<p>Chronic total occlusion (CTO) is a cardiovascular disease in which coronary arteries are completely obstructed by atherosclerotic plaques for more than three months. Percutaneous coronary intervention (PCI) treatment of calcified CTO is challenging because hardened plaques prevent the crossing and delivery of microcatheters and balloons. In this study, a two-step atherectomy method for CTO treatment using a miniature electroplated nickel (Ni)-diamond wheel is proposed. The Ni-diamond wheel first drills a hole in the CTO lesion with rotational and oscillatory translational motion along a guidewire and then grinds the lesion using orbital motion to enlarge the hole beyond the diameter of the grinding wheel. The feasibility of the proposed two-step atherectomy method, combining drilling and grinding, and the forces exerted during drilling and grinding were experimentally investigated using two types of calcified CTO plaque surrogates: gypsum cement and ex vivo bovine bone. Drilling experiments were conducted in both manual and automated feeding modes. The experimental results demonstrate that the proposed miniature wheel drills through both types of CTO surrogates in the manual and automated feeding modes with more consistent drilling forces of approximately 0.046 and 0.027 N in the rapid and slow modes under automated feeding, respectively, than under manual feeding. During grinding, the miniature wheel generates orbital motion in the hole and expands the hole diameter from 0.85 to 1.26 mm within 120 s. The proposed integrated drilling and grinding approach has promise in addressing the clinical challenges of microcatheter- and balloon-uncrossable lesions in PCI treatment of CTO.</p>