Aspiration catheter systems and methods of use

A coaxial catheter system, the system comprising:

• a catheter comprising:
• a distal, catheter portion having a lumen, and a distal end region, and a distal-most end having an opening from the lumen, the lumen having an inner diameter at the distal end region of at least about 0.052″;
• and
• a proximal extension coupled to and extending proximally from the distal, catheter portion, the proximal extension being less flexible than the distal, catheter portion;
• and
• a catheter advancement element comprising:
• a tubular portion having an inner diameter that is at least about 0.014″ up to about 0.024″, an outer diameter, wherein the outer diameter has at least one snug point, wherein a difference between the inner diameter of the distal, catheter portion and the outer diameter of the tubular portion at such snug point is no more than about 0.010″;
• a proximal extension coupled to and extending proximally from the tubular portion, the proximal extension being less flexible than the tubular portion;
• and
• a tubular, polymer tip portion located distal to the at least one snug point of the tubular portion, wherein the tip portion has a length and tapers along at least a portion of the length of the tip portion,
• wherein the coaxial catheter system has an advancement configuration characterized by:
• a) the catheter advancement element positioned coaxially within the lumen of the distal catheter portion, wherein the at least one snug point of the tubular portion is substantially aligned with the distal end region of the distal catheter portion, and
• b) wherein the tip portion in the advancement configuration has at least three points spaced along the length of the tip portion, the at least three points comprising:
• a distal point of the at least three points located a distance proximal from a distal-most end of the catheter advancement element, the distal point having a first bending force that is no greater than about 0.05 Newtons;
• an intermediate point of the at least three points located a distance proximal from the distal point, the intermediate point having a second bending force;
• and
• a proximal point of the at least three points located a distance proximal from the intermediate point, the proximal point having a third bending force;
• and
• c) wherein the coaxial system in the advancement configuration has at least two system points along a length of the coaxial system, the at least two system points comprising:
• a first system point of the at least two system points located proximal to the distal-most end of the catheter portion, the first system point having a first system bending force;
• and
• a second system point of the at least two system points located distal to the first system point by a distance that is at least about 1 mm distal to the distal-most end of the catheter portion, wherein the second system point can be the same or different from the proximal point, the second system point having a second system bending force,
• wherein a difference between the second bending force and the first bending force divided by a distance between the distal point and the intermediate point equals a first flexibility slope;
• wherein a difference between the third bending force and the second bending force divided by a distance between the intermediate point and the proximal point equals a second flexibility slope;
• wherein an average of the first flexibility slope and the second flexibility slope defines an average tip portion flexibility slope;
• wherein a difference between the first system bending force and the second system bending force divided by a distance between the first system point and the second system point equals a third flexibility slope;
• and
• wherein a ratio of the third flexibility slope to the average tip portion flexibility slope is less than about 25.