investigate the diagnostic performance of µQFR in side branch after single-stent treatment for bifurcation lesions in patient with obstructive coronary artery diseases.

The Murray law-based quantitative flow ratio (µQFR), derived from single-view angiography, is an established computational method for non-invasive functional assessment of coronary stenoses. Its utility in guiding percutaneous coronary intervention (PCI) in selected patients with straightforward lesions is recognized. However, its diagnostic reliability remains unvalidated in the context of coronary bifurcation lesions. These lesions exhibit inherent geometric and hemodynamic complexity due to altered flow patterns and shear stress distribution, both pre- and post-intervention. This complexity is particularly pertinent to side branches following single-stent strategies. Significant alterations in the local hemodynamic environment occur after stent deployment in the main vessel, potentially impacting side branch physiology and the accuracy of µQFR calculations specifically within this branch. Consequently, an evidence gap persists regarding the performance of µQFR for functional evaluation of the side branch after bifurcation PCI. This study specifically aims to evaluate the diagnostic performance of µQFR for assessing the functional significance of side branch stenoses after single-stent treatment of bifurcation lesions in patients with obstructive coronary artery disease (CAD). The primary objective is to determine the diagnostic performance of post-procedural µQFR measurements within the side branch of such complex lesions. The second objective is to investigate potential factors influencing the diagnostic performance of µQFR.

Inclusion Criteria:

1. Age ≥ 18 years and provision of written informed consent for biospecimen donation upon hospital admission.
2. Clinical suspicion or diagnosis of CAD requiring coronary angiography and physiological assessment.
3. Angiographically confirmed true bifurcation lesions, including but not limited to: left main-left anterior descending-left circumflex (LM-LAD-LCx), left anterior descending-diagonal (LAD-Dg), left circumflex-obtuse marginal (LCx-OM), and right coronary artery-posterior left ventricular-posterior descending artery (RCA-PLV-PDA).
4. Bifurcation lesion vessel diameter ≥ 2.5 mm with visually estimated angiographic diameter stenosis ≥ 50%.

Exclusion Criteria:

1. Acute myocardial infarction.
2. Cardiogenic shock or severe heart failure (Killip class IV).
3. Serum creatinine > 150 μmol/L or estimated glomerular filtration rate (eGFR) < 45 mL/min/1.73 m² calculated using the CKD-EPI formula.
4. Known allergy to iodinated contrast media.
5. History of coronary artery bypass graft surgery.

Patients with obstructive bifurcation lesions who intended to undergo single-stent treatment.

IPD sharing might be possible upon reasonable requirement and under institutional administrative regulations.