In study-1, the purpose of this study is to compare the long-term outcome of provisional stenting between EES and SES deployment. In study-2, it is to prove the following hypothesis " Asymmetrical expansion in the bifurcation lesion leads to frequent inhomogeneous intimal growth on the strut and thrombus attachment."

Kissing balloon inflation brings asymmetrical expansion which may lead to a risk of disturbance of endothelialization. We will investigate the following issues.

1. Impact of asymmetric expansion induced by kissing balloon technique on mid and long term results
2. Difference between SES and EES
3. Impact of abnormal OCT findings on long-term clinical outcome (3yr)

Inclusion Criteria:

1. Coronary bifurcation lesion which stenotic lesion exists in the MV and / or in the side branch (SB).
2. The lesion is appropriate for the provisional MV stenting.
3. The reference diameter is more than 2.5mm in the MV and more than 2.0mm in the SB.

Exclusion Criteria:

1. Left main coronary bifurcation
2. Acute myocardial infarction and unstable angina which culprit vessel contains obvious thrombus
3. Left ventricular ejection fraction < 30%
4. Shock state
5. Inappropriate candidate for the dual antiplatelet therapy, administration of contrast medium and radiation