Apparatus, systems, and methods are provided for delivering a lead or other instrument into a patients body using a tubular device including a proximal end, a distal end sized for introduction into a body lumen, and a lumen extending therebetween, thereby defining a longitudinal axis. The tubular device includes a sidewall surrounding the lumen including a reinforcing layer embedded in one or more layers of base material, and a slittable seam in the sidewall extending from the proximal end partially towards the distal end substantially parallel to the longitudinal axis. In addition, slitter devices are for slitting, splitting, or opening the slittable seam. Methods are also provided for making catheters or other tubular devices including slittable, e.g., re-welded longitudinal seams that may be preferentially slit, split, or otherwise opened.
