 This is an acute, observational, prospective, multi-center clinical study to evaluate Coronary Flow Reserve using the Volcano FloWire after treatment with Orbital Atherectomy and stenting of de-novo severely calcified lesions due to Coronary Artery Disease. 15 subjects will be enrolled in up to 3 active U.S. study sites. Subjects who undergo successful revascularization using Orbital Atherectomy and stenting will be eligible for enrollment. All enrolled subjects will be treated with the OAS and stenting and seen at 24 hours or at discharge, whichever is earlier. The purpose of the study is to evaluate coronary artery flow reserve following successful treatment of severely calcified coronary lesions with the OAS and stenting. 