Inclusion Criteria:  Age above 18 years Persistent angina despite medical therapy and/or evidence of inducible ischemia De-novo lesion in a native coronary artery Severe calcification of the target lesion as determined by visual estimation at coronary angiography Unsuccessful lesion preparation with standard non-compliant balloon (< 30% reduction of baseline diameter stenosis at maximal pressure) Written informed consent.  Exclusion Criteria:  Target lesion is located in a coronary artery bypass graft Target lesion is an in-stent restenosis Target lesion is a chronic total occlusion Target vessel thrombus Limited long-term prognosis due to other comorbid conditions