<qa>  What is the most common form of heart disease?Coronary artery disease CAD affects over 16 million subjects in the United States, making it the most common form of heart disease. The American Heart Association 2010 Update on Heart Disease and Stroke Statistics reported that in 2006 an estimated 1,313,000 inpatient percutaneous coronary intervention PCI procedures were performed in the United Sates. Despite advances in interventional equipment and techniques, there are still patient populations who remain challenging to treat. One of those patient subsets consists of individuals with lesions that have calcium deposits. Up to 50 of stents deployed in calcified lesions were found to have asymmetric stent expansion. Research has also shown that an increased amount of calcium deposits leads to a higher incidence of major adverse cardiac events MACE when compared to non-calcified lesions.In addition, lesion calcification has been shown to be associated with vessel dissection during PCI, failure to deliver a stent, balloon ruptures, and un-dilatable lesions. Unlike PTCA and stenting procedures where the calcified lesion is cracked and the stenotic lesion materials are crushed into the arterial walls, atherectomy procedures remove the stenotic lesion materials, especially the calcified portion of the lesion. Removing, as opposed to displacing, stenotic material may potentially lead to reduced acute vascular traumas, lessen the stimulus for neointimal hyperplasia that is commonly associated with in- stent restenosis, and facilitate stent delivery and expansion. Adequate plaque preparation or modification may improve both acute and long term outcomes in subjects with complex lesions, especially heavily calcified lesions. 