Backgrounds: Abnormal blood flow patterns promote inflammation, cellular proliferation and thrombosis and is established by local changes in vessel geometry after stent implantation in bifurcation lesions. We sought to quantify altered hemodynamics due to main branch (MB) stenting and subsequent side branch (SB) intervention in a coronary bifurcation lesions using computational fluid dynamics (CFD) analysis.
Methods: CFD models of SB angioplasty and SB stenting with and without kissing balloon inflation were generated from representative intravascular ultrasound images and Finet's law (Figure). Aggressive kissing balloon inflation model had an over-expanded segment at the distal part of proximal MB. Virtually implanted stent was a Express2 stent (Boston Sci,USA). Time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI) and fractional flow reserve were quantified.
Results: SB fractional flow reserve was >0.75 in all models. MB stenting followed by various SB intervention strategies induced areas of low WSS(< 4 dyn/cm2), but was not different among the SB intervention techniques except for a model without a SB stent. MB/SB stenting followed by aggressive kissing balloon inflation showed the highest OSI (Figure).
Conclusions: These findings indicate that the most commonly used percutaneous interventional strategy for a bifurcation lesion causes abnormal local hemodynamic conditions. These results may partially explain the high clinical event rates in bifurcation lesions after complex intervention.

Figure. Area of low wall shear stress and high oscillatory shear index after various side branch intervention strategies