(a) an elongated catheter body enclosing a longitudinally disposed fluid flow lumen, said catheter body having an inner surface, an outer surface, a proximal end, and a closed distal end, said catheter body being comprised of a polyurethane material; and

(b) a one-way, two-position infusion valve operatively associated with said catheter body, said valve comprising:

(i) a planar proximal infusion slit formed through said catheter body from said outer surface to said inner surface thereof,

(A) said proximal infusion slit extending between a first proximal infusion endpoint and a second proximal infusion endpoint disposed on a circumferential proximal infusion arc on said outer surface of said catheter body, and

(B) said proximal infusion slit being contained in a proximal infusion slit orientation plane, said proximal infusion slit orientation plane intersecting the longitudinal axis of said catheter body at a single point and containing a single diameter of said catheter body, said proximal infusion slit being so disposed about said longitudinal axis of said catheter body in said proximal infusion slit orientation plane as to be traversed by a line in said proximal infusion slit orientation plane perpendicular to said single diameter of said catheter body; and

(ii) a planar distal infusion slit formed through said catheter body from said outer surface to said inner surface thereof distal from and proximate to said proximal infusion slit,

(A) said distal infusion slit extending between a first distal infusion endpoint and a second distal infusion endpoint disposed on a circumferential distal infusion arc on said outer surface of said catheter body distal from said circumferential proximal infusion arc

(B) said distal infusion slit being contained in a distal infusion slit orientation plane, said distal infusion slit orientation plane intersecting the longitudinal axis of said catheter body at a single point and containing a single diameter of said catheter body, said distal slit being so disposed about said longitudinal axis of said catheter body in said distal infusion slit orientation plane as to be traversed by a line in said distal infusion slit orientation plane perpendicular to said single diameter of said catheter body,

(C) said distal infusion slit orientation plane being disposed at a divergence angle to said proximal infusion slit orientation plane, whereby the longitudinal cross section of said catheter body between said proximal infusion slit and said distal infusion slit assumes a wedge-shaped trapezoidal configuration having the longer of the parallel sides of said trapezoidal configuration oriented toward the exterior of said catheter body.