Two-phase technique to restore artery patency and a catheter temperature control system in atherectomy

1. A method of two-phase atherectomy for removal of plaque within an artery forming a stenosis, the method comprising:

a first phase of rotational drilling by exerting a rotational force on a cutter to form a channel within the plaque having a diameter substantially equal to a diameter of the cutter, the cutter being rotated at a first rotational speed sufficient to maintain rotation of the cutter about a rotational axis, wherein the rotational axis is stationary during the first phase; and

a second phase of orbital impact by exerting a rotational force on the cutter to result in radial orbital motion of the cutter within the channel resulting in periodic impact of the cutter upon the plaque to form micro-fractures within the plaque and enlarge the diameter of the channel to a diameter substantially greater than the diameter of the cutter, the cutter being rotated at a second rotational speed sufficient to result in the radial orbital motion of the cutter such that the rotational axis of the cutter generally orbits an orbital axis, the rotational axis being offset from the orbital axis.

2. The method according to claim 1 wherein the radial orbital motion of the second phase is due to fluid mechanics within the artery.

3. The method according to claim 1 wherein the periodic impact of the cutter upon the plaque comprises the cutter hitting the plaque, bouncing away from the plaque due to the impact force, and then hitting the plaque again due to centrifugal force.

4. The method according to claim 1 wherein the first rotational speed is in the range of about 90,000 to about 170,000 revolutions per minute.

5. The method according to claim 1 wherein the first rotational speed is about 135,000 revolutions per minute about the rotational axis.

6. The method according to claim 1 wherein the second rotational speed is in the range of about 170,000 to about 250,000 revolutions per minute.

7. The method according to claim 1 wherein the second rotational speed is about 185,000 revolutions per minute about the rotational axis.

8. The method according to claim 1 wherein the first phase of rotational drilling further comprises a pecking motion being a periodic engagement and disengagement of the cutter with the plaque.

9. The method according to claim 1 further comprising:

monitoring a temperature of at least one of the cutter, a guidewire, a drive shaft, and a sheath; and

introducing a fluid within at least one of the sheath and the artery during at least one of the first phase and the second phase.

10. The method according to claim 9 wherein the monitoring a temperature comprises disposing a temperature sensor within the sheath and providing a temperature regulator introducing the fluid.

11. The method according to claim 1 wherein the cutter comprises an abrasive coating disposed on both a leading face and a trailing face thereof.

12. The method according to claim 1 wherein the cutter comprises a plurality of discrete abrasive sections disposed along a shaft thereof.

13. The method according to claim 12 wherein each of the plurality of discrete abrasive sections is about 100 μm thick.