A rotational atherectomy apparatus, comprising: a flexible, elongated, rotatable drive shaft (20; 102) having a proximal end and a distal end opposite the proximal end, the drive shaft (20; 102) being rotatable in a cutting direction and in a grinding direction opposite the cutting direction; an expandable atherectomy head (30; 50; 70) disposed proximate the distal end of the drive shaft (20; 102), the head (30; 50; 70) rotatably expandable from a rest position with a rest diameter when not rotating to an expanded position with a rotational diameter when the drive shaf (20; 102) is rotated at a high rotational speed and due to centrifugal forces in both the cutting direction or the grinding direction, wherein the rotational diameter is greater than the rest diameter, the head (30; 50; 70) comprising: a first arm (31; 51; 71) pivotally attached to the drive shaft (20; 102) at a first drive shaft anchor point near the distal end of the drive shaft (20; 102), the first arm (31; 51; 71) being pivotable in a first plane tangential to the drive shaft (20; 102) at the first drive shaft anchor point and from the rest position to the expanded position due to centrifugal forces generated; the first arm (31; 51; 71) having a first arm free end (33; 53; 73) that leads the first drive shaft anchor point when the drive shaft (20; 102) is rotated in the cutting direction and trails the first drive shaft anchor point when the drive shaft (20; 102) is rotated in the grinding direction; the first arm free end (33; 53; 73) having a first cutting feature on a leading edge of the first arm free end (33; 53; 73) as the drive shaft (20; 102) is rotated in the cutting direction; and the first arm free end (33; 53; 73) having a first grinding feature adjacent to the first cutting feature and leading the first cutting feature as the drive shaft (20; 102) is rotated in the grinding direction. a flexible, elongated, rotatable drive shaft (20; 102) having a proximal end and a distal end opposite the proximal end, the drive shaft (20; 102) being rotatable in a cutting direction and in a grinding direction opposite the cutting direction; an expandable atherectomy head (30; 50; 70) disposed proximate the distal end of the drive shaft (20; 102), the head (30; 50; 70) rotatably expandable from a rest position with a rest diameter when not rotating to an expanded position with a rotational diameter when the drive shaf (20; 102) is rotated at a high rotational speed and due to centrifugal forces in both the cutting direction or the grinding direction, wherein the rotational diameter is greater than the rest diameter, the head (30; 50; 70) comprising: a first arm (31; 51; 71) pivotally attached to the drive shaft (20; 102) at a first drive shaft anchor point near the distal end of the drive shaft (20; 102), the first arm (31; 51; 71) being pivotable in a first plane tangential to the drive shaft (20; 102) at the first drive shaft anchor point and from the rest position to the expanded position due to centrifugal forces generated; the first arm (31; 51; 71) having a first arm free end (33; 53; 73) that leads the first drive shaft anchor point when the drive shaft (20; 102) is rotated in the cutting direction and trails the first drive shaft anchor point when the drive shaft (20; 102) is rotated in the grinding direction; the first arm free end (33; 53; 73) having a first cutting feature on a leading edge of the first arm free end (33; 53; 73) as the drive shaft (20; 102) is rotated in the cutting direction; and the first arm free end (33; 53; 73) having a first grinding feature adjacent to the first cutting feature and leading the first cutting feature as the drive shaft (20; 102) is rotated in the grinding direction.