An improved atherectomy catheter and methods of making and using a catheter are disclosed. In one embodiment, the catheter comprises a housing shaft having a torsionally-reinforced outer layer concentrically disposed over a polymeric inner layer, with an inflation tube disposed concentrically over the housing shaft to define an annular inflation lumen. A housing is attached to the distal end of the housing shaft, and may contain an interventional device such as a cutting blade. Apparatus for urging the housing against a vessel wall, such as a balloon, is attached to the housing opposite the an interventional device and is in communication with the inflation lumen. A drive shaft may be rotatably disposed through a longitudinal lumen in the housing shaft, the drive shaft being coupled at its distal end to the interventional device. The method of the invention facilitates construction of a catheter shaft through the steps of forming a flexible tubular polymeric outer layer with a first melting point over a tubular polymeric inner layer with a second melting point, the first melting point being lower than the second melting point; heating the outer layer to at least the first melting point and less than the second melting point, and impregnating a wire braid into the outer layer up to the inner layer. In a preferred embodiment, the inner layer is a fluorocarbon polymer, and the outer layer is a thermoplastic elastomer which is stable near body temperatures, impregnated with one or more layers of a stainless steel wire braid.