This is a prospective, single-arm, multi-center study to evaluate the safety and performance of the OAS in treating de novo, severely calcified coronary lesions in adult subjects. Study is going to enroll up to 429 subjects in up to 50 U.S. study sites. The primary safety endpoint is 30-day MACE and primary efficacy endpoint is procedural success. All subjects will be treated with the orbital atherectomy system and adjunctive stent. All subjects will be followed in clinic at 30 days. Additionally, all subjects will have an annual phone call or clinical follow up at each anniversary until study is closed.

Inclusion Criteria:

• Subjects must be 18 or older.
• Subjects must have a clinical indication for coronary intervention.
• CK and CK-MB must be less than or equal to the upper limit of lab normal value within 8 hours prior to the procedure.
• The target lesion must be a de novo coronary lesion that has not been previously treated with any interventional procedure.
• The target vessel must be a native coronary artery with a stenosis of >= 70% and < 100%.
• The target vessel reference diameter must be >= 2.5mm and <= 4.0 mm.
• The lesion length must not exceed 40 mm.
• The target vessel must have a TIMI flow 3 at baseline.
• The target lesion must have evidence of severe calcium deposit at the lesion site based on the protocol criterion.
• The lesion must be crossable with the study guide wire.

Exclusion Criteria:

• Inability to understand the study or a history of non-compliance with medical advice.
• Unwilling or unable to sign the ORBIT II Informed Consent Form (ICF).
• History of any cognitive or mental health status that would interfere with study participation.
• Currently enrolled in any other pre-approval investigational study (does not apply to long-term post-market studies unless these studies might clinically interfere with the current study endpoints (e.g., limit use of study-required medication, etc.).
• Female subjects who are pregnant or planning to become pregnant within the study period.
• Known hypersensitivity or contraindication to aspirin, heparin, ticlopidine or clopidogrel without adequate alternative medications.
• Known sensitivity to contrast media, which cannot be adequately pre-medicated.
• Diagnosed with chronic renal failure or has a serum creatinine level >2.5 mg/dl.
• Experienced acute MI (STEMI or non-STEMI: CK and CK-MB greater than 1 times the upper limit of lab normal) within 30 days prior to index procedure.
• History of major cardiovascular intervention within 30 days.
• Evidence of current (within 6 months) left ventricular ejection fraction ≤ 25%.
• NYHA class III or IV heart failure.
• History of a stroke or transient ischemic attack (TIA) within 6 months.
• Active peptic ulcer or upper gastrointestinal (GI) bleeding within 6 months.
• History of bleeding diathesis or coagulopathy or intention to refuse blood transfusion if one should become necessary.
• Concurrent medical condition with a life expectancy of less than 12 months.
• History of immune deficiency.
• Uncontrolled insulin dependent diabetes.
• Evidence of active infections on the day of the index procedure.
• Subject has planned cardiovascular intervention within 60-days post index procedure.
• Subject is not an acceptable candidate for emergent coronary artery bypass surgery.
• Subject with known allergy to atherectomy lubricant components such as soybean oil, egg yolk phospholipids, glycerin and sodium hydroxide.
• Subject with 3 lesions requiring intervention.
• Subject with 2 lesions unless the treatment of the lesions is staged. The non target lesion must first be treated at least 12 hours prior to the index procedure. The subject's CK and CK-MB must be less than or equal to one times the upper limit of the lab normal value 12 ± 2 hours post procedure and there were no procedural complications during the first lesion intervention.
• Target lesion is located in a native vessel distal to anastomosis with a saphenous vein graft or LIMA/RIMA bypass.
• Target vessel has other lesions with greater than 50% diameter stenosis based on visual estimate or on-line QCA.
• Target vessel has angiographically visible or suspected thrombus.
• Target vessel has a stent from previous PCI.
• Target vessel is excessively tortuous.
• Target lesion is an ostial location (within 5 mm of ostium) or an unprotected left main lesion.
• Target lesion is a bifurcation.
• Target lesion has a ≥ 1.5 mm side branch.
• Angiographic evidence of a dissection prior to OAS treatment.