 The coronary bifurcation lesions pose a therapeutic problem with high rates of periprocedural complications, higher rates of in-stent restenosis and stent thrombosis. These are lesions where stenting is not superior in comparison to balloon angioplasty in regard to side branch. It was demonstrated many times, in literature and in daily practice, that angiographically high grade ostial side branch stenosis is not flow limiting and do not cause ischemia, therefore do not require treatment. From the other side, our own data with MRI before and after bifurcation PCI demonstrated that occurrence of angiographic stenosis more than 70 in diameter is associated with periprocedural myonecrosis in the region of side branch. This fact puts a very important question about the mechanisms of this myonecrosis. If the jailed side branch has no significant flow limiting stenosis, but there is some degree of residual ischemia, which after some period of persistence could lead to myonecrosis, will mean that more aggressive treatment of ostial stenosis is needed. It is interesting that the strategy of treatment is very important, because techniques with second stent implantation with primary purpose to limit SB ischemia are associated with higher grade of troponin increase. Of course this is association and not causality, despite that in randomized study NORDIC I it was confirmed also. 