A rotational atherectomy device includes a drive shaft, a cutter mechanism coupled to the drive shaft and configured to cut occlusive material from a lesion, and a multi-stage macerator coupled to the drive shaft and configured to macerate cut occlusive material into a fine slurry. Successive stages of the multi-stage macerator macerate the cut occlusive material into successively smaller particles, which are moved proximally through a lumen of a sheath of the device that surrounds the drive shaft proximal to the macerator. The device may include a movable cutter mechanism guard that is passively rotatable between a first position in which it covers the cutter mechanism and a second position in which it exposes the cutter mechanism. One or more features of the device may limit a depth to which the cutter mechanism is able to cut the occlusive material to reduce a likelihood of undesirable tissue dissection.