Even in the era of drug-eluting stents, bifurcation lesions remain one of the most challenging lesion subsets in coronary intervention practice. This study was performed to evaluate the functional outcomes of pressure wires (IFR)-guided jailed side-branch intervention strategy.

Fractional flow reserve (FFR) measurements require minimal and constant microvascular resistance which is routinely achieved by intravenous adenosine infusion. Adenosine-induced hyperemia establishes an optimal vascular environment for FFR measurement. However, breathlessness and chest tightness are common adverse events during adenosine infusion and severe asthma occurs occasionally. The Introduction of an adenosine-independent index (instantaneous wave-free ratio [iFR]) into clinical practice offered easier and hyperemia-free method for lesion assessment.

Physiological changes and clinical evaluation of iFR warrants further research. Therefore, the investigators conducted this study to evaluate the functional aspects of iFR-guided provisional jailed side-branch intervention strategy and compare clinical endpoints to conventional non-iFR-guided operations.

Inclusion Criteria:

• Patients with acute coronary syndrome
• Jailed side-branch of a vessel size > 2 mm
• Vessel length > 40 mm
• Lesion length < 10 mm by visual estimation

Exclusion Criteria:

• Significant stenosis in the left main coronary artery or the main branch proximal to the stented segment
• Totally occluded bifurcation lesions
• Primary myocardial disease
• Serum creatinine level of ≥ 2.