BACKGROUND: Severe coronary artery calcification has been associated with stent underexpansion, procedural complications, and increased rates of early and late adverse clinical events in patients undergoing percutaneous coronary intervention. To date, no lesion preparation strategy has been shown to definitively improve outcomes of percutaneous coronary intervention for calcified coronary artery lesions. STUDY DESIGN AND OBJECTIVES: ECLIPSE (NCT03108456) is a prospective, randomized, multicenter trial designed to evaluate two different vessel preparation strategies in severely calcified coronary artery lesions. The routine use of the Diamondback 360 Coronary Orbital Atherectomy System is compared with conventional balloon angioplasty prior to drug-eluting stent implantation. The trial aims to enroll approximately 2000 subjects with a primary clinical endpoint of target vessel failure, defined as the composite of cardiac death, target vessel-related myocardial infarction, or ischemia-driven target vessel revascularization assessed at 1 year. The co-primary endpoint is the acute post-procedural in-stent minimal cross-sectional area as assessed by optical coherence tomography in a 500-subject cohort. Enrollment is anticipated to complete in 2022 with total clinical follow-up planned for 2 years. CONCLUSIONS: ECLIPSE is a large-scale, prospective randomized trial powered to demonstrate whether a vessel preparation strategy of routine orbital atherectomy system is superior to conventional balloon angioplasty prior to implantation of drug-eluting stents in severely calcified coronary artery lesions.