The invention provides a rotational atherectomy system, device and method comprising a bi-directional drive shaft with a flexible ablation element disposed at the distal end of the drive shaft. The flexible ablation element comprises a first retracted position for insertion into vasculature and a second expanded position for ablation, i.e., cutting, sanding and/or grinding. The ablation element comprises more than one flexible finger or blade which allows changing, in certain embodiments, of curvature radius to fit inside a deployment catheter and/or enlarge to the diameter of larger lumens, up to at least 9 mm in diameter. Bi-directional rotation of the expanded ablation element allows cutting in one rotational direction and grinding and/or sanding in the opposite rotational direction.