After successful drug eluting stent implantation, patients will be randomized into two groups: Group A with no further dilatation, and Group B with additional post-dilatation with a noncompliant balloon. The investigators will performed IVUS analysis in groups A and B just before randomization and after post-dilatation in group B. Post dilatation will be performed with noncompliant balloon and with a nominal diameter 0.25mm larger than stent balloon.